[TowerTalk] OWAs or Fans?

[Roger (K8RI) on TT]

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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