First, electrical engineering is not a science, it's an art as
compromises must be made. Fresh water is a terrible ground, so using a
ground independent antenna is a compromise. Yes, a 1/4 wave antenna over
ground will not be great for DX, but does allowm entering the 40 meter
nets. Having said that, the antenna will be a 1/2 Wave on 20; that will
lower the main lobe. You may not get the re-enforcement over fresh
water, but it's more radiated power than using a vertical with a very
poor ground system. We can debate the phenomena, but no mater a
compromise is going to be required. Like I said at the top, EE is an art
and not science and this artist has chosen to approach a solution swet
this way. I'm quite sure there are other artists who may have other
compromises.
73,
Barry
K3NDM
------ Original Message ------
From: "Jim Brown" <[email protected]>
To: [email protected]
Sent: 6/9/2020 6:24:37 PM
Subject: Re: [Elecraft] K3 on motorboat.
On 6/9/2020 3:13 PM, Barry wrote:
I counsel inverted Vs as they are ground independent.
Not really -- the earth in the near field is lossy (including fresh water) and
in the reflection from earth in the far field combines with the direct signal
to produce the vertical pattern. Almost any horizontal antenna for 40M or lower
that we can rig on a small boat will be a low one, so will be a high angle
antenna, over fresh water, a lossy one. In general, verticals are better than
than horizontal antennas over water, fresh or salt, because of the far field
reflection, as long as a suitable counterpoise is provided.
73, Jim K9YC
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