| Carasat Field Day 2004 Photos by Ed Cabic & Jon Wilson (JW) 6/26-27/2004 |
Report by Ed N2EC
What A Difference A Year Makes
Last year we did most of our operation on AO-40 that had a high Molniya-type orbit where it appeared to hover for hours at the top of its orbit. It was easy to "find" ourselves on the bird during this long period of time and to make 28 contacts.
This year AO-40 was not available. We had to try to make contact with the low earth orbital (LEO) satellites including the International Space Station (ISS). The passes for these satellites vary from about 6 to 14 minutes. During this brief time we have to first hear the beacon to make sure the bird is there and then try to "find" ourselves (i.e. to hear ourselves on the downlink as we send a test signal up on the uplink). For most of the LEO passes that we tried, we were not able to hear ourselves, let alone make a contact.
Friday Setup
Art and Ed were out Friday afternoon to set up the tent and the
antenna.
SSTV
Our first task of the day on Saturday was to make a Slow Scan TV (SSTV)
contact on a sked at 2:30 with W3GR the Historical Electronics Museum ARC on
10 meters. This was a first for us -- we had never used our MixW software to
receive a SSTV image. As Murphy’s law dictates we were not receiving a
complete transmission. The operator there was Les WR3X who was very helpful
with us. He continued to send the image and to make suggestions on what we
might do. He had us try a couple of SSTV receiving modes, but we were never
able to receive a complete image because of the "static" that
would always appear in the image as it was being received. We now believe
the problem was that there was too much interference from the 10 meter
transmissions on our HF stations as well as the GOTA station. Also we were
not using the decoding program MMSSTV ver. 1.09 that Les said was the best.
Les came out to our site later that afternoon to visit and we have a photo
of him above.
Our One Contact
As mentioned above most of the time we were not able to hear
ourselves on the satellites. Our guru for operating Uni-Trac is Art and he
was not able to be there on Saturday. Pete and his son Paul were operating
for us without having had any prior use of the system.
During late night Saturday another team of operators including Mark, KB3GJE, and Doug, AA3S, obtained a 150 watt 2 meter Mirage B215 amp from Bob, KC3VO. This would improve our uplink on FO-29, AO-7 Mode A and the FM birds. Throughout the night, the crew tried unsuccessfully to make contacts through each of the satellites. We could hear the birds, but could never find our own signal.
After trying to make contacts all day Saturday including into the night Art arrived Sunday morning to also find that we were still not able to hear ourselves. Finally at 11:05 am on Sunday Art made our first voice contact with:
NX2Q in Northern New Jersey on FO-29
We achieved our goal of making at least one contact so as to qualify for the 100 point bonus for operating a satellite station.
The remaining section will discuss the birds we tried to work and to provide some of our post Field Day analysis.
Single Side Band Birds
AO-7
This old satellite (launched in 1974) has lost its batteries and so it
only operates when it is in sunlight because then it receives power from its
solar panels. The other problem is that it randomly is either in Mode A with
a 10 meter downlink or Mode B with a 2 meter downlink. To find out which one
it is in you have to listen for the beacon on 10 meters and then 2 meters to
see which mode it is in for that pass.
When it was in Mode A with the 10 meter receive we encountered interference problems with our 10 meter stations
FO-29
This is the satellite that we finally were able to work.
FM Birds
The problem with FM birds is that there is only one frequency. The
station with the strongest signal will capture the satellite. Since we
normally did not have an amplifier on our transmit, we apparently were not
"captured" and thus not heard by these birds.
International Space Station (ISS)
In the early passes they were not operating on voice, but instead had
the packet mode operating. We did not receive any packet messages,
although one reason may be that we had never used the new MixW packet
software before.
On the pass Sunday morning at 10:26 am we hear a strong voice signal from ISS, but we could never be heard by them.
AO-27
We were able to hear others, but again not ourselves.
SO-50
We heard others on the bird, but not ourselves. The bird requires a tone
of 67 Hz. Since we never heard ourselves, we don’t know if UniTrac
provided that tone as we programmed it to do.
Digital Birds
UO-22
We tried MSK in MixW, but without success.
Post Field Day Analysis – Lessons Learned
1. UniTrac – We don’t fully understand how to operate it.
a. We would like to be able to send CW dots on our uplink frequency so we
can tune the downlink to hear it. But UniTrac would not let us send CW.
b. We assumed that since UniTract knew our uplink frequency it would
therefore tune the downlink frequency so we could hear ourselves. This did
not happen. We would like to know why. We also would like to be able to
adjust the receive frequency manually so that we could hear ourselves and
then have UniTrac use that found downlink frequency and then modify it to
make the required doppler shifts. But the program would not do that.
2. Communications needed when a new unit is added to the system.
We appreciate that Bob loaned us his Mirage amplifier late Saturday night.
However, when the Sunday morning shift came on they had no idea as to the
requirements needed to have the Mirage operate properly.
a. We were finally able to talk to Bob abut this and he indicated that the
transmit knob on the Yaseu radio has to be at the 9 O’clock position so
that the radio was not sending too strong of a signal to the Mirage
amplifier (i.e. it only needs 2 watts) .
3. True North – Azimuth calibration
The azimuth was set with a small pocket compass. During Field Day someone
went home and did an internet search to find that at our location there is
an 11° difference between magnetic north
and true north. For next year this needs to be taken into account. Although
there is the technique of pointing at the Sun and using the keps for the Sun
to calibrate the azimuth, when we were setting up the antenna it was cloudy
and there was no visible Sun at which we could point the antennas.
4. We need a good packet program to work the digital satellites and practice using it.
5. Securing the 2 meter and 440 antennas to the beam.
With all of the movement switching from one satellite to another, the two
parallel antennas were not pointing in exactly the same direction. We need a
better way to secure them to the main beam so they both point together in
same direction.
6. Problems with the 440 antenna
After Field Day the 440 antenna was given to Don W4VQA to check out because
there was a question about its performance. Don found that the antenna
matching network was filled with dirt and foreign material and that the
antenna needed to be tuned. Don also noted that with the long length of our
440 antenna, it has to be accurately pointing at the satellite. By having
another 440 antenna with a shorter length, it would have a better tolerance
in receiving the satellite signal even if it was not pointing exactly to the
satellite.
The following people were seen at the Satellite tent this year and helped
out.
Andy KC8UFR
Art N3OY
Bernie K3BAZ
Bob KC3VO
Chuck KS3M
Dave W8AJR
Dave N3OYF
Doug AA3S
Ed N2EC
Gerry WA1SHD
Jon KF3O
Larry W0NQW
Les WR3X
Mark KB3GJE
Paul KB3KFD
Pete K3IN
