I've read Jim's choke cookbook, and I won't pretend to say I understand all
(maybe even any) of the math involved.
However, I can't escape the feeling you both reading too much into his
design of an RG-213 choke on cores?
He does also talk about compact bifilar windings on fewer cores, and
quadrifilar windings on dual core stacks, although not in as great a detail
on construction as the coax loops.
I agree, the coax loops might be a challenge for mounting to a yagi: Does
anyone see any instance where his cookbook shows those chokes on a yagi?
IIRC, most of his coax chokes are on wire antennas.
What I took away from Jim's RG-213 choke is this: for the right application,
for about $25 in cores and some coax from your collection, you can produce a
choke comparable to or superior than some of the commercial products costing
anywhere from $60 to $200.
At the base of a vertical, as an isolator for an end-fed coaxial dipole
(where the isolator-to-feedpoint part of the shield is one half of the
dipole) or as the feedpoint of an inverted vee (use a non-conductive sidearm
as an antenna support and mount the choke on the sidearm), are they not
useful and inexpensive? On an end-supported dipole with the feedpoint
suspended in the air, is the coax choke significantly heavier than an Array
Solutions box?
In the spirit of ham-radio frugality, is that not worth something?
Methinks there's a bit of a straw-man argument here in criticizing Jim for
something he never said.
73, kelly
ve4xt
On 11/4/14 7:56 AM, "Stan Stockton" <wa5rtg@gmail.com> wrote:
>
>>
>> ### My problem with the K9YC balun winding technique, as described
>> in his tutorial, is the winding technique itself. He depicts these huge
>> loops of coax on the outside of the cores. How is the completed assy
>> mounted to the feedpoint of the typ yagi ?
>
> I also have trouble contemplating having a big wad of heavy cores hanging from
> the driven element of a large Yagi where the driven element may be 30 feet or
> more from the mast.
>
> Reading K9YC materials it appears that anything less than 5-9 cores just
> wouldn't be good enough to do a good job on 14-30 MHz.
>
> Look at the specs on the Balun Designs two core choke wound with RG-400, rated
> at 5KW and sealed in a plastic box. Are those specs wrong or is there a
> discernible difference between that one and one wound on more cores? Will
> that choke, rated at 5 KW, handle 1500 watts in a contest?
>
> One other thing that is difficult for me to understand... Why would anyone
> ever consider using RG-58 or relatively huge diameter, heavy RG-213 (requiring
> more cores) as suggested in the material when silver plated,Teflon insulated,
> higher power handling, stranded center conductor RG-400 is available for very
> little money.
>
> I am gathering the ingredients to make some chokes. Do not want to be in
> situation where what I don't know DOES hurt me. Heretofore most of my
> antennas have had coax wound on a piece of PVC.
>
> I am hoping the end result is worth the trouble and not like an A/B real world
> comparison of a tower base with a PE stamped rebar cage design versus someone
> throwing in a big handful of rebar pieces one at a time as the concrete was
> poured for a guyed tower.
>
> 73...Stan, K5GO
>
>
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