[amsat-bb] Duplex HTs vs 2 Simplex HTs

John Kopala jkopala at gmail.com
Tue Jul 27 10:05:44 PDT 2010

Another thought about Duplex HT for Satellite.

A few full duplex HTs are equipped with 2 tuning knobs which allow tuning either the primary band or the secondary without having to change bands.  This is a great feature for satellite doppler tuning with a UHF downlink.  Alternatively, I have chosen to use 2 HTs for satellite work to enable tuning the doppler on the downlink and uplink without any extra steps.  This also eliminates the need for a duplexer.  In my case, this is somewhat of an overkill, because I am using 2 Full Duplex Yaesu FT-470 radios, each on a single band.  But this also allows me to be tuning the downlink doppler while transmitting on the uplink.  Most radios will only allow you to tune the active band, requiring you to switch back and forth every time you need to tune the UHF downlink.  Typically, AO-51 requires 5 tuning steps on the downlink for many passes.

With satellites such as AO-51, I have found that with a good antenna and no obstructions, you can pretty much work the satellite from horizon to horizon.  I have made a home brew version of the arrow antenna (with arrows for easy assembly / disassembly for travel and storage) with 4 elements on 2 meters and 9 elements on 70 cm.  That being the case, I have also chosen to use a tripod and constructed a tripod mount to hold the 2 HTs, a voice recorder, and mount the antenna on a hinged support so that it can be rotated to allow for satellite polarity.  For anyone who hasn't already discovered it, the downlink works best with vertical polarization for most satellites.

A picture of my portable satellite setup can be seen on QRZ at N7JK.

Good luck on the birds,
John Kopala

> From: Randy Hall <listk7age at gmail.com>
> Subject: [amsat-bb]  Duplex HTs
> To: AMSAT-BB at amsat.org
> Message-ID:
> 	<AANLkTi=t-aK6AYop2sEqyrhkwT2bR3wcgVWZENjQu4uR at mail.gmail.com>
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> Hi

> I receive emails all time from guys looking for HTs to use on AO-51.
> Many want duplex HTs to allow them to hear themselves coming back from
> the satellite.

> So, what of the current HTs provide duplex operation?

> Which of the older HTs do duplex. I know my trusty FT-51 does!

> Plus as a bonus, any of these come with BNC connector anymore?  I
> really do not like SMAs on my radios.

> Thanks

> Randy

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