Bill,
Took your advice and downloaded the video. You are so right! This
will virtually destroy HF reception. Every ham operator needs to comment
right now on the FCC's ECFS Express system. You can get there from the
ARRL site. Don't wait for someone else to do it. The more response the
better!
Dave
W2QU
On Wed, 06 Aug 2003 22:20:59 -0400 Bill Tippett <btippett@alum.mit.edu>
writes:
> The interference from BPL is so bad you owe it to
> yourself to see (and hear) this video!!! Please visit this
> site and comment to the FCC before the window closes
> August 20.
>
> http://www.arrl.org/news/stories/2003/08/08/2/?nc=1
>
> 73, Bill W4ZV
>
> _______________________________________________
> DX mailing list
> DX@mailman.qth.net
> http://mailman.qth.net/mailman/listinfo/dx
>
>
>From ccc@space.mit.edu Thu Aug 7 11:21:12 2003
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Date: Thu, 7 Aug 2003 11:20:25 -0400
To: towertalk@contesting.com
From: Chuck Counselman <ccc@space.mit.edu>
Subject: Re: [TowerTalk] Twin-coax balanced line and Ant Sys
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"Chris BONDE" <ve7hcb@rac.ca> wrote:
>I think that I remember something from long time ago. Twin lead was
>inexpensive, coax was expensive, dipoles multi dipoles and
>non-resonant dipole were fed with twin lead or home-brewed twin
>lines.
I remember this, too; and it remains true today; doesn't it?
>Now, I think that this was terminated by an open air coil with multi
>taps outside of the house. The tapes were moved for the best
>connexion via two pieces of short length coax to the tuner or pie
>net work next to the Tx. Is this correct?
I don't remember hearing about an open-air coil outside the house;
and, anyway, an open-air coil outside seems to me a bad idea. It'd
be unsafe; insects and small birds would nest in it (Yeah, I know,
not for long; but there'd be residue.); and, where I live, it'd be
full of snow and/or ice for much of the winter.
So let's assume that we enclose it. Changing bands would require a
trip outside (Bummer!) unless you had a remotely operable switch or
relay arrangement.
Now removing my Grinch hat....
I have a very nice remote antenna tuner, made by RCA apparently for a
military or commercial application, and which I picked up as
surplus, which does more or less what you describe. It's in a large
weather-tight metal box with a removable, gasketed, access door and
two big beehive ceramic feed-throughs for connecting balanced
open-wire line to go to the antenna.
Inside is a 3-inch-diameter tank coil with several balanced pairs of
taps, and a big ceramic rotary switch for selecting a tap-pair. The
taps can be repositioned on the coil manually, and continuously
rather than just discretely, with a screwdriver. The switch is
operated by a stepper motor.
An additional deck of switch contacts selects a resonating capacitor
for each pair of coil taps. The capacitors are big ceramic
transmitting types. A screw-terminal strip is provided for changing
capacitors. (There's enough room in the box that I've considered
installing one or more continuously variable capacitors, for speedier
tuning. However, a continuously variable capacitor is not strictly
necessary, because the coil taps are continuously variable.)
The input to this tuner is by a single coaxial cable and is
link-coupled to the big tank coil. I suppose that you could connect
the coax shield directly to the midpoint of the tank coil, and the
coax center-conductor directly to a point on one side of center;
however, link coupling is superior because it provides excellent
common-mode isolation.
I haven't used this tuner yet, but some day....
73 -Chuck, W1HIS
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