[Lowfer] Re: antenna info

Thu, 4 Apr 2002 16:15:59 -0500

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
>
> _______________________________________________
> Lowfer mailing list
> [email protected]
> http://mailman.qth.net/mailman/listinfo/lowfer

_______________________________________________
Lowfer mailing list
[email protected]
http://mailman.qth.net/mailman/listinfo/lowfer