Interesting 144 foot Dipole
 

A ham over on eHam.net wanted to know if a 40m EDZ
would work on 80m. Of course it will if fed correctly
since it is about 166 feet long. The question is: Is
there a fixed length of ladder-line that will work both
on 40m and 80m? I fired up EZNEC and started cut and
trying. I found that a 144 foot 40m "EDZ" would yield
some interesting results. I went out and extended my
130 foot dipole to 144 feet and was impressed.

I found that a 144 foot center-fed dipole fed with
~88 feet of 450 ohm ladder-line was resonant on
7.150 MHz and my IC-756PRO would tune it over the
entire 40m band. 40m is my favorite band.

In addition, the IC-756PRO tuner will tune the same
antenna system over a 3.7-3.9 MHz range on 80m.

In addition, the IC-756PRO tuner will tune the same
antenna system on 30m and 17m.

I've already got a rotatable dipole for 20m-10m and
this antenna tunes on 80m, 40m, and 30m.
--
73, Cecil http://www.w5dxp.com

Interesting 144 foot Dipole
 

In article ,
Cecil Moore wrote:

A ham over on eHam.net wanted to know if a 40m EDZ
would work on 80m. Of course it will if fed correctly
since it is about 166 feet long. The question is: Is
there a fixed length of ladder-line that will work both
on 40m and 80m? I fired up EZNEC and started cut and
trying. I found that a 144 foot 40m "EDZ" would yield
some interesting results. I went out and extended my
130 foot dipole to 144 feet and was impressed.

I found that a 144 foot center-fed dipole fed with
~88 feet of 450 ohm ladder-line was resonant on
7.150 MHz and my IC-756PRO would tune it over the
entire 40m band. 40m is my favorite band.

In addition, the IC-756PRO tuner will tune the same
antenna system over a 3.7-3.9 MHz range on 80m.

In addition, the IC-756PRO tuner will tune the same
antenna system on 30m and 17m.

I've already got a rotatable dipole for 20m-10m and
this antenna tunes on 80m, 40m, and 30m.

interesting , resonant too hmm wonder how the waves look on that dipole?

Interesting 144 foot Dipole
 

ml wrote:
interesting , resonant too hmm wonder how the waves look on that dipole?

The free demo copy of EZNEC available from www.eznec.com will
display the current waveform. Here's a copy of a posting I made
to eHam.net

The following results are approximate but show the resonance trend on
80m Vs dipole length. Take a certain length dipole and adjust the length
of the 450 ohm ladder-line for resonance on 7.15 MHz. i.e. NOTE: All of
the following antenna systems are resonant on 7.15 MHz. and cover the
entire 40m band with an SWR of 3.5:1 or less (good for built-in
autotuners). Here are the approximate results:

dipole length : feedline length : resonance on 80m

170' : ~85' : 3.62 MHz (3.52-3.72)

160' : ~87' : 3.7 MHz (3.6-3.8)

150' : ~89' : 3.8 MHz (3.7-3.9)

140' : ~91' : 3.92 MHz (3.82-4)

130' : ~92.8' : 4.06 MHz (resonant out of band)

120' : ~94.7' : 4.23 MHz (resonant out of band)

Yesterday I had a 130' dipole that exhibited the above characteristics.
I have changed it to a 144' dipole and now, with one length of
ladder-line, the antenna covers all of 40m and 200 kHz of 80m using the
limited range autotuner built into my IC-756PRO. A bonus is that the
autotuner also tunes this fixed antenna system on 30m and 17m.
--
73, Cecil http://www.w5dxp.com

Interesting 144 foot Dipole
 

Cecil Moore wrote:

The following results are approximate but show the resonance trend on
80m Vs dipole length. Take a certain length dipole and adjust the length
of the 450 ohm ladder-line for resonance on 7.15 MHz. i.e. NOTE: All of
the following antenna systems are resonant on 7.15 MHz. and cover the
entire 40m band with an SWR of 3.5:1 or less (good for built-in
autotuners). Here are the approximate results:

dipole length : feedline length : resonance on 80m

170' : ~85' : 3.62 MHz (3.52-3.72)

160' : ~87' : 3.7 MHz (3.6-3.8)

150' : ~89' : 3.8 MHz (3.7-3.9)

140' : ~91' : 3.92 MHz (3.82-4)

130' : ~92.8' : 4.06 MHz (resonant out of band)

120' : ~94.7' : 4.23 MHz (resonant out of band)

Yesterday I had a 130' dipole that exhibited the above characteristics.
I have changed it to a 144' dipole and now, with one length of
ladder-line, the antenna covers all of 40m and 200 kHz of 80m using the
limited range autotuner built into my IC-756PRO. A bonus is that the
autotuner also tunes this fixed antenna system on 30m and 17m.

Happy New Year, Cecil. Really neat design. Can you describe the
balun you used?

Thanks,

Jim, AC6XG

Interesting 144 foot Dipole
 

Jim Kelley wrote:
Can you describe the balun you used?

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
measurable common mode current on an MFJ-853. As you
know, the stress on the balun is reduced when the
resonant current maximum point is located at the
output of the balun-choke. That's another bonus for
the matching system that I use.
--
73, Cecil http://www.w5dxp.com

Choke balun (was: Interesting 144 foot Dipole)
 

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.

I plan on erecting a multi-band inverted V with several insulators and
associated shorting connectors along each leg so that with all connectors
open, the antenna is resonant on 10m; with the first insulator on each leg
shorted, the antenna is resonant on 15m; with the first and second insulators
on each leg shorted the antenna is resonant on 20m; et cetera. Shorting and
opening insulators is easier than winding accurate chokes!

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, only specifying that
18-21 feet of coax be used. Can you (or anyone else on RRAA) tell me if there
is an optimum diameter, considering that most of my operations will be on 20m?
(On that page, UJW has two balun projects -- see the first one.)

Warmest regards,
Jeff KH6O

Chief Petty Officer, U.S. Coast Guard
Mathematics Lecturer, University of Hawaii System
--

Choke balun
 

Jeffrey Herman wrote:
Hi Cecil,
It seems like it's been a decade since we debated on RRAP. I hope all is
well with you.

Things are terrible. I can't dunk a basketball anymore. :-)
Good to hear from you.

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, only specifying that
18-21 feet of coax be used. Can you (or anyone else on RRAA) tell me if there
is an optimum diameter, considering that most of my operations will be on 20m?

This subject was recently beat to death over on QRZ.com or
eHam.net, I can't remember which. Here's some actual
measurements showing how the choking impedance varies
with frequency:

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

An ugly balun (N turns of coax) will not cover a 10:1
frequency range very well. If it performs well on 10m,
it doesn't have very much choking impedance on 80m. If
it performs well on 80m, it will have reached its series
resonant low impedance point before it reaches 10m. An
ugly balun performs reasonably well over a 3:1 frequency
range. And the choking problem worsens considerably with
non-resonant antenna systems.

However, the necessary choking impedance is minimized
if the antenna is low impedance resonant as yours will
be. I made some measurements on 20 turns of coax on a
2 liter pop bottle. It was parallel resonant at 14 MHz
(good high impedance) and series resonant at 28 MHz
(bad low impedance). It would probably function pretty
well from 40m to 15m.

A toroidal 1:1 choke-balun is much more broadbanded than
an ugly balun. For your antenna, ten turns of RG-400 on
a FT-240-61 toroid would, like mine, be good enough.
The AB-240-kit contains that toroid and comes with
instructions for winding a 1:1 choke-balun, all for $9.
However, I would not recommend that balun for non-
resonant antenna systems where three of those toroids
stacked would be about right. That web page is at:

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

Choke balun (was: Interesting 144 foot Dipole)
 

"Jeffrey Herman" wrote in message
...
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.

I plan on erecting a multi-band inverted V with several insulators and
associated shorting connectors along each leg so that with all connectors
open, the antenna is resonant on 10m; with the first insulator on each leg
shorted, the antenna is resonant on 15m; with the first and second
insulators
on each leg shorted the antenna is resonant on 20m; et cetera. Shorting
and
opening insulators is easier than winding accurate chokes!

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, only specifying
that
18-21 feet of coax be used. Can you (or anyone else on RRAA) tell me if
there
is an optimum diameter, considering that most of my operations will be on
20m?
(On that page, UJW has two balun projects -- see the first one.)

Warmest regards,
Jeff KH6O

Chief Petty Officer, U.S. Coast Guard
Mathematics Lecturer, University of Hawaii System
--
How do you plan on actuating the switches? I tried some knife swithes and
thought I could switch them using a hook on a pole. This didnt work very
well for an all band antenna.

Choke balun
 

Jimmie D wrote:
How do you plan on actuating the switches? I tried some knife swithes and
thought I could switch them using a hook on a pole. This didnt work very
well for an all band antenna.

When I was in high school, I built my dipole with
a pulley at each end. For changing bands, I just let
the dipole down and either installed or removed the
jumper wires across the insulators. An Inv-V would
only require one pulley.
--
73, Cecil http://www.w5dxp.com

Choke balun
 

"Cecil Moore" wrote in message
et...
Jimmie D wrote:
How do you plan on actuating the switches? I tried some knife swithes and
thought I could switch them using a hook on a pole. This didnt work very
well for an all band antenna.

When I was in high school, I built my dipole with
a pulley at each end. For changing bands, I just let
the dipole down and either installed or removed the
jumper wires across the insulators. An Inv-V would
only require one pulley.
--
73, Cecil http://www.w5dxp.com

Yeah I thought about this but was trying to stay away from raising and
lowering the antenna. I used to have the antenna on a pulley but found that
sometimes the neighbor kids would lower it for me. The ones who were doing
it arent around anymore so I guess its safe to put it back up now.

Choke balun
 

On Sat, 6 Jan 2007 11:31:45 -0500, "Jimmie D"
wrote:

The ones who were doing it arent around anymore

Hi Jimmie,

Is it possible you had the key down when they last tried lowering it?

73's
Richard Clark, KB7QHC

Choke balun
 

Jimmie D wrote:
Yeah I thought about this but was trying to stay away from raising and
lowering the antenna. I used to have the antenna on a pulley but found that
sometimes the neighbor kids would lower it for me. The ones who were doing
it arent around anymore so I guess its safe to put it back up now.

Them "not being around anymore" could mean any number
of things. :-)
--
73, Cecil http://www.w5dxp.com

Choke balun
 

"Richard Clark" wrote in message
...
On Sat, 6 Jan 2007 11:31:45 -0500, "Jimmie D"
wrote:

The ones who were doing it arent around anymore

Hi Jimmie,

Is it possible you had the key down when they last tried lowering it?

73's
Richard Clark, KB7QHC

No, they were reallly good kids over all, they didnt get into half as much
as I did when they were my age. At least I dont think they ever fished with
pipe bombs. They also kept my grass cut while I was away for a really
reasonable price.

Interesting 144 foot Dipole
 

Cecil Moore wrote:

Jim Kelley wrote:

Can you describe the balun you used?


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
measurable common mode current on an MFJ-853. As you
know, the stress on the balun is reduced when the
resonant current maximum point is located at the
output of the balun-choke. That's another bonus for
the matching system that I use.

Hi Cecil,

I guess what I meant to ask was, how do you interface ladder line with
your IC756 output connector?

Thanks,

Jim, AC6XG

(And hello to fellow SCHS alum, Jeff Herman)

Interesting 144 foot Dipole
 

Jim Kelley wrote:
I guess what I meant to ask was, how do you interface ladder line with
your IC756 output connector?

I've got an SG-500 between the IC756 and the antenna.
Coax out of the SG-500 goes to a 1:1 balun-choke and
then to the ladder-line.
--
73, Cecil http://www.w5dxp.com

Choke balun
 

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

Choke balun
 

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

Choke balun
 

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

Choke balun
 

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

Choke balun
 

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

Choke balun
 

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

Choke balun
 

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

I hate when kids mess with my antenna stuff!

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