Topband: W8ji ATR-10 design 160M?

[Shoppa, Tim]

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 at 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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