A very important caution about the performance of T-verticals
vs. Inverted-L verticals.
If the performance of your 40 meter antennas is important to
you and your T-vertical is within 300 feet of your 40 meter
antenna, its important that the top of your T should be less
than 55 feet long or more than 80 feet long.
Why? If the T-top is 55-66 feet long it will act as a 40 meter
director. If its 66-80 feet long it will behave as a 40 meter
reflector. Don't ask me how I discovered this...
If the top of a T-vertical needs to be 55-80 feet long and within
300 feet of a 40 meter antenna that you don't want to degrade,
its better to use an inverted-L vertical, which has little or no
affect on nearby higher frequency antennas.
73
Frank
W3LPL
----- Original Message -----
From: "Guy Olinger K2AV" <k2av.guy@gmail.com>
To: "Jerry Keller" <k3bz@verizon.net>
Cc: "REFLECTOR: Topband" <topband@contesting.com>
Sent: Tuesday, December 6, 2016 5:05:37 AM
Subject: Re: Topband: Inv L Config
The horizontal section also radiates, more or less than the vertical
depends on the specifics. Easy to see in a very simple NEC model. If you
are opposed to radiation from the horizontal on principle, then put up a T.
But the radiation from an L's horizontal fills in the doughnut hole in the
pattern, essentially getting the energy for that by taking it away from
ground losses. Assuming that on 160 one has RX antennas because TX antennas
are notoriously noisy, then you only care about what happens to TX. Filling
in the doughnut hole helps to minimize or eliminate skip zones, and help
keep a run frequency running low power.
The effect of a particular change to wires applies more to where the
current is more. Given that, doubling the vertical wire is what you do. But
I would model that and see what it buys you. Do the change both in free
space and over ugly dirt.
73, Guy K2AV
On Mon, Dec 5, 2016 at 11:37 PM, Jerry Keller <k3bz@verizon.net> wrote:
> Is it advantageous to make both the vertical and the horizontal sections
> "fat" (for improved bandwidth), or is it enough to "fatten" the vertical
> (radiating) section ? How much BW will 3" diameter spacers give me?
>
> 73, K3BZ
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