[amsat-bb] Re: ISS - Mission Control Comm Check
Ransom, Kenneth G. (JSC-OC)[BARRIOS TECHNOLOGY]
kenneth.g.ransom at nasa.gov
Wed Jul 14 08:26:55 PDT 2010
A couple of corrections to Miles' post.
Packet is on 145.825 simplex.
VHF-1 does de-sense the D700 radio but not completely (I have see a station break through) but it takes a big gun to do so.
The VHF-1 transmitter is only planned to be keyed when in range of the US ground stations as indicated by the crew timeline (10-20 minutes depending on the orbit and number of ground stations in the footprint).
Kenneth - N5VHO
From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On Behalf Of MM
Sent: Wednesday, July 14, 2010 7:29 AM
To: amsat-bb at amsat.org; Bob Christy
Subject: [amsat-bb] Re: ISS - Mission Control Comm Check
When the VHF-1 transmitter is Running, the Amateur Radio receivers in the 2-meter band will go deaf (Receiving on 145, 490, 145.200, 145.990).
This is because the Transmitting antenna for VHF-1 is less than 50 feet away from the Amateur Radio antennas.
The VHF-1 transmitter is usually left running for a few hours at a time for ground stations to test against. If you wish to test this theory, just try to ping the Amateur radio packet station ISS during a VHF-1 transmitter test.
When VHF-1 is transmitting, you will not see any packet activity, other than internally generated Beacons on 145.800 (down 145.800, uplink 145.990). When VHF-1 shuts down, normal packet access will resume.
Marex discovered this problem with the Mir Amateur Radio station. We then custom designed a filter by DCI, to resolve the issues. No such filter exists on ISS.
--- On Wed, 7/14/10, Bob Christy <bob at zarya.info> wrote:
> From: Bob Christy <bob at zarya.info>
> Subject: [amsat-bb] ISS - Mission Control Comm Check
> To: amsat-bb at amsat.org
> Date: Wednesday, July 14, 2010, 4:47 AM
> Today's ISS crew schedule shows VHF
> comm checks from the Russian segment while over North
> America. Ground stations are at White Sands and Wallops.
> The pass is from 20:00 UTC (west coast) to 20:15 UTC (east
> VHF-1 is 143.625 MHz FM, there may also be something on
> VHF-2 at 130.167 MHz.
> Bob Christy
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