QO100 portable receive system

It is our local club(s) rally on Sunday. ESWR has been running for many years and is the product of several local  clubs.

I seem to have been given the job of organising the UKuG guest interest group stand. I’m a bit surprised as I am no longer the Group Chairman and not even on the Committee this year. However..........

I have asked Jason, G7OCD, to bring his portable QO100 uplink system that he has demonstrated at several local clubs. To save effort his demos have usually used the web SDR, located at Goonhilly, for receive.

I felt it more appropriate that we demonstrate a ‘real’ portable downlink at ESWR. To that end I have been  busy.

Earlier this year I bought a portable ‘caravan’ satellite dish and stand. The dish is an offset 45cm steel unit and fits to the tripod stand. Instead of the original low quality, low cost, LNB, I decided to use a Gooby LNB (£5.60 each on Amazon). These are 25MHz crystal controlled PLL LNBs.

Obviously, the crystal in the PLL is of insufficient quality to provide good stability when mounted out in the open on the dish.

I decided not to use an external 25MHz reference, like I use in my home station satellite system. Instead I decided to try the beacon locking system now incorpoated in several pieces of software. I decided to use SDR Console v3.0.9

My initial attempts to run this version of SDR Console on my now elderly Sony Vaio laptop resulted in the program freezing, so I was starting to think about running unlocked after all. Sunday is getting close.

This evening I decided to try the program one last time and to my surprise and delight, it worked first time. I still don’t know what I was doing wrong previously.

With SDR Console I select ‘geostationary beacon’, then follow the instructions and the software locks on to the PSK beacon and stays there when I tune away to listen to stations. It is not foolproof and does still show some drift, although none of any consquence in the time I was listening. Some of the drift may also have been due to the reference in the RSP2Pro SDR I was using at 739MHz, also contributing to drift. Inam goingbto check that my locking the RSR2pro usingbits external reference input.

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My laptop drives the RSP2Pro and supplies its voltage via the USB socket. The Gooby is powered from a portable 12v 12000mA/h lithium pack (Lidl) and seems quite happy. I use a protected-against-short bias tee to supply the LNB over a single coax.

Now, I hope, with Jason supplying the 2.4GHz uplink, we will have a working 10GHz downlink to complement it to show rally visitors all about QO100.

The gazebo and table and chairs are being provided by other local  club members, so I don’t need to worry about them!

73 de Sam

G3JVL

I was sorry to receive the news that Mike, G3JVL, has passed away.

I first met Mike back in the 1970s at the Crawley Court, Winchester, Microwave Round tables.

Subsequently, I joined the RSGB Microwave Committe back in the 1980s and Mike was afellow member.

We had a lot of dialogue during those years, Mike made me a 2.3GHz quad loop yagi that I used for many years and then in the 1990s I visited with him and saw his home station. From that I was loaned a small (2.5W) TWTA that I used in my home 3cm station. I had never seen a TWTA with only three (or was it 4?) connections previously. Mike showed me how to use it and I had many long distance QSOs on 3cm,  not only with Mike, but also with many of the other 10GHz narrowband home and portable stations that were around during the 1990s.

I later met Mike, again, when we were both attending the Plano, Texas, Microwave update. I think that was around 2000. Mike was visiting with his daughter who, I recall, lived local in the Plano area of Texas. 

I don’t think I ever saw Mike again. I am sure he continued active to be active on the bands,  but our paths never crossed again. Ioften wondered what he was up to.

I guess I will never know,  now.

Vale Mike.

23cm on the IC9700

I have been busy bringing my IC9700 on-line in place of my 23cm transverter based system.

It is not that straightforward. One of the problems is that the radio is on my operating desk whilst the linear is in the rack. They are either side of a door, so the cable route between them  is about 3m, at shortest. I do have coax and control cables running between the desk and rack. But, it is impractical to run large, low loss cables, so with Ecoflex cable the 10W from the IC9700 is not enough to drive my 200W SSPA to anywhere near full output. In fact just to 80W output. My answer?

I have a now rather elderly twin brick M57763 amplifier with about  30W output, when driven at 400mW. I have turned down the IC9700 to about 5 to 6W output, drive the cable to the twin brick, situated in the rack next to the 200W SSPA and then use a 12V coax relay to separate transmit and receive path. I have a 6dB/10W SMA attenuator in the twin brick input to bring the input down to about 250mW (don’t forget the cable loss). With this arrangement I can drive the main amplifier to around  150-180W output and I have some power control by turning down the IC9700 when required.

I’ve still got to tidy up the cabling, reset power levels and then connect to the dish antenna.

BTW, there’s a lovely bright, near full, moon out there this evening, but it is low in the sky.

Sam

IC9700 progress

I have been conducting more tests on the radio and talking to a number of more experienced RF engineers to get a better ‘handle’ on the transceiver’s performance. I’ve also been using it extensively on air on the three bands during contests, using satellite mode, D Star and FM on repeaters and giving FT8 a good airing on 2m.

My user review for PW is nearly complete and I’m awaiting feedback on the draft from the editor.

I will comment further on some other measurements done on the transceiver a bit later.

Regard this as a place holder!

Sam

RSGB PSC meeting

Just back from an RSGB PSC (propagation studies committee) meeting in Leicester. Just a corresponding memeber, but try to get to one meeting a year. Very enjoyable. Great committee. Serious discussions.

More IC9700 learning

I spent some time on Saturday talking to local SDR/DSP experts and as a result have a much better idea of how the IC9700 works.

I am on a steep learning curve!

I hope to publish my thoughts on this in my blog in due course.

More 9700

No measurements today. I have been reflecting in some of these numbers and measurement techniques.

NPR would be a much better way to test the SDR architecture, but the appropriate filters are not available to me. I used to do NPR measurements on microwave link equipment, so I am familiar with the technique.

I had a first contact using the IC9700 this evening.  Admittedly it was ising the 9700 only on receive on the QO100 satellite. As much as I would have loved to use the transmit side for the uplink, I could not find an 8 pin DIN to connect up the SEND output to drive the transverter and PA, so I had to connect up the FT847 for transmit.

My contact was with G7OCD. Jason was using a Lime  Mini for transmit and receive.