[amsat-bb] Telemetry system on ISS, MM

MM ka1rrw at yahoo.com
Tue Mar 17 05:09:26 PDT 2009

Hi all:

I guess I should have used the word “Transponder” rather than the word “Repeater” in my last memo.  The device on ISS appears to act more like a Transponder, rather than a true FM repeater. The Transponder will repeat any signal it hears on the input and retransmit that signal on the output.
At the end of this memo I attached an email from the person that provided the recording made last year.

[SCPC-FDM,SAT DX] 143.625 ODD CommsTuesday, 
July 8, 2008 11:12 PM
From: "Jody" 
 Add sender to Contacts To: SCPC-FDM at yahoogroups.com

This morning, sometime before 12 EST time local here I copied some
strange comms from the ISS frequency of 143.625. The modulation mode
was WFM. Other known ISS frequencies were active with data
transmissions at the same time. Attached is a link to a recording I
made of the 143.625 Frequency. You can tell at the start of the
recording  I was tuning in the Narrow FM mode, 5.5Khz bandwidth, after
switching to wide FM mode on my Icom R8500 I was able to copy the
comms. For some reason the crew was retransmitting aircraft comms. In
the clip you hear a center controller and some other aircraft. One
aircraft heard in the clip was Cessna 38 Uniform. it appears that
aircraft was based in Colorado from a registration lookup. Also the
center controller made references to Memphis center. It sounds very
much like someone was tuning around the airbands and it was getting
retransmitted. I was told by one that it could been a possible Comm
test for a upcoming EVA. Take a listen and see if you can pull
anything more from the recording. I was using a Icom R8500 and a
discone antenna. No chance of intermod. Poor signal quality due to the
antenna not being resonant, it’s was 225-400Mhz mil discone being used.

Link to audio:

One aircraft in recording:

North Georgia


The DCI filter was a custom Job for Space Station Mir.  

Picture of Filter

The problem:
When the VHF-1 Transmitter was active, the Amateur radio station would go deaf.  The Russian crew used the VHF-1 transmitter frequently over the USA during joint American missions.
This would manifest its self by seeing the Kantronics KPC-9612 packet system send out a consecutive series of 7 Retries to the person that was last logged in.  No other packet would be seen coming down.  It was just like someone was logged in and then the receiver was turned off.  If you switched over to the VHF-1 frequency you could hear a strong down link signal and voice.

I tested this theory again with a phone patch to Jerry Linenger and his brother in Detroit.  The first few seconds of the phone patch went good via the Kenwood TM-733, then Jerry could not hear my signal any more.  I quickly checked the VHF-1 channel and found the Mir crew members talking to Moscow via the Houston VHF-1 ground station.
I was finally able to punch through the interference for a few seconds while Mir was directly over my house.  I was using a Yaesu FT-736R, M2-CP22 antenna, AZ/EL rotor and EIRP 2-5 kW.

I was finally able to convince ARISS the filter was a needed project and they agreed.  ARISS generate the appropriate paper work and Russia flew the filter to Mir in the spring on 1998, just in time for Andy’s mission.

The Solution:
Ralph at DCI used one of this stock 4 cavity filters and added a 5th cavity.  The extra cavity contained a Notch filter aimed at the frequency of VHF-1.  The Notch filter provided an additional 20-25 dB of attenuation.  With the new filter the Kenwood radios could be used to receive down to the 145 MHz range, while the VHF-1 transmitter was active.

At the present time ARISS does not believe their is any noticeable de-sensing problems with the Amateur Radio station on ISS, so the DCI project for ISS is on hold until we have proven there is a need.

Special thanks to Jody  at the Yahoo SCPC-FDM,SAT DX group for providing the recordings from ISS

And thanks to Kenwood for building radios that can survive for years inside a manned space station.

73 Miles WF1F Marex, (4 project in flight an growing)



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