"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.

My personal experience has been that the coax Baluns didn't have enough
choking impedance, allowing the antennas lowest SWR frequency to be much
lower that what it really was, because the coax was also radiating and
acting like part of the antenna. But this was on a beam antenna, and not
a fiberglass type antenna.

Suggest its worth a try, to add a choke Balun at a 1/4 wavelength below
the antennas connection.

Jay in the Mojave



DrDeath wrote:
"Jay in the Mojave" wrote in message
...

Hello DrDeath:

Why do you want a Balun, and on what type installation are you going to
use it????

Jay in the Mojave


DrDeath wrote:

I am trying to build a balun. I chose the one on this web site as I like
the design
http://www.hamuniverse.com/balun.html
It states that, and I quote
"The number of turns is not critical because the inductance depends more
on the length of the wire (coax) than on the number of turns, which will
vary depending on the diameter of the plastic pipe that is used."
But it does not give the formula. It just says 18 to 21 feet.
I plan to use 4 inch pvc and I want to cover as much of the upper 11
meters as I can. Am I better off at 18 or 21 feet?


I'm just messing around with a home made dipole. I want the balun to cut
down on the TVI.

I don't have a toroid large enough laying around, and the goal of this
project is that I end up with a working antenna without spending any money.
I like Chad's idea, I have lots of PVC in different sizes. If this doesn't
pan out, I will try yours or Jim's idea.

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

"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.

"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

"Chad Wahls" wrote in message
...

"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


Absolutely nothing but time : )