Idea Box. QO-100 Downlink Reception.

For quite a while the setup for my QO-100 activity has been rudimentary:

For uplink I have used an old IC-821 as transmitter, with a lot of attenuation, followed by a low cost Chinese up-converter (BU-500) indoors, about 15m RG6 coax, with a so-called 8W WiFi booster that can deliver 2 - 2.5W without modifications, feeding a 4x patch "WiFi antenna and a 1.1m dish reflector.

This provides a decent signal on the downlink side, and certainly never overloads the transponder (triggering LEILA).

For the downlink I am using a 60cm dish, a low cost synthesizer controlled LNB, modified to be controlled by an external 25MHz reference signal.

The 25MHz reference oscillator is indoors in the shack in order to minimize the temperature drift. As this is an uncompensated DIL oscillator there is, of course some drift, up to a few kHz to each side. Actually not too bad for such a simple setup.

The LNB converts the the 10489MHz signal down to 739MHz, so for now I have used an older AOR multimode scanner receiver, the AR8600. This works, and I have made some QSOs, and often participated in the Danish-speaking net on Sundays. It is a bit inconvenient with the drift, as I have to compensate by manually checking the AR8600 frequency for the beacon, and then remember to calculate the offset.

Further, the IF filters in the AR8600 are low cost ceramic filters, so for SSB and CW the selectivity is not what I am used to from my HF/VHF transceivers.

Here comes the idea: The AR8600 has an IF output on 10.7MHz, with a bandwidth of 4MHz. Why not use that to feed one of my HF radios? That way I can use the better filters of the HF radio. On top of that, a quick manual compensation of the LNB frequency drift can be made by switching to one of the beacon frequencies and retune the AR8600 so the beacon is in the pass band of the IF receiver. Then the recalculation of the offset becomes unnecessary.

This is the simplest way to improve the downlink receive system with the equipment I have at hand.

It does require using two radios, as the AR8600 is simply used as a second down converter.

If I want to eliminate the AR8600 from this there is another idea. This requires more construction, so I think I will use the AR8600 in the first instance.

I have some older TV tuner modules with synthesized local oscillators. With a bit of programming of the synthesizer chip using a microcontroller, the Arduino or the like, this can function as a down converter to an IF of 28-40MHz. One little disadvantage is that the TV tuner as-is inverts the IF band. 

This can be eliminated in two ways:

1) a second down converter inverting the band once more. This adds complexity to the system, but can be done without too much building.

2) retuning the RF filters of the tuner, so the LO moves below the signal input frequency. This is the simple way, but requires more test equipment. I do have enough test equipment to do this, so if I go the TV tuner way, this is the likely way to do it.

For now, the AR8600 with HF receiver will be the way, after all the Christmas activities. I am looking forward to improving my QO100 setup.

I am still looking into what next year's "challenge" will be. It should require some activities from my side, on the other hand it should also be fun.

I do think that a part of this will be running the most used parts of my station on solar (with battery backup, of course) hopefully on solar power, even through the winter. I may have to switch parts of it on mains power in the poorest sunlight conditions. The really power hungry parts, like big linear amplifiers will be running on mains power in any case, but they will not be running a lot in any case.

Using only the IC705 in December I have been able to get the battery up to 80%, but that has been with saving the time I was using it.

Es'hail 2 Sattellite, aka Qatar OSCAR 100

The Es'hail 2 satellite has been launched and has entered geostationary orbit. This satellite has TV transponders, and something new for radio amateurs : a 2400MHz to 10GHz transponder in geostationary orbit.
The coverage should be all of Europe and Africa, to the East into India, and to the West a tiny bit of Brazil. Even Antarctica should be within range, if some of the research stations are within the footprint of the satellite I assume that some testing will be going on before the transponders go online, but this is an exciting time for radio amateurs interested in satellite communication.

First update:
The sat is in orbit and the amateur radio transponders are now operational.
They work very well. An SSB uplink with 60cm dish antenna and linear polarization produces a readable signal, a around 10-20 dB above the noise, as I have heard on the WebSDR.
On the spectrum of the WebSDR it is even possible to see the effect of running too much uplink power. This creates dark bands on the waterfall spectrum, and sometimes audible attenuation of received signals.
Frequency stability is the main problem with the uplink and downlink, for obvious reasons.
As a first attempt at working through the satellite I was thinking of purchasing a relatively low cost up converter from SG-Labs in Bulgaria for the uplink. This has about 500mW output, and with a 1W power amplifier at the feed point it should be possible to be heard via the transponder with SSB, and certainly with CW.
A fun experiment would be trying FT8 or JT65 with a much lower ERP.
Receiver side will be with a low noise satellite PLL LNB, possibly with a later modification of the reference oscillator.
I have decided to take time to attempt a simple up converter made of Chinese modules available on eBay.

Second update :
10GHz reception converter (arriving shortly) for downlink:
LNB suitable for OSCAR 100 reception has arrived. Octagon OSLO (PLL controlled Local oscillator.
Initial test will be done with the unmodified LNB.
It will need a modification for better suitability: External reference oscillator, preferably a TCXO, at a stable temperature, fed through the cable (disconnect the internal XO, info on the Internet).
Alternatively, for even better stability, a GPS locked oscillator could be used.

2.4GHz uplink:
Modules from China have been ordered :
1) Synthesizer : ADF4350, covers 137MHz - 4.4GHz Needs to be programmed. There seems to be a library for the Arduino microcontroller. Price per unit about 10 GBP
It turns out, looking through my stock that I have a single AD4350 and an Arduino UNO, so it is possible to start the process of building the local oscillator for the transmit converter. Now for learning some Arduino (variant of C) coding.I ordered a few mor ADF4350s as spares in case I have an accident of destroying the one I have.
Learning the coding could easily take the time needed for the stuff from China to arrive, unless I find a suitable program that just needs a simple modification. No need to invent everything all over again.
2) Passive up (and down) converter modules (also to have some spares). Price per unit about 8 GBP
3) 1W amplifier modules. Price about 10 GBP
I ordered a few, because I have a long run of cable, and would like to have one as output for the indoor unit, and one at the antenna feed point.
The official uplink power for the satellite is regarded to be about 10W into a 60 - 90cm dish. However, an output of 1W appears to be sufficient to make SSB contacts via the satellite, as I have heard several stations with similar set-ups via the WebSDR.
4) Double balanced RF mixer (down conversion) Price about 5 GBP.
Why a down converter ? Well, it is a simple addition adding receive functionality, creating not just a satellite uplink transmit converter, but getting a 2400MHz transverter, making simple two-way contacts possible on that band, albeit with low power. It will most likely be possible to make some local contacts, and possibly a bit more during tropo conditions.

I already have some amplifiers capable of an output of about 100mW on the band, more than sufficient drive for the 1W amplifier mentioned above. Those were priced about 5 GBP.
One more thing is needed for this to work without making interference. A band pass filter.
I need to look into the best solution for that.

If (when) I succeed in getting a signal through the satellite, the adventure begins. Optimization of all aspects of reception and transmission, and experiments with very low power. I was told by OZ2OE that he had heard a Dutch station running a 75mW CW signal into a 1m dish, and it was audible at 539.
Also, running 1W into a much smaller antenna is an idea I want to play with. I have a tiny Wifi yagi, 40cm boom length and 17 elements. That will be an interesting comparison with the 80cm dish I have, and a good comparison. Constant gain from the yagi, and seeing the different improvements to the dish and feed.

I see quite a bit of experiments and lots of optimization in my future.