K4SAV wrote:
> Lee
>
> Here are a few items to consider about your planned 160 antenna.
>
> Warning: This post is long and has a lot of detail which may bore some
> of the readers, but I'm sure Lee will be interested.
>
> Lee said: ..."A mil-spec balun from Antenna Products rated at 2-30M 4Kw PEP
> http://www.antennaproducts.com/BINDEX.htm<about:blank> SM-153."...........
>
> Where did you find the data on this balun? All I could find was on
> their website and it said 1 KW av / 2KW PEP. There was no other info,
> no mention of what type balun it is. You said it was MIL Spec.
And what MIL-STD would they be talking about anyway? 810? 461?
"mil-spec" is a term just thrown around a lot, often for anything a bit
more rugged that crummy and painted green. Either you cite the actual
number, or (better) give the specs that you're actually meeting.
Temperature? Humidity? Salt Spray? Paint?
> I am not familiar with 9931 coax. Did you mean to say 9913? If so, it
> would not be my choice for 160 meters. It's low loss but if you let
> water get into it, it's trash. Most coax has little loss on 160. I
> would recommend inexpensive RG213 for this.
Uh.. there's no such thing as RG-213 anymore (except as decades old
surplus), just "RG-213 similar" or "RG-213 type", since that designation
was obsoleted some years ago. But we do use that (as well as RG-8) as a
shorthand for .405" OD coax with solid PE dielectric and AWG 13 center
conductor, probably ANY of which would be fine at 2 MHz.
At that frequency, almost anything would be ok (unless you have a
positively horrid match and hundreds of feet of coax).. center conductor
diameter is going to be the real issue.. bigger is better, because the
loss is lower. The dielectric loss at 2MHz is going to be negligible for
almost any dielectric that's used in coax (or even zip cord, for that
matter). I don't know I'd make my tuning capacitor out of window glass
or beer bottles though.
> Lee said: ... 50 feet of 9931 coax with a 6" PVC air choke made from 25
> feet of 9931 wrapped....
Get yourself a bunch of 31 mix toroids of appropriate size (2.4") and
make your choke that way (you can get 5 or 6 turns of RG-213ish coax
through without any trouble). Lots less coax involved, and probably a
better choking impedance to boot, as well as not having to deal with
self resonance.
Jim, W6RMK
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