Working the Russian RS-12 Satellite

The RS-12 up-link band is 21.210 to 21.250 Megahertz and is translated by the satellite to the down-link band of 29.410 to 29.450 Megaherts.

When you use one transceiver, you either have to use an antenna switch or the antenna has to work on both up-link and down-link frequencies.

Operating takes a little practice. I set the radio for SPLIT so that the receive and transmit frequencies can be different. I tune in the station on 29.4 MHz I want to call. Then I switch to 21.2 MHz and hit the transmit button and (without talking) tune to the corresponding up-link frequency, then call. e.g. 29.440 compares to 21.240. If I call CQ, this of course is reversed.

As the satellite passes you have to retune the receive frequency due to doppler shift. Don't change the transmit frequency. That's the other guy's problem. Doppler: Remember? That's what made the Good Humor man's music box keep changing key while you asked mom for a quarter. If the pitch was falling, it was too late.

My antenna is an inverted vee tuned for 4.242 MHz. That's right. It is a center-fed half-wave at 4.242 MHz. But it's a center-fed, 5 half waves at 21.210 MHz. Not only that, it is a center-fed, 7 half-waves at 29.694 MHz, close enough to do a good job receiving the down-link.

Making the antenna length odd multiples of the desired frequencies puts one of the half-waves in the center of the antenna so that the feedpoint is at a current loop. And since it's an inverted vee it comes close to matching 52-ohm coaxial cable.

Using the formula ...

    Half-wave (Feet) = _____492_____
			4.242 (MHz)

the total starting length of the antenna is 115 feet. Then when I trimmed the antenna for resonance at 21.210 MHz, it ended up at 112 feet.