On Mon, 4 Jan 1999 10:52:53 -0000 Peter Chadwick
<Peter_Chadwick@mitel.com> writes:
>
>Carl says
>
> >Agreed. That is why I often find a 1dB NF preamp very usefull
>on
>15-10M.
>
>With a 4 ele yagi at 68 feet, 2.2dB of cable loss ( measured) and an
>8dB NF
>receiver, I've never yet not managed to measure a minimum 4dB increase
>in
>noise in switching from a 50 ohm source to the antenna on 10m. That's
>in a
>rural QTH, beaming in the quietest direction late on a winter's night
>with
>the bands closed above 10MHz. So 1 dB NF wouldn't help me. Some
>Collins
>studies years ago suggested that 8dB was all the NF needed at HF, even
>on
>short whips.
I did not measure but was told that the stock TS-940 has a 12-13dB NF at
28MHz. The preamp at 1dB NF/10dB gain gave me a system NF of roughly 5dB.
There were several times that the preamp improved the readability of pee
weak polar path winter DX.
Many times my rcvd signal report was less than flattering leading me to
believe less than ideal RX conditions at the other end. Local 100W
stations were wasting electricity.
At this end 1200W, various combinations of a 4/4/4/4 array and .5dB main
feeder loss from 1" CATV line.
73 Carl KM1H
BTW, if anyone is interested I have several 200-500' lengths of Andrew 1
5/8" LDF7-50 Heliax for sale. Several with connectors.
>
>But returning to the thread...........when you have a good antenna,
>then you
>want a good amplifier. I claim I cause less QRM by calling once than
>by
>calling half a dozen times.
>
>Even then, you can get 6dB by good operating as opposed to bad!
>
>73
>
>Peter G3RZP
>
>
>
>
>--
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>Problems: owner-amps@contesting.com
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>
>
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