Category Archives: WSJT

A big Dish, a big Bird and a big Signal

January 6th, 2015

Jan, PA3FXB, and I skeduled a very special ISCAT test on 23 cm for today. The CAMRAS team had planned to operate PI9CAM with the 25 m radiotelescope in Dwingeloo for some astronomical experiments this afternoon. Before starting with that, we used an ISS pass with low elevation to try ISS bounce with the big dish. Such a pass ensures slow variation of azimuth end elevation angles, which is essential to track moving object like the ISS (or other spacecrafts in low orbits) with an antenna of a weight of 120 tons.

DSC_0384aWe had very strong reflections right from the beginning, but no decodes. Maybe the signal level was to high? This has to be investigated. Then we changed to aircraft scatter, although the dish had to be kept elevated at 10° by safety reasons, I got strong reflections from airplanes quite close to PI9CAM. Not as strong as from the ISS, but decodable now and it was possible to work in CW too.

Despite the fact, we had no QSO via ISS bounce, we learnt, that it is possible to track objects in low orbits with the 25 m radiotelescope, as long as the elevation keeps low. This opens up a perspective to make use of other spacecrafts as reflectors.

ISS Bounce again: now in ISCAT

January 4th, 2015

Jan, PA3FXB, and I were discussing the use of digimodes on ISS bounce for quite a while. Today we tried it with ISCAT-B and were successful with the first shot. As in the tests with Ronald, ON7FLY, on AS, we used 15 seconds periods.

 

From the moment on, traces could be seen in the waterfall diagram, decodes were possible.

2015-01-04 12_14_58-

When the ISS culmiated and the variation of the dopplershift was fastest, the frequency correction came to its limits. But while I am used to ISCAT in the meantime, I needed no decodes to hear, that Jan was transmitting RRRRs.

 

At least I decoded a 73 from him. The experiences with ISCAT in ISS bounce are very promising, although the 15 seconds periods are too long. So we have to discuss it and try with shorter ones.2015-01-04 ISCAT QSO

ISCAT – a new experience

January 3rd, 2015

Inspired by an article, published by Rex, VK7MO, and David, VK3HZ, in the latest DUBUS [1], Ronald, ON7FLY, and I performed a first test in using ISCAT-B mode (by K1JT) for aircraft scatter on 23 cm. When looking on AirScout it doesn´t seem to be very challenging to have an QSO. But Ronald is obstructed by a hill in eastern directions and he didn´t expect to have an opportunity to work eastwards on 23 cm at all.

2014-12-27 16_37_03-AirScout - ON7FLYRonald is located in JO10LT and the distance is just 388 km. He uses a 44 element yagi with only 2 W at the feedpoint. On my side a 3 m dish and 150 W are in use. First of all we tried in SSB and were able to complete a QSO after a while. I could copy ON7FLY very weak, but readable. Then we tried in ISCAT-B with 30 seconds periods and it was amazing to see, that Ronald´s signal could be decoded even when only traces appeared in the spectrum.

2015-01-02 15_28_46-His signal can be seen in the center section (The drop outs are reactions of the AGC on radar noise). The above sequence could be decoded to:

2015-01-02 15_29_22-Since the periods of 30 seconds were far too long, we needed certain airplanes to complete. then we tried FSK441 with no decodes and switched to JT6M and completed the third QSO. In the meantime I found a hint in the above mentioned article, how to reduce the T/R periods to 15 seconds. So we completed a fourth QSO in ISCAT-B again in shortest time: 2015-01-02 18_02_00-

 

[1] Rex Moncur, VK7MO, David Smith, VK3HZ, Aircraft Scatter on 10 and 24 GHz using ISCAT: DUBUS Vol. 43 4/2014

Digital World – Digital Moon

March 11th, 2013

Despite all the discussions about using digital modes in moonbounce I want to gather own experiences. After installing WSJT last Xmas I could decode a couple of stations on EME without any problems. First TX tests resulted in an intolerable frequency drift, which could be limited with the installation of a crystal heater. Then I started with real tests, but in all skeds no one could decode me! I had no clue what went wrong. So I changed – quick and dirty – the PC producing the audio stream. Now OK1CS, HB9Q and G4CCH could be worked in JT65C. Last sunday morning I saw a big signal in the waterfall diagram of my SDR. It was JA6AHB and it was a question of a few minutes to put him to the log. All stations worked so far, have been audible in my headphones.

I think, in general it is nice to use digital modes to work others via EME. But there is much more skill in involving the ears to have success in completing an QSO. It´s always great to HEAR the final rogers. Despite that I will not deny the use of digital modes. Why not working someone digital and then, maybe after some improvements, top it in working him in CW again? As long as all information like callsigns, reports and rogers, necessary for a complete QSO, have passed the radio channel, it will be a valid QSO. This is my position.

I will continue to explore digital modes:

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The TX signal will be processed on my FT-987 with a seperate PC. RX is done with my SDR and another PC. By not typing in the other callsign or using call3.txt on the RX side I am quite sure in ‘really’ receiving the callsigns.