[TowerTalk] Suggestions for 80, 160m?

[Ken Hirschberg]

Hello, Jonathan - FYI, CAL-AV Labs, of Tucson is introducing some large (about 16
feet high x 36feet long, 6" dia. tubing) for 80/160.  You may wish to consider
one of these.  They require a substantial ground plane, but one very much smaller
than that required for a full size "FCC" vertical ( 1/4 wave radiator over 120
radials, etc.).  Modeling shows that these antennas will slightly outperform the
full-size quarter wave owing to the effect of the two out of phase vertical
segments;  this effect has been verified by field tests on 40M, using a 4' x 8'
loop.
Sincerely, Ken Hirschberg, K6HPX
President, CAL-AV Labs.



Bill Coleman AA4LR wrote:

> On 5/11/00 5:30 PM, Jonathan Kaplan at jonk@jskent.com wrote:
>
> >       I'm think of putting up an antenna to cover 80 and 160 m bands and
> >I find all the argument about low band antennas somewhat confusing, so I'll
> >just ask straight out: What kind of antenna will give me DX on low bands?
>
> Most DX transmitting antennas for the low bands, when used with (relative
> to the wavelength) short supports are verticals. Horizontal antennas, low
> to the ground aren't that effective. (Although I did work TM2Y on 80m
> with a 15 foot high 80m dipole and 90 watts....)
>
> >       I have a 55 foot tower (crank-up) on a hilltop near the ocean
> >  with a 40m rotatable dipole and a TH7DX on the top.
> >There is a 20 foot pole available about 100ft away downhill, available for a
> >sloper if needed and it probably would be difficult to bury radials.
> >       Given  all that, what kind of antenna would work best?\
>
> Why would it be difficult to buy radials?
>
> I'm planning a similar installation, with a 49.5 foot bracketed tower, an
> A3S with a 40m kit. For 80m, I plan to shunt feed the tower, using a
> gamma or omega match. With the beam acting as a capacity hat, it should
> be close to a proper quarter wavelength vertical. For 160m, I haven't
> decided yet. Seems like the tower is much too short to be an effective
> radiator for 160m. (like less than .1 wavelength)
>
> An alternative would be an inverted L. These work well. You could slope
> an inverted L for 160m down toward your pole 100 feet away with good
> effect.
>
> The key to either shunt feeding or an inverted L is an effective radial
> system. With the shunt feed, you just about have to use ground radials. I
> plan on as many and as long as I can fit in my lot. If you elevate the
> feedpoint of the L, you can use elevated radials. The supposed advantage
> of elevated radials is that you don't need as many to make an effective
> radial system. (This is a matter of some debate -- there are a lot of
> success stories, but the field strength measurements comparing a proper
> ground radial system with an elevated system don't match) The
> disadvantage of elevated radials are that a) you lose some of the
> effective hieght of your support and b) you have to find a way to support
> the radials.
>
> Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr@radio.org
> Quote: "Boot, you transistorized tormentor! Boot!"
>             -- Archibald Asparagus, VeggieTales
>
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