[R-390] Antenna question

[Thomas W Leiper]

On Thu, 18 Jul 2002 08:20:26 -0500 "Scott, Barry (Clyde B)"
<cbscott@ingr.com> writes:
> What is/was the recommended "standard" antenna and feedline for the 
> R390A? 

There is no recommended standard because the radio was
used in so many applications. The only installation documentation
I have ever seen showed unbalanced was for whip antennas and
the balanced for a doublet (if you are under fifty read "dipole")
fed with twisted pair. I use twisted pair and even CAT5 cable
with multiple dipoles and get excellent results with good zeroing
of the antenna tuner on all bands. The twisted pair also has the
added (and primary) advantage of making the antenna system
immune from noise not detected by the antenna elements, such
as the PC computers in the shack that everybody is always
complaining about, because twisted pairs cancel out induced
currents...which is why the phone company can smash thousands
of them together in a bundle, and why your CAT 5 cable works
at 100 Mhz without any shielding...imagine that.

Running an unbalanced feedline invites local noise, and using a
balun to then feed it into the balanced input accomplishes nothing
more than adding more loss and yet another tuned artifact into the
system. If you really want the extra stage gain on the unbalanced
input, do the Navy mod, which grounds one side of the balanced
input (making it unbalanced) and feeding the other side out the
unbalanced bulkhead connector. That gives you an unbalanced
75 ohm system which not only allows you to use cheap TV coax
like RG-59 or RG-11, but also just happens to be the impedance
at the feedpoint of a resonant half wave dipole.

WOW...Isn't that exciting? Now, listen to this...magnified ninety
two thousand times, the sound of the viscious Afgan panther lizard
visiting the chemist...

Twisted Twit Hammarlund

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