QO-100: Bigger Uplink Dish, and Experiments.

I have been updating the QO-100 set-up again.

I picked up a 110cm dish at a nearby radio ham who had used it for QO-100 before upgrading, so he could transmit DATV over the wide band transponder.

This, with the 4-patch feed antenna, makes my SSB signal quite readable. There was, however, a problem with the audio frequency spectrum of the SSB signal, low frequencies were too high, and the higher frequencies too low. An external microphone with a tone control helps, but I suspect that some other solution needs to be found, either a full realignment of the transceiver (which may be needed for the frequency accuracy, anyway

The frequency stability of the up-converter appears to be quite good, though the precision lacks a bit. less than 1kHz offset is not too bad for a non tuneable TCXO. An external reference will remedy this.

I found, however, that making the modification for an external reference requires very good SMD soldering techniques, so I might go to someone with capabilities for this, as I do not think I have a sufficiently fine tip, and the fine motor skills to do it myself. The mod requires moving a "0-Ohm" resistor.

On the receive side I have used a very simple solution for an external 25MHz reference for the LNB. It is placed indoors in a foam insulated enclosure, but the temperature drift is more than I like, about 1kHz per degree Celsius around 25kHz. I can slow the drift with the foam insulation, but the drift is there none the less.

I am actually impressed because the oscillator is a simple 5V DIL-oscillator in a small metal casing, no TCXO or other stabilization (except for the crystal, of course). This has provided very good performance otherwise. The oscillator results in an offset somewhere around 5 - 15kHz, too much for easy re-setting of the receiver frequency after being absent from the receiver.

I have used the same oscillator for controlling a simple LNB (without dish or a further horn antenna) for some beacon monitoring.

The last few days I have tested a low cost Chinese 25MHz TCXO - claimed 0.1ppm stability. The stability was excellent, but the resulted was poor sensitivity (in spite of a sufficient output to the LNB(s)). Further, I observed some spurious responses 200 and 400kHz offset from the wanted frequency. A check with a spectrum analyzer showed, as expected, clear sidebands 200 and 400kHz to each side of the nominal signal, both about 60-70dB down. No wonder I had spurious signals, when that modulation is multiplied by almost 400. 

Further, I suspect that the sideband noise of the oscillator (which I cannot measure) is too high, so the LO signal on 9750MHz is spread out, reducing the signal-to-noise ratio. So right now I am back to using the simple DIL oscillator.

With the simple DIL oscillator, what can be done to stabilize that further? I can think of 2 things:

1) Making a simple "oven" to stabilize the temperature, then adjust the supply voltage to generate the correct frequency.

2) Build a TCXO with a 25MHz Xtal

3) Build or find a VCXO for 25MHz and incorporate a PLL circuit to lock it to a 10MHz reference (OCXO, Rubidium standard, or GPSDO

4) Use a GPSDO set to 25MHz

5) Take a 10MHz reference signal, square it, divide-by-2 (5MHz) and extract the 5th harmonic with a bandpass filter and/or lowpass filter.

Because I need a 10MHz reference frequency (for the uplink converter and other microwave stuff) anyway, I should probably try (3) or (5) first, as it is the simplest. If that works to my satisfaction I am all set with respect to frequency stability, and I can thing of other refinements and other projects on frequencies high and low.

Getting QRV on 472kHz?

 I looked up how to get on 472 kHz with a minimum of effort.

Looking at 472khz.org I saw them claim that the IC-7300 and the IC-7100 could be used if they had been modified for TX in the full range. I tested my two TRXs with a dummy load, and this is what I found:

The 7300, however, shows an extremely high SWR when connected to a dummy load (filter in-line? - maybe the cable). I would not use that one.

The 7100 seems to run fine up to 50W, showing SWR of close to 1:1. In order to protect the PA ferrite cores. However, I would probably run lower power (e.g. 10W or less) and add an amplifier if I want to run higher power.

Also, I looked at the option for simple CW TXs for the 2 bands:

136kHz: A (ceramic resonator) VXO using a 5500kHz ceramic resonator should be able to cover the full 136kHz band using a divide by 40. 74AC74 and 4017 should provide a clean square-wave.

472kHz:

- a XO of 14296, 14300 or 14318kHz with a division by 30x (/3 then /10) can provide an in-band signal. 2x 4017 should work nicely and provide a clean square-wave.

 - a VXO on 7160 (with a crystal or a ceramic resonator) should provide a few kHz coverage in the band, with a division by 15 (/5 then /3) A good (LP) filter will be needed to generate a clean signal.

- maybe a VXO with a 480kHz ceramic resonator, generating a signal directly on the frequency. I should probably beware of feedback, maybe causing some chirp. 

It will probably take a while to get a decent station up and running, but I think I should be able to make a very local QSO (a few km or so). Even if the radio can generate a TX signal, there is still the question of making a decent antenna. For a first experiment a long piece of wire and a match box might be sufficient, we shall see.

Intermistic Repair of Low Cost Spectrum Analyzer.

 I purchased a low cost spectrum analyzer from China.

This is the LTDZ spectrum analyzer that covers a frequency range of 35 to 4400MHz, with some limitations. 

The first limitation is that the frequency coverage in a single sweep is limited to 350MHz. This does make the analyzer more cumbersome to use, but id does make it possible to "see" signals up to 4.4GHz, and that I could not do before.

The second limitation lies in the type of detection. The LTDZ uses a direct conversion approach to the frequency making the signal visible twice (no image rejection) in narrow sweeps.

The analyzer does have different "IF" bandwidth settings ranging from 5kHz to 500kHz, so it makes for a fair, but far from excellent, resolution of signals in the low microwave range. I suspect the dynamic range will be the limiting factor for this device, but a good indication of spurious signals is better than none.

The model I purchased has no tracking generator, but it it in a shielded case and it does have a built-in screen and battery, making it a good portable device. Just make sure there are no strong transmitter signals nearby, if you use it with an antenna - another repair job to do. I speak from experience, I destroyed the input mixer of an LTDZ, just by having a hand-held transceiver transmitting nearby. 

On the casing it says that you should have no more than "10dB" at the input. I have to assume this means 10dBm. In any case, the linearity of the mixer is probably not sufficient to make good measurements at this level, I suspect that the maximum input level for decent linearity is probably around -20dBm, but this will have to be tested.

When the device arrived the ON/OFF switch had been destroyed. I decided that, rather than having the hassle of sending the device back to China and wait for a repair, I would change the switch myself. OK, I do not have such a small switch at hand, so a preliminary, "emergency" repair has been done.

The existing switch has been removed, and a larger switch has been connected with two wires to the solder pads of the original switch. The external switch is attached to the outside of the casing, duct tape is such a good invention (if it was good enough for the astronaut on Apollo 13, it must be good enough for me ;) ).

I now have a working LTDZ.

One thing, however may need to be attended to. When it is running, the battery indicator seems to jump from a good battery level, sometimes to a zero battery level. It does not seem to interfere with the functionality, but it is annoying to see the battery indicator show an empty battery periodically.

The missing tracking generator is not a huge loss for two reasons:

I do have a NanoVNA v.2, working from 50kHz to 3GHz, so I can make filter and antenna measurements up to 3GHz. Also, when I get the software installed, I do have a PCB based LTDZ board with a tracking generator and a directional coupler covering 3.5 - 8.8 GHz (Would likely work nicely on 3.4GHz, too), so filter measurements are not a problem on the 3.4GHz band. With an external signal generator and a wideband power meter measurements of filters and antennas should work nicely on 5.7GHz.

I do have a signal generator covering up to 13GHz, and with another directional coupler (that I have) and a wideband power meter, measuring on the 10GHz band is possible.

So, in the not too far future a power meter capable of measuring up to the 10GHz band is in the planning. While I do have a bolometer HP-432A, this is not portable, so measuring antennas will be a bit tricky, therefore I intend to get a digital-readout (logarithmic) power meter up and running, and get it calibrated as well as possible.

Oh, yes, I have collected a few pieces of test equipment in my time, but a bit more is needed, now that I have entered a phase of my life with more time for experimentation. 

Small Update on the QO-100 Uplink.

 The uplink signal using the single patch antenna resulted in quite a weak signal on the satellite, There were even instances where a station simply continued calling CQ while I called them, I could easily hear my signal on the downlink, but it was not strong enough to get any attention.

While I am planning on improving the set-up with a bigger dish and with a helical feed antenna, I was browsing for QO-100 feed antennas, and came across this 4-patch feed which has circular polarization. I realized that I have a small WiFi antenna, a so-called 14dBi panel that I estimated having 4 patches phased together, a bit like the feed in the link, albeit this just with linear polarization.

I taped the panel to the dish, got it aligned, and sure enough, the signal is a few dB stronger than before.

Further, I had removed a 10dB attenuator between the 432MHz TX and the up-converter, and when I received a report on a spurious signal on the CW signal I tested with reduced power, and sure enough the distortion disappeared and the tone was clean again. The S/N was even better, now close to 10dB in SSB bandwidth, a quite comfortable level for receiving a CW signal.

Further, after some email exchanges with PA1GSJ, and some of my previous thoughts, I will be testing some more improvements on the uplink.

- a circular polarized feed antenna, such as a helical.

- replacing the low cost satellite cable with RG-6 may provide a sufficiently low loss to eliminate the "driver" Edup amplifier and the extra filter in the outdoor unit.

- a larger dish for the uplink is contemplated, such as a 100cm one.

- I do have a 80cm dish, and I might replace the 60cm receive dish with this one.

- a better reference oscillator (set) 10/25MHz is on the way, so I know better which frequencies I work on

- a second receive converter , so I can use my dual band 2m/70cm TRX in satellite mode (70cm for the uplink and 2m for the downlink), and having the TX and RX tracking.

This is quite a list, so I will take my time and slowly improve/optimize the satellite system.

Up-link Up Converter and System for QO-100, and Some Success.

Finally, I got some test equipment for 2.4GHz up and running. It is not yet complete, but I could start testing the up converter and power amplifiers in the lab.

A few tests and measurements were done, with the following results.

For temperature stability reasons I decided to place the up-converter per se indoors. The unit can deliver between 1.5 and 2W. The outdoor unit contains a Chinese WiFi booster, a so-called 8W unit, the Edup AB-003. Tests show the saturated output power just under 4W, and with 3W it would probably have sufficient linearity for SSB on the satellite.

The test was done in the lab, with a cable length approximately the length that will be used from the indoor to the outdoor unit, 15 - 20m. I decided to go low cost and use low cost, i.e higher loss, cable, since a really low loss cable would be overly expensive and un-flexible.Loss is about 15dB.

With this setup it was impossible to get more than 2W out of the Edup (actually a bit less). Ach! too little drive for the Edup. What to do?

Next test, simulated indoor unit with an extra Edup amplifier, only a little less than 3W out. Hmmm! Now what?

One more test: (Simulated) outdoor unit with 2 Edup amplifiers in series. That helps. Just under 4W is now easily possible, the system gain is good. 

Next "problem": With lower gain/output of the indoor up-converter the local oscillator and image rejection is reduced. I want as clean a signal as I can reasonably get. OK, a 2.4GHz PCB "hairpin" filter mounted between the two Edup amplifiers in the outdoor unit should do it. The filter should improve the LO rejection about 30dB, easily compensating for the reduced rejection. On top of that the output of the up-converter has to be increased due to 5-6dB loss in the filter. Still sufficient system gain, as expected. The image rejection for a 432MHz IF is improved about 45dB. All looks good. 

Testing this setup results in just under 4W saturated out of the Edup amplifiers, and we are ready for an initial live test. The amplifiers and the filter are mounted in an (electrician's) distribution box A 2.4GHz patch antenna is connected to an extended cable. At this point, the first test will provide 2W saturated at the patch antenna that will be mounted on a 60cm dish. This should deliver a good CW signal over the transponder. SSB, however will sound ugly because of the threshold for the RF sense in the amplifiers.

A set of attenuators in series have been connected, and should provide sufficient attenuation of the 35W from the transceiver, not over-driving or destroying the up-converter mixer.

The system has now been set up, and is tested. It is far from ideal, many improvements and optimizations are possible.

The test with CW is a qualified success. The signals are not very strong, and the first evening there were no replies to my CQ calls, even though I could receive my own signal (too late for much activity). The afternoon/evening after (today, Saturday) 12 QSOs have been made, and most of the stations could receive my faint signals.

I was warned that the patch antenna is not ideal, so at some stage I will make a helical feed - and yes, I will have to make sure to get it wound the correct way.

A shorter cable from the outdoor PA, combined with the helical, should provide at least 5dB better signal-to-noise ratio, and a bigger dish (the present one is 60cm) will provide even more gain. It looks like I can find a 110cm dish from a local amateur.

A modification of the Edup amplifiers for constant TX mode will have to be done, so SSB transmission will be possible. About 3W to the antenna should be possible. A higher power amplifier may be convenient to have.

All in all much to do to improve the system, a part of it (indoor activities) can be done anytime, but a bit of the outdoor stuff should be done soon, before winter.

 Other improvements will be increased frequency stability and precision. At the moment I have completely separate transmission and receiving systems, and the frequency offsets are different, so tracking transmit and receive frequencies is cumbersome. I will likely end up with a GPS locked system, but slowly, slowly, not too hasty.

More Work On the 10GHz Beacon Monitoring System.

 Today I got the 10GHz RX beacon monitor outdoor work done:

- extended the stacked fiberglass mast by about 60cm, and got a modified LNB mounted just under the feed point of the 2m/70cm vertical used for monitoring "Raketten" (a local 2m/70cm cross band repeater), and turned the LNB in the correct direction, close to WSW.

- got the cables in through the wall, so the utility room window can be closed properly again. 

- connectors for the RX system and the reference frequency system (F-connectors)

- a satellite signal splitter for the 25MHz signal was sufficient to supply both the beacon monitoring system and the QO-100 system  with a decent temperature stability.

Future improvements: 

- Improving the reference frequency generator(s). Will probably use, initially, a 25MHz ref for the beacon monitor LNB and maybe a second 25.xxxx ref for the satellite RX, providing an IF of 434MHz, so a "proper" receiver can be used. I have TCXO(s) for those two frequencies. 

- converters for both LNBs for using amateur band receivers (2m, 10m, maybe 6m) as base receivers. Mostly for use with better CW filters than the AR-8600s have (they have no CW filter, and a rather poor SSB filter - Whether they can be replaced/improved I do not know - also lowest frequency step is 50Hz, too much for serious weak signal work - even good narrow filter CW work).

Another 10GHz Experiment. Murphy Canceled.

The OZ7IGY beacon has been reinstated on all bands but 2m (That one needed repair after the power cable had been cut by someone digging at the site.

Today the weather was quiet, so around noon I repeated the experiment with the LNB on the 13m telescopic mast.

This time the signal came up immediately with rain scatter, and a bit of tone now and then. 

The signals have been there for at least an hour now. Is it, maybe tropo scatter ? The rain radar does indicate some light rain in the area around the beacon.

The test needs to be repeated on a dry day.

This test indicates that it would be interesting to have a rotatable ,low gain antenna, system for 10GHz, for monitoring. A 10 - 15dB horn antenna is not too large to fit on top of a rotating structure. 

After an afternoon of testing, the signal is mainly (rain?) scatter, not much tone. 

The LNB has been lowered to about 9m, scatter signal still there.

After the end of rain scatter, with the LNB lowered to about 9m, the signal is very weak, coming in and out of the noise, but it is mostly there. Given the temperature drift of the LNB 9750MHz LO, it can be tricky to find the beacon. It looks like it needs just 10dB more gain, then the signal will be there, almost constantly. 

Final experiment today:

Lowering the LNB to about 3.6m, and moving it to a position where the trees at the other end of the garden do not block the view in the direction of the beacon. The signal is quite weak, but generally audible. With the LNB pointing towards OZ7IGY, the OZ9GHZ beacon in a direction about 60 deg. offset is quite audible, with S-meter deflection.

While writing this, sitting in the other end of my living room, I can hear the OZ7IGY from the speaker, quite clearly. I suspect there is a little bit of evening tropo, because before dark the signal was barely audible, but with a stable receiver and a good CW filter it would be 100% readable.

I have achieved another goal in phase 1 of my 10GHz activities, hearing OZ7IGY on a more regular basis, all with a very simple receiving system:

- a PLL-LNB, unmodified

- a bias tee for the LNB

- a "scanner" receiver, the AOR AR-8600 receiver.

I am quite happy with today's results.

The next step will be using modified LNBs w/connection for an external reference frequency (25MHz). Then, possibly more gain and a rotating receiving system.

A Failed 10GHz Experiment, Murphy's Law. Then Some Success.

 Todays experiment was setting  a LNB up, taped to the 12.5m fibreglass telescopic mast. Tried to listen for the OZ7IGY beacon on 10GHz. Still not audible, landscape, or maybe its radiation pattern, combined with the low gain of the raw LNB is the most probable reason. OZ9GHZ, as expected, is still quite strong - no surprise because there is an even better path to it with this set-up. (See below for the real explanation)

The mast is leaning on the old (no longer) rotating antenna, and initially toppled. Now a bit better "trapped" between the old 6m antenna and the 2m antenna radials, so it should stay up for the day.

It turns out that the OZ9GHZ beacon is audible, even when the signal has to go through the neighbour's roof (thatched), so it is likely a bit of a scatter signal. The signal was quite good, readable all the time.

It turns out the OZ7IGY test was in vain, because later I noticed that all the OZ7IGY beacons I have disappeared. A friend reported that the beacon(s) disappeared around noon, and I did the test in the afternoon. So ... I will have to redo the test another day when OZ7IGY is in operation. Let us just say that this was an example of Murphy's Law in action.

The LNB was then brought indoors, placed on the window sill of a window facing the OZ9GHZ beacon. The signal is much weaker, but still audible, and because the LNB is indoors, the drift of the local oscillator is much less. Opening the window increased the signal considerably (10 - 20dB). Double glazing is not good for 10GHz signals.

In conclusion, monitoring the OZ9GHZ beacon is quite easy at my place. I should probably make a permanent setup for this, maybe with a RTL-SDR for decoding and monitoring the 10GHz beacon band in the Southern direction.

A More Expensive, But Not That Expensive, Portable Receiver.

On Ebay I purchased the Tecsun PL-660 portable radio receiver.

The PL-660 covers long wave (LW), medium wave (MW, AM band),  short wave (SW) up to 30MHz, the FM broadcast band (76 - 108MHz)  and the 118 - 136MHz air band (using AM). The receiver is also capable of AM synchronous demodulation and SSB  reception.

The receiver has a digital signal processing demodulator at the IF, and provides two bandwidths on AM reception, and that is a very useful feature, I found.

The receiver has an antenna input jack, specified to work on SW and the FM band. A test shows that it sooks like working in the air band as well. An external (active) antenna for air band reception should provide useful,  an FM antenna should be interesting, too.

The receiver uses 4 AA size cells for it power supply. These can be 1.5V (alkaline) or 1.2V rechargeable cells. I used a set of Eneloop (NiMH) cells, and when fully charged, they showed "battery full" on the indicator, and also tells that I was using NiMH batteries. It stayed like that throughout the testing of the radio.

The air band would have been perfect for my propagation monitoring if the VOR band 108 - 188MHz were included, but I reckon that I could use a low cost SDR for that, if need be.

A quick test showed that the sensitivity of the receiver is quite good on MW,SW and FM, as well as the lower part of the air band. The higher part of the air band seemed to lack gain, maybe due to bad tracking of the input filter.

Speaker quality sounds quite good for its size.

To me, however, it sounds like the DSP (demodulator/IF filter) could be improved, I detected some distortion, especially with somewhat noisy signals, that I never noticed on a fully analog receiver, or with my Icom IC-7300 and similar SDR/DSP heavy radios. OK, I guess that I got what I payed for ;)

I do think that this could be improved in later models. I suspect that it is not possible, or at least not easy, to update the firmware of the PL-660.

The accompanying power adapter, however was a bit of a disappointment. The adapter from US plug to EU plug did not fit into a mains socket, and just bent completely out of shape, no matter how carefully I tried to insert the plug(adapter). So I could simply not test the power adapter. I should probably try to find a suitable adapter, or simply cut the cord with the plug for the radio and make my own 6V power supply for this receiver.

All in all it is a nice and usable addition to my receiver park, I like monitoring a lot of frequencies simultaneously, to get an idea of the radio propagation conditions, be it on LW,MW,SW or VHF/UHF/Microwaves. The previously purchased "cheap" receiver is no more than just a toy, unlike this one. 

Maybe I should make another post or a few, about the setup I use for propagation monitoring. I think, however, that this should be at a later stage when I have completed more of the system.

Local Tropo and Other Propagation on 2m.

 In August we had some beautiful sunny weather, providing some excellent tropo propagation on 2m, and, as reported by others, also on the higher bands. Now we are back to the classical Danish weather, a little bit of sunshine, some heavy rain, even cloud bursts.

A few evenings the local FM channel had S9 signals from distances between 100 and 200km (60 - 120 miles). I refer to this kind of propagation as "Local Tropo", mostly because running SSB/CW regularly provides longer distances than this. 

Don't get me wrong, "Local Tropo" is quite fun, but I prefer working the longer distances, using SSB/CW, and sometimes the weak signal modes, like FT8. 

Mind you, on 2m FT8 is an excellent addition to the arsenal in tropo openings, but for sporadic E the fading in and out is often too fast for finishing a QSO, whereas with SSB or CW the signals can be quite strong for a very short period, then disappear forever, but in that time a QSO can be easily worked with CW or SSB. If the sporadic E lasts longer, the signals are often quite strong for a long time, and it is not necessary to use FT8. 

While this is true for Sporadic E, there might be some longer lasting scatter-like propagation making contacts possible with FT8, that could not be made otherwise, so I cannot totally discard it as being useful. As an example, some weak, slightly longer lasting sporadic E or some scatter mode, extended by tropo propagation just might provide some possibilities for 3-5000km distances for a station location like mine, not particularly suited for long haul tropo (-scatter). Yes I am not located close to an ocean, where really long sea ducts can occur.

Portable Radio on the Cheap.

I have tested the Retekess radio. All analog. Price about 20 GBP on amazon UK. I wanted to play a bit with a modern cheap radio with short wave.

Power supply is a single 18650 cell, rechargeable in the radio via a micro USB connector. I like that. The cell can, of course, be replaced. 

The radio covers FM 88 - 108MHz, SW 8 - 18MHz and MW 530 - 1710kHz.

FM works mostly nicely, tuning is OK, a little fiddly, but doable. Good sensitivity.

MW tuning quite fiddly, sensitivity poor to mediocre. Probably due to a small ferrite antenna.

SW: One band 8 - 18MHz. practically impossible to tune to a station. Sensitivity barely sufficient with the built-in telescopic antenna.

Very nice sound from the speakers, surprisingly good for such a small radio, will probably be in use.

The radio, as it is, is unsuitable for short wave reception, it is essentially impossible to tune it to a single station, mostly due to backlash in the tuning system, and due to covering 8 - 18MHz in a single band. It is essentially just a toy for SW reception.

I might be possible to make it tuneable on SW with a fine tune addition, but the modification might not be fit into the casing.

All in all a somewhat decent portable FM receiver with a medium wave performance only sensitive enough for local reception of strong transmitters.

Interesting Propagation on 6m Today. Update.

Today's FT8 monitoring of 6m had some interesting results. Propagation into North America.

While this takes place in the sporadic E season I still do not think this is classical multi-hop Es, but a different mode. Because it appears in the Es season it is correlated, for sure, but what causes this propagation is not really understood.

Between 1617 and 1847 UTC signals were detected from KP4. K8, N3, N5 and XE. First time I have detected a signal from Mexico, albeit in the Northern part near Texas, there the N5 was located.

This is where a digital weak signal mode makes things interesting. We discover propagation that we could not see before because the signals were too weak to be detected reliably in SSB or CW.

The strongest signal detected was the XE with -10dB S/N, and that could probably have been detected in the CW mode. The others were much weaker, and would have been non-detectable with my setup.

Now, my setup is **very simple**: I am using the IC-7600 transceiver with a vertical triband antenna for 70cm, 2m and 6m, the Diamond V-2000. With a beam antenna, even a small one, I am sure that I could have heard more.

Of course, all this happened while I was away from the radio, but OK, I detected the propagation.

Update, Monday July 13th:

Many stations seen this afternoon, from Texas, Minnesota, Georgia, South Carolina, a host of North-Eastern states, and one Canadian station: VA3DX.

Also, I noticed that, as opposed to May and June, in July there are more openings to Northern Scandinavia. I seem to recall that this has been the case in previous years. If anyone has more data on this I would appreciate some information.

Revival of Old Sealed Lead-Acid Batteries.

I now have some more solar panels, but not enough batteries to match them.

Enter an amateur radio friend of mine. He has a large solar array at his house, and he has a bunch of old dis-used 12V/48Ah batteries. Only trouble is that they have all but died.

He told me that it is possible to bring them back to life, probably not with full capacity, but also warned that it could take quite some time, sometimes a month or so, to bring them into a useful state.

The trick is to provide a voltage of 14.2 to 14.4V to the batteries, and if there is any current, even a few mA, it should be possible to revive the batteries. 

I got 4 batteries to try out.

Talking about this on the radio I may have found a second source of (used) batteries, we shall see how that goes.

For that purpose I got myself some modules from China:

- a 24V/14A switch mode power supply

- a few adjustable DC/DC buck converters with voltage as well as current limitation, both adjustable.

Now the DC/DC converters can be set to 5 - 23V, the current limit to 0 - 5A. That is the specification, but I intend to limit the current to considerably less for the revival process.

Having the modules connected, the process has now started.

After a week or so, the first (best initial voltage) battery does draw more than 1A current with 14.2V, but because a cell might be bad I have set the current limitation to 300mA. The voltage is now slowly - very slowly - increasing, and has reached 9.7V. Yes, there is still a long way to go, so we shall see how it goes, and how long it takes.

The second battery was connected a few days ago, and is now drawing about 100mA at 14.2V. It is slowly increasing, in the beginning the current draw was just about 5mA.

It may be a good idea to mount the two regulator modules in a box, at the moment they are just loosely attached to a shelf - or maybe make it wall mounted, with the 24V supply at the back of the shelf.

The two other batteries had an extremely low initial voltage, so I doubt that they can be revived. They may truly be dead, and if so they will go to scrap metal.

Apart from the radio activities there are some interesting times ahead.

The battery revival does not claim too much time, just some monitoring a few times a day, so other activities can slowly re-start. The electronics workbench/test-bench is still quite messy after starting the reference oscillator activities as well as the battery revival equipment. 

I see a lot of tidying and organizing  in my future ;)

Receiving FT8 With a Pixie.

After a long wait I received some crystals for the FT8, JS8Call and WSPR/QRSS frequencies on 40m and 20m, ordered some time in March.

The Ebay seller was not at fault, I suspect that the COVID-19 situation had left the package stranded somewhere on the way, for a long while. Other packages from the USA have not arrived yet, either, but who knows, they may appear one sunny day.

One set of crystals has 3 crystals per band:

7074kHz (FT8)

7078kHz (JS8Call)

7038.6kHz (WSPR/QRSS)

14074kHz (FT8)

14078kHz (JS8Call)

14095.6kHz (WSPR/QRSS)

In previous posts I have written about some experiments with the Pixie kits, and now is the opportunity to continue with that

The original 7023kHz crystal was unsoldered and a 7074kHz crystal soldered in. I am leaving the long leads at the crystal, as I think I will use it for a different receiver (or, maybe a transceiver). The frequency was adjusted to 7074.00kHz, so the test could begin. During the day not too many signals were heard, but in the evening the signals are coming in very nicely.

The antenna is a low hanging 10-15-20-40-80m dipole, so not the best, but this is excellent for the test.

Connecting the Pixie to the antenna and a set of computer speakers, FT8 signals were heard, immediately.

A quick test with a laptop, using its microphone, yielded immediate FT8 spots. A USB sound interface was found and connected in place of the speaker/microphone, and the spots poured down the screen. In the span of less than 2 hours spots were seen from North and South America, Europe, Africa and Asia. 

The system is actually working.

I left the system running over night, and in the morning I could add Oceania to the list (Indonesia). No Australia or New Zealand, but that was to be expected at this time of the year.

The experiment is a success, so now I consider the next step:

- setting the same receiver up with a raspberry Pi running headless, but using VNC, or

- inserting the 7038.6kHz crystal and setting up with a Raspberry Pi for QRSS, and maybe also WSPR.

If I just set the Pixie up for QRSS with an older Raspberry Pi, this could make for a low power, solar powered QRSS grabber system, so that is a tempting option.

Further steps could be a low power DSB or phasing SSB transceiver for FT8 or JS8Call, at first for 40m, later for 20m.

Now, if I could find a corresponding set of crystals for 60m or 80m, that could be interesting, too. On 80m, however, I could possibly use a ceramic resonator and tune it to the FT8 frequency (3573kHz). For the JS8Call a standard NTSC colour crystal (3579kHz) could be used, re-tuned to 3578kHz. It *may* be possible to use a Super-VXO (2 or more crystals in parallel) type oscillator for generating the 3573kHz signal.  

As always, too many ideas, but it is never boring.

Test of OCXO and Rubidium Standard. And Building a Bit.

I wanted to test some 10MHz OCXOs so I needed some stable reference. I have a surplus rubidium 10MHz standard, and tried it for the first time.

In the first instance I want to get my very old, but otherwise frequency counter up and running again. The counter did have a reference oscillator locked to the old transmitter frequency of the national long wave station of 245kHz, which moved to 243kHz in order to comply with the new frequency grid. The reference frequency of the counter is 1MHz, generated by a crystal oscillator, which cannot now be locked to the standard. A new reference oscillator is therefore needed. The counter does have an input for an external 1MHz reference.

When I last tested the counter, the frequency adjustment range of the oscillator had deteriorated, so it could not be adjusted to the correct frequency, so I decided  to generate an external frequency.

The intention is to use a oven controlled crystal oscillator (OCXO) which can then be calibrated occasionally with the Rubidium standard, or maybe later, with a GPSDO reference.

In order to test the OCXO an even better reference is needed. so I found my surplus rubidium  (Rb)standard and tested it for the first time. I do not know its exact frequency (well 10MHz), but I could see the classic frequency sweep for some minutes, and after some cycles it locked into place.

So now I have a stable 10MHz reference, which should probably be calibrated, but I will use it as it is for now.

The first OCXO needs a 5V supply, and the Rb but at the test bench I had only one variable supply and a fixed 13.8V supply. I then built a quick 5 and 9V supply, using two DC/DC buck converters. All went into a small plastic box, normally used for interconnections in electric installations. The voltage into the converters can be from 12 - 30V, so I connected it to the 13.8V supply, the variable lab Power supply was then available to provide power for the Rb standard-

In order to compare the frequency I connected the two oscillators to my 2 channel scope, triggered by the Rb standard (Ch1) and connected the OCXO to Ch2, after letting them warm up for an hour or two.

Of course, the signal from the OCXO will then move across the screen, because its frequency is different from the Rb standard. The trick is then to change the control voltage of the OCXO until the signal moves as slowly as possible across the screen.

I managed to adjust it to move across one period, taking 3min:40sec (220sec). This corresponds to a frequency difference of less than 5mHz (yes, *milli*Hertz), but it was still drifting a bit.

However, this is quite acceptable, because the OCXO was just lying on the test bench, and not even insulated. A well insulated OCXO should be sufficiently stable for my amateur use (when placed indoors), even up to 10GHz equipment.

What next? I think I should build one of the OCXOs into a box (w/insulation), then add some buffering for the 10MHz signal, so a few output signals can be generated, as well as a "converter" for generating a 25MHx signal for control of an LNB, and finally a divider for generating a 1MHz signal.

The intention for the 25MHz signal is using a divide-by-two (5MHz), then extract the 5th harmonic, and voilá ... 25MHz. A square-wave conversion circuit followed by a good filter is probably a good idea.

Oh!, and testing the other OCXOs need to be done, too

All in all this was a few productive days, getting more test equipment up and running. Always enough projects to do here.

Finally: 2m Sporadic E QSO, the First After I Moved Back to OZ.

Hooray !
After a few false starts, first receiving FT8 signals while away from the radio, and hearing sporadic (sic!) signals on 2m, I made my first QSO via 2m sporadic E, since I moved back to Denmark.

This is probably my first sporadic E on 2m since I moved to The Netherlands in late 1989.

Before this, today I heard a few signals, was calling EB1A, close, but no QSO. I was told that he had heard me, but we could not complete.

Then hearing a local, OZ6OL, working into HA, I could hear the HA, but no.

Then, after a bit of quiet, I worked YU7ACO in KN05rd. The MUF was clearly hig in some other places, but at least I got started.

First Baby Steps in the Solar Power Department.

A little while ago I received a 50W solar panel from a friend, and waited for a controller, so I could use it safely with a battery.

The quick setup has been done now, the wire feeding the panel's power to the controller and battery, mounted indoors.

At the moment it is just charging, so now I will have to decide what the power can be used for. I think I will go for some simple receivers used for monitoring fixed frequencies. Low power consumption, so they can run 24/7. One example is a simple receiver for the international beacon network frequency on 10m - 28.200MHz. I can probably keep the power consumption down to about 25mA for that one Very simple superhet with a 19.2MHz oscillator and therefore 9MHz IF. More on that later.

I had the idea of running a QRSS grabber with a Raspberry Pi, so I did a quick calculation for running it 24/7. I was surprised that the 50W panel with a good sized battery was only close to fulfil the requirements for full off grid operation. I will have to test the power consumption of the Raspberry Pi running the grabber software, in order to see if my estimate is too high (or, maybe, too low). The calculation includes some redundancy for several days without sunshine, buffering with the battery. Yes, the sunshine hours can be very unreliable in Denmark.

I do have some small, very low power solar panels that I will experiment with, with very low power requirement equipment, such as low powered receivers or active receiving antennas. I expect the battery used here  to be Li-Ion cells, with 3 for 11V or 4 for 14V supply voltage.

More on solar experiments later.  

More Signs of the Es Season on 2m.

While I was away doing other stuff, there was an opening on 2m, signals from I, IS0, F, EA, EA6 coming in via FT8. No spectacularly strong signals, mostly in the -10dB range.

This may be FAI (Field Aligned Irregularities), some kind of scatter signals, I think. The openings lasted about 2 hours, maybe more. Of course, 6 and 4m had openings, more typical Es type signals, and for longer.

I hope to make it to 2m sporadic E this year, it's been a while.

Edit 2130UTC: Later in the evening: Many stations have been received on 6m in EA8, CT3, CU3, CN and S01WS, plus very weak signals from across the Atlantic: KP4. - and, of course, most of Europe, East and West.

Signals from EA1 coming in on 4m right now. We shall see if I can make a QSO.

Sporadic E on 2 Meters

Yesterday and today I experienced Es on 2m for the first time this year.

In the morning of yesterday I detected an opening, but only after looking at my FT8 PSK-reporter map.

There was a solid signal from the Ukraine and a weak one from UA6, just East of the Black Sea.

Then, today the following appeared, almost while I looked at WSJT-X:

1016 RT3G   KO92up

1028 RK2T   KO93ad

Both were in the -15 - -20dB range, so quite weak, but they were there, none the less.

The past week there have been substantial Es openings on 28, 50 and 70MHz, but I did not detect anything on 2m until yesterday. Also, today Russian FM stations were there aplenty on 70MHz.

A few days ago I detected signals on 50MHz from Japan. No North America on 6m yet.

The season has really started. Interesting to see what this year's season will provide.

Build of a Small PCB Based Oscilloscope - and Another Oops.

A little while ago I purchased a kit for a small, very simple oscilloscope.
This is the JYE Tech DSO138, a kit with SMD components soldered, so only through-hole components need to be mounted.
The scope is a single channel device with a bandwidth of 200kHz, using a sample rate of 1Ms/s, and has a small, but readable 2.4" screen, if I recall correctly.
The kit went together all right, even if soldering was tricky, even with a quite hot soldering iron. The tip had trouble heating up the PCB pads, probably because they had a very narrow edge around the through-holes.
Otherwise, when I finally found the assembly instructions for the correct version of the board, the check/test went well, and after adjustments the screen shows a relative good square wave, using the built-in test generator.
This test was done with a USB cable connecting a 5V power supply to the scope.

Now came the test with the "normal" power (only) connector on the analog board (with all the switches etc). I found a battery and a red/black wire set mounted on the connector, got it connected, and - <snif> <snif> - something gets hot, and nothing on the screen.
A check revealed that the connector had reverse polarity .... Oops.

A correctly connected cable was found, and phew! The screen showed something. But not all was good.
I checked the voltages on the board, and the -5V voltage was essentially absent - a few 100s mV. Not good. I disconnected the output of the ICL7660 DC/DC converter IC, still no negative voltage output.
The 7660 has definitely gone to the eternal IC fields. The quad OP-amp could also be defective, so I have ordered spares of both.
The arrival of the spare parts is expected in a few weeks, so the project is now on hold. Not a huge problem, it is not a critical item that I need right now, and I have more than enough other projects to get to.

So, what can we learn from this? Oh, yes, when building kits and/or connecting power  to kits or modules, check, then double check the polarity of the power supply leads, and the polarity on the PCBs.
A pity that there is no standard for this, but what can we expect from stuff coming from different parts of the world?

Ha ! My Pixie Test Mistake. You May Laugh ;)

OOPS!

Looking at my radio desk I found out that I had not connected the 80m Pixie modified for transmission only, to the SWR-meter and the antenna. There was another BNC-BNC cable on the radio desk.

The stability and frequency offset was still not good, but the output was there. Also, the erratic behaviour of the frequency when keying the TX was gone. It was most likely due to RF floating all around.

The 472kHz version is still not good. No oscillation I can detect. Some experimentation with the oscillator circuit will probably provide oscillation, and some RF output from that version of the Pixie.

Laughing is allowed, I did chuckle when I saw the mistake.

Now I need to see if I can make a receiver version with sufficient stability. Otherwise I will have to go for some "real home brew".

Quick Pixie Updates: Ceramic Resonators for TX.

After some more experiments with the Pixie kits I am suspending the Pixie for a while.

Versions of the Pixie modified for transmit only, 80m version and 630m version with modified inductors and capacitors in the frequency dependent circuits, and the components specific to the receive mode have been omitted. For example, the diode and switch for RX oscillator offset has been removed. Further, a variable capacitor ("Polyvaricon") has been connected from the crystal to ground, in place of the diode offset "capacitor")

80m:
The oscillator does oscillate in the "RX mode", and the frequency range is about 3500 - 3600kHz. When keying, however the oscillator frequency still changes frequency, sometimes in an unpredictable way (sometimes up, sometimes down).
I suspect 2 reasons:
- the oscillator voltage is not stabilised
- the load of the oscillator changes when switching to "TX" mode.
Further, the output of the transmitter with the ceramic resonator in the circuit is too low to register on the SWR/PWR meter. Not exactly a resounding success. This could be due to a lower Q of the ceramic resonators, resulting in a lower oscillator output.

630m:
I could not register any output from the oscillator. There can be several reasons:
- the oscillator may be more loaded by the buffer stage
- the capacitive load of the oscillator capacitors may be too high
- the frequency determining capacitors may have a low Q
- the Q of the ceramic resonator may be too low for solid oscillator loop gain
- the capacitor ratio in the feedback loop may result in a loop gain below 1.

My conclusion is that the basic design of the Pixie is too simple for a wide range (ceramic resonator controlled) transmitter, though it may be brought to work OK with a crystal, with some VXO functionality. A few switched crystals may provide some coverage, especially in the 40m band. I have crystals resonating on 7000, 7015, 7023, 7030 and 7040kHz, possibly 7035kHz. From box73,de 7005, 7010, 7020, 7035, 7050, 7052, 7055 and 7070 are available This should provide some coverage of the 40m CW band, so I might try that and see how much of the band can be covered with such a setup.
I see that several Xtal frequencies for the 10MHz band are available at box73.de , so a 10MHz version of the switched Xtal TX may be feasible. Frequencies available from there:
10105, 10106, 10115, 10116, 10120, 10135 and 10145kHz. This should provide good coverage of the 10MHz band with a VXO circuit.
Also from Box73.de :
80m : 3530, 3540, 3550, 3555, 3560 and 3570kHz. Generally available is also 3579kHz Partial coverage of 80m looks possible.
160m: 1800 and 1820 available from box73.de. Generally available: 1843kHz. I do have a crystal for 1963kHz.

Experiments with crystal control of the Pixie should therefore be available to me on the following bands:
- 160m
- 80m
- 40m
- 30m

While I do have crystals for higher bands (14,18,21,24 and 28MHz) I consider that the Pixie is probably not suitable for those bands. I could do a test on 28MHz, just to see what the kit does, but I do not expect good results. It may possibly work with better transistors, and with lower power.

I am still looking for crystals in the 5250 - 5450 kHz band.

Receiver experiments, with the offset diode circuit removed, should prove interesting enough. For a receiver a stabilised voltage supply can easily be arranged

Other experiments have been suggested by VK3YE on his page :
The Pixie Hack Challenge

I may try out a few of those at a later stage.

As you can see, there are still many experiments/hacks possible with the Pixie kits. That is why I purchased quite a few before starting the experimentation.

I may have a pause in the Pixie play now. Many other projects I want to do. We shall see.

10m Openings to South America and the Caribbean.

While chatting locally on 2m FM I suddenly noticed that my 10m FT8 monitor showed a spot from Puerto Rico. This is very early for a sporadic E opening, so I wonder what the propagation mode(s) is/are.

All in all from about 2200Z to 2300Z stations came in from:
Caribbean:
KP4JRS, J69HZ and J69DS
South America:
PU5BOY, YY1ALE, YY5YAM, HK3GJ, HK4GSO, HC1DAZ

Though I tried to call several of them, no QSO could be made by me. Best signal strength was +1dB by one of the HK stations. He was detected sending RR73, then disappeared. Maybe he went QRT, maybe propagation disappeared in his direction.

6m was not tested, there may have been some reports on that band by others, I do not know.

Pixie tests with VXO and Ceramic Resonators.

Quick test today using ceramic resonators.
40m model:
Even with a 5 - 60pF variable capacitor the frequency could be pulled down to under 7.000MHz, with a ceramic resonator for 7160kHz. The stability, however, was not sufficient with the Pixie. The tuning was fiddly, and the TX signal had a significant chirp, and the receive frequency was drifting too much for my taste. Well, it was clearly audible ...
Further, the RX offset of the oscillator, when using a crystal in series with the variable capacitor, was insufficient at the lowest frequency, even when it was set to maximum, i.e. the RX local oscillator (BFO) was too close to zero beat.
The 80m version did not fare much better. Yes, it was a bit better, but still had chirp on the TX and some drifting on the RX the RX could not be pulled down to the band edge, either, but did have a sufficient range to have been useful.

More experiments with an inductor added to the VXO (crystal) should be an interesting experiment. It might provide for a better stability, and somewhat better offset. This needs to be tested.

It may be possible to use one Pixie as RX and another as TX, providing a "spot" function, but I doubt the stability will be sufficient with the ceramic resonators.

Because VK3YE has tested oscillators and even regenerative receivers with ceramic resonators, and achieved sufficient stability for CW operation, I would consider the Pixie as too simple for good results as a frequency agile CW transceiver. It would be quite suitable for simple fixed frequency operation, e.g. as a monitor receiver for FT8. Crystals for such a receiver (20m and 40m) should arrive in about a week, if not delayed by the corona virus situation. A test of the Pixie as a simple QRSS RX should be another simple experiment.

Pixie Transceiver Kit Building and Mods.

Over the pas year or two I have eBay'ed quite a few kits of the simple Pixie CW transceiver. Now was the time to build and test a few, one as the original and one modified.
All those kits are so cheap from Chinese eBay'ers that I can buy 3, sometimes 4 kits for the tax free limit to Denmark (about 12 - 13 USD). I purchased a few, then another few. For that low price the kits are excellent for experimenting.
More modified will be built, for all the lower bands, but here is the first impressions:

Kit #1: 40m CW on 7023kHz:
The kit is easy enough to assemble. I made good use of my PCB holder for stability.
Resistor marking was good old standard. Some markings were missing on capacitors, so they were checked. The inductors were checked, as well, as I was not sure of the colour coding for those.
First impressions of the finished kit. It was expected to be tricky making contacts with such a low power device only capable of operating on a single TX frequency.
Power output, measured with a SWR/power meter is estimated to be just over 300mW. A trim-potmeter varies the oscillator frequency for receiving, so a decent "side tone" can be achieved. For receiving an old speaker was connected. A low hiss was audible, but the audio level was too low for comfortable operation. Further, some odd noises and distortion were heard (more about that later).
The first test was done with a local friend and my low hanging HF dipole, at the massive distance of 3km (about 2 miles) ;) Reports received were 599 (yes, for real), but I could only give 539, most likely due to the low audio level.

The strange noises were identified, the LM386 did oscillate, apparently triggered by strong signals received. Not good.
An Internet search revealed that this is a general problem with the LM386 in this configuration when connected to a low impedance (8ohm) speaker. A test with connecting the to a set of active computer speakers showed no oscillations or distortion at all. So much for the simplicity of the kit.
With the extra gain of the computer speakers the receiver is more lively, too.

Kit #2: 80m CW on 3560kHz:
Components from the original (2nd) kit, and some components from a third kit were used like this:
the values of the capacitors and inductors in the RF part of the circuit were doubled in value. The inductors from the 2 kits were connected in series, and the capacitors in the oscillator resonant circuit and the low pass filter were coupled in parallel. Interesting enough, it was quite easy to fit the parallel capacitors in the mounting holes.
That was all. Connected to the computer speakers the receiver sprang to life, and the sensitivity seemed OK, the noise level increased a bit when the antenna was connected.
My friend was not available at the first test, so no test QSO was made (yet)
Power output of the modified 80m was close to 500mW at 9V power supply. A bit more than the 40m version, but not surprising.

Running a CW transceiver at low power, and at single frequencies is, of course an exercise in frustration, so the next test will be modification of both kits for some frequency agility.
For the 80m version the first test will be replacing the crystal with a ceramic resonator and a variable capacitor. This should provide coverage of a good part of the 80m CW band.

The 40m version is a bit more tricky The resonator available is a 7159 version, and might not be capable of covering the CW band portion of 40m. I do have a 7.02MHz ceramic filter, and that might cover a part of the 40m CW band. Otherwise a VXO with some switched crystals available will be sufficient. Crystals available to me are 7.000, 7.015, 7.030 and 7.040MHz. With those I would expect to cover most of the 40m CW band.

It should be possible to make versions for the 6m, 160m and 630m bands, with other modifications. I should have the necessary replacement components available, but that is for later.

Update: The 80m version was tested today, and provided a 599+10 report from my local friend. It works, most definitely.

HAM Radio and the Corona Virus.

The western world is closing down, for a while.
The Corona virus crisis has hit us all.
As someone in the rather vulnerable group I have, essentially been in isolation for a week now. Not quite, because this week I had appointments at the hospital for a blood test and subsequent CT-scan, as part of the follow-up on a cancer I had treated - successfully - in 2018.

Since I was out, I did go to the pharmacy, too, just to get supplies of medicine I have been using regularly, especially a means to reduce the effects of pollen allergies.

This crisis may take longer than we might expect, for me, at least, I will hesitate to venture much out into the world (or even in my own country), until we have seen and tested a successful treatment or a vaccine is available.

What does that mean to me? I am fortunate enough to have retired, so there is no **need** to go out much. I can get food supplies and other necessities delivered to my door. Even then, I should be careful not to be infected from the delivery people. The most essential company has already initialized measures in that respect.

Here is the thing for me. I am generally used to living on my own, and have not gone out among people a lot. Yes, sometimes I have gone for a larger event, but that is all on hold now.

This is why I like having HAM radio as my interest, among others I can pursue alone. But with HAM radio, I am still in contact with other people on a daily basis, probably even more so because we are all at home most of the time.

So if I can avoid getting infected I will get through that crisis. Others may not be so fortunate.

To everyone in doubt: If you are an essential part of health care and other necessary functions, take all possible precautions to stay healthy. Many others should be working from home, if at all possible, and so help reducing the spread of the virus. Those of us who are vulnerable due to age or previous sickness, stay home if at all possible, and help in any way you can, those who need it.

We will all need to stand together (with a distance) to get through this. If we do, most of us will be there on the other side, if not, we will see much fewer people succeeding.

Analog Vs Digital Multimeters.

When should one use analog, and when digital meters for (mainly) voltage and current measurements?

To me there is an easy answer.

If I am adjusting something for maximum or minimum values, the analog meter wins every single time. It is much easier to see when the max/min values are reached with a "moving needle" meter.

Will I go without the digital multimeter? No way. It makes for an easy measurement of more or less static values.

So yes, I have a set of digital multimeters with Volt/Ampere/Ohm measurement, and one with capacitance measurement.

A cheap Chinese PCB module serves as L-C meter, down to most of the values I need to measure, about 1pF and some nH (I need to test the latter).

I just took out 2 museum pieces: Unigor multimeters. Good quality analog meters for V/A/Ohm, all the way into the Mohm range. The only thing is the battery needed for resistance measurement. Most modern meters use AA or AAA cells, or a 9V battery. Those 2 meters use 1.5V D-size cells. Now I need to find out if I can still get those. If not, I will have to find/make an adapter.

OK, the resistance measurement on the analog meter is not that important, but why not restore the full function of those museum pieces?

Apart from the multimeters I still have 3 excellent analog meters: An AC (milli)volt meter with high impedance input, a DC (milli)volt meter, and a Bolometer with a thermistor probe for up to 10GHz, one that needs care, not exceeding 10mW input to the probe, in order to keep the meter functional. More than 10mW, even for a short while, and the probe burns out.

A set of older (second hand) attenuators (for use with the Bolometer (power meter)) will have to be tested, but I have some, at least, new ones that should be good for low power measurements, up to 1/2 - 1W.

With access to the test equipment I should now be able to do a bit of home construction activities again, be it kit building or fully home made circuits.

Update:
I found an adapter for mounting AA batteries in the Unigor meters.
One of the Unigor multi-meters is now in working order. Ranges:
10uA - 1A
100mV - 1kV (DC and AC (the AC is probably not precise in the lower ranges))
Resistance measurement not very precise, but for that the digital multimeter will probably work better.
The other meter probably requires disassembly. If I get it back in order, I can measure up to 10A with that one. This is for later.

Desk With Test Equipment.

Finally, I did a bit of tidying in the upstairs shack.
The shack has two desks, one should be dedicated to test equipment, the other should be used for some radio and computer equipment.

I almost cleared the upstairs desk for the test equipment. At least, the desk can now be used for more extensive testing than with the rudimentary set of test equipment at the ground floor radio (shack) desk.
Test equipment available for use at the desk:
- HP DC voltmeter
- HP AC voltmeter
- HP432 bolometer w/10GHz probe
- spectrum analyzer 10 - 1700 MHz w/tracking
- Marconi transceiver tester
- Tektronic 2 channel oscilloscope, 60MHz
- Velleman frequency counter
- modulation meter
- handheld multimeter, V/A/Ohm
- old Trio AF signal generator
- Fluke V/A/ohm, not functional, will need check and repair, if applicable
- Of course, (Velleman) soldering iron w/ power supply and multimeter
- a diode power meter built by a friend. can do 10GHz/max 100mW

There is more to come, e.g. a bit of test equipment/accessories for microwave and other measurements, such as:

- low frequency function generator and mini (cheap Chinese LF) oscilloscope kit

- modified satellite or MMDS down converters for converting microwave signals down to the range of the spectrum analyzer or frequency counter(s)

- VNAs (mini or Nano) for circuit/antenna testing (gain/frequency characteristics, SWR etc)

- directional couplers for 1.3, 2.4 and 10GHz

- Accessory mini frequency counters

- reference frequency generator ( TCXO, OCXO, Rubidium or GPS controlled)

- crystal tester(s)

- and more, to be described later

Second Crystal/Ceramic Resonator Tester. Update

I built a second crystal tester today. This time I used 470pF capacitors for the Colpitts oscillator "resonating capacitance", and a larger transfer capacitor.
As expected, this worked nicely with ceramic resonators (but not 3-pin filters) down to the lowest available, 400kHz, and up to about 2MHz (crystals). One 1843kHz crystal did not work, but a 1963kHz crystal did. Maybe the 1843 crystal was poor quality.

I expect that I should build the third one of of the crystal testers, this time with 100pF "resonating capacitance". This **should** provide tests the intermediate frequency range of 1.8 - 8MHz, at least for crystals and ceramic resonators.

All in all I am happy with the results, I was warned that the crystal tester kit, advertised as 1 - 50MHz crystal tester, was not working in the full range, so I had a few kits taken home.

I could see that one of the ceramic resonators (marked 480kHz) oscillated on 476kHz, i.e. inside the 630m band. I suspect that I can build a VXO with one of those resonators, covering the full 472 - 479kHz band. Oops ! Yet another possible project to try out. Maybe a modified Pixie kit can be brought to work on 472kHz - I would not be surprised.

Update:
A third version with 2x 100pF in the Colpitts oscillator was built. This appears to work nicely from 2 - 16MHz with crystals.
Ceramic resonators:
- The 3.5 - 4MHz range works well with some resonators, no filters.
- The 7.16MHz (3-pin) oscillates nicely just under 7MHz with the capacitors in the oscillator.
- 12MHz resonators oscillate fine.
- 5.5MHz filters do not oscillate at all.

My conclusion is that the three testers combined will provide some crystal and ceramic resonator/filter tests, but a dedicated (set of) oscillator(s) and a dedicated frequency counter with high impedance/low capacitance input is most likely necessary for a better test system.

Test Equipment: Crystal Tester Kit.

I just assembled a low cost Chinese kit claiming to test crystals from 1 - 50MHz, with a counter w/5-digit display). Assembly time, taking things easy, was about 1 hour.

I already suspected that the kit would not work down to 1MHz, for this reason: The crystal oscillator is a Colpitts oscillator with the capacitances across the crystal (B-E and E-GND) being only 22pF each. The capacitances in the Pixie kit's oscillators is much higher, and that was designed for 7MHz.
This was confirmed when testing crystals. Below 5MHz hardly any crystals would generate a countable signal. However, crystals up to 28MHz would generate countable signals.
I suspect that a different tester with, say 100pF capacitors would likely work down to about 2MHz, and 470pF capacitors down to about 400kHz.
I do have another kit or two, so I will probably build those with the above mentioned modifications.
One more test was done: Trying out ceramic resonators. Resonators (2-pin) or filters (3-pin) were tested. None worked on less than 10MHz in this circuit, but did work up to 20MHz, with rather consistent results for the resonators (2-pin), and inconsistently with some of the filters (3-pin). I suspect the low capacitance values are the reason for this.
Also, a more suitable oscillator type for the filters should be tested.
I may end up with a counter with an 8-digit display and some dedicated oscillators as my crystal tester. This could be interesting for testing frequencies for crystals to be used in crystal filters. It is likely that a set of modified Pixie oscillators would do the job.

Finishing one project creating more possible projects. Why am I not surprised.
I do have a few Pixie kits lying around, so maybe the next project should be an unmodified Pixie transceiver, with the exception of using an external crystal or ceramic resonator for the oscillator.

Idea Box: Simple Transmitter Circuits w/Ceramic Resonators.

Over the latest year or two I have collected some ceramic filters/resonators for different frequencies.

A simple oscillator (VXO) controlled by a ceramic resonator, either directly on the TX frequency or using a doubler or divider can generate signals in several amateur bands, and here are some ideas for the frequency generation:

Idea Box:
Simple TX for CW (maybe later DSB) for MF and HF bands with ceramic resonators:
- 472kHz: VXO w/480kHz ceramic resonator (472-479 ?) (CW)
- 1.8MHz: VXO w/3686kHz ceramic resonator and divide-by-2 (1800-1840?) (CW)
- 3.5MHz: VXO w/3580kHz ceramic resonator (3500-3575?) (CW)
- 3.6MHz: VXO w/3686kHz ceramic resonator (3600-3680?) (DSB)
- 5.2MHz: VXO w/5500kHz ceramic resonator (5350-5450?) (CW/DSB)
- 7.0MHz: VXO w/7160kHz ceramic resonator (7000?-7150?) (CW/DSB)
- 7.0MHz: VXO w/3580kHz CR and doubler (7000 - 7150?) (CW)(DSB?)
- 10MHz: Super-VXO with 5068kHz crystals
All with PA modules (per band), and a signal derived from the exciter, to a single LCD frequency counter, and, of course CW keying circuit/DSB modulator.
All this could be expanded to a simple TRX with direct conversion RX. RIT control will be needed, especially for the CW mode.

Using a PCB from the Pixie kit could provide some basis for the simple TX circuits, with suitable modifications, e.g. using a ceramic resonator in place of the original crystal, and a simple modification of the low pass filter. This idea comes from VK3YE who made the "Pixie Hack Challenge", providing ideas for different uses of this very low cost kit, with a few additional components, and sometimes removing some components. I think he came up with 12 ideas fo Pixie Hacks, but I do not think he had the transmitter mod. He did, indeed have a hack, using the Pixie as a direct conversion receiver, tuned with a ceramic resonator, but I do not see why that should not work with a TX hack as well.

Quick Test of Test Equipment Modules.

I have collected some test equipment stuff over the last several months.
I finally got to test some of it, and there is more to test. This was a quick test of the following test equipment (boards or in a casing):

- Signal generator, 500kHz - 470MHz, spec output: -70dBm - -125dBm. Signal could be heard on the frequency tested, so it appears to be in good working order.

- DDS function generator:
This was supposed to deliver a signal on a max frequency of 8MHz. Well, it does, but not variable up to 8MHz. Just 1MHz, 2MHz, 4MHz and 8MHz. Useless on amateur bands.
The function generator can deliver sine, sawtooth and square waves. Spec says from 1 - 65500Hz. I can only set the frequency with 100Hz steps at the moment. There may be another trick that I have not yet learned, to step with 10 or 1Hz.
This one was a disappointment. The function generator should be somewhat useful, though.

- Frequency counter modules some with possibility for IF frequency offset.
some LCD modules could be adjusted to show 432MHz nicely with 1-200Hz tolerance.
Similarly some LED (8 digit) modules could be adjusted to the same frequency tolerance.
One LED module was dead. No 5V output voltage from the regulator. I expect it can be fixed
One LED module had missing segments. A short at the PCB was the reason, and it works fine now.
One 500MHz module could not be adjusted to the wanted tolerance, the reference frequency offset was about 19ppm (too low). I expect that a different trimmer capacitor will make it possible to adjust correctly. Maybe a different crystal, I think I have some lying around.
All of the above (functional) counter modules were subjected to a quick test/adjustment with a 432MHz signal from a hand held TRX
A last (6 digit) counter module could not detect/count the 432MHz signal, must be tested with a lower frequency.
Finally, a larger counter module, supposed to count to 2.4GHz, was tested with the 432MHz signal, and had quite an offset. The reference frequency did not appear to be adjustable, it is a canned crystal oscillator. More investigation necessary. It may be that an external reference generator (GPSDO ?) is a good idea for this module.

- LCR meters:
Two LC-100 modules were tested. They seem to have survived getting connected to a 9V supply, when only 5V was "expected". (Display characters went rather dark)
Getting a correct 5V changed the display, so it became readable, and the modules appear to work correctly.

- 35 - 4000MHz signal generator with 1kHz frequency resolution:
A quick test showed a frequency about 3kHz too low on 144MHz. Needs adjustment or locking. This was at start-up, so it may improve.

A burn-in period test should be performed on all those units, to see how they work in a more stable state/environment, and then some more elaborate testing, maybe against some professional equipment.

After this, some radio construction can begin. This year should, first and foremost, be dedicated to antennas, especially adding some for monitor receiving purposes, and getting to transmit via QO-100.

After this, some microwave experiments, mostly local low power tests, and then some extreme low power experiments for different bands, ranging from MF to microwaves. The idea is working at least one QSO on as many bands as possible, with less than 1mW. Yes, micro-watts.

At some stage, some of the test equipment should be mounted in casings, mostly for protecting the test gear, and probably adding some RF shielding to the test gear. (inputs as well as outputs).

Winter VHF Day, In Ringsted.

This annual winter VHF day takes place in the second half of January, and if I am not prevented by a family occasion, I will usually be going.

This year had a bit of a theme on OSCAR (QO) 100.

A nice presentation by OZ2OE and OZ5N showing some simple and less simple home construction projects for receiving the down link on 10GHz, as well as different versions of an up-converter to 2400MHz, ranging from some older home made (and modified for the frequency) 13cm equipment to a setup made with low cost Chinese modules.
OZ2OE was presented with an award, the VHF profile of 2019, mainly for his work on publishing information about how to get on the QO100 satellite.

Another presentation on the GPS control by Bo, OZ2M, I did not attend, but it does relate to QO100, in the sense that knowing your frequency (TX and RX) makes the satellite operation much more convenient, and with narrow band digital modes it is a necessity.

As usual, it is always a pleasure to meet friends, old and new, so I had an excellent time there.

2m Tropo Over The New Year's Period.

Though I have had the cough and not too much energy, 2m has been good to me, mostly via FT8. When the voice is not good, it is a much better mode, and it is excellent for monitoring the propagation.

2m:
Coming back home on the 27th (I think) I noticed a cluster of spots from Southern France, all within a period of 10 minutes and in a relatively small area. This I consider a sporadic E opening, as other stations i Europe were working Es via a reflecting "cloud in the same area. My first experience of 2m Winter Es.
In the same opening LX1JX was worked as a new DXCC on 6m.
28th provided QSOs with 3 G stations and a PA. Not spectacular, but not too bad.
2nd January, just a single QSO on 2m with LY5P
5th gave me quite a surprise: I saw EA2XR in my FT8 display, only 17dB S/N, but I tried anyway. Much to my surprise he answered my first call, and the QSO was made. The surprise is more so, because he gave me a better report than I gave him: -6dB S/N. My guess is that I must have been lucky that he had his antenna precisely in my direction, and that his receiver is top notch (EME system?)
On 10m S01WS was worked.

All through this, I am surprised of the results using an omni-directional (Big Wheel) antenna on 2m, a long, lossy cable, and ... no preamplifier. There is plenty of room for improvement.

This is not a bad start of 2020.

2020 Has Started, And A Brief Look Back On 2019.

For me, 2020 started in the sign of the cough. It stared e few days before the New Year, and is still there, though it seems to be subsiding now.

2019 was a year of travel, and not too much radio activities.
The QO100 geostationary satellite was activated, and the amateur radio transponder went on line in February. I got a decent system up and running for receiving the narrow band transponder down link. This is actually not too complex, as a TV satellite LNB is sufficient for converting the 10GHz down link signal from the satellite. A bit of modification, and adding an external reference oscillator placed indoors proved necessary, was constructed and has been in use since then. An improved version is in the making.
Next step is - still - getting to transmit on the 2400MHz up link for the satellite.
Also on 10GHz, a simple experiment has been running: Using a LNB for reception of terrestrial signals, via rain scatter and tropospheric propagation. I am still impressed that I receive a beacon about 36km from here, certainly non-line-of-sight. It is there all the time, received with the LNB alone, no extra gain from a dish.
Also, a fair amount of sporadic E openings over the summer on 6m and 4m, with a few new countries worked on each band, and getting a fair amount of components for projects (mostly via eBay).
Not too many projects finished, and many more ideas appeared. It is a fact of life that getting ideas is easy, putting them into practise takes much more time.

2020 should probably see me finishing just a few projects, like:
- QO100 uplink capability
- receive antenna system for monitoring several frequencies simultaneously
- some QRSS activity, mostly grabbing (receiving) QRSS signals  and other weak signal modes

The beginning of 2020 (and the end of 2019) has seen some spectacular tropospheric propagation over the Atlantic.
On 2m the European distance record was broken for tropo signals, with a spectacular QSO between Cape Verde and Northern Scotland.
On 70cm the world record was broken with a QSO from Cape Verde to Scotland.
All this has been made possible by using weak signal modes, like FT8. I would not be surprised if those records will be broken again later this year. Exciting times on VHF and UHF, and possibly the microwave bands.

Happy New Year to all from here. Hope to work some of you guys.