http://www.amateurradio.bz/4_dollar_satellite_antenna.html
Here is a picture of the finished antenna:
Using this antenna, I've made 5-10 attempts to listen to the SO-50 FM repeater satellite, and in each case, I would either hear nothing at all or about 5-10 seconds of good signal around the middle of the pass. I'm using the dual-band Kenwood TM-V71A radio, and have been following all the proper procedures for listening to a satellite, including no squelch and adjusting the frequency for Doppler shift. I haven't tried transmitting to the satellite at all, since I can barely get good reception on the downlink frequency.
I was getting frustrated, and posted the above details on the Amateur Radio Stack Exchange website:
http://ham.stackexchange.com/questions/5195/why-can-i-barely-hear-the-so-50-satellite
One of the users there suggested that I might not be compensating for Doppler shift, and sent me the following link that suggests what increments to use when adjusting the frequency:
http://www.amsat.org/wordpress/wp-content/uploads/2014/01/Work_FM_Sats-20131010.pdf
(see the chart on the last page of the document)
It was at this point that I realized the problem. My radio only adjusts the frequency 25 kHz at a time on the 70 cm band. The SO-50 downlink frequency is 436.795 MHz. My radio will only receive on 436.825 MHz, 436.800 MHz, and 436.775 MHz. At first, I was adjusting across these values for Doppler shift, but wasn't hearing anything at all on 436.825 MHz or 436.775 MHz. I eventually gave up and just left the radio tuned to 436.800 MHz during the entire pass, since it was closest to the actual downlink frequency.
The chart above suggests adjusting the frequency 5 kHz at a time over the duration of the pass. This explains why I was only getting a signal for a few seconds at the middle of the pass. I likely got signal only when the satellite was at the 436.800 MHz point in its Doppler shift range. Adjusting 25 MHz up or down would be over-compensating and skip the signal frequency entirely.
EDIT: I wrote the following paragraphs before I realized that you can change the step frequency setting on the radio. The step frequencies that I mention refer to the default settings.
I did not realize this important detail when I purchased the radio. I bought a dual-band radio specifically because I wanted to do satellite contacts. Upon further research today, I noticed in the manual for the TM-V71A that it comes in three types, K, E and M4. The K and E models will only tune by 25 kHz at a time on 70 cm, but the M4 model will tune 10 KHz at a time. I did not know at the time of purchasing the radio that this would be an issue. I checked, and apparently I have the K model.
If you happen to be considering a purchase of the TM-V71A or any other dual-band radio for the purpose of satellite contacts, pay close attention to the step frequency in the downlink band of the satellite from which you intend to receive a signal.
In conclusion, I guess this means that I can't make satellite contacts with my particular radio. I didn't see any mention of a way to adjust the step frequency, so I assume that I would have to purchase an M4 model, or some other model of dual-band radio.
This is frustrating and disappointing, especially on top of my existing frustration with my coax cable issues for my vertical antenna. There just seem to be so many road blocks and details that you need to know, when just getting into the hobby and deciding what equipment to use. To be honest, it's making me lose interest in amateur radio somewhat, because part of the original appeal is gone, due to my equipment situation. I spent $420 on this radio, and now I can't do some of the things I was hoping to do with it.
EDIT: Good news! I figured out how to change the step frequency setting on my radio! I can now change frequencies in the 70 cm band by 5 kHz at a time. I will attempt more satellite contacts with this new setting and report back with an update.
