Perfecto, Reg!

This is exactly what I was looking for ...but I had forgotten you had
written this little jewel.

I am a bit surprised at the small effect on losses in the number of radials
once one gets above 8 radials of 20m length.

I need to play more with wire size (confounded mm!)

Thanks again for your contribution of this program. 73

....hasan, N0AN
"Reg Edwards" wrote in message
...

For single-band operation, an autotransformer comes to mind.
Wind a coil with about 12 microhenries of inductance. Transmitter
output goes to the top of the coil. Ground goes to the bottom.
Tap down from the top on the coil for the antenna feedpoint.
The transformation ratio is roughly equal to the square of the
turns ratio.
--
73, Cecil http://www.qsl.net/w5dxp

===============================

Cec, it seldom works. You forgot to mention the most important
parameter is the input impedance to the antenna.

For an analysis of an inverted-L or vertical antenna, plus tuner L and
C component values, download in a few seconds program ENDFEED from
website below. No unzipping inconveniences. Run immediately. Easy to
use.
----
.................................................. .........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. .........

Reg Edwards wrote:
For single-band operation, an autotransformer comes to mind.
Wind a coil with about 12 microhenries of inductance. Transmitter
output goes to the top of the coil. Ground goes to the bottom.
Tap down from the top on the coil for the antenna feedpoint.
The transformation ratio is roughly equal to the square of the
turns ratio.

Cec, it seldom works. You forgot to mention the most important
parameter is the input impedance to the antenna.

I didn't forget, Reg. The input impedance was given in the
original posting:

"Frequency = 3.71 MHz Impedance = 29.15 + J 0.308 ohms"

Assuming that is the input impedance, I think my advice was
reasonable. If I had to match 50 ohms to 29 ohms on a single
band, I would just wind an autotransformer.
--
73, Cecil http://www.qsl.net/w5dxp

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Thanks, Cecil, and yes, that would work just fine and I have some B+W coil
stock sitting on a shelf, should work fine. (I used part of it before for a
parallel tuned circuit to tap feed my half-square.)

....hasan, N0AN

"Cecil Moore" wrote in message
...
Reg Edwards wrote:
For single-band operation, an autotransformer comes to mind.
Wind a coil with about 12 microhenries of inductance. Transmitter
output goes to the top of the coil. Ground goes to the bottom.
Tap down from the top on the coil for the antenna feedpoint.
The transformation ratio is roughly equal to the square of the
turns ratio.

Cec, it seldom works. You forgot to mention the most important
parameter is the input impedance to the antenna.

I didn't forget, Reg. The input impedance was given in the
original posting:

"Frequency = 3.71 MHz Impedance = 29.15 + J 0.308 ohms"

Assuming that is the input impedance, I think my advice was
reasonable. If I had to match 50 ohms to 29 ohms on a single
band, I would just wind an autotransformer.
--
73, Cecil http://www.qsl.net/w5dxp

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Newsgroups
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Assuming that is the input impedance, I think my advice was
reasonable. If I had to match 50 ohms to 29 ohms on a single
band, I would just wind an autotransformer.
--
73, Cecil http://www.qsl.net/w5dxp

==================================
Cec, to prevent the transformer inductance from completely detuning
the antenna, the transformer would have to be wound with a lot of
turns on something like an E and I dust-iron core. It's not worth the
trouble when there are other, more simple ways of doing the job.

The only advantage of a transformer or auto-transformer is that it
will cover several bands or octaves with widely different antenna
impedances.

Nice to bump into each other again.
----
Reg.

Reg Edwards wrote:
Cec, to prevent the transformer inductance from completely detuning
the antenna, the transformer would have to be wound with a lot of
turns on something like an E and I dust-iron core.

Yep, somewhere around here I have a tapped autotransformer
wound on a #2 powdered iron toroid designed for 75m use.
I wound it to be installed at the twinlead/coax junction
on a G5RV to obtain a 1:1 SWR on the coax on 75m. It worked
but I found that a parallel 1000 pf cap works just as well
and is easier to clip on and off.
--
73, Cecil http://www.qsl.net/w5dxp

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"Hasan Schiers" wrote,

I am a bit surprised at the small effect on losses in the number of
radials
once one gets above 8 radials of 20m length.
===========================================

Hasan, why should you be surprised? Have you been reading the
plagiarised old-wives tales in the magazines? ;o)

There's another more accurate program, RADIALS2, which may be of
interest, which deals with shallow-buried radials of any length and
number, in conjunction with a simple vertical antenna of variable
height just to illustrate the practical effects.

Download program RADIALS2 from website below.
----
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........

I'm sorta surprised you would need to match it, if it's a
1/4 wave...I think your match in the real world, would
be better than on paper...I've never had to "match" a
1/4 wave here, L or straight.... But.....if I did, I would
just slap the tuner inline...On that band, any mismatch
would have to be large to give a high line loss. That
won't be the case for you just going from one part of
the band to another...Also, you should be able to get
a better match than 1.7:1, just by tweaking the wire
length.
MK