[R-390] Antenna question

[Scott, Barry (Clyde B)]

I'd like to try this.  Curious about a few things, though.

1.  Isn't the impedence of a plain-old dipole somewhere near 50 - 75 ohms instead of 150?  I realize this isn't too bad for a receiver, but just wondering if there's a way to get a better match.  I know a folded dipole makes for about 300-ohms at the feedpoint, but that's not much better.

2.  Not familiar with CAT5.  Is it possible to take some good, insulated wire (I have a large spool of 26-ish gauge, stranded, teflon coated wire -- good quality stuff) and twist my own twisted pair?  Something along the lines of 2 to 4 twists per inch maybe?

Thanks for the suggestion.  I would like to have a separate receiving antenna so I can run my xcvr without changing the antenna everytime.

Barry(III)- N4BUQ

> -----Original Message-----
> From: Thomas W Leiper [mailto:twleiper@juno.com]
> Sent: Thursday, July 18, 2002 11:39 AM
> To: R-390@mailman.qth.net
> Subject: Re: [R-390] Antenna question
> 
> 
> 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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