[amsat-bb] Review of HTs for sat use

Patrick STODDARD (WD9EWK/VA7EWK) amsat-bb at wd9ewk.net
Thu Sep 22 02:01:28 UTC 2016


Looking over the article, I now see that I didn't elaborate on
why none of these HTs were suitable for full-duplex operation on
V/U FM satellites like SO-50 and LilacSat-2. It's a simple reason,
unfortunately: the 2m transmitter in these radios desenses the 70cm
receiver, when trying to hear the weak downlinks from our satellites.
These radios are fine for full-duplex when transmitting on 2m, if the
70cm signal is much stronger than our satellite downlinks. Unfortunately,
that's not what we have at this time. It doesn't matter which antenna
you use with these radios, and whether or not you have diplexers
connected to the HT.

Using another HT with one of the Chinese-made HTs I mention in
the article would be one way to have a full-duplex station to work
V/U FM satellites like our current SO-50 and (when it is active)
LilacSat-2. SO-50's downlink in particular is a tough one for these
radios, as the 436.795 MHz (+/-) frequency is only a few hundred
kHz above the 3rd harmonic of the 145.850 MHz uplink. Many 2m/70cm
FM mobile transceivers can handle this, but only TH-D72A in terms of
HTs in current (for now) production.


Twitter: @WD9EWK

On Thu, Sep 22, 2016 at 1:46 AM, James Austin <ka2rvo at gmail.com> wrote:

> What was the problem with the Chinese HT's working full duplex in the V/U
> modes. I don't recall that being mentioned in the article.
> Jim/KA2RVO

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