[amsat-bb] AO-92's 1.2 GHz uplink, last Sunday

Patrick STODDARD (WD9EWK/VA7EWK) amsat-bb at wd9ewk.net
Thu Feb 8 16:28:21 UTC 2018


Hi!

I have been busy this week, and haven't been able to finish this sooner.
Better late than never...

Having the 1.2 GHz uplink active on AO-92 last Sunday was fun! I tried to
work
4 different passes, heard myself on one of the two morning passes, and
worked
stations on the two passes in the evening. It was fun to dust off a radio
and
some antennas for the uplink, and end up with a few QSOs by the end of the
evening.

The first of the 4 passes was a nice 25-degree pass Sunday morning at 1638
UTC.
To avoid the houses and other things around my house, I went to a city park
on
the DM33/DM43 grid boundary. This was my setup:

TX: Alinco DJ-G7T @ 1W, Diamond RH951S 2m/70cm/23cm whip (on Diamond
BNCJ-SMAP
    adapter)
RX: Kenwood TH-D74, Elk Antennas handheld 2m/70cm log periodic

The 145.880 MHz downlink was easy to hear, of course, but I never heard
myself
through the satellite. Between using an omni antenna on my uplink and
playing
whack-a-mole trying to find the right uplink frequency, I was a spectator.
With
the next pass 90 minutes away, I went home to regroup.

Before the second pass, I went looking through some boxes for more stuff I
could
use for the L-band uplink. I found a very old Comet CY-1205 5-element Yagi
for
the 1.2 GHz band. This antenna has a BNC connector on the bottom of the
driven
element, and was originally sold in two versions (BNC and TNC connectors)
to
be compatible with the radios available in the early 1990s. The listed gain
for
the CY-1205 is 11.0 dBi, which was an improvement over the 5.5 dBi gain for
the
Diamond RH951S whip used earlier. Gain figures aside, a directional antenna
should be a better performer than an omni antenna for satellite work - even
a directional antenna sitting on top of the radio.

The last pass for the morning was at 1812 UTC, to the west. It was lower,
with
maximum elevation of 14.4 degrees. I went outside with a slightly different
setup...

TX: Alinco DJ-G7T @ 1W, Comet CY-1205 5-element Yagi (on Diamond BNCJ-SMAP
adapter)
RX: Kenwood TH-D74, MFJ-1717 2m/70cm long duckie

For a few minutes, there was no activity on the downlink, and I heard the
voice
ID followed by more static. Around 1817 UTC, I heard the downlink come on,
and
Tom N6NUG in San Diego appeared. Now I was trying to find a combination of
uplink
frequency and antenna orientation to hear my signals through AO-92. I
finally
did, around 1818 UTC when the satellite was just under 14 degrees
elevation. By
that point N6NUG was nowhere to be heard. I heard later that N6NUG's 1.2
GHz
setup was for terrestrial operation, and he wasn't able to catch up with
the
satellite after the point I heard him. I was able to get through a couple
of
times, and this gave me encouragement for at least one of the two passes
coming
up in the evening.

For the evening, I saw a couple of passes - a shallow 7-degree pass at 0314
UTC,
followed by a 61.4 degree pass around 0445 UTC. From home, I didn't think
the 7-
degree pass would be a good one to try. I drove to a rest area along I-17
about
50 miles north of Phoenix, a location I use for low eastern passes. One
problem
there - all parking spaces at the south end of the rest area, the highest
part
of that location, were occupied. I think people, and especially truck
drivers,
were taking a break for the end of the Super Bowl game. I have never seen
that
rest area that full of cars and trucks, and went back to I-17. Ten miles
further
north, there is a junction for the AZ-69 highway to Prescott. I did not go
up
AZ-69, instead parking in a large lot on the east side of the freeway
behind a
McDonald's near the interchange. This spot, in grid DM34wh, turned out to
be a
good spot.

For the evening passes, I used the following setup:

TX: Alinco DJ-G7T @ 1W, Comet CY-1205 5-element Yagi (on Diamond BNCJ-SMAP
adapter)
RX: Kenwood TH-D74, Elk Antennas handheld 2m/70cm log periodic

I recorded these passes using the audio recorder function in the TH-D74,
which
stores the audio as WAV files with the time (hour/minute/second) the
recording
started in the file name - helpful to know when in each pass different
events
happened.

The first pass at 0314 UTC was very low to the east. I thought it would
clear the
hills east of the freeway, and I was able to hear the downlink about 30 to
40
seconds after the predicted AOS time. I heard a few stations, and I started
trying
to get through. A couple of minutes into the pass, I was able to hear
myself. Glenn
AA5PK in west Texas also heard me, and gave me a quick call. At this point,
AO-92
was almost at the midpoint of the pass, with elevation around 6 degrees. I
was
getting through! Jeff WB8RJY in Michigan also heard me, and gave me a call.
Now
the satellite was at its highest, just under 7 degrees elevation. Alan
WA4SCA also
called me, but I was not able to get back to him before LOS.

>From comments I saw online during the day, it was apparent that the nominal
uplink
frequency was higher than the published 1267.350 MHz. Most reports placed
it about
8 kHz or so higher than that. With my DJ-G7T and its 5 kHz tuning, I went
with
1267.360 MHz as the nominal uplink, and that helped to get through.

For the last pass of the evening at 0445 UTC, things started out well. I
heard
Jerry N0JY initially. Between tuning and twisting my HT/antenna
combination, I
wasn't able to get lined up in time for a QSO with him. I was eventually
able to
get through, and after a few minutes Greg KO6TH in northern California
appeared.
We started to chat slowly, mainly due to my need to tune and move the radio
around
to get each transmission through the satellite. During this time, AD5MT in
southern
California appeared. I made a quick QSO with AD5MT, but KO6TH wasn't able
to do
that. No other stations showed up during the pass, which allowed KO6TH and
me to
call out our uplink frequencies and the satellite's elevation on its way to
LOS.

I put the audio, pictures, and other files related to all of this in a
couple of
folders in my Dropbox space at http://dropbox.wd9ewk.net/ . Files from the
two
morning passes are available in the "20180204-AO92" folder, and files from
the
two evening passes are available in the "20180205-AO92" folder. Each of
those
folders has a PDF file with a 2008 article from CQ VHF magazine by Kent
Britain
WA5VJB for smaller 1.2 GHz Yagis with 4, 6, or 10 elements. The 4-element
Yagi
might be enough with a 1W HT to use the AO-92 1.2 GHz uplink. Since I was
able to
get through with a 5-element Yagi, it seems like the 6- and 10-element
versions
in the article should be good options for 1.2 GHz and AO-92.

Looking forward to more time to use 1.2 GHz...

73!




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


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