Tom,
I ran one on 80 meters for several years.
They work, but the internal automatic tuners are not likely to be able
to handle them.
For those who do not know what this antenna is, it is a half wave
length of wire at the lowest frequency you wish to work. As the name
implies, it is fed at one end by connecting one side of a piece of
open wire line or more likely now days, 450 ohm window line to the end
of the half wave length of wire. The other wire in the window line is
left un-terminated at the antenna end, but connected to the ground
terminal, or to the other side of the balun of the antenna tuner. This
un-used conductor basically works much like a counterpoise, and thus
becomes more or less the second half of the antenna.
The advantages of the end fed Zep are that it will tune on several
bands above the design frequency. Also because it is end fed, it is
often much easier to keep all or most of it hidden from the antenna
police.
One disadvantage is that it tends to be a little less efficient than a
center fed, although it certainly works well enough if you can get it
tuned.
The biggest disadvantage, however, is that matching the end fed zep is
very tricky.
The matching problem occurs because the antenna is fed at the end of a
half wave. This means the impedance is extremely high. Also, because
it is fed at a high rf voltage point, rather than at the high current
point in the center, not all tuners will handle the high voltage, even
at the 100 watt power level.
The one I ran was cut for 80 meters. It would tune fine on 40, 20, and
parts of 10 meters, but not well anywhere else.
There are some end fed zeps on the market that have a matching network
for one specific band, and that match the antenna directly to coax.
There is also at least one out there that claims to work on 40, 20,
and 10 meters.
We were trying to use that multi band model for our GOTA station at
field day last weekend. However, when we changed to a G5RV Junior, it
blew the end fed right off the planet on both 40 and 20 meters.
----- Original Message -----
From: "Tom Behler" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Sunday, July 01, 2012 4:18 PM
Subject: End Fed Zep Antenna
Hi, all.
As many of you know, I have been struggling with the Predator
screw-driver
antenna on my 31-foot Holiday Rambler RV, ever since my N2VZ
Turbo-tuner
became non-functional back about a year ago.
The Turbo-tuner issue is another story for another day, but suffice it
to
say that, due to the fact that N2VZ won't honor is "Lifetime
Warranty", it
is now not a viable option for me.
Anyway, in the interest of moving on, and pursuing other
possibilities, I am
wondering if something like an end-fed zep antenna might be an
easily-deployable HF antenna for the RV. There is not much room in
our RV
spot for a traditional half-wave dipole, or even an antenna like the
Alpha
Delta DXCC, but I thought an end-fed zep might be fun to try.
Does anyone have experience with these?
How much wire would I need to get up and running, say on 40 through
10
meters?
How easy or dificult would it be to make one?
I think I could run the antenna from the RV to a tree on the other end
of
our RV lot, if that would help.
Just exploring options here.
With the North American QSO Party CW contest coming up in early
August, I'd
like to have something up and running from the RV by that time, even
if it
is temporary.
73 from Tom Behler: KB8TYJ
|
