[amsat-bb] Re: Some Elmering requested for uplinking to ARISSAT-1

David Palmer KB5WIA kb5wia at amsat.org
Wed Nov 2 15:49:44 PDT 2011

Hi Burns,

My 2 cents -- sounds like things are mostly okay (your recieving setup
is obviously good if you can hear others in the transponder passband).
 The big factor that I can see is lack of gain on the uplink.  I've
successfully gotten into ARISSAT with my 5W QRP radio, but that's
using a 13 dBd gain yagi.  In theory the ERP of your 25W uplink isn't
too far below that, so it would be worthwhile trying the 50W to see if
that helps.  That or switch to an antenna outside with some gain...

Other factors to consider are sometimes the sats transponder is off
(so even if everything at your end is okay you won't hear your own
signal, nor anyone elses).  And the return signal varies greatly from
pass to pass, depending (I think) on the relative orientation of the
antenna stub.

Also be sure to try finding yourself on CW first .... SSB is often
very difficult to copy on ARISSAT, much easier to start with CW and
once you've found yourself switch over.

73! de Dave KB5WIA

> Can someone comment on my method, both in terms of technical goodness and
> good operating practice?  A couple specific questions:  1) Xmitting in the
> middle of the passband and just scanning, I should be able to at least
> briefly find myself without messing with doppler, right?  I was planning to
> lock the receive and transmit frequencies (constant sum) once I found
> myself and follow the doppler by hand, but I never got to that step.  2)
> I'm right that the sidebands are inverted from receive to xmit, right?  I
> think I would hear something even if that was wrong.  3) Finally, what
> about power?  How much have you required for success on ARRISAT?   I was
> running around 25W.  I could boost up to as high as 50, but I can only
> diddle so many knobs in 5 or 10 minutes :-)  3) I know a beam would be
> better, but trying to reduce variables, and pointing is one of them.
> Besides, I'm inside in my shack!  But has anyone successfully uplinked with
> an omni/circular?  I can always remove the parasitic elements and end up
> with a center-fed dipole to remove the circularity.  (Not sure how that
> would affect the impedance match...)
> Thanks!
> Burns, W2BFJ

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