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

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

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

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

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

Jack, I do think there's some confusion here. In cases where the balun
is a part of the tuner input, the tuner chassis is usually connected
directly to the transmitter chassis through the normal coax. You can
ground the tuner chassis to an external earth ground if you so wish.
Internally, the balanced output of the balun is connected to the "T"
components at the input side. The coil, of course is not at chassis rf
ground potential, but that is not relevant. It is, however, at DC ground
potential (via the balun winding). I don't see any additional lightning
issues associated with placing the balun at the tuner input.

73,
Chuck

wrote:
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

"chuck" wrote
Jack, I do think there's some confusion here. In cases where the balun
is a part of the tuner input, the tuner chassis is usually connected
directly to the transmitter chassis through the normal coax. You can
ground the tuner chassis to an external earth ground if you so wish.
Internally, the balanced output of the balun is connected to the "T"
components at the input side. The coil, of course is not at chassis rf
ground potential, but that is not relevant. It is, however, at DC ground
potential (via the balun winding). I don't see any additional lightning
issues associated with placing the balun at the tuner input.

73,
Chuck

Hi Chuck (and Jim), I was unclear on what the benefits would be, hence my
questions to Jim (and the Group). But the file I referenced earlier also
questioned the benefits, and explained the need for floating the tuner when
a Balun i used in front of it, which would be a very bad move if lightning
protection was an issue. There would be no ground connection to the tuner,
leaving it as a sacrifice gear but inside the shack!. That's not all that
uncommon to sacrifice a tuner by the way, but usually seen where the tuner
is up in the air at the feedpoint. Marine applications often use this
configuration. I don't! Hi!
--
6. Conclusions
As noted by Roy Lewallen, W7EL,[2] putting a choke balun on the input of an
unbalanced tuner to drive a balanced line is useless. It introduces a
``hot'' tuner case which must be isolated with no benefit over putting the
balun on the output.
--
I agree that a 4:1 after the tuner (or after coax from tuner to feedpoint
where laddr-line begins) is a compromise at best, offering beneficial
performance at some frequencies and degradation at others. All a matter of
choices I guess, make the decision that's safe (first) and best for your
needs after that.

As always, I find this group shakes out great comments and explanations. If
Roy L wants to add something to this I'm sure we would all be interested.


73,
Jack


wrote:
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

Jack Painter wrote:

As always, I find this group shakes out great comments and explanations. If
Roy L wants to add something to this I'm sure we would all be interested.


I think you gentlemen have pretty well covered the basics. I'll just
encourage everyone to read Kevin's (W9CF) excellent treatment at the URL
posted by Jack a short while ago.

Roy Lewallen, W7EL