[amsat-bb] Re: AO-51 Mode L/U

Gould Smith gouldsmi at bellsouth.net
Wed Apr 9 16:16:16 PDT 2008

Hello Jim,

I routinely get the downlink quite well using an 8 element 70 cm yagi, with 
a pre-amp at the antenna, fixed elevation, tracking in AZ . The digital 
transmission is currently about 500 mW, but you need a good S/N ratio to 
decode the data, even if your modem locks on to the clock.

The AMSAT Digital Guide has a very good description from actual experiments 
by Mike, N1JEZ on what is need in a 1.2 GHz uplink signal for digital 
operation on  AO-51.  GO-32 also has a 1.2 GHz uplink, but it has also needs 
more signal than you are delivering.

The downlink reception is pretty easily and inexpensively corrected.  I am 
not sure how the increase in TX delay time to a second will help your uplink 
as you didn't mention an amplifier needed to switch in.

A good deal of the enjoyment for many of us is the challenge of getting 
operations on the satellites and the multiple modes they present.  I am sure 
the digital guide would be of assistance to you.

Gould, WA4SXM

--- Original Message ----- 
From: "James Denneny" <57JNDenneny at comcast.net>
To: <amsat-bb at amsat.org>
Sent: Wednesday, April 09, 2008 3:16 PM
Subject: [amsat-bb] AO-51 Mode L/U

>I have had no luck uplinking on Mode L.  I even followed a suggestion to
> increase TX delay to 999 ms and tail time to 100 ms to give the bird extra
> time to grab me.  However, 10w from my 910H on 23cm with a single twisted
> helix 1.2G antenna does not cut the mustard.  I also have had very limited
> success on the 70cm downlink grabbing the DIR.  All in all - a bust.
> Jim
> K7EG
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