[Lowfer] Re: antenna info

Thu, 04 Apr 2002 17:56:10 -0500

John

Let me know how you make out.

Jay

john hoopes wrote:

> 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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