[amsat-bb] AO-85 and Puxing PX-UV973, full-duplex - report (not so long)

[Patrick STODDARD (WD9EWK/VA7EWK)]

Hi!

Another day, another radio to try on AO-85. I woke up early, and decided to
try another HT on a high AO-85 pass starting at 1350 UTC. I wanted to see
if it could work the satellite full-duplex. The radio, this morning: the
Puxing PX-UV973. After working AO-85 with it this morning, my (low)
expectations were met.

The Puxing PX-UV973 has been on the market a couple of years. It is
supposed to handle cross-band full-duplex operation. This radio is still in
production, and I picked mine up from Amazon for about US$ 78. It is less
expensive than the other radios I have tested so far for full-duplex
operation on AO-85, and it shows.

First, the simple question. Can the PX-UV973 work AO-85 full-duplex?

Yes, more or less.

The radio comes with a duckie antenna, and a 7.4V/1200mAh battery pack. The
battery pack is smaller than the standard packs supplied with the other HTs
I have tested so far. It is also a little bit smaller than the other HTs.
As with the others, I did not program any memory channels to work AO-85. I
used the two VFOs, putting the uplink into the upper (A) VFO, and the
downlink into the lower (B) VFO. Uplink and downlink can be done from
either VFO.

I used these VFO-specific settings with this radio, similar to what I have
been using with the other HTs:

Uplink VFO:

SQL (005): 9
N/W (014): WIDE
T-CDC? (019): 67.0
STEP ? (020): 2.50

Downlink VFO:

SQL (005): 0
N/W (014): NARROW
STEP ? (020): 2.50

Another setting I had to enable for full-duplex operation was:

DUPLEX (031): ON

With the smaller tuning steps, I could get the AO-85 downlink lined up
easily on my PX-UV973. It was about 5 minutes into the pass before I made
my first QSO, with Glenn AA5PK in west Texas. A couple of minutes later, I
made another quick QSO with Ed N7EC north of the Phoenix area. The receive
audio while I transmitted was not really good - despite the satellite's
elevation heading up to 56 degrees at the midpoint of the pass. The HT was
able to operate full-duplex, but the other HTs I have tested with AO-85
have done much better. I could still hear myself through AO-85 a couple of
minutes after these QSOs, until the trees in a neighbor's yard started to
make it tougher to hear. The CW beacon from XW-2F was also starting to
overlap with the AO-85 downlink, also.

Using my SDR receive setup (SDRplay receiver, HDSDR on an 8-inch Windows 10
tablet, AMSAT-UK VHF crossed dipole), my transmitted audio sounded OK. Not
loud, but it was fine - similar to what I've heard from the other Chinese-
made HTs I have tested. I have uploaded the audio recording I made from the
HT, the RF recording from the SDR receive setup, and some photos, to my
Dropbox space. You can get those files at http://dropbox.wd9ewk.net/ - look
for the folder "20151127-AO85_Fox1A_XW2F-DM43". I also heard XW-2F near the
end of the AO-85 pass, and I let HDSDR continue writing the RF recording to
cover XW-2F until its LOS.

Since the PX-UV973 has been on the market for a couple of years, I did not
have high expectations for it working AO-85 full-duplex. I was not
surprised to see that it was a poor performer. If I had to rank this with
the other 3 Chinese-made HTs I previously tested, this one would be at the
bottom of the list by default:

1. Wouxun KG-UV9D
2. AnyTone TERMN-8R
3. Wouxun KG-UV8D
4. Puxing PX-UV973

Don't be drawn in by the low price of the PX-UV973. If you already have it,
it can be used as one radio of a two-radio setup, probably as the uplink
radio. Or use it for terrestrial repeaters, where it would probably serve
that purpose adequately. I now understand why one dealer was hesitant to
offer an opinion about this radio's performance for FM satellite work, when
I asked about it early last year.

73!





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