> As I'm sure you know, you can tell when the vertical antenna is
performing better; the SWR goes up. A lossy vertical will have a low
SWR because the high ground losses are in series with the radiation
resistance and the sum comes out perversely close to 50 Ohms. A low
loss vertical is around 30 Ohms.
Not exactly. It more be more accurate to say that "you can tell when
a short vertical (or otherwise loaded) antenna is performing better
because the low-SWR bandwidth (e.g., the range over which the SWR
is less than 2:1) decreases."
Yes, I'm nit-picking here, but I think it's important to be clear
on this. With proper loading and matching, pretty much any usable
antenna can have 1:1 SWR on one specific frequency. But short
antennas have narrow usable bandwidth unless they are very inefficient.
>> That's why a horizontal dipole is usually preferred to a vertical if
there's sufficient space
>> to erect it.
That's the gotcha. If you have a horizontal dipole at the same height
as the top of a vertical dipole, in the broadside direction the
horizontal wins hands down, provided you have two supports high
enough to support the dipole. The current loop of the horizontal is
twice as high as the current loop of the vertical.
And, of course, those lucky Hams who can put their horizontal dipole up
about 1/2 wavelength where it works best get a huge advantage. At 20 degrees
it shows nearly 6 dB gain: equivalent to multiplying the transmitter power
by four times!
I work mostly "local" North American stations on 20 and below, but
once the 'spots come back I'll see what DX I can do on 10. 10 is
about the only band where my yard can realistically handle the
otherwise-mythical "half-wave dipole half a wavelength high".
My G5RV and 20 meter Moxon are both up about 15 feet. It's difficult
to give meaningful figure for G5RV height, partly because it slopes
down somewhat like an inverted-vee at both ends, but mostly because
the yard itself is not level and there is a sharp discontinuity more
or less under the feedpoint.
I think that there hasn't been enough discussion (in general, not
specifically on the Elecraft list) on the benefits of low beams
over low simple antennas. Too many articles on beams start out
with the assumption that you can put them up a 1/2 wavelength high.
Given the increasing urbanization of America and the trend toward
smaller yards, fewer and few hams are going to be able to do this
in the future.
If they really want record breaking contest results, they should
use a rare DX call, a seaside location and female operators on
SSB. The female voice seems to give you the same effect as another
6 dB in transmitting power. We have a "go for blood" contesting
group here in Maine that deliberately schedules as many female
operators as possible on Field Day to run up their score; it
really works. Of course this requires YLs who do not mind insects
and outdoor plumbing, and those are few and far between.
<smile>
Perhaps I should try that some time. Since I work
almost all digital modes and CW rather than SSB, I don't get
any advantage. :-)
Cathy
N5WVR
_______________________________________________
Elecraft mailing list
Post to: Elecraft@mailman.qth.net
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com
