Re: [amsat-bb] Mode J Recieve Desense Problems

[Roy Welch <rdwelch@xxxxxxxxxx>]

These traps are fairly sharp and may not cover the range of frequencies
needed.

STEVE DIGGS wrote:
> 
> -> Forget the complex fixes; try the cheapest first: a stub.
> ->
> -> This forms an electrical short-circuit at the frequency it is set for
> -> so, on the 70cm rig antenna line, you tee off a 2m stub. You tune it
> -> by starting with a length thats too long and snip bits off until you
> -> hit the sweet spot.
> -> Trouble is that I can't remember whether you want a quarter-wave or a
> -> half- wave ... and whether its open-circuit or closed. But I'm sure
> -> someone else on the -bb will know this and post.
> 
> Excellent suggestion, Richard! I have even used this fix on repeaters
> before, and forgot about it. The way I implemented it previously was to
> use a pass cavity tuned to the frequency I wanted to eliminate "teed"
> into the antenna/preamp circuit, and then a 50 ohm load on the other
> side of the pass filter. It works exactly like you describe, just no
> tuned radiator. A simple mobile duplexer would do the job as the pass
> band device.
> 
> Regards,
> Steve Diggs, W4EPI
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-- 
73, Roy

Internet: w0sl@amsat.org
Home Page: http://home.swbell.net/rdwelch
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