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

[Patrick STODDARD (WD9EWK/VA7EWK)]

Hola, Felix!

Your Midland CT-890 is very similar to the Wouxun KG-UV8D HT,
which has been on sale in much of the world for the past year
and a half. I have not seen the CT-890 here, but I'll offer
some answers to your questions based on the thought that these
radios are very similar, if not the same, but sold with different
model numbers...

1. Yes, you can use a log periodic antenna to work satellites
full-duplex using your CT-890, but not SO-50. The HT's 70cm
receiver is desensed when you transmit on 2m, and this happens
when using other antennas as well. You may be able to work
the new AO-85 satellite full-duplex with this HT, as you
would transmit to AO-85 on 70cm instead of 2m, and avoid
the internal desense issues you experienced when transmitting
to SO-50 on 2m. This is a common issue with a few of the
Chinese-made dual-band HTs that are advertised as having
full-duplex capabilities.

2. A separate receiver and transmitter for SO-50 should let
you work SO-50 full-duplex. You could use the Baofeng HT as
your transmit radio, and use the better receiver in your
CT-890 to hear the satellite downlink. This should also work
for LilacSat-2 (2m uplink, 70cm downlink) and AO-85 - but
you may be able to work AO-85 full-duplex with just your
CT-890.

I had written about my experiences using my KG-UV8D to work
AO-85 full-duplex in a couple of posts to this list in
October and November:

http://amsat.org/pipermail/amsat-bb/2015-October/055462.html
http://amsat.org/pipermail/amsat-bb/2015-November/056254.html

You can also read about my tests with a few other HTs with
AO-85 from another AMSAT-BB post I made early this month:

http://amsat.org/pipermail/amsat-bb/2015-December/056269.html

You may find these posts useful, as you work with your new
CT-890.

Buena suerte, y 73!!




Patrick WD9EWK/VA7EWK
http://www.wd9ewk.net/
Twitter: @WD9EWK



On Wed, Dec 16, 2015 at 9:59 AM, Felix Paez <ea4gqs at gmail.com> wrote:

> 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).
>
 ​
​<snip>​



> 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…
>
>
>