[amsat-bb] Elk Antenna, Midland CT 890 and Full Duplex

Felix Paez ea4gqs at gmail.com
Wed Dec 16 16:59:36 UTC 2015

Hi all,

First of all, thanks for your patience. Still learning!

Well, until few days ago I have been able to do many contacts throught
SO-50 using my Baofeng UV-5R and Elk antenna  in half duplex.

I wanted to go next step and try Full Duplex so I bought a Midland CT 890
Full Duplex handy (129 eur).

I can tell that the Midland receiver seems much better than the Baofeng
one. I have been able to work (still half duplex) even when the satellite
was a few degrees over the horizon. The Baofeng seems much deaf than the
Midland, but this my subjective experience. The measured sensitivities I
got from a review are: 0.179 uV  (12 dB SINAD) in VHF and 0.205 uv (12 dB
SINAD) in UHF but I don’t have the Baofeng values. If somebody has them It
would be nice if you share so we can compare.

I have checked that the Full Duplex mode works by transmiting with it and
at the same time receiving a signal from the Baofeng UV-5R but all this
using the whip antenna that comes with the Midland.

The problem comes when I connect the Elk antenna to it. If I press the PTT
the receiver noise goes to maximum. I tried to make a contact with the
SO-50 but I could not hear anything when I pressed the PTT. All was noise.
I had to disable the Full Duplex and then I was able to make some nice
contacts (EA1JM, CU2ZG…) in half duplex.

So my questions are…

 1.   Is it possible to use a single Log Periodic antenna (only one feed
point) as the Elk to work Full Duplex or two antennas are needed?

2.     In case that it is possible… Would this improve by using separate
receiver and transmitter with a filter that gives a feed point for VHF and
another one for UHF? (the Elk antenna only has a feed point)

I have to make more tests but at first time, It does not seem possible to
use the Midland CT 890 (and maybe other full duplex handys?) with the Elk
antenna in Full Duplex…

Thanks. Any comments are always welcome

Felix EA4GQS

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