On Aug 5, 1:33*pm, "Al Lorona" wrote:
Anybody with experience with this antenna? It appears to be a quasi-vertical
dipole with two "radials" attached to the bottom end and fed at the bottom.
At least this appears to be the case; I could be wrong.

What issues arise when feeding a dipole at one end (the bottom in this
case)? This can't be a truly balanced design, can it?

Al *W6LX

I've run plenty of base fed half waves, but never saw a need for
two lower elements.. You can't really call them radials in that case.
They have nothing to do with lowering ground loss.
But it's hard to tell, being I've never seen the antenna.
But if I were base feeding a half wave, I would not bother
with two lower elements spread apart. No real point in it.
The main difference in feeding at the base vs feeding in
the center is impedance. A much higher Z when base fed,
so you need a matching device. And for that I usually
prefer a single turn coil and a coax capacitor. Some have
called this a "gamma loop" matching device, which is
fairly close I suppose being as you tap the single turn
coil at the point of best match, much like the usual gamma
match. Truly balanced? Nope.. But that really doesn't
mean much. Even a center fed half wave can have common
mode problems. So it's not like that method of feeding cures
all feed line radiation problems.
They will both require decoupling sections for optimum
performance. But saying that, you can often run a half wave
with no real decoupling and have decent results.
It will vary to each installation.

On Aug 6, 7:38*pm, wrote:
On Aug 5, 1:33*pm, "Al Lorona" wrote:

Anybody with experience with this antenna? It appears to be a quasi-vertical
dipole with two "radials" attached to the bottom end and fed at the bottom.
At least this appears to be the case; I could be wrong.

What issues arise when feeding a dipole at one end (the bottom in this
case)? This can't be a truly balanced design, can it?

Al *W6LX

I've run plenty of base fed half waves, but never saw a need for
two lower elements.. You can't really call them radials in that case.
They have nothing to do with lowering ground loss.
But it's hard to tell, being I've never seen the antenna.
But if I were base feeding a half wave, I would not bother
with two lower elements spread apart. *No real point in it.
The main difference in feeding at the base vs feeding in
the center is impedance. A much higher Z when base fed,
so you need a matching device. And for that I usually
prefer a single turn coil and a coax capacitor. Some have
called this a "gamma loop" matching device, which is
fairly close I suppose being as you tap the single turn
coil at the point of best match, much like the usual gamma
match. *Truly balanced? *Nope.. But that really doesn't
mean much. *Even a center fed half wave can have common
mode problems. So it's not like that method of feeding cures
all feed line radiation problems.
They will both require decoupling sections for optimum
performance. But saying that, you can often run a half wave
with no real decoupling and have decent results.
It will vary to each installation.

I think there has been some efforts to improve feedline decoupling
when feeding a .5wl antenna using radials. This may be such an
attempt.

Jimmie