Thanks for sharing the patent info, Frank! Really interesting!
73,
Charlie, K4OTV
-----Original Message-----
From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of
donovanf@starpower.net
Sent: Thursday, October 17, 2013 12:15 PM
To: topband
Cc: Tim Shoppa
Subject: Re: Topband: W8ji ATR-10 design 160M?
Hi Tim,
This is the patent for the classic Edgar F. Johnson (E.F. Johnson)
transposition insulator:
http://reference.insulators.info/patents/patents/pdf/4/us002043754-001.pdf
http://www.google.com/patents/US2043754
I've seen these a few times at hamfests, without exception the sellers are
clueless about what they are.
73
Frank
W3LPL
----- Original Message -----
From: "Tim Shoppa" <tshoppa@wmata.com>
To: "Paul Christensen" <w9ac@arrl.net>, "topband" <topband@contesting.com>
Sent: Thursday, October 17, 2013 4:37:09 PM
Subject: Re: Topband: W8ji ATR-10 design 160M?
Very interesting! I remember seeing transposition blocks at hamfests when I
was a kid but I didn't know what they were at the time. Looking up some old
patents, e.g. http://www.google.com/patents/US2305688 and
http://www.google.com/patents/US2135344 show something very similar to what
I saw as a kid.
The advice I was always given about parallel lines, is to have some twist in
them, not just to help with balance, but to help prevent them from turning
into "sails" in high wind.
Where possible I try to put my tuner where the wire enters the shack. I
thought I was pretty clever the way I set up my link-coupled tuner,
wall-mounted L network, plugboard to select L and C based on band, etc.,
then I open an old issue of QST and there's a picture of a kid who had the
EXACT same setup on the wall of his shack 60 years ago. I mean, exact.
Tim N3QE
-----Original Message-----
From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of Paul
Christensen
Sent: Thursday, October 17, 2013 11:18 AM
To: topband
Subject: Re: Topband: W8ji ATR-10 design 160M?
> So what different bout your tuner, is it like the ATR-10 design?
Nothing special. It's just a symmetrical balanced tuner with a pair of
synchronized roller inductors and a large vacuum variable cap (with a very
small minimum C and large max C) that's switched with a pair of vacuum
relays. A 1:1 coaxial choke is used on the input since the circuit is
symmetrical. In fact, it's really just a variation of the AG6K tuner
described in QST some twenty years ago.
I went with this design since I'm presently restricted to wire antennas.
And due to the presence of switch-mode appliance noise, the goal was to keep
the open feeders as far away from the house as possible. Balanced open lines
are capable of a high degree of balance but on receive, their ability to
cancel noise is dependent on the orientation of the line to the direction of
the noise source. If you look at early literature from the 1930s, open
feeders often used transposition blocks. I own several different types made
by E.F. Johsnon as display pieces. Nice concept -- I'm not sure how
satisfied I would be with using them. Anyway, to better deal with the
household noise issues, the tuner is located outside of the house, in a
weatherproof enclosure. LMR400 is then used between the tuner and shack.
Paul, W9AC
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