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

In article E6tvd.6659$7p.4476@lakeread02,
Jack Painter wrote:

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.

The reason I've seen stated, is that many 4:1 balun designs only work
"as advertised" if they're working into something fairly close to
their design impedances. For example, a 4:1 balun intended to match
200 ohms to 50 ohms, will only provide a 4:1 ratio and good current
balance and efficiency when matching impedances fairly close to those.

If you put such a balun at the output of a wide-range transmatch, and
try to match up a difficult load, then the balun might "see" something
like 750-j250 or 25+10j on its "200-ohm" side. The result might be
poor current balance on the "balanced" side, or excessively high
current flows which would require de-rating the balun's power handling
capability. "Voltage" baluns seem to be most vulnerable to this sort
of problem.

Putting a 1:1 balun on the input side of the tuner, and using a
fully-balanced or pseudo-balanced tuner is one way around this, since
the balun "sees" only the impedance load for which it was designed.

Another approach, often suggested, is to use a 1:1 transmission-line
current balun on the output.

Using a link-coupled tuner (a classic Matchbox, or a Z-match) is yet
another option.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

"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

Yes, moving a current balun to a position before the tuner is a
"useless" exercise but it doesn't render the balun "useless" -- it's
equally effective at the input as at the output (provided that the tuner
case is floated if the balun is at the input).

To answer your question about why not use one at the input and output, I
recommend against using one at the input because the case of the tuner
has to be floated for one at the tuner input to be effective. This has
some potential safety implications. If you want to use two baluns in
order to increase the common mode impedance, I suggest putting them both
at the output. And for maximum effectiveness, space them about a quarter
wavelength apart at the most troublesome band.

Roy Lewallen, W7EL

Cecil Moore wrote:
Jack Painter wrote:

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.


The choke on the input is *still* in series with the common-mode
current and is still performing the choking function. Moving the
balun to the input doesn't relieve the stress on the choke but it
also does NOT render the choke non-functional as the word "useless"
implies.
--
73, Cecil http://www.qsl.net/w5dxp


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Roy Lewallen wrote:
To answer your question about why not use one at the input and output, I
recommend against using one at the input because the case of the tuner
has to be floated for one at the tuner input to be effective.

Sorry, that's NOT true for remote autotuners. When I was remote autotuning
my elevated-radial vertical, the autotuner was 20 feet from the antenna and
65 feet from the shack. Field strength improved the most with chokes on the
input AND output.
--
73, Cecil http://www.qsl.net/w5dxp



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Hm, that's interesting. Was the tuner case floating? Did you try putting
both baluns at the input or both at the output for comparison? And how
much did the field strength improve and how did you measure it?

Roy Lewallen, W7EL

Cecil Moore wrote:
Roy Lewallen wrote:

To answer your question about why not use one at the input and output,
I recommend against using one at the input because the case of the
tuner has to be floated for one at the tuner input to be effective.


Sorry, that's NOT true for remote autotuners. When I was remote autotuning
my elevated-radial vertical, the autotuner was 20 feet from the antenna and
65 feet from the shack. Field strength improved the most with chokes on the
input AND output.
--
73, Cecil http://www.qsl.net/w5dxp



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Roy Lewallen wrote:
Hm, that's interesting. Was the tuner case floating? Did you try putting
both baluns at the input or both at the output for comparison? And how
much did the field strength improve and how did you measure it?

The tuner case was tied to a ground rod at the base of the antenna
support. In the last version, the radials were up at 20 ft. I didn't
try it without a choke on the input but adding a choke to the output
improved the ground level field strength at ~200 yards by a little
over one dB on 40m, if memory serves me right. I can't locate my
notebook at the moment. The field strength was measured using a Palomar
FS-1 and ferrite rod pickup antenna. The choke on the output appeared to
slightly reduce the received noise which is the problem I was chasing at
the time. I never could get the received noise down to an acceptable
level compared to my horizontal dipole so the vertical is gone.
--
73, Cecil http://www.qsl.net/w5dxp


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