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Re: Radios for 1.2 GHz operation




Years ago, I remember changing the IF filter in my old FT736 to a 20 Khz 
unit and wrote a report on the increase in data that was downloaded from
UO-22 at the time. Most of the stock filters were either 12.5 Khz or 15 KHz
which were not optimal for receiving the 9600 baud data. Since a  9600 baud 
at 3 Khz deviation takes up 15.6Khz of bandwidth, the stock IF filter was a 
little too narrow and required tight control in tuning the signal for maximum data 
decoding. The wider filter reduced the tight tuning control and increased the 
amount of decoded data. The biggest improvement was decoding KO-25's broad 
signal. While most were having trouble decoding data from KO-25, I noticed that 
my data decoding ran very closed to 100% most of the time where it was very 
marginal on KO-25 before the IF filter change.


Tim - N8DEU
Huntsville, Alabama




----- Original Message ----- 
From: "Assi Friedman" <4x1kx@iarc.org>
To: "Bob Bruninga" <bruninga@usna.edu>
Cc: "Isaac Waldron " <iwaldron@wpi.edu>; <amsat-bb@AMSAT.Org>
Sent: Monday, July 07, 2003 9:50 AM
Subject: RE: [amsat-bb] Radios for 1.2 GHz operation


> Bob,
> The Techsat used a standard G3RUH compatible modem with typical 9600baud
> deviation (3.5KHz-4.0KHz). The only thing you want to watch out for in FM
> is the threshold limit. If you stay away from that, you can easily open up
> the receiver bandwidth so you can do one of two things:
> 1. Open is to a medium bandwidth, and then update the frequency periodically.
> 2. Open it to wide, and then never have to update the frequency during a
> pass.
> Assi 4x1kx/kk7kx
 

----
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