"Airy R. Bean" wrote in message
...
What do I do, however, for those frequencies for which it is close
to a half wave? PI network? Or L network?

An L network with reactances of several hundred ohms for
both inductor and capacitor.

Rick N6RK

A common solution is to use a parallel tuned circuit, approximately
resonant, with inductor and capacitor reactances of a couple hundred
ohms or so, and the capacitor being adjustable. Connect one end of the
network to ground and the other to the antenna. Connect the feedline
between ground and a tap near the bottom of the coil. Alternately adjust
the tap position and the variable capacitor for the best impedance match.

Roy Lewallen, W7EL

Rick Karlquist N6RK wrote:
"Airy R. Bean" wrote in message
...

What do I do, however, for those frequencies for which it is close
to a half wave? PI network? Or L network?


An L network with reactances of several hundred ohms for
both inductor and capacitor.

Rick N6RK

Presumably the roller coaster could be used for
a vari-tap, but then that means that the whole coil
will always be in circuit.

Time for a quikc .XLS for all bands.....

"Roy Lewallen" wrote in message
...
A common solution is to use a parallel tuned circuit, approximately
resonant, with inductor and capacitor reactances of a couple hundred
ohms or so, and the capacitor being adjustable. Connect one end of the
network to ground and the other to the antenna. Connect the feedline
between ground and a tap near the bottom of the coil. Alternately adjust
the tap position and the variable capacitor for the best impedance match.

Roy Lewallen, W7EL

Rick Karlquist N6RK wrote:
"Airy R. Bean" wrote in message
...

What do I do, however, for those frequencies for which it is close
to a half wave? PI network? Or L network?


An L network with reactances of several hundred ohms for
both inductor and capacitor.

Rick N6RK

There's no reason you can't make the inductor variable instead of the
capacitor -- as long as it has some way of making a variable tap. With
the method I described, you have to be able to adjust both the tank's
resonant frequency and the tap in order to assure getting a match.

Roy Lewallen, W7EL

Airy R. Bean wrote:

Presumably the roller coaster could be used for
a vari-tap, but then that means that the whole coil
will always be in circuit.

Time for a quikc .XLS for all bands.....

"Airy R. Bean" wrote in message
...
Presumably the roller coaster could be used for
a vari-tap, but then that means that the whole coil
will always be in circuit.


You've never seen a roller coaster I take it.

Presumably the roller coaster could be used for
a vari-tap, but then that means that the whole coil
will always be in circuit.


You've never seen a roller coaster I take it.

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

He just loves looking for problems where none exist.

On Sun, 29 Aug 2004 00:08:16 +0000 (UTC), "Reg Edwards"
wrote:


Presumably the roller coaster could be used for
a vari-tap, but then that means that the whole coil
will always be in circuit.


You've never seen a roller coaster I take it.

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

He just loves looking for problems where none exist.

Rollercoasters are hard to come by these days, aren't they, Reg? I
haven't seen one in 25 years or so now. :-(

--

"What is now proved was once only imagin'd." - William Blake, 1793.

Rollercoasters are hard to come by these days, aren't they, Reg? I
haven't seen one in 25 years or so now. :-(
===============================
Paul, From the above it is clear that you don't visit junk sales and flea
markets all that often ,if ever.

Roller coasters can be found ,be it at gradually increasing prices.
An amateur radio flea market 'pilgrimage' to continental Europe would
,no doubt, provide a good harvest.

In the UK , Birkett -Lincoln has them from time to time.

Frank GM0CSZ / KN6WH

For those of you who lack the necessary technical acumen
to qualify for a Ham Radio licence, the issue is two-fold....
A variable tapping point _TOGETHER WITH_ a variable inductance
require two independently variables, but the roller-coaster
provides you with only one.

"Reg Edwards" wrote in message
...
Presumably the roller coaster could be used for
a vari-tap, but then that means that the whole coil
will always be in circuit.
You've never seen a roller coaster I take it.
He just loves looking for problems where none exist.

I've obtained roller coaster and 350 pF TX capacitor.

"Rick Karlquist N6RK" wrote in message
news:Nb2Xc.42797$9d6.33881@attbi_s54...
"Airy R. Bean" wrote in message
...
What do I do, however, for those frequencies for which it is close
to a half wave? PI network? Or L network?

An L network with reactances of several hundred ohms for
both inductor and capacitor.

Rick N6RK