You guys crack me up. The poor guy wanted a simple longwire solution.

I want one too, and that's how I found this thread.

I read in W1FB's Antenna Notebook that you can take a 1 wavelength
piece of wire, feed it with 75 Ohm coax 1/4 wavelength in from one
end, with the hot side going to the 3/4 wavelength piece and the
shield going to the 1/4 wavelength piece. It looks like you don't
need any type of tuner.

Has anybody tried that? I'm looking for a simple antenna for PSK-31
QRP that the homeowners association won't even see, and this looks
like the deal, but I can't find any corroboration for the concept.

Dave Morris
N5UP
www.eQSL.cc

In article om,
wrote:

I read in W1FB's Antenna Notebook that you can take a 1 wavelength
piece of wire, feed it with 75 Ohm coax 1/4 wavelength in from one
end, with the hot side going to the 3/4 wavelength piece and the
shield going to the 1/4 wavelength piece. It looks like you don't
need any type of tuner.

Has anybody tried that? I'm looking for a simple antenna for PSK-31
QRP that the homeowners association won't even see, and this looks
like the deal, but I can't find any corroboration for the concept.

That sounds like a form of off-center-fed resonant doublet. Since the
radiator is 1 wavelength long, it will have current maxima 1/4 away
from each end (which is where you're feeding it).

I'd guess that it will provide a reasonable (although imperfect) match
to a 75-ohm coax... you might see an SWR of 2:1 or so on the coax.
The impedance seen by the rig will depend on the length of the
feedline, and a rig designed to drive a 50-ohm load might see a fairly
low SWR, or perhaps one as high as 3:1 or 4:1 (at a guess). If your
rig has a built-in ATU, it's probably adequate to flatten this sort of
SWR down to the point where the rig's finals are happy with it.

There's likely to be some amount of RF current present on the outside
of the coaxial feedline, due both to conduction at the feedpoint and
to induction from the wire (since the feedline is not located
symmetrically in the center of the radiating element). If this causes
sufficient "RF in the shack" to be a problem, you might want to add an
isolating choke where the feedline enters the building... and if there
isn't enough RF in the shack to cause problems, then don't worry about
it. In either case, it's probably going to be less RF-in-the-shack
than you'd get with an end-fed longwire, fed against the station
ground or a counterpoise.

Seems like a reasonable candidate for a "stealth" antenna, if you can
conceal the coax running up to the feedpoint, and use a thin-gauge
wire as a radiator (e.g. thin-gauge enamel-insulated magnet wire).

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

On Jul 24, 5:34 pm, wrote:
You guys crack me up. The poor guy wanted a simple longwire solution.

I want one too, and that's how I found this thread.

I read in W1FB's Antenna Notebook that you can take a 1 wavelength
piece of wire, feed it with 75 Ohm coax 1/4 wavelength in from one
end, with the hot side going to the 3/4 wavelength piece and the
shield going to the 1/4 wavelength piece. It looks like you don't
need any type of tuner.

Has anybody tried that? I'm looking for a simple antenna for PSK-31
QRP that the homeowners association won't even see, and this looks
like the deal, but I can't find any corroboration for the concept.

Dave Morris
N5UPwww.eQSL.cc

Be sure and coil 7 or 8 turns the coax as a choke, at the feed
point... Other than that it will work fine... Don't let the
technical types here discourage you with their analysis of your
impedence, etc......
Get on the air and make Q's...
denny / k8do

wrote:
You guys crack me up. The poor guy wanted a simple longwire solution.

We gots dummies like me here, and we gots really smart folks here.
Sometimes the threads veer off into discussions of how many angels can
dance on the head of a pin. But everyone means well.



I want one too, and that's how I found this thread.

I read in W1FB's Antenna Notebook that you can take a 1 wavelength
piece of wire, feed it with 75 Ohm coax 1/4 wavelength in from one
end, with the hot side going to the 3/4 wavelength piece and the
shield going to the 1/4 wavelength piece. It looks like you don't
need any type of tuner.

I'd be pretty skeptical that no tuner was needed, but see above for my
dummy status... ;^)


Has anybody tried that? I'm looking for a simple antenna for PSK-31
QRP that the homeowners association won't even see, and this looks
like the deal, but I can't find any corroboration for the concept.


You might want to try 2 20 meter mobile whips arranged as a dipole.
Quick and easy to set up and tear down.

That of course is assuming you are doing 20 meter psk, where most of
the activity is.

- 73 de Mike KB3EIA -

Michael Coslo wrote in
:

wrote:
You guys crack me up. The poor guy wanted a simple longwire
solution.

We gots dummies like me here, and we gots really smart folks
here.
Sometimes the threads veer off into discussions of how many angels can
dance on the head of a pin. But everyone means well.



I want one too, and that's how I found this thread.

I read in W1FB's Antenna Notebook that you can take a 1 wavelength
piece of wire, feed it with 75 Ohm coax 1/4 wavelength in from one
end, with the hot side going to the 3/4 wavelength piece and the
shield going to the 1/4 wavelength piece. It looks like you don't
need any type of tuner.

I'd be pretty skeptical that no tuner was needed, but see above for my
dummy status... ;^)


Has anybody tried that? I'm looking for a simple antenna for PSK-31
QRP that the homeowners association won't even see, and this looks
like the deal, but I can't find any corroboration for the concept.


You might want to try 2 20 meter mobile whips arranged as a
dipole.
Quick and easy to set up and tear down.

That of course is assuming you are doing 20 meter psk, where most
of
the activity is.

- 73 de Mike KB3EIA -

Hi All:

Just out of curiosity, I modeled a one wavelength antenna, on 14.07MHz at
32’ high over average ground. The wire, #12 was 68.75’ long feed 17.2 feet
from one end. The antenna was resonant at the design frequency, IE no
reactance with an impedance of 105 ohms. This would give about a 2:1 SWR.
The pattern is typical for a 1 wave length antenna. 4 lobes with the peak
gain at about 45 deg angles to the wire. The gain was 6.9dbi at a vertical
angle of 33 deg.
Two things to note about this design, at the time it was proposed a 2:1 SWR
was considered quite OK. The radios of the day could handle it just fine.
Also the feed line will radiate like mad. This is severely unbalanced
antenna and would benefit from a choke balun. A 2 to 1 balun would give a
good match.
It’s a usable antenna, maybe not the best antenna for today station, but
usable.
In fact the off center feed make it a nice antenna for a hidden antenna.

John Passaneau W3JXP