[amsat-bb] Re: full duplex w/ 2 HT's

Dobarrows dobarrows at aol.com
Mon Jun 4 08:53:01 PDT 2012

My portable setup using an arrow antenna doesn't use a diplexor or duplexor.

With the setup for 2m uplink, I connect my VX5R to the two meter driven element with a piece of RG-8X.

I connect my Icom IC R10 to the 432 mhz driven element with another piece of RG-8X.  Just turn the radios on,
adjust the frequencies, and wave the antenna around until you hear the satellite on the receive radio.  When I transmit and I can hear my signal in the IC-R10 I know that I may be heard.  If I hear someone else in the downlink, I stop transmitting and wait for another chance

Now note that my IC R10 is not a second HT, but just a receiver.  You should be able to swap in a second HT for the IC R10 with no problem.

Most of the time, I use a better setup by inserting a Down East Microwave preamp between the antenna and the IC R10.  The preamp improves reception on the downlink considerably.  By using a receive only radio with the pre amp, I don't have to worry about accidently transmitting on 432 and burning up the pre amp.  I run the preamp with two six volt lantern batteries in series.

When working a pass, I start with the receiver in usb mode and tuned about 10 mhz higher than the published downlink frequency.  This helps me zero in on the satellite.  When the signal gets better (the squawking noise listening to a FM signal with usb setting gets loud) I switch the receiver to FM and gradually tune down frequency to keep up with the doppler.  I usually don't touch the transmit frequency on the VX 5R.  I just keep it on the published downlink frequency for the whole pass.

73, W8IJ

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