[Lowfer] Re: antenna info

Thu, 4 Apr 2002 16:53:18 -0500

Thanks Jay. I'm going to give that a try for this next season. Hey, if it's
good enough for data buses and intercoms on aircraft it's good enough for
me!

73
John

 -----Original Message-----
From: 	[email protected] [mailto:[email protected]]
On Behalf Of Jay Rusgrove
Sent:	Thursday, April 04, 2002 4:49 PM
To:	[email protected]
Subject:	Re: [Lowfer] Re: antenna info

John

I have a center tap there and  it is grounded but in my setup there is
virtually
no change in noise or signal with it grounded or ungrounded. Not sure why
that
is.  The balance transformer works very well. If I unbalance either side by
touching it up comes the noise. I have been using this setup since December
and
it is definately quieter than coax cable even with the required decoupling
transformers.

Jay

john hoopes wrote:

> Jay, got a question on your loop. Is the CAT5 side of your transformer
> center tapped? I've been thinking about doing the same thing using twisted
> pair to carry the cigs back to the house.
>
> John
>
>  -----Original Message-----
> From:   [email protected] [mailto:[email protected]]
> On Behalf Of Jay Rusgrove
> Sent:   Thursday, April 04, 2002 3:35 PM
> To:     [email protected]
> Subject:        Re: [Lowfer] Re: antenna info
>
> John
>
> Just a quick followup.
>
> My receivers are sensitive enough that I don't need a preamplifier so the
1
> turn
> coupling loop (3/4 the size of the 17 loops)  just goes direct to the
CAT5.
> Inside I have an FT-114-77 balanced to unbalanced (conventional winding)
> with
> multiple taps so I can adjust the loading of the antenna. Assuming the
> receiver
> is 50 ohms (which it is - I measured it) I can present different loading
to
> the
> 1 turn antenna coupling loop and therefore have some control over the Q of
> the
> antenna. I'm currently using 13 turns on the 50 ohm receiver side and 18
> turns
> on the CAT5 side. This is the best ratio for my situation with the antenna
> near
> the ground. When the receive antenna was up at 70 feet for a day or two,
the
> transformer ratio was somewhat different.
>
> One of the other CAT5 pairs in the same bundle carries voltage to my
> motorized
> variable capacitor (1.5 VDC) out at the loop. Another pair was used to
carry
> receiver audio back out to the antenna before I had the motorized variable
> capacitor hooked up. There is no interaction between any of these pairs.
>
> Will be interested to hear of your results with the Star Quad cable.
>
> Jay
>
> John Andrews wrote:
>
> > Jay, et al:
> >
> > Your message about the Cat 5 receiving feedline brings to mind something
> > that I briefly tried over the winter, and want to explore more
> > quantitatively before next season.
> >
> > I am presently using RG-58 to as a feedline from a balanced antenna to a
> > balanced input on my in-the-shack preamp. Since I'm in the broadcast
audio
> > business, it occurred to me that this was a pretty dumb approach.
> >
> > Canare makes a great microphone cable for professional audio use with
> > balanced mikes and balanced inputs. They use the copyrighted term "Star
> > Quad" for their method of laying out the conductors in the cable. You
can
> > find out more about it at:
> > http://www.canare.com/cablemainframe.html
> > Just follow the links for "Star Quad."
> >
> > This is not a "Monster Cable" kind of thing. This is a standard
> professional
> > audio product. The characteristic impedance (for what it's worth) is
about
> > 45 ohms.
> >
> > Anyway, I borrowed an unfortunately too-short length of Canare L-4E6S
> cable
> > from work, and tried it with the loop. I wired it as I would for a
> broadcast
> > application, using the white wires connected together at each end, and
the
> > blue wires connected together at each end. I grounded the shield at the
> > shack end ONLY, to prevent a ground loop.
> >
> > Since the cable was short, I had to run it through an open window, and
it
> > was too darn cold to keep the test up forever. My conclusion was that I
> > seemed to get a little less local electrical noise with the mike cable.
> >
> > When I get a chance, I'll order some cable long enough for my regular
path
> > into the house, and will try some meaningful comparisons between it and
> the
> > RG-58. This would represent the ultimate in keeping-things-balanced with
> my
> > setup. I'll post the results here.
> >
> > John Andrews
> >
> > _______________________________________________
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>
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