Jeffrey Herman wrote:
Cecil Moore wrote:
When one feeds the antenna system at a current maximum
point, the balun is non-critical. I am presently using
ten turns of RG-400 on an FT-240-61 toroid with no

Hi Cecil,
It seems like it's been a decade since we debated on RRAP. I hope all is
well with you.
.... and here *I* am again. Anybody heard from Gary Coffman?

For a balun, I'm considering N4UJW's "Ugly Balun"
(see http://www.hamuniverse.com/balun.html).
UJW leaves the diameter of the coil form to the reader,

So, my question is about choke baluns too. I just put up a shiny new GAP
Eagle (yah, yah, I know short multiband verticals are snake oil, if I
had a big lot I might do something different.) They recommended a small
coax coil balun, but when I did that (as compared to just checking the
resonance at the little tail coming out of the antenna) the 20M
resonance went to pieces-- previously it had been 1:2 SWR (compared to
50 ohms) throughout the band, it went to 1:3 (but pretty flat)
everywhere. I ended up just using a ferrite-bead choke balun I had
around, and everything was fine. So, does anybody here have any idea
why the coax coil choke and the ferrite bead choke would have been so
different?

Rich, K6RFM

On Tue, 09 Jan 2007 23:47:41 -0800, Rich McAllister K6RFM
wrote:

So, does anybody here have any idea
why the coax coil choke and the ferrite bead choke would have been so
different?

Hi Rich,

I have been using a GAP Eagle for years, and it resonates in every
band as advertised (which is not to be mistaken for works miracles in
every band).

It comes with its own ferrite choke (aka 1:1 BalUn) on the pigtail
lead coming out of the bottom. Over the years and with wind, that has
chipped and broken, but replacing it returned the original
performance. By the way, I did have it elevated 10 feet up - this
makes a difference.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
On Tue, 09 Jan 2007 23:47:41 -0800, Rich McAllister K6RFM
wrote:

So, does anybody here have any idea
why the coax coil choke and the ferrite bead choke would have been so
different?

Hi Rich,

I have been using a GAP Eagle for years, and it resonates in every
band as advertised (which is not to be mistaken for works miracles in
every band).

Sure, any small antenna like this is going to be a compromise. I was
actually pleasantly surprised by the performance on 40M during the RTTY
Roundup last weekend, I expected the Eagle to pretty much suck wind
compared to my old full-size dipole, but it compared very favorably.


It comes with its own ferrite choke (aka 1:1 BalUn) on the pigtail
lead coming out of the bottom. Over the years and with wind, that has
chipped and broken, but replacing it returned the original
performance.

I've got the GAP-supplied ferrite choke protected with heatshrink
tubing, and the whole thing secured pretty well to the mast, so I'm
hoping not much will flop around and it will last a good long time.

By the way, I did have it elevated 10 feet up - this
makes a difference.

I've got it at the same spot as my old Cushcraft R5, a 10-foot mast on
the porch roof secured to the main roof rafters so the mast sticks up
about 3 feet over the main roof, the base of the Eagle ending up about
30 feet in the air. This basically is the only spot I have which is
both reasonably accessible in case I need to fiddle with the connections
and a good distance (at least 20 feet) away from major metal like
power/phone lines, etc. It's also just about the midpoint of my lot so
I keep the radiation as far away from my neighbors as possible;I figure
that has to help with RFI and also helps me do the radiation-exposure
self-evaluation with a clearer conscience.

Rich, K6RFM

Rich McAllister K6RFM wrote:
So, does anybody here have any idea
why the coax coil choke and the ferrite bead choke would have been so
different?

Was the coax choke single layer or bunched?
How many turns on what diameter? Here's some
measured data:

http://www.k1ttt.net/technote/airbalun.html

Note the narrow bandwidth of the coax coils
Vs the broad bandwidth of the beads.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
Rich McAllister K6RFM wrote:
So, does anybody here have any idea why the coax coil choke and the
ferrite bead choke would have been so different?

Was the coax choke single layer or bunched?
How many turns on what diameter?

Just 4 turns about 6" diameter, bunched up and secured with cable ties
as GAP recommended. Hard to believe there was some kind of narrow-band
resonance that just hit 20M, but I guess stranger things have happened.

Rich

Rich McAllister K6RFM wrote:
So, my question is about choke baluns too.

Here's some good technical information on the
various ferrite materials.

http://www.amidoncorp.com/aai_ferritecores.htm
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
Rich McAllister K6RFM wrote:
So, my question is about choke baluns too.

Here's some good technical information on the
various ferrite materials.

http://www.amidoncorp.com/aai_ferritecores.htm

The K material appears to have been developed for baluns.
--
73, Cecil http://www.w5dxp.com