Receiving SSTV From ARISS Using Moxon Yagi at Fixed Azimuth and Elevation

Receiving SSTV From ARISS Using Moxon Yagi at Fixed Azimuth and Elevation

Yesterday I had posted my attempt at receiving SSTV from International Space Station using my Omnidirectional VHF Antenna without Doppler correction. Today I have attempted receiving SSTV using my Moxon Dual bander Yagi kept at fixed elevation, in the direction of the maximum elevation of the pass. But as my antenna tilting mechanism did not work, it was pointing slightly downwards instead of towards the sky! I used manual Doppler correction in the radio. Antenna tracking was not possible as it was a fixed external antenna without a rotator and I was in the shack using my base station. Anyway the images were much better than yesterday because of the directional antenna.

This was inspite of the fact that it was a 64 degree pass yesterday while it was only a 14 degree pass today. Even a fixed directional antenna fares better than a vertical omnidirectional antenna in this case. But my Moxon Yagi will have a fairly good beam width as it has only two VHF elements, the Moxon driven element and the Moxon reflector. Remaining five elements are UHF elements which couple passively to the VHF driven element for use on voice transponders. If my antenna could have been placed at least 10 degrees upwards, I would have received a much better picture.

This is the image I received yesterday with omnidirectional antenna and no Doppler correction. Only part of the image was received.

Here is the video recording of the image being received today, in my mobile phone kept near the loud speaker of the radio with Robot 36 app decocoding the image from the audio received. I had to change the frequency once during the recording according to the live display on Argentinian Amsat website. As my radio has only steps of 5 kHz, the Doppler tuning was not very accurate. The website displays in steps of 10 Hz! I tried decoding once again from the audio recorded in this video. But there is was no improvement in picture quality, possibly because of low signal strength from a low elevation pass and intermittent noise pickup. Moreover, the antenna was in a fixed position and not tracking the pass of the satellite, all needed for receiving good pictures. If I had a handy and a hand held antenna, results would have been much better, I presume. Yesterday’s pass would have given excellent images if received from outdoors in that case. Many of my peers have posted excellent quality images to our group chat.