[amsat-bb] AO-85 and Wouxun KG-UV8D, full-duplex - report (long)

Sun Nov 29 06:24:29 UTC 2015

Hi!

After testing a few different HTs over the past week using some common
settings, I went back to an HT I tried the first weekend we had AO-85 in
orbit and gave it a try with those settings. The Wouxun KG-UV8D, which had
been on the market since early 2014, was a radio that I thought showed some
promise for full-duplex operation with U/V FM satellites. I tried it with
the Fox-1A engineering model at the 2014 ARRL Centennial Convention and
2014 AMSAT Symposium. With some adjustments in how I used the HT, trying to
simulate working a satellite in orbit, I was convinced last year that this
radio would be an option for full-duplex operations with the Fox-1 series
of U/V FM satellites. I held onto the KG-UV8D to try it with a U/V FM
satellite, whichever one was launched and operational first.

Simple question - can the KG-UV8D work AO-85 full-duplex? This was already
answered last month, but I'll answer it again here in a word...

Yes.

This radio is slightly larger than the KG-UV9D I previously wrote about, a
fatter HT when held. It has a menu system like most of the Chinese-made
HTs, including the KG-UV9D which has replaced the KG-UV8D on the market.
There are differences in the menus between the KG-UV8D and KG-UV9D, but I
was able to use the same key settings in each VFO of the KG-UV8D:

Uplink VFO:

STEP (01): 2.5
SQL (02): 9
WN (08): WIDE
T-CTC (16): 67.0

Downlink VFO:

STEP (01): 2.5
SQL (02): 0
WN (08): NARROW

It doesn't matter how each VFO is used. I prefer the upper VFO for the
uplink frequency, but that is not mandatory. I plugged an audio splitter
into the speaker jack, feeding audio to my Sony audio recorder and an
earpiece. Using an earpiece or some sort of earphones is recommended when
using a radio for full-duplex operation, to prevent receive audio from
feeding back into your microphone. With HTs like the KG-UV8D using receive
filtering that is sharper than what is typical in the Icom/Kenwood/Yaesu
HTs, I find that using the smaller tuning steps and making adjustments on
both uplink and downlink frequencies is recommended.

I worked an AO-85 pass Saturday (28 November) afternoon at 2252-2306 UTC,
a 67-degree pass to my west. During that 14-minute pass, half of it (just
over 7 minutes) saw the satellite at or over 20 degrees elevation, which
I found last month as my "magic number" when trying to work AO-85 with
less transmit power - like we have with HTs. What was interesting about
this pass is that I could quickly change the downlink signal from good
copy to poor with a slight twist of my antenna. When I first tried
transmitting to AO-85, and if I wasn't lined up with the downlink, I
would hear some additional noise and - at some points - it sounded like
mixing that yielded the local National Weather Service radio station in
my ear. Around the midpoint of the pass, the mixing was not present, but
I could tell that the downlink would quickly degrade if I didn't have
the antenna lined up with the downlink. I started with 145.980 MHz as my
downlink frequency, and during the pass tuned down to 145.9875 and then
145.975 MHz for the last part of the pass. These adjustments were the
only times I needed to switch VFOs during the pass.

Not many were on the pass, and I was able to work everyone I heard on the
pass. John K8YSE/7 was on as the satellite came up from my northwest, and
he was joined by a few others - Wyatt AC0RA in Iowa, Frank K4FEG in
Tennessee, Ed N7EC north of Phoenix, and Ron N8RO in Texas. As I was using
the KG-UV8D and Elk to work these stations, my SDRplay SDR receiver with an
8-inch Windows 10 tablet and HDSDR connected to my AMSAT-UK VHF crossed
dipole was making an RF recording of the AO-85 downlink. The RF recording,
along with the MP3 audio I recorded from the HT and other files, have been
uploaded to my Dropbox space at http://dropbox.wd9ewk.net/ (look for the
folder "20151129-AO85_Fox1A-DM43" and the recordings with names having the
time around 2250 UTC).

Even after this test of using the KG-UV8D to work AO-85, I won't change my
ranking of the Chinese-made HTs I have tried with this satellite:

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

Wouxun learned from the issues with the receiver in the KG-UV8D, leading to
the improvements I saw using the KG-UV9D on comparable AO-85 passes. If the
receiver didn't have the extra noise and mixing taking place when the AO-85
downlink wasn't strong, this could have been tied with the AnyTone TERMN-8R
for second on my list. The issues I heard with the KG-UV8D receiver, on the
other hand, are not as bad as what I heard from the Puxing PX-UV973 - a
small benefit, but still (in my opinion) a reason to rate the KG-UV8D above
the PX-UV973.

When I saw that the KG-UV8D was able to work AO-85 full-duplex last month,
that vindicated my comments last year after testing it against the Fox-1A
engineering model. At the same time disproved some comments I saw on the
QRZ.com satellite forum from 18 months ago like:

"... the '8D - like the Puxing UV973 - although are true dual-receive
units, that they are not suitable for U/V nor V/U sat ops ... Considering
Alinco couldn't accomplish that with a $250 HT, I wasn't really surprised
that these $100 units couldn't do it."

I have seen similar comments to the above in other forums, and in
reference to other dual-band HTs that I have recently tested against
AO-85.

This ignores the fact that before AO-85, the last time we had a U/V FM
satellite (excluding the ISS U/V cross-band voice repeater) was SO-35,
which went silent in 2001. Unless you went rogue and used an HT on a U/V
transponder, there wasn't a satellite that could be used for a true real-
world test of this HT like I have done with AO-85. As for the reference to
the DJ-G7T, that radio arrived on the ham market in 2009, 5 years before
the KG-UV8D, and what Alinco was (or wasn't) able to do with the DJ-G7T
really isn't relevant to what Wouxun did with the KG-UV8D. Even though none
of the Chinese-made HTs I tested are able to work V/U FM satellites like
SO-50 and LilacSat-2 full-duplex due to receiver desense, Wouxun certainly
learned lessons and improved the receiver from the KG-UV8D to the KG-UV9D.

After these tests, I have used 5 different HTs and an Icom IC-2820H 2m/70cm
FM mobile radio to make QSOs via AO-85 in the past 7 weeks. It has been fun
to try these radios out with similar settings. Having this knowledge helps
to answer questions I get via e-mail, in online forums, and at events where
I represent AMSAT (i.e., hamfests). After the initial disappointment that
HTs would not be able to work this satellite from AOS to LOS, I think it
should be clear that HTs are a viable option for working AO-85 during
portions of higher passes. Working a U/V FM satellite is different than the
V/U FM satellites most have been familiar with, but there are now a few
options for using a single handheld radio to work AO-85 full-duplex - and a
two-radio setup remains a viable option for full-duplex operation.

73!

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