[TenTec] OT: coax versus parallel wire

[Denton]

I am using homebrew ladderline with 4 1/2 inch spacing to feed a 230 ft 
horizontal loop. Would you consider that to be excessive for use on 10 
meters
I am using the loop on 80 thru 10 meters. Can redo the spacers easily 
enough.
----- Original Message ----- 
From: "Dr. Gerald N. Johnson" <geraldj at storm.weather.net>
To: <tentec at contesting.com>
Sent: Tuesday, June 10, 2008 3:43 PM
Subject: Re: [TenTec] OT: coax versus parallel wire


> On Tue, 2008-06-10 at 14:24 -0700, Jim WA9YSD wrote:
>> doc, I am missing something here  you said for 160M .001 - .01 Wave 
>> length right?  For 80M I come up with 3.4 to 24 inches spacing.  That 
>> does not sound right, or is it?
>>
>>  Keep The Faith, Jim K9TF/WA9YSD
>>
>>
> Well, I figure I couldn't say 6" was too wide on 160m while I allowed
> 1/4" on 1296 or even 1/2" on 2m, though I know 3/4" is probably actually
> too wide at 6m. The closer the spacing, the better. And remember that
> the ARRL hand book formula for characteristic Z is WRONG for low
> impedances, below about 250 ohms. Their formula has the conductors
> overlapping at about 160 ohms, yet the correct formula allows even 1 ohm
> Z for balanced pairs, though it does require large conductors spaced
> only a few microinches.
>
> The best reason for wide spacing is power handling, but with 1/8" space
> in the tuner capacitors, its unlikely to flash over a transmission line
> with 1" space. Just maybe that sometimes a wider spacing allows sturdy
> conductors and a high enough impedance to come close to matching the
> antenna (such as a full wave zepp). I think VOA used 12" spacing at
> Dixon, Delano, and Bethany with 250 KW output on AM (1 MW peak), maybe
> 18". At Collins we used two 150 ohm coaxes in push-pull, made of 1/2"
> copper water pipe center conductors in separate 8" aluminum (irrigation
> tubing) outer conductors. That made the closest spacing we could support
> about 8". We did occasionally flash over those lines, about the time the
> SWR on the dummy load was rising as it burned up again. A MW peak at HF
> can get unruly.
>
> The trade off is that the wider spaced line radiates (or receives) more.
>
> 73, Jerry, K0CQ
>
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