"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.

"Chad Wahls" wrote in message
...

"DrDeath" wrote in message
...
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 built one and it does a great job of keeping feedline currents down, no
more RF in the shack. Iwas having problems regardless of grounding.
Here's some pics. If you want inside detail I have pics of that too.

http://i6.photobucket.com/albums/y23...f/HPIM1678.jpg

http://i6.photobucket.com/albums/y23...f/HPIM1676.jpg

http://i6.photobucket.com/albums/y23...f/HPIM1666.jpg


Chad


That's pretty much what I am going for. Sweet setup. The best part is I have
everything I need to build it laying around the house.

"DrDeath" wrote in message
...
"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.



Just form 4 turns or so of coax in a coil perhaps a foot or so in diameter.
This will form a choke which will kill the current backfeed down the outer
side of the coax. You can actually build an endfed dipole out of coax.
Feed the hot (center) wire into about 9 feet of wire and form a loop (4 or 5
turns of coax) about 9 feet away from the feed. The outer conductor
(shield) of the coax will form the other half of the dipole with the coil
(choke) stopping the rf at that point. Simply move the coil (by turning
towards or away from the center feed) to adjust your SWR. No rf on the
outside of the coax. Presto

Questions, e-mail me at and I'll see if I can take a
digital photo for you. finger crossed - old digital camera which sometimes
has problems with close-ups LOL



73 from Rochester, NY
Jim

Questions, e-mail me at and I'll see if I can take a
digital photo for you. finger crossed - old digital camera which sometimes
has problems with close-ups LOL

Is it a Kodak? G

"Scott in Baltimore" wrote in message
. ..
Questions, e-mail me at and I'll see if I can take
a
digital photo for you. finger crossed - old digital camera which
sometimes
has problems with close-ups LOL

Is it a Kodak? G


Scott, you old son-of-a-gun ....

Yep )


73,
Jim
ps - still not on Echo Link very much .... send me an e-mail.

ps - still not on Echo Link very much .... send me an e-mail.

Look in *BALT*

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.

"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?

"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