[amsat-bb] Icom IC-W32a, Heil Mic, Arrow SMA Diplexer, AMSAT magazines ...

Patrick STODDARD (WD9EWK/VA7EWK) amsat-bb at wd9ewk.net
Thu Apr 7 23:28:52 UTC 2016


It is nice to see that you are selling equipment to help a couple of
organizations. Since you are using this list to promote your auction, I
felt it was appropriate to question the listing for one of the items in
your auction here.

One of the items in your auction is a Puxing PX-UV973 2m/70cm FM HT. In the
listing for that radio, you say that this "was the first of the recent crop
of Chinese HTs to actually perform well in true, full-duplex mode for
working V/U FM ham satellites."


Huh? Maybe when used with another radio, but certainly not by itself on
SO-50 or LilacSat-2, our current V/U FM satellites.

Near the end of summer 2013, you ordered and received a PX-UV973. You
mentioned this on a mailing list for the PX-UV973 at that time:


When you were working for another importer of the PX-UV973 in late 2013 and
early 2014, a few months after you received your first PX-UV973, you were
asked about its full-duplex performance on SO-50 in a thread on the eHam
satellite forum:


Your response to one question in the thread was:

"Is is an excellent performer as a true dual-receive unit ... great
second unit to work full-duplex."

I think you may have been going for "It is an excellent performer as a true
dual-receive unit", which is not the same as an endorsement of this
radio's performance for V/U FM satellites. I pointed out in that thread the
fact there are many dual-band HTs with dual-receive capabilities,
which is different than cross-band full-duplex operation. You later
responded to one of my posts in that thread about its full-duplex
performance on SO-50 with:

"Tentatively, I am not pleased with that mode on the UV973."

And now you are saying the PX-UV973 performs well with V/U FM satellites?

I bought a PX-UV973 last summer, and tried it with FM satellites over the
past few months. Although it could work AO-85 full-duplex, it was the worst
performer of the 4 Chinese-made dual-band HTs I tried during the few weeks
after AO-85 was launched - and AO-85 is a U/V FM satellite. A recap of
those reports I posted on the AMSAT-BB list is available at:


An article about my tests with these radios working AO-85 full-duplex will
appear in the March/April 2016 AMSAT Journal. I have also tried the
PX-UV973 with SO-50 and LilacSat-2, and it - like the other 3 Chinese-made
HTs I tried with AO-85 last fall - was incapable of working either of those
two V/U FM satellites full-duplex.

The PX-UV973, like those other 3 Chinese-made dual-band HTs, might do
better with V/U FM satellites if the downlinks were much stronger than what
we have from SO-50 and LilacSat-2. I'm not sure that AO-27's downlink would
have been strong enough to overcome the 70cm receiver desense when
transmitting on 2m. It might have taken AO-51's 70cm downlink running at
much more than milliwatt power to overcome the 70cm receiver desense when
transmitting on 2m. The ISS cross-band repeater was rarely on in V/U mode,
and hasn't been on in several years. Maybe this would have been a
"satellite" where the PX-UV973 and other radios could work V/U full-duplex
successfully, given its higher transmit power than our other FM satellites
in the recent past.

Unfortunately, with the current crop of V/U FM satellites, the PX-UV973 is
just not up to the task of full-duplex operation without the use of a
second radio. Its performance may be acceptable for non-satellite work on
terrestrial repeaters, as a cross-band repeater when dealing with signals
much stronger than satellite downlinks, or as one of two radios for a full-
duplex V/U FM satellite station, but that's not what is in the auction
listing. Listing it as a radio that performs well with V/U FM satellites
isn't accurate - or I am sure we would have heard from you a couple of
years ago about the performance of this radio on SO-50.


Twitter: @WD9EWK

On Thu, Apr 7, 2016 at 5:44 AM, Clint Bradford <clintbradford at mac.com>

> The list of items up for an auction that benefits two humanitarian
> organizations is growing ...
> ​<snip>​

> Puxing UV973 Dual-band, true full-duplex HT
> Crossband repeater, too!

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