Satgen349  Operating Fo20 Mode JA Pt4     by GM4IHJ            2 Dec 95

You can get good contacts on Fo20 using simple quarter wave receiving and
transmitting antennas, but if you want real DX, you need a highly
directional yagi receiving antenna. But a long yagi has a narrow beam and
if you are not within 10 degrees of the satellites azimuth bearing, you
will hear very little. Equiped with a computer and suitable tracking
software you should be able to shift the antenna rotatator every two
minutes or so in order to stay within 5 degrees of the satellite, better
still if you have automatic computer tracking you should have no trouble
at all, provided your software Keplerian elements are up to date. Out of
date Keplers are much more dangerous with Fo20 than they would be with a
mode A satellite.

Your transmitting system is a matter of choice . A 25 watt transmitter
feeding a quarter wave antenna will get you contacts. Fo20 is very
sensitive. But you do sometimes meet a combination of Faraday rotation of
the 2m uplink and/or awkward attitude of the satellite which can reduce
your uplink access and downlink reception quality for several minutes
during a satellite pass. So a 5 element yagi can be very useful for your
uplink provided you have azimuth rotation . Given a 5 element yagi and a
10 watt transmitter, you should have no difficulty at all if you are using
CW modulation. If however you are using SSB you will find 25 watts is
needed at times to make yourself heard. Uplink on SSB must be on LSB Lower
Sideband to allow for Fo20s subtractive transponder mixer, and this
produces an Upper Sideband signal on the downlink.

QSOs on Fo20 SSB are not easy for beginners. You can start by sitting on a
frequency and calling CQ, making the other stations tune to you. But
sooner or later if you want DX contacts you must go looking for other
stations and tune onto them. This is the difficult bit, and there are two
basic ways to do it. The impolite method , has you tune his signal on your
receiver , then immediately take a guess at your corresponding transmitter
uplink requirement, and start calling him on SSB or worst still start
whistling and tuning your Tx until you finally get on tune having QRM'd
him for perhaps 20 or 30 seconds. Polite people by contrast shift their Tx
to CW and switch their clarifier on to give a Tx offset of about 2 KHz
high. A quick dot on the key tells you how far you are off his tuning
point and you adjust Tx tuning to zero beat your very brief CW. Once you
are zero beat you switch off your clarifier and switch your modulation to
LSB. Then waiting for a break in his transmission you transmit on voice.
If you got the clarifier offset right you should be exactly on tune on
SSB. You can of course practice this well clear of anyone else signals by
deliberately checking this switch tuning on different clear Rx frequencies

>From then on you can proceed with your QSO, tuning your Tx to keep your
audio on the same downlink frequency . Some people have in the past
advised tuning your Rx not your Tx, but this can result in you gradually
wandering into other peoples QSOs. You will of course find that at times
the other man is drifting away from you. This will be least if he too is a
Tx tuner. It is unavoidable because his doppler rate of change is often
different from yours, but the problem is made worse if in this situation ,
he simply tunes his Rx.