10m Is At It Again.

After a low in solar activity it is now up again. Solar flux 121 that last two days is quite a bit, and a daily sunspot number of over 100.

10 has seriously woken up this week end.

From East Asia in the morning and almost until noon, Australia morning/noon, and fro the first time I have seen it in Cycle 25. my receiver spotted New Zealand. 

Around noon the 4X6TU was through, and in the mid afternoon the South Americans were there, lots of them.

Then, still mid afternoon I heard the 4U1UN beacon in New York was there while I was elsewhere in the house. Checking the PSK-reporter, yes, sure enough there were several spots from the East Coast of  the US. 

Then a bit quiet in the early evening, and suddenly spots from near the West Coast of the US, around 9PM local time here. This looks very much like trans-polar propagation, not unheard of at this time of the year.

Definitely an interesting day on 10m.

Rough Layout for a 2.4GHz Transverter - "LEGO-Style".

After yesterday's test I found a shielded box with dividing walls that should be usable for starting the build of a 2.4GHz transverter and/or QO-100 up-converter. 

2 amplifiers are added to the design, one for receiving and one for transmitting, and a further filter for transmitting. The extra TX filter might be better placed in an amplifier box, we shall see. This might provide a better balance in the filter/amplifier gain/attenuation, maybe even a better LO and image rejection. 

What I did is simply putting the "LEGO" modules in their approximate places. Of course, the modules will be mounted parallel to the surfaces of the box, but the picture below gives an idea of what the layout should be. 

The mixer, filters and the hybrid will be placed at the bottom of the box, the two amplifiers at the sides inside the box.

The image gives a rough idea of the layout. The bigger casing next to the module box is the LO,  a non modified 2009MHz oscillator, at this moment. Initial tests, like the test yesterday, will be with my signal generator at 391MHz, and with a receiver capable of 391MHz.

Modifications of the LO will come later It needs to generate a 1968MHz signal for converting between 2400 and 432MHz.

I would expect the TX output of this to be around -10dBm (100uW), and the RX sensitivity not too good. With the modified LO, however, it could be used for a short range experiment on 2400MHz.

Now for some mechanical work, and that takes me longer, then some tests of the set-up.

For the record: The idea is not my own, I first heard about it from OZ2OE, Ole. The mechanical set-up is my own, though ;) .

Quick Experiment With the LO Module and Some Chinese Modules. 2.4GHz signal achieved.

 Today I got a quick set-up to see how some of the modules I have could be used as a transverter or up-converter from 432MHz to 2400MHz.

Here are the parts:

- the 2009MHz oscillator module I tested a few days ago

- a mixer PCB module, IF DC-1.5GHz, RF/LO 1.5-4.5GHz

- a 2.4GHz filter PCB module using "hairpin" resonators

- a Wilkinson combiner/divider hybrid PCB module

All this was just lying loose on the lab desk, connected with SMA cables with the first port to the 35-4400MHz spectrum analyzer and the second port of the hybrid terminated with a 50 Ohm load. The second port is intended for use in 2.4GHZ reception

For the test I set my signal generator to a 391MHz IF, mixing with 2009MHz to get 2400MHz out.

The raw signal out of the mixer was as expected, a bit of 2009MHz LO feed through with LO +/- IF signals about 30dB stronger

Adding the filter (and the hybrid) provided a solid signal on 2400MHz. The LO signal was about 45dB down, and the image frequency was about 55dB down.

The results are encouraging. I would expect the stray LO and image signals would be better attenuated when the mixer/filter/hybrid  modules are mounted in a shielded casing, but for the transmitter path I intend to mount a second filter between some of the amplifier stages, in a second shielded casing.

For a receive path in a transverter A second filter is probably also a good idea, but at present it may not be necessary. In principle this is a very low powered and very insensitive 391/2400MHz transverter.

What comes next (in no particular order)?

- modifying the LO module to generate 1968MHz, so a 432MHz  can be used as the IF.

- building an amplifier chain, so I can get a minimum of about 500-800mW output.

- building the modules into shielded casings Except the LO, it is already in an excellent shielded box.

- Start mounting this arrangement into a sufficiently large casing

- adding circuitry for supplying and controlling the LNB used for QO100 reception. Right now the QO100 set-up has separate transmitter and receiver.

- adding receive amplification/filtering for 2.4GHz.

- adding control circuits, such as T/R switching, band switching etc.

- adding a second down converter, so the LNB's IF signal can be received on 144 or 139MHz

- maybe a bit more when I can think of it.

Results of the Solar Panel Relocation.

After relocation the illumination of the panel is clearly improved. Last year, at this time of the year, the battery got too discharged, as it was supplying the charge controller.

This year, after relocating, and making sure that snow was removed from the panel, the voltage has been kept above 12V, often around 13V. A considerable improvement over last year's performance.

In the spring I should get more set up, along with a lot of maintenance of my antenna system.

It looks like next year will have much more outdoor activities for me.

Testing A 2GHz Brick Oscillator, And My Microwave Testing Limitations.

Some time ago I purchased a few surplus 2GHz oscillator modules fro RF-Microwaves in Italy, designated SU-03. They are now sold out, but I finally got to start testing a few of them.

Those are synthesized modules operating on 2009MHz, with a reference crystal of 8MHz. From the description it is indicated that with a modified reference frequency the unit could be modified to operate in the 1960 - 2035MHz band.

The SU-03 requires a dual power supply of +/- 12V. For the test I used my standard variable lab PS with 12V, and a set of 3 Li Ion cells to provide the negative voltage. The negative voltage is needed, as the unit has 2 GaAsFETs that need a negative gate bias.

Power output is specified to 10dBm (10mW), so to be sure not to over-load (and destroy) the probe of my old HP432 I connected a 10dB attenuator at the SU-03 output. That was good, as the measured output turned out to be +15dBm (30mW, well above the spec of the thermistor probe). Better safe than sorry. I now have 3 units tested and in-spec for the +10dBm output. This should be quite sufficient for use with a passive (diode) mixer. 

Next step: Look at the spectrum coming out of the SU-03. Here is where I think that the limitations of the low cost Chinese spectrum analyzer, covering 35 - 4400MHz comes in. This is a device costing less than $100, so how can we expect miracles? Well, we can't.

First of all, the maximum scan bandwidth of the spec-an is 350MHz with a 500kHz "IF" bandwidth, so in order to "see" the full spectrum I need to look at 300MHz at a time, then switching to the next segment, etc. It takes some time, and it is tedious, but it can be done. 

Second limitation I see is, as I suspect, the local oscillator - I guess an ADF4351 (or a clone) - has a square wave output, so subharmonics of the original input frequency show up on the display (1GHz, 666MHz, 500MHz) quite strongly. Well, knowing the limitation is half of getting more reliable results. 

Between 2GHz and 4GHz I see no spurious coming out of the oscillator, at least they are about 60dB or more down from the wanted signal. Also, between 1 and 2 GHz I see no spurious signals. This indicates that the output from the oscillator is rather spurious free.

When looking at a more narrow frequency span, the limitations of the low cost spectrum analyzer really shows. The curve is no longer a curve, but has steps of about 5dB in the in the spectrum, and further it is possible to see the effect of the direct conversion design in the analyzer, in that the center null is somewhat visible. 

When looking at a moderate bandwidth,  some asymmetric sideband noise is visible. I can not se if this comes from the oscillator block or the local oscillator in the spectrum analyzer, but I suspect it comes from the low cost local oscillator in the analyzer.

Clearly, the low cost solution, while not useless, is not very efficient, but for now it will have to do, as I do not have a (more expensive) analyzer covering up to 2GHz or above. What I do have is a rather old (analog) model covering up to 1.5GHz. With that I can test for spurious output(s) below 1.5GHz, that's all.

Next test of the oscillator will be a frequency test. While I do have a frequency counter covering up to 2.4GHz it is not locked to a frequency standard, neither does it have an input for doing so. So high precision frequency measurements are not possible.

The frequency counter that does have such an input just covers up to 1.3GHz. What will be necessary to use my GPS controlled 10MHz source is a divide-by-10 (counter), because this particular counter requires a 1MHz external reference frequency. Some soldering work needed.

There is, however, the possibility of adding a pre-scaler to it so all is not lost. It looks like I should get the soldering iron going again, so I can get a divide-by-4 pre-scaler up and running, with that one I should be able to measure frequencies up to 3.5GHz (with the use of an added calculator) with good precision. .More soldering work. Also, this would be my first (fully) microwave construction, not just using modules or adding modulators or doing small modifications. Now it gets interesting (hopefully not in the Chinese sense of the word ;) )

What is this (modified) oscillator brick useful for? Let me see, with modifications:

- 1968MHz is within the range of operation of the VCO, so a local oscillator for a 432 < - > 2400MHz transverter (or QO100 up converter) is possible

- possibly a base oscillator for a 10GHz transverter (followed by a x5 frequency multiplier, e.g. 1987.2 x5 -> 9936MHz - LO for a 10368/432MHz conversion)

- a precise 2000MHz oscillator for down conversion of 2400MHz to frequencies that a better spectrum analyzer or frequency counter. Possibly with a divider to 1GHz and/or a frequency multiplier for higher frequencies. We shall see. what I do

Small update: 

I tested the oscillator with the old spectrum analyzer (up to 1500MHz) No subharmonic signals could be seen. The oscillator is free of spurious signals from 0 - 1.5GHz on this one. Nothing could be seen from 1-2GHz and 2-4GHz. My conclusion is that this oscillator module is very clean, at least with regard to spurious signals. I cannot measure phase noise, but I can probably get that done at a ham radio friend with better instruments. 

This looks like an excellent candidate for 2.4 and 10GHz transverters with 432MHz IF. It is fair to say that a ham radio friend recommended this at a small ham meeting, so I mostly expected this.

The interesting part comes when I try a modification for an external reference frequency signal, how much it depends on the purity of the reference signal.

More on that later.

Idea Box: Putting the 10GHz Amplifiers to Good Use.

Now that I have some decent amplifiers, it is time to make a project to make good use of them. since they have a high gain it is essential to avoid over-driving them. 

Here are some ideas:

The easiest modules to employ are the 2-400mW modules, as they only need a single, +15V power supply. The modules are rather small, and heat up quickly, so some kind of heat sink is necessary for those. Not unexpected when I saw the size, and they do have holes for mounting on a heat sink.

The 1-2W module needs a -12V and a +12V supply, as does the amplifiers in the up-converter module I have tested earlier. Those units *need* the -12V to be supplied before the +12V, so some kind of sequencing/safety circuit is necessary.  

For this reason the first construction tests will be done with the low power modules. Here are some options for experiments. 

1) a WBFM modulated DRO, such as a modified HB-100 module driving the amplifier. The HB100 module needs to be modified for use as an exciter for the amplifier, and a modulator is needed, too. The modification would consist in disconnecting the RX mixer circuit and the transmit antenna on the PCB, adding a semi-rigid cable at the "antenna output" and building the HB100 into a shielded box. One more thing is needed, an attenuator in order to avoid over-driving the amplifier.

Adding the attenuator has one more advantage, it provides some isolation of the DRO, giving less drift and external influences.

Such a transmitter can be used together with a satellite LNB and a WBFM capable scanner running in the 600-700MHz range. Separate antennas can be used for simplicity.

It could also be used as aWBFM test TX ("Beacon") when used with an audio frequency keyed system, e.g. with a microprocessor, such as the Arduino with a suitable program. Of course, this could also include a keyer input for manually keying the audio tone.

The range with such a transmitter will be significantly improved when compared to a simple system with the HB100 "stand-alone".

2) A set-up using a cheap 70cm transceiver as the source for the TX signal. This is a bit more involved, but some of the circuitry can be used for other experiments later.

The circuit needed is a frequency multiplier chain, for example 432x2 -> 864x2 ->1728x2 ->3456x3 ->10368MHz (x24 multiplication, so other orders of the multipliers could be useful). A bit of offset from 432 would be good, as I want to avoid running WBFM in the narrow band segment. The advantage of this will be the improved frequency stability, as the reference frequency is usually synthesized. Yes, an attenuator is needed after the 70cm TX, but that is not too difficult, since such a TX can run a power as low as 0.5-1W, and the load impedance is not overly critical for the TX.

Otherwise the multiplied and filtered signal can be used as in example 1 above.

This was all wideband, and this does have its limitations with respect to range, so I would like to use the amplifiers for narrow band transmission as well.

3) Narrow band CW (FM) transmitter. Using the multiplier from example 2 it is then a matter of generating a 432MHz signal with sufficient stability. For a simple, single frequency CW TX, e.g. a "beacon", I have some TXCOs running on 14.4MHz. As those oscillators are likely to generate a square wave, taking out the 5th harmonic on 72MHz and amplifying it should not be tricky. After that a frequency doubler, followed by a tripler will generate a signal on 432MHz. As I have done a bit of VHF construction before I would not expect this to be too difficult, especially as this comes after trying making the higher frequency multipliers. Good shielding and decoupling is a known construction technique for me. Keying can be done in one of the multiplier stages, and this can also be used as marker signals for 2m, 70cm, and 23cm.

200mW CW should be quite good from a hill top.

Because I do not know any people near me running WBFM, this might be a better option to make a first QSO on 10GHz, if I do not build a second simple WBFM set, or find someone who has one or wants to build his or her own.

Now, although I know some, not all people doing microwaves can do CW, so what comes next?

4) Up-converter from a VHF or HF station, so all modes are possible. The receive side can still be a satellite LNB (modified for better reference frequency), so here goes:

Among the stuff I ebay'd lately, there is also a 10-11GHz mixer circuit. The IF connector is not a standard SMA, so it looks like I am going to make a modification so that all three connectors will be SMA. Otherwise I can use the one from the up-converter I already have (and tested), modified, so that the DRO is removed and a multiplier chain (as above) is used in stead. I will probably need a new multiplier chain, but that should be doable, if I can get the first version (above) working. In the up-converter there is (what looks like) a decent band pass filter centered on about 10330MHz. This has to be re-tuned as 10368 is outside the band pass.The amplifier chain in the up-converter as it originally was, is quite bulky, and could be replaced by the 2-400mW amplifier. I suspect there will be sufficient gain.

All in all, it will be interesting to see what I can do with the surplus equipment/modules I have got now. A bit more is on the way, more on that later. There is enough work for quite some time with the speed I normally build stuff. For now, the HB100 modulator is back in the front again. I received some (SMD) 4001s, so the morse tone generator can be made, even if I need to use an adapter from SMD to "normal" (old fashioned) PCB soldering.

Solar Panel Re-Location.

For a while I have had a 50W solar panel running with a sealed (gel) lead-acid battery indoors, running with a charge controller.

Last year I realized that the panel was part in the shade during the deep of winter,  and the battery had been discharged, just by supplying the controller. but at the time it was too late already, so nothing was done.

Looking outside today around noon I saw that the panel was only  about 2/3 illuminated, so I got to change it. 

The panel is now about 1m above ground level, and placed a bit further from the building shading it. Yes, the sun is very low above the horizon at this time of the year here, somewhere around 10-15 deg. at winter solstice, so it does not take much to put the panels in shade.

There will only be a few hours of charging, but it is dfinitely better than at the previous position.

This brings me to another project that should be worked on this winter (apart from the 10GHz equipment). I have been working on re-conditioning some gel-batteries, but they are not yet ready for deployment. I have now decided that as a start, I will get some new batteries, so I can increase the storage capacity,.

Apart from this, I do have a small store of a few 30W (small, flexible) panels, and some very small solar panels. Some of the smaller panels I should use with some LiIon cell chargers (yes they are with BMS) to supply some low power consumption stuff, like a HB100 TX or the like.

The aim is to have some simple low power equipment for monitoring purposes powered entirely by solar, and with the panels and batteries I already have that should be possible.

To be sure, this location of the panel is temporary, and a more permanent location (more mechanically stable) is needed.

Oh, well. I am probably never running out of things to do or try. No time to be bored here. Was there ever?