[amsat-bb] Re: really strange RX

Mark L. Hammond n8mh at embarqmail.com
Sun Feb 17 17:57:10 PST 2008

Hello Auke,

You may very well be hearing IO-26, ITAMSAT.  

IO-26 is currently in MBL mode transmitting PSK at 435.790 MHz +/- Doppler, so it's quite a bit lower than the published/launch frequency of 435.822.  It has drifted a good bit!

If you share a footprint with my station, you might very well be hearing some MBL telemetry and/or packets coming from IO-26.   Keep tuned for more information in the coming weeks  :) 


Mark N8MH

>Well, I got a chance to listen again and there it was again!  I took some 
>better notes this time and even got a recording.  There didn't seem to be 
>any telemetry frames transmitted, just the steady AFSK carriers.  I picked 
>it up about 1/2 way through the pass.
>I am 90% sure that these signals are coming from IO-26.  the LOS occured 
>precisely at 21:05:39UTC Just as IO-26 met my horizon here in DO-33, and the 
>signal was strongest with my antenna pointed in the direction of that 
>satellite.  All this is according to my Orbitron display.  The only problem 
>is that the frequency is NOT on any list.  I worked out the transmitter 
>frequency to be 435.790MHz, where it was 435.7825 when it disappeared. 
>FO-12 was also in view at the time, just as it was the first time I heard 
>this, but it was in the opposite direction from me.  LOS happened to occur 
>at about the same time too, hence my less than 100% sure-ness.  FO-12 also 
>happens to have it's beacon set to a more believable 435.795, but again, the 
>signal was stronger in the opposite direction from there. One last thing of 
>note about the reception is that I noticed pronounced fading as if the sat 
>was spinning, which seemed to mirror how AO-16 fades both in severity, and 
>rotational frequency.  the fades occur about every 10 seconds, for about 1 
>second, as observed on my 7 element Sinclair Yagi fixed at horizontal pol 
>and fixed elevation of 20 Deg.
>Can anyone here offer any help for me to understand these observations?  Is 
>it even possible for a satellite to drift this far off-frequency?  Can 
>anyone else confirm or dis-prove that these are coming from, or very near 
>IO-26's closest downlink frequency is listed as "Downlink 435.8670 MHz AFSK 
>1200 BPS"
>as seen here on AMSAT's page: 
>Auke de Jong
>From: "Auke de Jong, VE6PWN" <sparkycivic at shaw.ca>
>To: "AMSAT-BB" <amsat-bb at amsat.org>
>Sent: Sunday, February 03, 2008 2:28 PM
>Subject: [amsat-bb] really strange RX
>>I cannot identify what it was that I just heard:
>> at 20:55, i was bringing my dial up to try and hear IO-26, but I was 
>> startled when I came accross another signal several hundred KHz below my 
>> destination!  I stopped to see if it was juse local noise, and found that 
>> it was indeed LEO in origin.  I picked it up at about 435.801MHz while 
>> rotating the beam from the north to my east.  As far as I can tell, there 
>> is no satellite using a frequency in that range, on the list found on the 
>> AMSAT website under "Satellite Frequencies".  The signal seemed to be 
>> strongest in the direction of IO26/KO25.  judging by the rate of 
>> doppler-shift it must probably be either one of those satellites.  It also 
>> faded out just before IO26/KO25 were near my horizon, given the inaccuracy 
>> of my PC clock, they might have been exactly at the horizon.  It's been a 
>> week since I synchronised my clock, it was 4 seconds behind.
>> The signal sounded exactly like AO-16 MBL mode before they put it in voice 
>> mode.  I think I even heard a packet or some form of data transmitted once 
>> during this pass.
>> Is it just a typo where IO26 is actually lower in frequency by about 
>> 60KHz?  Might it somehow have drifted that far down?  Or is it another 
>> satellite altogether?
>> Auke de Jong
>> DO33go
>> Edmonton, AB

Mark L. Hammond  [N8MH]

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