On Fri, 16 Oct 1998 18:49:58 -0400 "Roger Rehr" <rrehr@epix.net> writes:
SNIP
>
>P.S. the rig is SSB preamp on the mast, SSB 2304 to 144 transverter,
>ICOM
>970H 144 MHz receiver. When I turn off the mast mounted preamp this
>and all
>other sigs disappear due to my coax (1/2 inch andrews heliax to
>LMR600UF)
>run being 200 feet long.
I dont have a loss chart handy for 1/2" but I'm guessing about 4 dB per
100' if my old memory still works. In that case shutting off the preamp
will add 8dB or so to the NF. If it goes away with the preamp off I would
suspect it as the primary culprit since you should still be able to hear
a prior S5-7signal. The lack of directivity is a major clue IMO.
Relocate the preamp in the shack and see what happens.
Another possibility is that the xcvr cant handle the combined xvtr and
preamp gain and is taking off.
I had a similar problem with an IC-451A and ARR preamp combo when I
changed the 451A front end device to a hotter one. Had to add extra
shielding then all was OK again.
73 Carl KM1H
] The system "works", as I have worked into
>the
>Philadelphia area and also New Jersey on 2304. I can't recall a time
>when
>the noise hasn't been there; I get around it by putting in the narrow
>CW IF
>filters.
>
>Thanks for your comments...
>
>
>>73 from
>Roger Rehr W3SZ ex-AA3QK ex-WA3JYM
>mailto:rrehr@epix.net FN20ah
>http://www.epix.net/~rrehr
>2 Merrymount Road, Reading, PA 19609
>610.670.8687
>
>
>
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