Re: 50 Or 75 Ohm Coax For Receive Only Application ?

On Sat, 25 Feb 2006 18:22:39 -0800, Roy Lewallen <w7el@xxxxxxxxx>
wrote:

Owen Duffy wrote:
. . .
In this rx only application, especially below 15MHz, even if the RG6
was a few dB worse than 50 ohm line, it would not be worth spending
the money on RG213.
. . .

I think Owen means, "even if the RG6 was a few dB *lossier*". In
receiving applications at HF, added loss (within reason) doesn't
translate to any reduction in signal/noise ratio. So one line can be
considerably lossier than another without making it even one little bit
worse in this application. There's no point in spending extra money on
line which won't make any improvement at all on your ability to receive
signals. It might, on the other hand, be worthwhile to pay extra for
line which will last longer or is more physically rugged. Or it might not.

Quite.

The chart at http://www.vk1od.net/bpl/AreYouReady.htm shows that for a
good HF receiver, the ambient galactic noise is more than 10dB above
the rx noise floor. For an older receiver, the rx noise floor might be
10 to 15dB higher. The ambient noise due to man made and atmospheric
sources would be even higher than the galactic noise plotted in the
chart.

Owen
--
.

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