Hi Rob (and gang),
I would like to make one point that should be considered in this discussion.
A true vertical which is what I use (not an inverted L) on 160 meters is
sometimes horrible on 160 meters for skywave that originates from close in
(200 miles or less as an example). During contests I sometimes can't hear
a station calling me on my vertical since it's deaf to NVIS signals
(signals arriving at a very high angle), but when I switch to one of my
pennants suddenly I'm hearing the station 18dB to 38 dB over my noise floor
(really an amazing phenomena). The pennant RX antenna gain is only 5 dB
down on NVIS (for signals arriving directly overhead) compared with the max
gain of the pennant which is at 31 degrees above the horizon. In
comparison my 68 foot base loaded vertical has a gain of -20 dB or worse
for NVIS at an angle 85 degrees or higher above the horizon compared to its
max gain at 22 degrees.
Therefore while I don't disagree that a vertical on 160 meters is a great
antenna especially for DX work, for working stations in close it sometimes
can be a disadvantage. Based on modeling it looks like a dipole only 15
feet off the ground on 160 meters would perform much better than my
vertical for signals arriving at very high angles (as an example).
Therefore depending on Gary's goal, a true vertical on 160 meters may or
may not be in his best interest (but an inverted L might be).
Just one of the many things to consider.
73,
Don (wd8dsb)
On Wed, Dec 2, 2015 at 12:53 PM, Rob Atkinson <ranchorobbo@gmail.com> wrote:
> Hi Gary, It would make a nice receiving antenna.
>
> Let's start with a question: Would you put up a loop for 20 meters
> that is 6 feet off the ground? Height for horizontal antennas must
> always be thought of in terms of _wavelength_. There is only one
> effective transmitting antenna for medium wave, assuming you do not
> have 200 foot tall supports for stringing up a horizontal wire
> antenna, and that is some sort of monopole over a good ground system.
> Period. And good ground system means a lot of radials. A lot. Not
> 10 or 20. You don't get to cheat on the laws of physics. You have to
> bite the bullet and do the work. The excited vertical part has
> options. T, inverted L, or an insulated tower are all fine provided
> the vertical part is at least 50 feet tall (more is better).
>
> Don't take this personally--it's just that I get tired of piss weak
> signals on 160 from hams who seem to think they have an exemption from
> Mother Nature. A dead giveaway that a ham is using a low dipole, 20
> feet or so, is rapid deep QSB. Even 50 feet is too low. Inverted Vs
> are worse. the effective height is halfway between the apex height
> and the height of the ends. A big horizontal loop on transmit does
> nothing for you but cause more of your RF to get lost to ground
> coupling.
>
> 73
>
> Rob
> K5UJ
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