wrote
Yes, thank you..I have been thinking about modifying an existing tuner
with the balun on the output. The problem is that ALL components must
be isolated from ground. I suppose I could pull that off, but it is
not as simple as you might think, especially with a tuner that uses a
tapped inductor in a T match. I t would probably be easier to float a
roller inductor than a tapped inductor because of the switch. The
caps are usually above ground already in a T match, so thats not a
problem. I'm thinking about it, but it would be nice if there was a
good affordable balanced tuner out there.
Jim

Jim, your original query and subsequent comments leave a couple of
questions:

1. Is an ATU desired?
2. Will it operate a balanced line? (other antennas as well?)
3. Why is isolation from ground so important to you?

Radio Works puts out some good products, one of them is the Line Isolator
for just the situation you are possibly describing:

http://www.radioworks.com/PDFLineIsolator.htm

However it should be noted that this is offered by Radio Works (in my
opinion) mainly because they promote the Carolina Windom style antennas,
which are designed to radiate vertical components of feedline. Most antenna
types, especially anything using a Balun at the feedpoint would have no such
radiation on the feedline or shield. Antennas requiring good RF ground or
radials would do so, those that don't still require bonding and grounding
for lightning protection, at least in any area that can have lightning. So
the multiple use of line isolators, and/or your insistence on having all
components isolated from ground may correct RF problems that should be
addressed at their cause, and at the expense of maintaining safe bonding and
grounding of the station equipment for lightning protection.

As Bob Miller also added (fwiw): I use two MFJ tuners, the 962D 1.5kw
air-core inductor and the 994 600w ATU "Intellituner". Both perform very
well for me on end fed wires and dipoles. Isolating anything in my station
from ground is out of the question, as it should be for anyone who remains
connected to either or both power and antennas during thunderstorms.

73,
Jack Painter
Virginia Beach VA

THe only alternative I know, Ten Tec sells their variable caps and
variable inductors that they use in their tuner as open stock items.

MFJ will sell the roller inductor they use in their tuners. I bought one at
the MFJ exhibit at a hamfest. They indicated that they will sell pretty much
any part of their products if you call and let them know what you want. I
built my tuner out of the MFJ inductor and Ten Tec capacitors. It's my MFJ Tec
tuner. Parts cost around $150, works well and has handled the legal limit.
73 Gary N4AST

Hello Jack
Yes, the tuner is required, because I use a balanced line to feed a
multiband doublet.
The issue is placeing a 1:1 balun at the input of the tuner, rather
than the output. In order to do that with an existing T match type
tuner, all components must be isolated from ground. This is uncommon,
because a typical T match grounds one side of the inductor.
I have read that a 1:1 balun at the input of a T match is desireable
over a 4:1 at the output.
Thanks

Interesting..what did you use for a cabinet? I have been looking
around for one that might fit the bill.

wrote
Hello Jack
Yes, the tuner is required, because I use a balanced line to feed a
multiband doublet.
The issue is placeing a 1:1 balun at the input of the tuner, rather
than the output. In order to do that with an existing T match type
tuner, all components must be isolated from ground. This is uncommon,
because a typical T match grounds one side of the inductor.
I have read that a 1:1 balun at the input of a T match is desireable
over a 4:1 at the output.
Thanks

Hi Jim,

I can't imagine what's possibly gained by 1:1 in front of the tuner v. 4:1
(when applicable, some antennas recommend this, including for twin-lead)
after it. Can you recall the writing you saw the recommendation to isolate
from ground before the tuner? I just don't see what it will do for you, but
as I said there is at least one good reason not to do so. Ungrounded and
especially unbonded equipment should be disconnected from antennas and power
supplies before the chance of a thunderstorm. An exception could be if you
totally isolate the antennas from ground, and no balun can safely do that.
But a similar principle called a high voltage isolation transformer could,
and so could a fiber optic isolation transformer. Both are pretty expensive
alternatives to staying with generally accepted lightning protection plans
for the shack. Even if you intend to toss the feed out the window before a
storm, I'm still curious what is gained by a 1:1 between transceiver and
transmatch.

73,
Jack

Here is a quote from one site:
Of interest is the 1:1 balun mounted at the input of the tuner (rather
than the output where it would be exposed to highly reactive loads).
The various components are floated above chassis ground. When properly
adjusted, the balun sees a 50 ohm load both at the input from the
transmitter and at the output. Its not a perfect replacement for the
link coupled circuits of yesteryear, but in my experience so far, it
perfoms significantly better than competing tuners employing 4:1
baluns. I've tried a few of these matching networks and not one of them
provided an output to tuned feeders even close to being balanced. The
AT4K-BAL is a leg up on this account.

There are dozens of other sites, but it is all the same info..including
several ARRL articles.
The issue is not lightning protection, as you suggested.
Thanks

Hi
I tried to reply to your post, but it does not seem to have made it..so
here is another try:
This is a quote taken from one site:
Of interest is the 1:1 balun mounted at the input of the tuner (rather
than the output where it would be exposed to highly reactive loads).
The various components are floated above chassis ground. When properly
adjusted, the balun sees a 50 ohm load both at the imput from the
transmitter and at the output. Its not a perfect replacement for the
link coupled circuits of yesteryear, but in my experience so far, it
perfoms significantly better than competing tuners employing 4:1
baluns. I've tried a few of these matching networks and not one of them
provided an output to tuned feeders even close to being balanced. The
AT4K-BAL is a leg up on this account.
I have seen dozens of other sites with the same info, including several
ARRL articles.
Thanks

wrote
Hi
I tried to reply to your post, but it does not seem to have made it..so
here is another try:
This is a quote taken from one site:
Of interest is the 1:1 balun mounted at the input of the tuner (rather
than the output where it would be exposed to highly reactive loads).
The various components are floated above chassis ground. When properly
adjusted, the balun sees a 50 ohm load both at the imput from the
transmitter and at the output. Its not a perfect replacement for the
link coupled circuits of yesteryear, but in my experience so far, it
perfoms significantly better than competing tuners employing 4:1
baluns. I've tried a few of these matching networks and not one of them
provided an output to tuned feeders even close to being balanced. The
AT4K-BAL is a leg up on this account.
I have seen dozens of other sites with the same info, including several
ARRL articles.
Thanks


Your first post did make it, and I also found that reference that shed no
light, but further:

http://fermi.la.asu.edu/w9cf/articles/balun/ (quoted below)

4 Baluns on the input and output of unbalanced tuners:
Roy, W7EL, worked out the math for moving a current balun from output to
input of an unbalanced tuner using his model of a choke balun and found that
essentially nothing changed.

....the most sensible place to put a balun is on an unbalanced tuner's
output, like it is on nearly all commercial tuners, and not on its input

--

Interesting theory presented there, but does not support the wives tale
either.

And yes you can stand-by-for-fireworks if you think lightning protection
isn't an issue. Anyone that thinks "floating equipment chassis" (isolated
from ground) is a good plan, lives in a place where lighting is something
they watch only on the Discovery Channel.

73,
Jack

On 14 Dec 2004 02:31:11 -0800, "
wrote:

Here is a quote from one site:
Of interest is the 1:1 balun mounted at the input of the tuner (rather
than the output where it would be exposed to highly reactive loads).
The various components are floated above chassis ground. When properly
adjusted, the balun sees a 50 ohm load both at the input from the
transmitter and at the output. Its not a perfect replacement for the
link coupled circuits of yesteryear, but in my experience so far, it
perfoms significantly better than competing tuners employing 4:1
baluns. I've tried a few of these matching networks and not one of them
provided an output to tuned feeders even close to being balanced. The
AT4K-BAL is a leg up on this account.

There are dozens of other sites, but it is all the same info..including
several ARRL articles.
The issue is not lightning protection, as you suggested.
Thanks

The few balanced tuners that are being manufactured nowadays all seem
to employ the balun on the input side. To use the words from MFJ's ad
copy for their balanced tuners:

"A 1:1 current balun is placed on the low impedance 50 input side to
convert the balanced T-Network to unbalanced operation. The balun is
made of 50 ferrite beads on RG-303 Teflonâ„¢ coax to give exceptional
and efficient isolation. It stays cool even at maximum power."

Basically, the balun hooks the balanced tuner to the unbalanced output
of the transceiver.

In years past, there have been heated discussions in this group as to
whether the balun belongs on the input or output -- you could do a
Google search if you're interested.

Bob
k5qwg

And yes you can stand-by-for-fireworks if you think lightning
protection
isn't an issue. Anyone that thinks "floating equipment chassis"
(isolated
from ground) is a good plan, lives in a place where lighting is
something
they watch only on the Discovery Channel.

73,
Jack


Jack
Let me assure you, my station is well grounded, Hi! I even have an
abnormal passion regarding grounds.
My remark was in regarding to a "floating" balanced antenna tuner,
which is not grounded anymore than is a balanced line fed doublet.
Certainly everything before the tuner is well grounded. I even have a
spark gap type lightning protector on the balanced feeds.
As far as the debate regarding baluns at the input or output, I would
be delighted to be convinced that it either does not matter, or is
better at the output..because it makes my life a lot simpler. Right
now I am using about 5 feet or so of LMR400 from my unbalanced tuner to
a Radio Works remote balun, terminated with 300 ohm transmitting
twinlead, feeding a 40 meter doublet. Works like gangbusters.
Jim