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

Fri Apr 2 08:46:22 EDT 2021

Nathan -- Yes, still there! On the Fieldfox you'll want to zoom in on 401.25 MHz. A span of 50 kHz (or so) or less should allow you to clearly see the sidebands created by the digital modulation burst every ten seconds.

Larry -- it doesn't appear there's a DORIS tx site in the Hampton Roads area. Thanks for checking!

________________________________
From: Nathan West <nate.ewest at gmail.com>
Sent: Thursday, April 1, 2021 10:05 PM
To: Larry Kumjian <larry51 at aol.com>
Cc: Andrew Clegg <andrew_w_clegg at hotmail.com>; 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?

Is it still active? I’ve got a couple of good vantage points in Roslyn I can check from tomorrow with a fieldfox and gr-fosphor.

On Wed, Mar 31, 2021 at 7:25 PM Larry Kumjian via Scan-DC <scan-dc at mailman.qth.net<mailto:scan-dc at mailman.qth.net>> wrote:
For what it's worth, I tried monitoring 401.25 MHz down here in Hampton
Roads with negative results.

-----Original Message-----
From: scan-dc-bounces at mailman.qth.net<mailto:scan-dc-bounces at mailman.qth.net>
[mailto:scan-dc-bounces at mailman.qth.net<mailto:scan-dc-bounces at mailman.qth.net>] On Behalf Of Andrew Clegg
Sent: Wednesday, March 31, 2021 8:44 AM
To: Scan-DC at mailman.qth.net<mailto: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<https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.sirgas.org%2Ffileadmin%2Fdocs%2FGGRF_Wksp%2F26_Soudarin_et_al_2019_DORIS_and_IDS.pdf&data=04%7C01%7C%7C191cd39d837342461ecc08d8f57be092%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637529259682518795%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=vuQkvrhu4OvhWGkqLin0G0zJue2WCRG98hLyKJFaYN4%3D&reserved=0>> 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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