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Re: [TowerTalk] OWAs or Fans?

To: towertalk@contesting.com
Subject: Re: [TowerTalk] OWAs or Fans?
From: "Roger (K8RI) on TT" <K8RI-on-TowerTalk@tm.net>
Date: Thu, 16 Jun 2016 01:19:35 -0400
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Already looked at it. I hate to say it but I'm anti open wire feeders. Hate 'em with a passion. Every time I've been near one it's caused trouble. I much prefer coax and a good choke to get rid of common mode. Typically use your pages that hold a wealth of information, but with the 5 slopers, I see more headaches with open wire than with coax. I'll put up with a little more loss for convenience. I can still usually join a pileup and still work the DX on one or two calls, I remember not too long ago, the station was laughing and said, now there's a ham with confidence, he only gave his call once, which I had and it worked. I just listened for a minute or two, saw a pattern after a few contacts, waited for a lull and gave my call. In most instances, it's timing, not power. OTOH there are some rock crushers you just wait out.

BTW: They may be over kill, but I think my open, multi core, with spacing, implementation of your designs will handle the legal limit, key down, no time limit.

73

Roger (K8RI)


On 6/15/2016 Wednesday 10:58 PM, Jim Brown wrote:
On Wed,6/15/2016 5:32 PM, Roger (K8RI) on TT wrote:
With that set up, it worked well at 200 W, but as I increased the power, around 1 KW (maybe a little less) every LED in the system lit up. Instead of hanging more weight at the feed point, I added another choke with 5 cores and 6 turns ( wound much tighter) where the feedline reaches the tower. That completely cured the problem up to full power out.

Hi Roger,

Look at Slide 17 in k9yc.com/7QP.pdf for a bifilar-wound choke connected as parallel wire transmission line. This is a #31 core. The choke design is mine, but the slick mechanical design is by Glen, W6GJB.

This choke is good for at least 600W at contesting duty cycles for CW, SSB, and even RTTY if installed in a center-fed resonant antenna. For greater power handling, a second choke either in the air or farther down the line is needed. This choke CAN fry (I've done it) at high duty cycles of legal limit CW (calling CQ after you've already worked everyone on the band). :)

The wire is THHN, so Zo is 80-90 Ohms; antennas like the C3SS (which we really like for portable operation) doesn't like it (I think the mismatch screws up N6BT's coupling method), but the C3SS works fine if you wind it with a tightly spaced pair #12 enameled wire.

We did something similar in concept with different hardware in

http://k9yc.com/80M-FDVertical.pdf See slide #26. Designing conservatively, we used three chokes, but actual operation showed that two was enough. Our use was with a KPA500 on CW for 7QP.

You asked about an OWA; I've lost track of what OWA is short for. :)

73, Jim K9YC


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