Hello Chad:

Wow good point here you have made.

Yes I agree with you here, the mast would become the counter poise, if
currents are choked at the coax. This is why these none ground plane
antennas will still work when a coax Balun is placed right at the
antennas connector, a Great point made here.

In the 1980's I had a terrible time installing a Sigma 4 antenna. As the
mast was pushed up the SWR changed. So I figured some how the mast and
maybe the coax, was apart of the antenna, and dropped the mast down a
foot at a time to get a decent SWR. I wish I had a Balun then.

Placing the balun down the coax at a 1/4 wavelength might work well on a
fiberglass boat and such.

One of the things while adding such things and testing them, is to keep
an eye on the field strength of the antenna. If something is done and
the field strength increases or decreases you want to see this.

In some cases antenna ranges will monitor the antennas swr as compared
to its field strength.

Jay in the Mojave


Chad Wahls wrote:
"Jay in the Mojave" wrote in message
...

Hello Dr Death:

Ok good deal I saw the impressive photos that Chad had there.

One thing to consider is that those fiberglass none ground plane
antennas use the coax outer shield as the counter poise or other end of
the antenna, so current will be seen on the coax. And in some case you
will see SWR changes from different lengths of coax, because the coax is
actually radiating, acting like a antenna.

I have had customers add in a line coax Balun on these type of antennas.
The Balun uses a Toroid Core, with the coax would around it. But the
trick here is that the Toroid Core is placed at 1/4 wavelength or about
102 inches down from the antennas connector. This allows the coax to
radiate for a 1/4 wavelength, possibility allowing for a low take off
angle, then choking off the currents beyond the 1/4 wavelength. Or the
coil wound coax Balun can be tried.



As you may have guessed the antenna is an Imax 2000. Which mounts to the
mast via a metal base that is directly coupled to the mast/tower. This
being said wouldn't the mast become the counterpoise at this point if the
coax is not? (The outside of the PL259 is directly coupled to the mounting
provisions.)

The balun was made out of spare junk on the premise that I NEEDED a reason
to go out to the shop, drink some beer and relax. What a better project, a
free one I made it removable for obvious reasons and have thought about
Jay's points a couple times when they were brought up after construction of
said device. This spring I hope to have a new (different) tower and at this
time will play with moving the balun from the feed point to right before the
ground rod next to the house. This will allow the coax to act as it should
and hopefully keep my feedline currents down, wadda ya think?

This could also be one reason of the "36 Foot" myth It is said that best
results are obtained when the A99 or Imax is at 36' to the feed point.
Maybe it's not the relationship to ground as much as the length of the mast
acting as the counterpoise. If you want to go more than 36' then a ground
plane kit is recommended to lower the take off angle. Many have noticed good
results with the GPK above 36' but found it a waste below 36', HMMMM. I'm
only at 20' now on a push up with a tower coming in spring to get me to 36'
I don't want to go much taller A. because the wife would freak, and B. it
would become a lightning magnet in my one-horse-town.

Another thing to ponder is that the addition of the Balun may help the ERP
because you are eliminating one of the 2 counterpoises (mast and coax) which
would certainly have 2 different velocity factors. This could possibly act
as a phasor in certain instances and cause an omni antenna to be "not so
omni"

There is a possibility that my ERP may have gone up after the balun
installation. Although problems associated with feedline radiation in the
shack decreased, the audio problems with the stereo in there shack increased
slightly. Maybe there is a tad more coming out of the stick and not being
wasted elsewhere?

Once again just pondering, I may be WAY off

Chad


"Jay in the Mojave" wrote in message
...
Hello Chad:

Wow good point here you have made.

Yes I agree with you here, the mast would become the counter poise, if
currents are choked at the coax. This is why these none ground plane
antennas will still work when a coax Balun is placed right at the antennas
connector, a Great point made here.

In the 1980's I had a terrible time installing a Sigma 4 antenna. As the
mast was pushed up the SWR changed. So I figured some how the mast and
maybe the coax, was apart of the antenna, and dropped the mast down a foot
at a time to get a decent SWR. I wish I had a Balun then.

Placing the balun down the coax at a 1/4 wavelength might work well on a
fiberglass boat and such.

One of the things while adding such things and testing them, is to keep an
eye on the field strength of the antenna. If something is done and the
field strength increases or decreases you want to see this.

In some cases antenna ranges will monitor the antennas swr as compared to
its field strength.

Jay in the Mojave


Chad Wahls wrote:
"Jay in the Mojave" wrote in message
...

Hello Dr Death:

Ok good deal I saw the impressive photos that Chad had there.

One thing to consider is that those fiberglass none ground plane
antennas use the coax outer shield as the counter poise or other end of
the antenna, so current will be seen on the coax. And in some case you
will see SWR changes from different lengths of coax, because the coax is
actually radiating, acting like a antenna.

I have had customers add in a line coax Balun on these type of antennas.
The Balun uses a Toroid Core, with the coax would around it. But the
trick here is that the Toroid Core is placed at 1/4 wavelength or about
102 inches down from the antennas connector. This allows the coax to
radiate for a 1/4 wavelength, possibility allowing for a low take off
angle, then choking off the currents beyond the 1/4 wavelength. Or the
coil wound coax Balun can be tried.



As you may have guessed the antenna is an Imax 2000. Which mounts to the
mast via a metal base that is directly coupled to the mast/tower. This
being said wouldn't the mast become the counterpoise at this point if the
coax is not? (The outside of the PL259 is directly coupled to the
mounting provisions.)

The balun was made out of spare junk on the premise that I NEEDED a
reason to go out to the shop, drink some beer and relax. What a better
project, a free one I made it removable for obvious reasons and have
thought about Jay's points a couple times when they were brought up after
construction of said device. This spring I hope to have a new
(different) tower and at this time will play with moving the balun from
the feed point to right before the ground rod next to the house. This
will allow the coax to act as it should and hopefully keep my feedline
currents down, wadda ya think?

On Tue, 10 Jan 2006 01:31:51 -0500, Scott in Baltimore
wrote:

+The amount of inductance is determined by the number of coils
+and how closely spaced together they are. There is not going
+to be much difference in three feet. Maybe wrapping the coil
+with aluminum foil would help to increase the coupling on
+the coil to increase the inductance.
+

If you want to increase the inductance wrapping aluminum foil on the
outside is not going to produce adequate results. Instead, place
ferrite material within the form so that it sits inside the windings.
If you want to decrease the inductance use aluminum inside the
windings.

This is how tunable inductors work.

+The inductance in the coil only affects the outside of the shield,
+the exact place you don't want current flowing. It won't affect
+the signals inside the coax.
****

Coiling coax up to form a choke balun places an impedance inline with
the outer conductor of the coax. It is this impedance that limits or
"blocks" unwanted current from flowing down the outer shield of the
coax. Coiled baluns should be located as close to the feed as
possible.

james

Hello Chad:


Chad Wahls wrote:
This could also be one reason of the "36 Foot" myth It is said that best
results are obtained when the A99 or Imax is at 36' to the feed point.

I have watched received and transmitted field strength signals, from a
antenna being cranked up on a crank up tower. All I ever see is the
higher the antenna the stronger the signals. I never see a sweet spot or
anything that is magic at 36 feet.

Maybe it's not the relationship to ground as much as the length of the mast
acting as the counterpoise. If you want to go more than 36' then a ground
plane kit is recommended to lower the take off angle. Many have noticed good
results with the GPK above 36' but found it a waste below 36', HMMMM. I'm
only at 20' now on a push up with a tower coming in spring to get me to 36'
I don't want to go much taller A. because the wife would freak, and B. it
would become a lightning magnet in my one-horse-town.

The ground plane kits I have seen do not impress me. I see shorter than
a 1/4 wavelength, and tilted down. I don't think this is worth the
effort. I have always wanted to add on 4 each 96 or 102 inch long
fiberglass whip antennas, mounted at the base of the antenna, and flat
and level. But you need to compare the field strength with the before
and after ground plane installation. And at different heights.

The difference will only be a dB or so (I haven't measured it either)
maybe even less than a dB or more! Let those with field strength
measurements tell all.

Another consideration is, how much is a dB or 2 dB worth in antenna
performance, as compared to distance in quiet skip times. Quit a bit!

Another thing to ponder is that the addition of the Balun may help the ERP
because you are eliminating one of the 2 counterpoises (mast and coax) which
would certainly have 2 different velocity factors. This could possibly act
as a phasor in certain instances and cause an omni antenna to be "not so
omni"

This is all good stuff here Chad! This all may be true, again field
strength measurements will tell who's lying and who ain't.

There is a possibility that my ERP may have gone up after the balun
installation. Although problems associated with feedline radiation in the
shack decreased, the audio problems with the stereo in there shack increased
slightly. Maybe there is a tad more coming out of the stick and not being
wasted elsewhere?

This would be a place to add on the level 1/4 wavelength ground plane
radials and test the audio interference again. It may be significantly
attenuated.

Once again just pondering, I may be WAY off

Chad

When it comes to antennas, no one can see where the RF Energy is going,
so field strength testing will set us free. I think your on the right track.

Jay in the Mojave

"james" wrote in message
...
Coiling coax up to form a choke balun places an impedance inline with
the outer conductor of the coax. It is this impedance that limits or
"blocks" unwanted current from flowing down the outer shield of the
coax. Coiled baluns should be located as close to the feed as
possible.

james

When you say as close to the feed as possible. Do you mean the radio or the
dipole? I'm assuming the dipole.

"Chad Wahls" wrote in message
oups.com...
As I have said before TVI is TV INTERFERENCE due to HARMONICS. You
need a low pass filter for that or a good tuning. If you are having
flat out AM rectification audio problems, it ain't gonna work. RF out
is RF out. I had feedline problems in the immediate vicinity of the
gear in question. RF rectification problems stayed there, kinda as
expected. I even brought a spectrum analyzer in to sort it out. My RF
was clean as a whistle. Cleaner than a "stock CB". Regardless of
power there is a blanketing area for broadcast applications. Cleaning
up the RF audio is a good step too. Audio distortion is allowed to
become funky modulation (audio crossover distortion is ugly at an RF
level), unlike pro broadcast where clipper limiting is used. Granted
"CB" limiters suck but limiting of some sort should be used. I had an
old Invonics in front of my now declared POS Galaxy (FCC accepted)
Radio. With the limiter "clipped" and it was nice. I DID NOT MODULATE
OFVER 100%, but I kept it there

Could you elaborate more on the issues you are having? Maybe you have a
"working antenna" but the stuff interfered with is working too well as
a receive antenna. it can and does happen at all levels of radio, even
the best pros. You may be clean, the other stuff may not.

Chad

The audio is clean from my olds school 148. I was just trying my hand at
making my own dipole since it was mentioned in an earlier post I noticed
that while attempting to adjust the swr, I was getting interference on my PC
monitor whenever I keyed. I have the sw at 1.5, when I tried to lower it
further it started going back up. I remade the dipole (I have tons of wire)
got it back to 1.5 but still radiating TVI. I figured I would try the balun
to see what would happen. Might also throw a low pass filter in it to see if
that will fix the problem.

"Jay in the Mojave" wrote in message
...
Hello Chad:

Greetings Jay:

The ground plane kits I have seen do not impress me. I see shorter than a
1/4 wavelength, and tilted down. I don't think this is worth the effort. I
have always wanted to add on 4 each 96 or 102 inch long fiberglass whip
antennas, mounted at the base of the antenna, and flat and level. But you
need to compare the field strength with the before and after ground plane
installation. And at different heights.

The difference will only be a dB or so (I haven't measured it either)
maybe even less than a dB or more! Let those with field strength
measurements tell all.

Another consideration is, how much is a dB or 2 dB worth in antenna
performance, as compared to distance in quiet skip times. Quit a bit!


I agree with your assessment on Ground plane kits. I don't have one because
it works now! Why change it? On another forum they are big on flattening
them out a tad to change the take off angle, those who have done this have
experienced coverage improvement. I don't know the exact angle but I can
get it for you if you want.





This is all good stuff here Chad! This all may be true, again field
strength measurements will tell who's lying and who ain't.




Yeah I know I worked in broadcast and have access to a field strength meter
from friends. They would be more than happy to drink my beer and play with
it That's who I borrowed the Spectrum analyzer from to make sure I was
clean on the output.



This would be a place to add on the level 1/4 wavelength ground plane
radials and test the audio interference again. It may be significantly
attenuated.




Or better yet it's time to fix the problems with the audio systems The
one with the most power (well over 1KW RMS) and proper wiring does not have
any noise AT ALL! It's just the stuff that has been known to have problems
in all installs be it amateur or not.



When it comes to antennas, no one can see where the RF Energy is going, so
field strength testing will set us free. I think your on the right track.

I agree, Thanks for you input and interest. I am no pro by any means. When
I worked in broadcast I was an audio guy, after it hit a composite signal I
was done with it I learned any RF from shutting up and listening, I would
then go home and ponder to come back the next day with questions.



It's nice to have someone with your experience around to share thoughts
with. I really appreciate it!



Have a great weekend,



Chad

echolink is a good place for you, scottiekins. lots of idiots there,
you will feel at home.

idiot, too stupid to build a balun without help. The drugs are showing
now.

"DrDeath" wrote in message
...
"Chad Wahls" wrote in message
oups.com...
As I have said before TVI is TV INTERFERENCE due to HARMONICS. You
need a low pass filter for that or a good tuning. If you are having
flat out AM rectification audio problems, it ain't gonna work. RF out
is RF out. I had feedline problems in the immediate vicinity of the
gear in question. RF rectification problems stayed there, kinda as
expected. I even brought a spectrum analyzer in to sort it out. My RF
was clean as a whistle. Cleaner than a "stock CB". Regardless of
power there is a blanketing area for broadcast applications. Cleaning
up the RF audio is a good step too. Audio distortion is allowed to
become funky modulation (audio crossover distortion is ugly at an RF
level), unlike pro broadcast where clipper limiting is used. Granted
"CB" limiters suck but limiting of some sort should be used. I had an
old Invonics in front of my now declared POS Galaxy (FCC accepted)
Radio. With the limiter "clipped" and it was nice. I DID NOT MODULATE
OFVER 100%, but I kept it there

Could you elaborate more on the issues you are having? Maybe you have a
"working antenna" but the stuff interfered with is working too well as
a receive antenna. it can and does happen at all levels of radio, even
the best pros. You may be clean, the other stuff may not.

Chad

The audio is clean from my olds school 148. I was just trying my hand at
making my own dipole since it was mentioned in an earlier post I noticed
that while attempting to adjust the swr, I was getting interference on my
PC monitor whenever I keyed. I have the sw at 1.5, when I tried to lower
it further it started going back up. I remade the dipole (I have tons of
wire) got it back to 1.5 but still radiating TVI. I figured I would try
the balun to see what would happen. Might also throw a low pass filter in
it to see if that will fix the problem.


That's just RF man. The balun may help you though because it will reduce
feedline radiation. That's kinda the same problem I was having. I say go
for it, give it a try, what do you have to loose?

Chad