[Scan-DC] 401.25 MHz DORIS beacon coming from Goddard or somewhere else?

[Andrew Clegg]

Thanks Dewey. I tried to find a local online SDR that covers the 400 MHz band, but I was unable to find such a resource.

________________________________
From: scan-dc-bounces at mailman.qth.net <scan-dc-bounces at mailman.qth.net> on behalf of Dewey <dewey3 at gmail.com>
Sent: Wednesday, March 31, 2021 8:58 AM
To: Scan-DC at mailman.qth.net <Scan-DC at mailman.qth.net>
Subject: Re: [Scan-DC] 401.25 MHz DORIS beacon coming from Goddard or somewhere else?

Greetings Andy!

I just checked using SDRSharp with a NooElec SMArt RTL-SDR dongle and the
Airspy Mini, and punched the frequency into the 536, all on the outside
antenna, and not getting anything near the PG/Charles County line along the
Maryland shore line.  So given our locations, I would say that your thought
about it coming from Goddard is probably accurate.

Dewey

-----Original Message-----
From: scan-dc-bounces at mailman.qth.net <scan-dc-bounces at mailman.qth.net> On
Behalf Of Andrew Clegg
Sent: Wednesday, March 31, 2021 08:44
To: scan-dc at mailman.qth.net
Subject: [Scan-DC] 401.25 MHz DORIS beacon coming from Goddard or somewhere
else?

Hi all,

I notice a beacon on 401.25 MHz that, based on its characteristics, seems to
be part of the DORIS
system<http://www.sirgas.org/fileadmin/docs/GGRF_Wksp/26_Soudarin_et_al_2019
_DORIS_and_IDS.pdf> of ground-based beacons that help satellites in orbit
determine their position to very high accuracy. It's sort of a reverse GPS
(ground-to-space). The beacon is a CW tone, with a 0.8 second data burst
every ten seconds, at 1 second before each ten seconds (i.e., 9 seconds, 19
seconds, 29 seconds, etc., past the minute).

I am in Arlington and the closest official DORIS tx site I see listed is at
Goddard. Seems kind of far away for me to be hearing it pretty clearly in
Arlington, especially if it's designed to point up.

Is anyone located near Goddard and could see if there is a signal that fits
this description that's very strong there? Or do other people hear this in
areas that are not near Goddard? I think you'd need a receiver that can do
CW or SSB mode to be able to hear it.

DORIS also transmits on 2036.25 MHz but I can't hear that here, although I
do hear a constant weak CW tone about 10 kHz off that frequency, but no data
burst.

(Apologies if this is too wonky, but I think it's cool finding exotic
signals on the airwaves!)

73,
Andy
W4JE

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