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Re: Suitsat X band activation


Excellent questions; here are some plausible answers (maybe):

At 12:31 PM 2/5/2006 -0500, Luc Leblanc VE2DWE wrote:
>X stands for cross band
>I read that Bill was unable to hear Suitsat shortly after they reenter ISS
>if stations on earth can hear even with very low signal i'm asking why they 
>cannot copy the signal at a so close range???

I puzzled this one.  I wonder if the ISS antennas are oriented on side in
the direction to Suitsat or is the body of ISS in the way?  I believe ISS
antennas are low-gain semi-omni directional.  The HT is FM with no preamp
to assist.  Yet if Suit sat were only 50-100 miles away and LOS it should
be heard on ISS.

I have not attempted to determine by reverse engineering the actual ERP of
Suitsat.  Originally it was 500mw (assuming no antenna gain).  I would
guess actuall ERP < 50mw since it takes my eme array to hear it.  My eme
array is ~10dB more gain than the 9dBd vertical-whip (Cushcraft ARX-270) I
used to talk with Bill McArthur a couple weeks ago (his 5w signal was a
strong S-9 in the FT-847 w/o internal preamp).  500mw would => S-3 signals
on the same antenna.  I saw 3 to 6 s-unit signals on the eme array briefly
as Satsuit rotates into a favorable attitude.  Even with those signal
strengths the audio was difficult to copy (low modulation?).

>This is making no sense as QRP signals makes their way to ISS very often. I 
>don't know if the frequency drift as no doppler effect is present or could
>the signal was so low at the beginning that it was nearly impossible to
copy it 
>even at close range.

I  copied Suit sat at 145.989 to 145.988 MHz.  Is this enough off frequency
that ISS might not hear it?  Doesn't seem so.

>Another technical interrogation the Kenwood HT as many other one are very 
>dependant of the DC voltage for their output power. I don't know how they 
>connect the suitsat batteries to the HT but is it possible the HT internal 
>battery pack freeze draining or lowering the voltage from the suitsat 

I guess you saw the post that the internal battery was not used.

>With a 5 elem linear yagi i copy at TCA a very faint signal doppler
affected on 
>the 0900Z pass. Spectran recorded it too. It is time to test our VHF
>equipment lets say it is a new week signal test session.

Well that is one way to look at it! :-)

I am VERY interested when someone can hear the telemetry message.  Battery
voltage is given and that would shed a lot of information on what is going
on.  The big problem is the rapid tumble rate of Suitsat reduces reception
time to about 1 second (at least for my qth - I get no overhead passes).

A message was posted on the MoonNet e-mail reflector about getting reports
from eme stations.  I guess we will see?
Ed - KL7UW  
http://www.qsl.net/al7eb - BP40iq 
144-EME: FT-847, mgf-1801/1402, 4xM2-xpol-20, 170w
432-EME: FT-847, mgf-1402, 1x21-ele (18.6 dBi), 60w
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
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