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[jamsat-news:632] * SpaceNews 08-Sep-97 *
- From: "John A. Magliacane" <kd2bd@kd2bd.org>
- Date: Sun, 07 Sep 97 13:55:49 -0700
SB NEWS @ AMSAT $SPC0908
* SpaceNews 08-Sep-97 *
BID: $SPC0908
=========
SpaceNews
=========
MONDAY SEPTEMBER 8, 1997
SpaceNews originates at KD2BD in Wall Township, New Jersey, USA. It
is published every week and is made available for non-commercial use.
* MIR FREQUENCY EXPERIMENT *
============================
The Mir International Amateur Radio Experiment (MIREX) will be conducting a
three week 70 cm experiment with the Mir PMS station. The PMS station will
be switched from the 2-meter band to the 70cm band using 437.650 MHz simplex
worldwide.
The MIREX team believes this temporary frequency will an ideal learning
opportunity to verify the impact of 70cm Doppler phenomena on FM voice and
packet operations. The experiment is being conducted as a result of
suggestions from several amateur radio satellite groups who would like to
verify the feasibility of operating Mir and the International Space Station
on 70 cm. MIREX has contacted AMSAT International and received approval from
AMSAT International to operate Mir and the Mir PMS on 437.650 MHz. This
frequency is also compatible with the ITU International Satellite band plans
and with the IARU Satellite operations.
The information the team expects to gain from the three week experiment:
1. Is the 70cm band interfered with by existing commercial VHF equipment on
Mir?
2. How many stations around the world have access to 70-cm FM equipment?
3. Does 70-cm Mir operations cause any interference to any of the equipment
on Mir?
4. Can simple ground stations compensate for 70 cm Doppler and work Mir on
voice?
5. Can simple ground stations compensate for 70 cm Doppler and work Mir on
packet?
MIREX will be running the 70-cm test from September 6, until September 28, 1997
worldwide. After the completion of the test, the Mir PMS frequency will be
switched back to 145.985 MHz on September 29th.
In 1993, the MIREX team began to hear reports of problems with 2-meter packet
operations when Mir was using its commercial VHF transmitter on 143.625 MHz.
The reports seemed to indicate that the 2-meter station on 145.550 MHz was
desensed by the commercial transmitter. The information that MIREX received
about this problem was very limited, and the problems only occurred over
Europe. Such problems did not exist over the USA, and the MIREX teams was
not able to fully analyze the problem until 1996 when 143.625 MHz operations
started over the US. With 143.625 MHz in operation, it was impossible to
work the Mir space station on any frequency below 145.900 MHz. The frequency
145.940 MHz was barley usable when ground stations used over 3000 watts ERP.
Theses uplink power levels are just not realistic, and a better solution
needed to be found. MIREX is working on a filter, that if approved, will
solve the communications link interference problem on Mir. The MIREX filter
project is still awaiting official approval. No date has been confirmed for
its delivery to Mir.
MIREX still encourages stations to use the least amount of transmitter power
necessary for reliable communications with Mir. Another possible solution
is to try to use the 70cm equipment already on board Mir. The existing
external antenna is a dual band 2-meter/70-centimeter antenna. The existing
transceiver, a Kenwood TM-733 (European version), supports both 2-meters and
the 435-437 MHz portion of the 70-cm satellite subband. MIREX began testing
of the 70-cm operations for voice and packet during the spring of 1997. The
equipment appears stable enough to allow access to the general public. The
team originally had planned to operate both bands simultaneously, but ran
into equipment and power limitations. Therefore, the test is being scaled
back to test just the 70-cm band for a limited time.
For the duration of the 70-cm test, the 2-meter operations will be turned off.
After the 70-cm test is completed in about three weeks, operations will move
back to the 2-meter band. Groundstations should use at least 25-watts ERP
for 70-cm communications with Mir.
The effects of Doppler shift will be the biggest challenge to groundstations.
On 70-cm with a low-earth orbiting satellite such as Mir, the Doppler shift
amounts to +/- 10 kHz. Most 70-cm FM voice transceivers on the market can
only tune in 5 kHz increments. To contact Mir on voice, groundstations will
need to be within 3 kHz of the receiver frequency on Mir. On packet, the
error must be less than 2 kHz. Groundstations capable of tuning in 5 kHz
steps are not recommended for packet communications.
Groundstations with programmable transceivers (in steps of 2 kHz or less)
can use the following approach to compensating for Doppler shift. Channel
1 should be used at the beginning of the pass. Remember, on 70-cm, the
transmitter and receiver must be tuned in opposite directions during a Mir
pass.
Program the following channels in the order presented:
TX channel RX channel
1 437.640 437.660 (+10 kHz) <-- AOS
2 437.642 437.658 (+ 8 kHz)
3 437.644 437.656 (+ 6 kHz)
4 437.646 437.654 (+ 4 kHz)
5 437.648 437.652 (+ 2 kHz)
6 437.650 437.650 ( 0 kHz) <-- TCA
7 437.652 437.648 (- 2 kHz)
8 437.654 437.646 (- 4 kHz)
9 437.656 437.644 (- 6 kHz)
10 437.658 437.642 (- 8 kHz)
11 437.660 437.640 (-10 kHz) <-- LOS
For groundstation transceivers that can only tune in 5 kHz increments,
program the following set of 5 channels in the order listed:
TX channel RX channel
1 437.640 437.660 (+10 kHz) <-- AOS
2 437.645 437.655 (+ 5 kHz)
3 437.650 437.650 ( 0 kHz) <-- TCA
4 437.655 437.645 (- 5 kHz)
5 437.660 437.640 (-10 kHz) <-- LOS
This frequency change will undoubtedly generate some positive and negative
comments. The primary reason for the change, of course, is experimentation.
Comments and observations should be directed to Dr. Dave Larsen, N6CO at:
doc@volcano.net (Internet) -or- n6co@n0ary.ca (Packet)
And please do not bother the Mir crews about the UHF and other Mir Amateur
Radio Experiments. The crews are going a great job by letting people use
their valuable electricity.
[Info via Dr. Dave Larsen, N6CO, and Miles Mann, WF1F]
* MIR ATTITUDE *
================
TIME ORBIT REVOLUTION (summary) MIR Complex 16609
(For the period day = 86 to day = 244, 1997)
revolution/day
I
15.5500 I
I
15.5600 I
I
15.5700 I
I
15.5800 I
I _______
I I --------_______/\_______
15.6000 I I -------------________
I______I
I
15.6500 I Epoch time
I__x__________x__________x__________x__________x__________x______
Apr May Jun Jul Aug Sep
Progress M34 docking: 11-Apr-97
Adjust orbit: 15-Apr-97
Fire aboard Mir: 22-Apr-97
STS-84 Docking: 23-May-97
M34 collision with Mir: 25-Jun-97
Progress M35 docking: 07-Jul-97
Soyuz TM26 docking: 07-Aug-97
[Info via Jean-Claude, FB1RCI]
* G3IOR BACK HOME *
===================
Pat, G3IOR, advised Ray, W2RS, on the evening of 04-Sep-97 that he is
home from the hospital after a week's stay, and has recuperated well
enough already to operate his packet station.
As mentioned earlier, Pat has no Internet facilities, but get-well messages
may be addressed to him via satellite gateway at G3IOR @ GB7LDI.#35.GBR.EU,
or via snail-mail to his home QTH, 17 Heath Crescent, Hellesdon, Norwich,
Norfolk NR6 6XD, England.
[Info via Ray, W2RS]
* FEEDBACK/INPUT WELCOMED *
===========================
Comments and input for SpaceNews should be directed to the editor (John,
KD2BD) via any of the paths listed below:
WWW : http://www.njin.net/~magliaco/
PACKET : KD2BD @ KS4HR.NJ.USA.NA
INTERNET : kd2bd@amsat.org, magliaco@email.njin.net
SATELLITE : AMSAT-OSCAR-16, LUSAT-OSCAR-19
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/EX