At some point a resonance will occur Reg. And while some particular
combination may work - i.e. 7,427 ferrite beads along 841 feet of coax. I
have found no practical balun that does the deed from 1.8 to 30.

Those that work well at 1.8 seem to end up with a resonance somewhere over
20 Mhz..

One solution may be ferrites to cover the low end in series with a solenoid
coil for the high end.

Again, what I am looking for is a simple chart that says for a 10, 15, and
20 meter beam a solenoid of 8 turns on a 4 1/2" pvc coil form will provide
the following impedances ...

Also most people will tell you that just looping the coils together will
cause problems because of capacitance. I don't see that as a bad thing.
Again I need to see data to confirm or discount my assumptions.

If nothing else it will be a fun learning exercise.

I ran into some problems with an all band no tuner antenna and started to
try various combinations of beads recommended by the Gurus. While it worked
OK on 160, 75 and 40, at 15 and10 meters the beads has insufficient
impedance.

Ergo, I have mounted my steed and wooden lance in hand am off to fight the
evil forces of unbalance.

"Reg Edwards" wrote in message
...
The only things I know for sure is that no balun covers from DC to
daylight,
or even 1.8 to 30 Mhz.

==============================
Fred, I'm afraid you're wrong.

Slide a sufficient number of ferrite beads over the coax line and it
will easily cover 1.8 to 30 MHz. Alternatively, wind sufficient turns
around a largish ferrite ring of the correct grade of material.
----
Reg.

In article ,
Fred W4JLE wrote:

Again, what I am looking for is a simple chart that says for a 10, 15, and
20 meter beam a solenoid of 8 turns on a 4 1/2" pvc coil form will provide
the following impedances ...

http://www.bcdxc.org/balun_information.htm#Ed,%20WA2SRQ has some of
that sort of information, for a few specific combinations of turns,
diameter, and winding style.

Also most people will tell you that just looping the coils together will
cause problems because of capacitance. I don't see that as a bad thing.
Again I need to see data to confirm or discount my assumptions.

What I have heard is that scramble-winding the turns tends to create a
higher distributed capacitance, and lowers the frequency at which the
balun exhibits self-resonance.

This appears to be born out by the table in the URL I gave above.
Compare the "8 turns, 6-5/8" columns for single-layer and bunched
windings. The single-layer coil has its peak impedance at 12 MHz.
The bunched-turn coil peaks somewhere between 6 and 7 MHz (highest
displayed impedance is at 6 but the phase is still very positive, so
I'm inferring a higher-impedance peak between 6 and 7 MHz).

The impedance of the bunched-turn coil seems to drop faster, on either
side of resonance, than that of the solenoid-would coil.

This suggests to me that the bunched-turn coil, measured and trimmed
carefully, might be a convenient choice for a low-HF monoband
antenna's choke, since it'd need fewer turns of coax to achieve a high
choking impedance. The solenoid-wound coil appears to have a somewhat
broader effective frequency range, and thus might be a better choice
for a 10/15/20 tribander.

--
Dave Platt AE6EO
Hosting the 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!

Fred W4JLE wrote:
At some point a resonance will occur Reg. And while some particular
combination may work - i.e. 7,427 ferrite beads along 841 feet of coax. I
have found no practical balun that does the deed from 1.8 to 30.

Those that work well at 1.8 seem to end up with a resonance somewhere over
20 Mhz..
. . .

You're using the wrong kind of ferrite. Type 43, the most common type
used for large cores, has a Q of 1 in the middle of the HF range. That
is, the resistance equals the reactance at that frequency. So over the
HF range a balun wound on a type 43 core with no air gap or by using
beads W2DU-style looks basically like a resistor. You'd have to have
extremely sensitive equipment to detect any resonance effects.

70 series ferrites have an even lower frequency Q=1 point, along with
more impedance per turn squared, and that's what I mostly use. But a
balun made with type 70 can sometimes get uncomfortably hot if you're
running a kW.

Roy Lewallen, W7EL

For the performance/behaviour of a solenoid-wound coaxial choke,
download program SELFRES from website below.

Enter dimensions of the coil and the resonant frequency and impedance
versus frequency in a test circuit is calculated.
----
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........

The performance of a coaxial choke inserted at the antenna end of the
feedline cannot be properly studied without knowledge of the
feedline's length in wavelengths and how the feedline is terminated at
the transmitter end. No two systems are the same.

Choke performance depends on the condition of the system before the
choke is inserted. The choking effect depends on the impedance seen
by the choke looking into the outer conductor of the coaxial feedline.

The input impedance of the coaxial outer conductor depends on Zo, 400
to 550 ohms, of the single-wire line, its length in wavelengths, and
on the very uncertain resistance of the ground connection at the
transmitter end.

If the ground connection at the transmitter end is very low and the
line is an odd number of 1/4-wavelengths there will be a very high
impedance at the antenna end and longitudinal current will negligible.
Insertion of the choke will have no effect.

If the line is a whole number of 1/2-wavelengths, with a low
resistance ground the input impedance of the coaxial outer conductor
will also be very low and longitudinal current in the line will be at
a maximum. Insertion of the choke will be very effective.

With the usual random line length and on different bands, choke
performance will always be completely random and unpredictable. Which
explains the different opinions and arguments about whether a choke is
necessary or not.

Program SELFRES3 models choke behaviour.
----
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........

Reg Edwards wrote:
If the line is a whole number of 1/2-wavelengths, with a low
resistance ground the input impedance of the coaxial outer conductor
will also be very low and longitudinal current in the line will be at
a maximum. Insertion of the choke will be very effective.

To complicate things a little more, the common-mode current may
consist of standing waves. If the choke is installed at a current
minimum point, it may have little effect.
--
73, Cecil http://www.qsl.net/w5dxp

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"Cecil Moore" wrote in message
...
Reg Edwards wrote:
If the line is a whole number of 1/2-wavelengths, with a low
resistance ground the input impedance of the coaxial outer
conductor
will also be very low and longitudinal current in the line will be
at
a maximum. Insertion of the choke will be very effective.

To complicate things a little more, the common-mode current may
consist of standing waves. If the choke is installed at a current
minimum point, it may have little effect.
--
73, Cecil http://www.qsl.net/w5dxp
====================================

Dear Cec, It doesn't complicate things. It merely repeats what I have
already said. When the line is an odd number of 1/4-waves long and
there is an (albeit indeterminate) ground at the transmitter end, then
there will be a high impedance at the choke (DUE TO STANDING WAVES)
and the choke will then be wasting its time.

If you havn't, moons ago, already downloaded the program then do so
and read the program notes. There are so many unknowns in it the
results are only approximate but nevertheless sufficiently accurate
for the intended purpose - which is just to demonstrate choke
behaviour.

The only accurate result is the calculated-from-first-principles
self-capacitance of the coil on which the impedance/frequency response
depends.

I had checked calculations, years back, by winding many coils of
various sizes and shapes, (one 7 feet long), with various numbers of
turns and measuring the coils' self-resonant frequency over the HF
band using hand-held instruments with coils suspended in free space
from strings. I always knew the results would be useful at some time
or other, never even dreaming about choke baluns.

Did I ever tell you that for several years I was Head of a
Measurements Standards Laboratory which I personally set up from
scratch and which was in the 2nd echelon from the British National
Physical Laboratory. The NPL.

There were certain electrical parameters for which the laboratory was
capable of making measurements more accurate than the NPL but for
obvious political reasons it was not possible for the laboratory to
claim such performance on calibration certificates.

Some time after I had left the position on promotion, the wicked Mrs
Thatcher had the laboratory dismantled and sold it off in bits because
it did not produce any immediate, short-term profits. She was a
chemist who went into politics. Often I still wonder what happened to
the oven-enclosed battery of 12 standard Western cells.

One day, if I can force myself to find the time, I may write my
memoirs. I could tell you some amusing stories.
----
Yours, Reg, G4FGQ

Reg Edwards wrote:
When the line is an odd number of 1/4-waves long and
there is an (albeit indeterminate) ground at the transmitter end, then
there will be a high impedance at the choke (DUE TO STANDING WAVES)
and the choke will then be wasting its time.

And what I am saying is that exactly the same thing can happen NO
MATTER WHAT THE LENGTH OF THE FEEDLINE if the choke is located at
a current minimum point. I'm not arguing with you - just expanding
upon what you said.
--
73, Cecil http://www.qsl.net/w5dxp

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On Wed, 24 Aug 2005 16:01:06 +0000 (UTC), "Reg Edwards"
wrote:


One day, if I can force myself to find the time, I may write my
memoirs. I could tell you some amusing stories.
----
Yours, Reg, G4FGQ


Please force yourself, Reg, we'd all like to hear those stories. And
they should be published for all to read.

Walt