[amsat-bb] Enhance your Easy Sat Experience!
Clayton Coleman W5PFG
kayakfishtx at gmail.com
Thu Jan 5 19:42:43 PST 2012
Have you thought about upgrading your station to full-duplex capability?
I realize that many amateurs jump into the satellite fray by utilizing
an existing handheld radio and an antenna like the Arrow, Elk, or
tape-measure beam. It's a great way to get your feet wet and make
that "first" contact via the birds.
Now, let's look at how we can do BETTER.
Full-duplex has a very important purpose in the satellite world. It
allows you, the ground station, to know that your signal is being
received and retransmitted by the satellite. I’m not saying it is a
mandatory but once you see its benefit, you may never want to go
How do you really know you are being heard by the bird if you can't
hear yourself? Answer: You don't.
How do you know another station wasn't already being captured by the
bird and in the middle of a QSO when you transmit? Answer: You don't.
Let's talk about HOW to do full-duplex. First of all, you don't need
base-station radios like the Icom IC-9100, IC-910, Kenwood TS-2000, or
Yaesu FT-847. If you own two handhelds, chances are you have what you
What you need is at least one radio capable of transmitting on the
uplink and one radio capable of receiving on the downlink. For
example using AO-27:
1. A 2m-only HT, set to the satellite's uplink, ~145.85 MHz.
2. A 70cm-only HT, set to the satellite's downlink, ~436.795 MHz.
One added benefit is that while hearing the downlink, you can twist
antennas (like the Arrow) to match polarity and peak your uplink.
Technically you do not even need a radio capable of transmitting to
hear yourself on the downlink. A scanner or pocket receiver works
To get into full-duplex inexpensively, there are numerous options.
You can buy a NEW Baeofeng UV-3R for about $50-60 USD, shipped. This
radio could serve as an uplink or downlink radio, depending on your
need. I’m not peddling these radios but using them as an example.
If you have the Arrow with the built-in diplexer, simply bypass it by
running a patch cord from each radio to the respective UHF and VHF
beams. If you are running an Elk or tape-measure 2m beam, you will
need an inexpensive diplexer to give you both 2m and 70cm feed points.
One can be constructed easily or purchased from numerous vendors for
Give full-duplex a try. You will not only help the satellite
community by eliminating unnecessary hetero-dyning tug-of-war, it will
generally make you sound better on the birds! Oh, and use a pair of
earphones or a headset when you give it a try to avoid feedback.
Here are some more example full-duplex combinations:
Wouxon HT - Downlink
2m only-HT - Uplink
FT-60R - Uplink
Baofeng - Downlink
Handheld scanner - Downlink
Dual-band HT - Uplink
More information about the AMSAT-BB