On 4/14/2012 3:26 AM, Jim Brown wrote:
> On 4/12/2012 7:44 PM, Dan Hearn wrote:
>> If you would rather buy the chokes complete in weather tight boxes
>> they are sold by Balun Designs.
> I want to make it clear that I have no idea what Balun Designs is
> selling, I don't know them, I have had no communications with them, I
> have no business relationship with ANYONE selling chokes based on my
> designs, nor have I licensed ANYONE to sell them. For what it's worth,
> putting a choke in a weatherproof box confines the heat that is produced
> within it, and can cause destructive failure.
My question is, why put the balun in a box? Your designs survive out in
the elements just fine and normally receive maximum cooling that way.
The only changes I've made have been to tack the cores together with a
few dabs of epoxy. This does restrict the cooling a bit, but not nearly
as much as in a box, makes them easy to wind and keeps things from
shifting around. I often run the coax out of the choke through a 1/2"
of plexiglass for support. This basically leaves the entire balun
exposed to the elements.
> Any of my designs can be built VERY inexpensively, especially the ones
> that are bifilar wound with THHN in the form a parallel wire
> transmission line around a single #31 core, and were specifically
Inexpensive is a relative term. I purchased a whole case of 2.4" # 31
cores and use them liberally. They are likely to end up costing a
couple dollars more than a W2AU balun, but are far more effective. Any
of current chokes/baluns in the tutorial can be wound with up to 6 turns
of LMR400 or Davis BuryFlex and those with 6 cores (IIRC) will cover
160. It might take a little wire soap, but they can be made fairly
compact. With wire antennas I sometimes add a lightning suppression
device either at the antenna or the grounding bulkhead where the coax
enters the building to prevent static buildup.
> inspired by the needs of our brethren in the UK who appear to be getting
> ripped off by outrageous markups of Fair-Rite products by distributors
> with exclusive relationships, and where max legal power is 400W.
> 73, Jim K9YC
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