[amsat-bb] Re: [Fwd: DO-64]

Alan Cresswell alancresswell at xtra.co.nz
Tue Aug 5 01:19:52 PDT 2008

Hi Wouter

Bear in mind that this happened about a minute or two before LOS and took me
by surprise so these are not scientific observations.
I was monitoring the beacon both by ear and with a visual display on
spectran.  When the CW started the normal display gave way to the CW signal
only and it appeared to be on the centre frequency of the DSB beacon signal.
I assumed at first that this was simply a new mode for the beacon.  There
were a few CW characters and then the beacon resumed.  The same thing
happened about 15 seconds later and then a couple of times more before LOS.
I then realised that this is the exact pattern of RS-30, 5 or six CW
characters at 15 second intervals.  When I brought RS-30 up on my display I
discovered that RS-30 and Delfi have orbits that converge from opposite
directions once on each orbit and this convergence just happened to occur
over ZL on that pass.  My next chance to have another look at this is the
2246 UT pass on 6 August but I would think this can be checked before that
on rev 1484 over Europe at about 0930 UT on the 6th August.


-----Original Message-----
From: Wouter Jan Ubbels [mailto:wjubbels at gmail.com] 
Sent: Tuesday, 5 August 2008 07:08
To: Alan Cresswell
Cc: albi at delfic3.nl; Delfi-C3 Mission Control
Subject: Re: [Fwd: DO-64]

Hi Alan,

that is very strange. 435.315 is not a command frequency and is far
away enough of the transponder uplink and the actual command
frequencies so should not cause any trouble...
How did you find out that the CW on 145.870 came from RS-30?
Would be interested in your further observations!

thanks a lot and 73!

Wouter PE4WJ

On Tue, Aug 5, 2008 at 3:47 AM, Delfi-C3 Mission Control
<missioncontrol at delfic3.nl> wrote:
> fyi
> Hi Delfi team,
> With no one other than myself to talk to on a 2226 UT DO-64 pass this
> morning I decided to monitor the beacon towards the end of the pass.
> Shortly before LOS the beacon stopped and sent CW for a second or two and
> then the beacon restarted.  A few seconds later the same thing happened.
> eventually realized that the CW was the RS-30 downlink signal at
> The two spacecraft were on opposite tracks and approaching each other at
> this time.  Why the 435.315MHz signal should stop the beacon and appear on
> the 145.870MHz beacon frequency is a mystery to me.
> I was about to post this on the amsat bulletin board when it occurred to
> that there could be a slight possibility that the effect on the beacon
> be because the RS-30 signal hit a command and control frequency at
> 435.320MHz so thought I would send it to you direct just in case.
> In the absence of any comment I will post the info on the Amsat bb for
> general interest.
> With the current orbits of Delfi and RS-30 they are in this relationship
> a regular basis so I will see what happens next time to the linear
> frequency.
> Alan

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