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Re: AO-40



Hi Emily

For your info.
I use a Kuhne MKU 232-A2 preamp at the helix feed on a 34 inch solid spun
dish .
That preamp has a NF of 0.7 dB,  41 dB gain and a 1268 mHz stub at the
input ( L mode de sense )
I  use 102 feet of Belden 8262 ( RG-58)  type coax into the shack where I
keep the down converter (DC)  .
This provide near zero frequeny drift of the LO in the DC after initial
warm up. 
My QTH is in Nebraska.
I can reduce this warmup drift to zero if needed.
This Belden coax was chosen for the desired signal attenuation at 2400
mHz for input to the DC.
Additional fixed atenuation can also be used if needed .
The significant issue here is having the first low noise active devise at
the feed antenna .
There would,  I suggest,  be a cost difference between the LMR 400 and a
Belden 8262 RG-58
Also the difference in the preamps referenced for costs is not that great
.
I'd suggest that the same system at 1.7 gHz would also work ok.
I have also elmered other systems on AO-40 using the same design.

I hope this helps the thinking.

Joe  K0VTY
===========================

Sun, 23 Nov 2003 12:01:38 -0800 Emily Clarke <eec@clarke-design.com>
writes: 
> At 12:45 PM 11/23/2003 -0600, Ryan Butler wrote:
> >Most people use a downconverter to conver the 2401 mhz signals down 
> to
> >either 123 mhz or 145 mhz which is well within the reach of your 2m 
> SSB
> >radios.  The reason for this is two fold, not many radios come with 
> 2400
> >mhz receive, and the losses going from the feed to the radio 
> before
> >detecting the signal make it next to impossible.
> 
> This raises an interesting question I'm sure I know the correct 
> answer 
> to.  If you have a 13cm preamp like the DEMI which gives you 20db of 
> gain, 
> it would seem on the surface that it is OK to use a 2400MHz receiver 
> with 
> even a 200 foot coax run of LMR-400?  Maybe I'm missing something 
> though.
> 
> What I'm really wondering about is if you could do this for 1.7GHz 
> for GOES 
> reception - I seem to remember reading about someone using a 
> wideband CATV 
> amplifier to bring the signal in from their dish to an Icom R-8500 
> or 
> something like that.
> 
> 
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