Help with commercial VHF mobile antenna
On Wednesday, July 3, 2013 8:36:44 PM UTC-5, Jeff Liebermann wrote:
There was an article in QST last
year demonstrating that the signal comes from directly overhead. While
DX'er try to optimize the takeoff angle to match the equal angles of
incidence and reflection, perhaps it would more interesting to try
maximizing the gain straight up?
Heck, that's what we have done for years on the lower bands.
"NVIS" On 80m, with the usual distances used for general jibber
jabber, most signals do arrive at fairly high angles.
And this was always on our minds when choosing an antenna.
But it's fairly handy that a dipole or horizontal loop at the
most used heights does shoot the bulk of the power at high angles,
with max often straight up.
For rag chew type stuff close in, a dipole is almost always preferred
over a vertical.
In my case, I always had max gain at high angles, so the only
thing left to improve was system efficiency.
Which leads me to feed with coax with no tuner used for a very
high system efficiency. Coax is slightly more lossy than ladder
line, but at 4 mhz the loss using good coax is so low you would be hard
pressed to tell the difference with the average length feed line
vs say the Cecil method using a tuned ladder line with no tuner.
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