2019-06-29

Local Beacon Monitoring on 10GHz.

I recalled that I had a "free" cable to add another LNB.

I found one of the inexpensive ones I had, a single IF output version, unmodified as yet.
I mounted it with duct tape, just below my 6/2m/70cm vertical, about 6m above ground, and just the feed horn pointed in the direction of the local beacon I have heard earlier. Yes just testing without any substantial gain.
Of course, it drifts with temperature, but I found the OZ9GHZ beacon easily, at a distance of 36km (just around 23 miles), and without line-of-sight, but the landscape has a downward slope from my antenna, down to a part of the path (about 20km) over water.
I am aware that there may be some tropo involved, but I can, at least test that now. The signal strength varies from S3 to S7, as estimated by ear.

Now I just have to wait and see if I can hear it at all times, and see if other beacons in a similar direction will pop up at some time.

Successful 144MHz Tropo from my station.

Last night and this morning we had strong tropospheric propagation on 144MHz.
Half a score of G stations,,  a few DL, PA, LA and SPs. have been worked with my Big Wheel antenna. Yes, I still do not have any beam antenna mounted for 144MHz, just the omnidirectional

The Big Wheel is not really an ideal antenna, but much better than a vertical for working DX on 2m, and it can take more power than the vertical. I was working with about 200W at the antenna.

This morning I noticed that DL7QY in Southern Germany was reporting "my" local 10GHz beacon OZ9GHZ. I still have the 10GHz RX setup used for QO100 only, but at some time I must mount some (at least) RX setup for 10GHz terrestrial listening.

2019-06-25

Partly Successful 10GHz Reception Test With Small Dish. Updated.

Today I tested beacon reception with a small dish antenna and an unmodified PLL LNB.
The test was done in my garden with obstructions all the way round.

I have done reception tests before, but this had two limitations:
- Polarization was vertical, while the beacons transmit with horizontal polarization.
- The 60cm dish is fixed, pointing to the satellite.

The limitation of today's test was that the dish is smaller (35cm) and mounted even lower than the dish for OSCAR100. Just a tripod.
Antenna polarization for this test is horizontal, which should be a significant advantage.

As before, I hear no sign of OZ7IGY at 26km distance, with a heavily obstructed path, both by trees at the edge of the garden, and the landscape rising about 20-30m. OZ7IGY has not yet been heard without the aid of rain scatter.

OZ9GHZ at 36km, but in a different direction with much less obstruction. The worst part is probably a bit of forest about 100m away but no landscape obstructions I can think of, and the middle of the path there are some km of sea. This should prove much better, and indeed it does.

With the correct polarization and the dish pointing closer to the horizon I found a gap between two houses (the neighbour's and mine), and got the dish aligned, and voilĂ  !
The signal is always audible in spite of the lack of line-of-sight, and it is the strongest signal I have heard on 10GHz yet. Stronger than the OSCAR100 beacon, indeed!

A test with the LNB without the dish still provides a clearly readable signal. I am wondering if I am experiencing some "local tropo" propagation. Time and more tests will show.

The experiment is a qualified success, and gives me hope that I can work some 10GHz from home when a corresponding transmitter becomes available.

At the moment I can not use this setup permanently, it uses the setup for the OSCAR100, and the cable comes in through an open window. I should test if the LNB behind a window will work. More experiments to do.

Update: The LNB behind the window is not that good. Probably coating in the windows

I am thinking of mounting a horn antenna as high as possible, hopefully looking above (most of) the local obstructions, and a dish in a lower position. This is in order to reduce visibility and wind load, and is for a later consideration.

A fixed box with a few LNBs pointing in different directions, and mounted as high as possible is also under consideration.

One thing is sure, I need some modification of the LNBs, so I can connect an external reference, the drift I have with the unmodified LNB is too high for weak signal work.

Microwave Parts and Modules Part 2: Surplus PCBs and Modules.

Some weeks ago I went to a small ham gathering at the site of a  local repeater.

I had a talk with local hams about uplink equipment to the QO100 satellite. Many people are planning getting active on the satellite, so equipment for the 2400MHz band is in higher demand.
I had been planning to use some cheap Chinese modules for the local oscillator, but one suggested to find some better modules with Franco, alias RF-Microwaves.

Looking at the site I found that they have a lot of interesting stuff, especially in their surplus dept. Here are a few examples:
- A local oscillator module running at 2009MHz with the standard 8MHz crystal
- Some LNB modules without feed horn, but with input connectors
- PCBs with 4 HEMT FETs, where the PCB is arranged, so that it is possible to cut out two low noise amplifiers
- WLAN PCBs with several good components, including some 2.4GHz band pass filters
- 15GHz oscillator modules with several 10s of mW output.

I ordered a few of each, and some microwave absorbing foam. The service from Franco is excellent, I ordered one afternoon, and 2 days later, in the morning, the goods were delivered. The exception would if he is at a ham gathering, such as the Friedrichshafen Ham Meeting, probably the biggest in Europe.

Now for the goods, some of which are the last few left.

The 2GHz local oscillator module (about €20):
This is a complete module with casing and mounted with vibration absorption. Looks really good. On the website there is some modification information. The VCO can be used from about 1960 - 2040MHz, and the modification consists of making an external reference oscillator, replacing the internal 8MHz crystal oscillator. The external reference can be made with a well filtered DDS module.
For the IF of 432MHz the LO frequency should be 1968MHz, which is in the VCO range

As s second use of the LO module, it should be feasible to add a multiplier x5, for a local oscillator for a linear 10GHz transverter/converter.

A brief description of the LO module is on Franco's website.

LNB module (about €3):
This is a DRO controlled down converter module for satellite TV, with the mixer/oscillator in a single chip.
F6CXO has proposed the use of this module as a down converter for a (lower frequency) spectrum analyzer. The modification involves removing the 11/12GHz amplifiers and the filter. This cannot remove the image frequencies, so one needs to be aware of the frequencies that can be generated by the circuit you are testing. For amateur use, it does present a possibility to see what is going on in the 10GHz band, without having a more expensive spectrum analyzer. Mine covers up to 1.7GHz, so with a LO tuned to 11GHz the frequency range of 9.3 - 12.7GHz can be monitored.
Max RF input for the converter is about 0dBm (1mW). The RF input connector should be changed to a SMA, for the original ones it is probably very expensive or difficult to find a source for them.
The modification, if done carefully and with antistatic precautions, should provide you with 3 working GaasFETs, apart from the intended converter. I would probably make 2 converters, the second one using the lower LO frequency of about 9.7GHz, thus covering 8.0 - 12.7GHz with my analyzer.
A description of this modification is posted at Franco's website.
I would propose a few uses for the module, apart from sourcing components:
- Using the converter as it is, as a WBFM down converter to the 600 - 800MHz range.
- Adding a connector to the output of the 10/12GHz  preamplifier (before or after the (modified) band pass filter, providing a simple 10GHz amplifier with a gain of 15 - 20dB, likely with 20-30mW output.
- It might be possible to add injection locking to one of the DROs, if so the converter could be used as a simple narrow band down converter for 10GHz.
- Using the LNB as it is, for rather unstable down converter for wideband FM.
- Using the casing (moulded aluminium?) as it is for other modules I should build
I am sure other uses, apart from being a source of components, will turn up ...
Not bad for a €3 module.

PCBs with 4 HEMT FET amplifiers:
There is a document on this PCB, too, on Franco's website.
Here are some uses the document suggests:
- A low noise 10GHz LNA from a cut-out piece of the PCB. Each PCB could provide two of those in a relatively easy way, also salvaging two HEMT FETs. Yes, the board has 4 amplifiers, it looks like it has come from a dual head LNB. A negative supply for the gate of the FETs is necessary to add to the simple amplifier.
- Using a piece of the 50ohm stripline as a piece of test equipment, e.g. a component tester or for a bias-tee. The PCB material is good for up to 20GHz.
- Making 1 12/24GHZ doubler.
- The FETs are useable on 24GHz with up to +13dBm output and a gain of about 7dB.
This looks like an excellent source for building microwave stuff.
Like with the "connector-LNB", you get a lot for €3.

The WLAN PCB looks like a good source of components for building some 2.4GHz transverters/converters.
I was buying them, mostly for the 2.4GHz filters, but there is a PLL IC, a prescaler, and other good components there.

The last one, the LO PCB:
This contains two LO chains for around 14/15GHz:
- A straightforward receiver LO, starting on around 2.5GHz, adding multipliers. A tripler for 7.5GHz and a doubler for 15GHz
- A TX LO which also includes a modulator, meaning that it looks useable as a (WB)FM modulated transmitter, with a suitable PLL oscillator modification of the 2.5GHz part.
The output transistors, (two) coupled with a hybrid, are supposed to be capable of delivering about 100mW on 14GHz. I am now wondering if the hybrid is broadbanded enough to cover 10GHz, but that is something that needs to be tested. Also the 14/15GHz filters should probably be bypassed and replaced with some 5 and 10GHz filtering. I am hoping to be able to use a modified version of this PCB as a 10GHz power amplifier with 100mW output, if the hybrids have sufficient bandwidth. It may, however be necessary to design a separate PCB or set of PCBs, using the output FETs. With that, I will have to ask someone with **much** more experience than I have. I know, my general knowledge will probably not be sufficient for such a design ... yet.
- Also, an excellent source of components, FETs, MMICs etc.

Oh, well, so many ideas to try out, and lots of other activities. It will take time, and learning some new skills, but, as a start, I have a few of those modules

2019-06-22

Getting More Tidy?- and TV Tuner Modules.

With a house full of stuff it is not the easiest thing to keep tidy.
Here is an on-going project that started right after my move back to Denmark, and with a break because of a serious illness.

I am - slowly - beginning to know where more of my (radio) stuff is, but there is a long way yet.
It looks like I need to make some sort of inventory (what do I have, and where?).

This week I found some old TV tuner modules which may be useful for converting the IF signals from a satellite TV LNB down to a second IF, where a WBFM demodulator (or base receiver) can operate. Some of those are synthesized with the synthesizer on board, others just have VCOs which may or may not be PLL controllable (with or without modifications).

In any case, some low cost 10GHZ system looks feasible with the tuners, others may have  interest in using them, too.
The old fashioned TV tuners are getting more tricky to find.

Why not use the cheap USB TV tuner modules, like the RTL-SDR, you may ask. Well such a tuner needs a computer and SDR program, so the complexity goes up right there. A simple PLL can be programmed by a small single chip processor, like the PIC/PICAXE or the Arduino, drawing much less power. Certainly a high priority if you want to go portable.



2019-06-18

Microwave Parts and Modules, Part 1: Old 10GHz Stuff.

Lately, I have purchased a fair amount of microwave components and (PCB) modules, as well as some stuff I have had for a long time, before I moved back to Denmark.
Unfortunately I may not have brought everything (I now want to use) with me, so it was time to take stock of what I have available.
I have already written some posts about the 10GHz HB100 module, and that should result in some wideband FM equipment at some stage.

Last week I ordered some surplus boards from rf-microwaves.it .
Along with that some bonus parts were in the package, some of them not yet identified, so I have more to sort out.

First stage was a box with some old 10GHz parts. Some of those were not really suitable for 10GHz, waveguides (WG) too big or too small, but here is a list of some useable stuff:

Two small horns (probably 15dBi) and a slightly larger one (probably near 20dBi) fit a WG17/WR75 waveguide, as does a slightly larger one. Both appear to be made from PCB material, and all have a WR75 flange.
Two horn antennas (probably about 15dBi) with WR90 flanges.

A bit of WR90 waveguide material, e.g. some twisted WG with flanges.

a DRO with a WR75 flange. This is built into the casing for an older LNB, and there could be enough space for building a 10GHz power amplifier, up to a few 100s of milliwatts.

3 old single band LNBs with WR75 flanges. those could most likely be used as a preamplifier for a separate receiver. If the DRO in it can be frequency locked, it may be possible to use it as a simple converter for narrow band, maybe for an experiment with a "local rain scatter" monitor with a horn pointing up into the sky.
Maybe, with another PCB, it could be used as a 30-50mW amplifier for a transmitter.
If nothing else, it may be used as a coax-to-WG transition. A bit of matching with a screw or two may be needed for that.

If I got it back to Denmark at the move, I may find some more old 10GHz stuff, like:
- a simple tiny WG/horn with a Gunn oscillator, another small horn with a detector diode
- some Doppler Gunn modules with a tiny, tiny horn antenna.
- some Gunn oscillator/detector with small horn antennas, probably 10dBi
- one or two Gunn/detector modules without  horn antenna, but with a flange.
- I seem to recall a small double-horn Doppler module.
Some of this would probably be useable for making coax-to-WG transitions, if I can find it.
All this may have been discarded at the move, but it may also be inaccessible at this time, due to a major reorganization (well slowly tidying up) in the big shed.

I am - slowly - finding more radio stuff after the move, so I may still find this, exactly.

2019-06-15

10GHz Reception: Update

The rain scatter seems to be gone for now, but it looks like reception of the OZ9GHZ beacon is still possible with the dish pointing at about 25 degrees elevation.
At least, I hear it now, weak, with a tropo scatter-like signal with an occasional short burst of an increased signal. I am not sure what the burst was, but I suspect a plane reflection is the most likely explanation, given the high elevation of the beam.
I am aware that the reception mentioned above may not be completely reliable, but time will tell, at least I have some new monitoring to try out.

Because the main use for this dish is reception of the  QO-100 downlink I did make a system capable of using a signal splitter, so more receivers, e.g. a SDR, can be connected to the same LNB.

I am thinking of adding 3 SDRs:
- one for monitoring QO-100
- one for monitoring the 10GHz beacon band (10368.800 - 10369.000)
- one for monitoring the low band where most of the narrow band activity is expected to take place (10368.000 - 10368.250)

A set of 3 Raspberry Pi 3+s with RTL-SDR should be sufficient for this kind of monitoring. Later on, I may try to mount a modest receiving setup with a smaller antenna - maybe even just the LNB with is feed horn, or a system with a higher gain horn, just to see what I can hear with that system. This should preferably happen before the end of summer, and the rain scatter season, but given other projects it may have to wait. After all, setting up GNU Radio is not for the faint of heart, as I understand it.

There is more than enough room for more technical-scientific experimentation.

10GHz Reception: Terrestrial Mode: Rain Scatter

As you may know, I have been listening to the QO-100 satellite downlink on 10GHz for a while.
At the moment some heavy rain showers are approaching my area. I tried to re-tune my receiver to
the terrestrial narrow band segment of the band.
Nothing heard around 10368.100 yet, but the nearest beacon, OZ7IGY on 10368.920 about 26km from here, with no line of sight, has been heard for 1/2 to 1 hour here.
The propagation mode is known as "rain scatter", something that can happen when the signals pass via heavy rain showers with rather large rain drops.
further, a weaker signal from about 30km away is also being heard, albeit weaker OZ9GHZ in a somewhat different direction.

The rain scatter signals have a significant Doppler spread, and a bit of Doppler shift, and sound like something I got used to many years ago: Aurora signals.

This is my first reception of terrestrial signals on 10GHz, so something of a mile stone for me.

This makes me want to get to transmit on 10GHz narrow band (as well as wideband), even if it is with a small station. It should be possible to build something with my current components/modules, running up to about 500mW, maybe 1W. For more power I will need to purchase modules or better components. The main problem will be mechanical construction and weather proofing.

2019-06-14

One 10m Antenna With Multiple Receivers.

Some time ago I made a modification to my IC-703. It was a RX antenna adapter, originally made for the IC-7300.
It was possible to fit it into the IC-703, albeit with a bit of extra work: I had to file a bit of the adapter's plates an a bit in the radio casing, but it looks acceptable to me.
For a while I only had it connected to loop back the receiver signal, but this week I connected a signal splitter, so it is possible to connect more receivers in a way that does not destroy the receivers when I transmit with the radio.
Yes, when I transmit, I cannot receive anything on the 10m antenna, but I consider that an acceptable compromise. Further, it is possible to use a more complex system, so a transverter could be connected to the transceiver, too.
A TX power amplifier I have, I can connect it to the RX part/common connector, so I can transmit up to 200-250W with that combination

This is how the system looks right now:

10m vertical --- IC-703 ---                               !--- IC-703 RX input
                                         !                             !
                                         !                             !--- RX monitoring 28.074 (FT8)
                                         --- Signal Splitter --
                                                                       !
                                                                       !--- RX monitoring the international beacon project
                                                                             on 28.200

The splitter has more outputs
At the moment the signal splitter is just hanging next to the TRX, but it is the intention to build a casing for the system, so a preamplifier (attenuation in the splitter is too high for some of my receivers) and a switch for transverter or separate RX antenna can be added. For now, the system just has to work as it is, as well as possible. Improvements can come later, after other projects have been done, at least in part.

I would like to have a similar system for the higher bands (6-4-2m and 70cm), but that will have to wait.

2019-06-12

High precision TCXOs


While I was away, I received 2 TCXOs for 25MHz, with a claimed accuracy of 0.1 ppm. For 10GHz this would mean less than 1kHz drift/offset in the temperature range 0-40 at least when the oscillator is adjusted properly.

If the oscillator is put in an insulated (e.g. foam) casing, the drift should be slow enough for the LNB (converter) or TX up-converter LO, to be quite useable for SSB/CW activities. On top of this, it should be possible to find stations, knowing the frequency within 1kHz.

It has to be tested if the oscillator has a low enough phase noise, because some people have reported high phase noise, but there are also claims that it can be improved with a better DC regulator, or just a larger electrolytic capacitor at the output of the regulator.  Investigation will follow given the time. I am working on a report of the travel I had, too.



Pipe Caps Received. Filters for 2.4 and 10 GHz.

I am just back from some non ham radio related travels.
I have received some copper pipe caps, suitable for making simple filters for the 2.4GHz and 10GHz bands, and a length of semi-rigid coax cable.
On the way: 2009MHz LO modules, can be modified for 1968MHz (2400MHz TVTR LO for 432MHz IF) or possibly 1960MHz  (for 439MHz IF) with an added PLL or DDS in place of the internal XO.

I have been reading up on articles about those filters, and it looks possible, even with my not too good skills in mechanical construction, to make a few filters.

Finally, I also found a filter with a centre frequency of 2375MHz and bandwidth of close to 300MHz. This could be suitable for a transverter with 432/439MHz etc IF. I knew I had it, but could not find it before, due to the mess of moving.

The equipment necessary to test the filters for 2,4GHz filters I have. It is the MiniVNA vector network analyzers, covering all bands from a few 10s of kHz to 3GHz.

For the 10GHz filters I will have to rely on a simple signal generator like the HB100 radar module, possibly modified, and a microwave uW/mW meter.
A friend had made one with about 60-70dB range, and I intend to use that. It only provides a simple tuning aid, but I think I can get access to some better test equipment at a local ham with an extensive set of test equipment, for better alignment of filters.

Things are slowly starting moving.