I also wonder if a 1/1 balun would help. I think it'll isolate the coax from the loop.
----- Original Message -----
From: Tom Fowle <[log in to unmask]>
To: [log in to unmask]
Date: Sunday, December 13, 2015 6:50 pm
Subject: Re: Report on 10M Loop Project, and Request for Feedback
>
>
> Richard,
> So far as I can tell, your math is correct. I aggree with others, fixing it
> will most likely make no audible difference for RX.
>
> You should be able to remove pipe from only two opposite segments of the
> loop, it will be a bit "squished" that way but much less work and again
> shouldn't make any operational difference.
>
> but if you're being obsessive, go haead and cut some off all the sections,
> what the heck! <GRIN>
>
> I wonder if placing a small varriable capacitor across the feed point would
> let you adjust for a better match, but again, probably no difference on RX
> and you'd have to have an analyzer available to fiddle with it.
>
> Tom Fowle WA6IVG
>
> On Sun, Dec 13, 2015 at 06:58:55AM -0800, Richard B. McDonald wrote:
> > Hi!
> >
> >
> >
> > I want to report on my 10M full wave loop (FWL) project, and ask for
> > feedback on it. My aim was a resonant antenna at 28.4 MHz for RX only on my
> > TS-2000. I viewed this project as practice for the antenna I *really* want
> > to make - an 80M FWL for both RX and TX (inspired by Ron).
> >
> >
> >
> > To make my loop, 14 gauge insolated stranded copper wire sits inside 1" PVC
> > ~12' atop my wooden shack. It is in the shape of an octagon. I measured
> > the length of the wire at 1005 / 28.4 = 35.39', which I rounded to 35.5'.
> > There is a 25' run of 75 ohm coax (the kind for TV, which I was told is fine
> > for RX antenna purposes like this) properly soldered to the ends of the
> > wire.
> >
> >
> >
> > So, my friend from our ham club measured this antenna with his analyzer. It
> > turned out to be resonant at 25.5 MHz : ( Now, only because I am obsessed
> > with my project and by way of learning, I should like feedback on the
> > following:
> >
> >
> >
> > 1) I am told that one thing affecting resonance is the "velocity
> > factor" of the wire. Apparently, the insulation of both a) the wire itself
> > and b) the PVC affects the velocity factor. I have no idea what "velocity
> > factor" is, nor how it affects the calculated length of a wire for a FWL as
> > per the above.
> >
> > 2) To bring the resonant frequency up to 28.4 MHz, I *think* I need to
> > decrease the size of what I have built. Is that right? "Decrease" as in
> > shorten rather than "increase" as in lengthen?
> >
> > 3) To decrease the size of my loop, I plan to cut 6" (0.5') off each of
> > the eight sides of the octagons for a total of 4' (including obviously the
> > wire therein). Check my math (reasoning) on this. 28.4 / 25.5 = 1.11;
> > meaning I am too big by 11%. 0.11 * 35.5 = 3.9; say 4'.
> >
> >
> >
> > Incidentally, even though my loop is a little off, it seems to RX better
> > than my 43' vertical does on 10M. Some have said that for RX only this
> > resonance differential is insignificant. In other words, they say that even
> > if I tune my loop precisely to 28.4 MHz, on 10M it would be imperceptible as
> > to 25.5 MHz for RX. What do you think about this?
> >
> >
> >
> > 73,
> >
> > Richard KK6MRH
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