Jeffrey Angus wrote in news:j5vfh4$uh1$1@dont-
email.me:

Recently acquired an LDG tuner. Nice part.
I'm looking forward to the not having to twist knobs every
time I change frequency.
It comes with an adapter cable for Icom radios, but it's a
4-pin Molex connector and the manual doesn't show what the
connections/signals are for the radio.

I think your question relates to the connections between the LDG and that
Molex plug.

Was it LDG who supplied the adapter? If so, ask them. Seems a bit silly
that would supply the thing without adequate information on how to use it.

Owen

On 9/28/2011 7:00 PM, Owen Duffy wrote:
I think your question relates to the connections between the LDG and that
Molex plug.

Was it LDG who supplied the adapter? If so, ask them. Seems a bit silly
that would supply the thing without adequate information on how to use it.

Owen

Well, I did ask LDG and they were kind enough to send me the application
note describing the connections.

And the more I looked into this the more I realized, "You have an
antenna tuner built in into the Icom IC-761."

Homer Simpson moment, "Do-oh!"

However, the specified tuning range of the internal tuner is 16.7
to 150 ohms. The LDG is specified as 6 to 1000 ohms. A bit more
latitude.

OK, "How did I get side tracked like this?"

Earlier this year I got an MFJ Versa Tuner to use with the doublet
antenna. It works fine. But of course, it's manual. (But it does
have a 4:1 balun inside.) So I get the LDG in a swap for some
goodies. No balun inside. Ok, I ordered an MFJ 4:1 current balun.
And those do work a LOT smoother tuning that with the internal
4:1 voltage type the MFJ tuner has.

It was while obsessing over the "talk to the radio" cable for the
LDG that I realized, "Oh right, this is designed for radios that
don't have internal tuners." For example, my Icom IC-726 has the
correct interface to talk to the LDG. I do have the matching AT-150
auto-tuner for the IC-726. That is specified the same as the IC-761
tuner.

Once the balun gets here, the FIRST thing I'm going to do is to
find out if the internal tuner has enough range to deal with my
antenna.

I just love wild goose chases, because in the end, you usually do
learn something useful in the process.

Jeff-1.0
wa6fwi



--
"Everything from Crackers to Coffins"

Jeffrey Angus wrote in
:

....
I just love wild goose chases, because in the end, you usually do
learn something useful in the process.

Yes, there is always a risk of that.

The auto tuner can be a path to hiding shortcomings in an antenna
system, in search of the holy grail, low VSWR.

Whilst you seem critical of the 4:1 voltage balun in the MFJ, it is my
perception that they are still the most popular balun. My theory on that
is that antenna systems that exhibit extreme impedance can often be
'matched' with that configuration, assisted by the loss in the balun.

It is an example of how the device's operation can be misunderstood.
There is little doubting the considerable anecdotal evidence that 4:1
voltage baluns work 'better', it is understanding what is meant by
'better' that is revealing.

That leads into the question of whether a 4:1 balun is 'better'.

If you were selling product, you would concentrate on the things that
deliver good VSWR, because that is all that is in the minds of most
buyers.

Owen

PS: for avoidance of doubt, nothing above should be interpreted to
recommend a 4:1 voltage balun or a 4:1 balun.

On 9/28/2011 7:31 PM, Owen Duffy wrote:
The auto tuner can be a path to hiding shortcomings in an antenna
system, in search of the holy grail, low VSWR.

This is a 102' doublet with 40' of open wire balanced feed line.
Except for the input of the tuner looking like 50 ohms to make the
transmitter happy, there is no such thing as "low VSWR" on this
type of antenna.

Whilst you seem critical of the 4:1 voltage balun in the MFJ, it is my
perception that they are still the most popular balun. My theory on that
is that antenna systems that exhibit extreme impedance can often be
'matched' with that configuration, assisted by the loss in the balun.

It is an example of how the device's operation can be misunderstood.
There is little doubting the considerable anecdotal evidence that 4:1
voltage baluns work 'better', it is understanding what is meant by
'better' that is revealing.

Actually, the MFJ 949b Versa Tuner has an internal 4:1 voltage balun.
The reason for that is simple. One large toroid and you're done. There
isn't room inside the case for a 4:1 current balun.

If you disconnect the open wire line from the internal voltage balun
in an MFJ tuner and replace it with an external current balun you will
find that the tuning of the match on the tuner is a lot smoother as
opposed to almost erratic. (But still obtainable.)

Due to the location of my station on the 2nd floor over looking a
covered porch, having a "good RF ground" is not going to happen.
The current balun forces the antenna and feed line into a truly
balanced condition. No ground needed, other than a proper bonding
of all the related equipment to a common reference in the station.

The whole purpose of the tuner is to allow the transmitter to see
a 50 ohm unbalanced load that it was designed for. Accomplishing
that, allows the most power to be transferred to the antenna. The
102' doublet with open wire line seems to do a remarkable job at
radiating. (And equally well at receiving.)

That leads into the question of whether a 4:1 balun is 'better'.

Better than what? A 1:1 balun or none at all, which seems to be
the selling point of the G5RV antenna and it's clones.

Jeff-1.0
wa6fwi

--
"Everything from Crackers to Coffins"

Jeffrey Angus wrote in news:j60h8s$ao0$1@dont-
email.me:

On 9/28/2011 7:31 PM, Owen Duffy wrote:
The auto tuner can be a path to hiding shortcomings in an antenna
system, in search of the holy grail, low VSWR.

This is a 102' doublet with 40' of open wire balanced feed line.
Except for the input of the tuner looking like 50 ohms to make the
transmitter happy, there is no such thing as "low VSWR" on this
type of antenna.

Well to "make the transmitter happy" is jsut the new language for low
VSWR.

... There
isn't room inside the case for a 4:1 current balun.

But there is probably room for an effective 1:1 Current Balun.


If you disconnect the open wire line from the internal voltage balun
in an MFJ tuner and replace it with an external current balun you will
find that the tuning of the match on the tuner is a lot smoother as
opposed to almost erratic. (But still obtainable.)

Ok, so in your experience, you haven't yet come across a load that could
be matched with the voltage balun, but not with an external current
balun.

Due to the location of my station on the 2nd floor over looking a
covered porch, having a "good RF ground" is not going to happen.
The current balun forces the antenna and feed line into a truly
balanced condition.

Ideal conditions like "forces" and "truly balanced" don't often exist in
the real world. It would be of more interest if you had measured and
reported the differential and common mode current at various
frequencies.

The whole purpose of the tuner is to allow the transmitter to see
a 50 ohm unbalanced load that it was designed for. Accomplishing
that, allows the most power to be transferred to the antenna. The

Yes. It is the meaning of "most" that is relevant. Most doesn't need to
mean 100%, or close to it, you make compromises for frequency agility
and multiband use, but "most" is often unknown. Perhaps some DX QSL
cards can substitute.

102' doublet with open wire line seems to do a remarkable job at
radiating. (And equally well at receiving.)

Yes, they can be a good antenna, but it is not a no-brainer.

For example, a correspondent recently reported problems with just such a
thing on 40m. Turns out his feed line length was such that at 800W into
the feed line, the voltage between the wires was some 4000+V and was
causing flashovers in a 3kW rated ATU. In this case, I recommended that
since he could not lengthen or shorten the feed line enough, that he
shorten the antenna so solve the problem.

He had previously smoked up a CWS Bytemark 5kW rated current balun on
80m with another antenna, caused by unlucky feed line length.


That leads into the question of whether a 4:1 balun is 'better'.

Better than what? A 1:1 balun or none at all,

1:1.

4:1 reduces the voltage impressed on the ATU components, which is good
for high impedance loads, and poor for low impedance loads.

There is no simple thing that always works best on a random set of loads
(which is the case for many multi band antennas).

which seems to be
the selling point of the G5RV antenna and it's clones.

Perhaps to some. There is good argument for use of a balun with a G5RV
and not-balanced transmitter. Varney conceded that in one of his later
articles. Most people who are adament about what Varney did or did not
describe have not read his articles. Antenna manufacturers are not a
good source of factual information.

Owen

On 9/28/2011 8:54 PM, Owen Duffy wrote:
Jeffrey wrote in news:j60h8s$ao0$1@dont-
email.me:

On 9/28/2011 7:31 PM, Owen Duffy wrote:
The auto tuner can be a path to hiding shortcomings in an antenna
system, in search of the holy grail, low VSWR.

This is a 102' doublet with 40' of open wire balanced feed line.
Except for the input of the tuner looking like 50 ohms to make the
transmitter happy, there is no such thing as "low VSWR" on this
type of antenna.

Well to "make the transmitter happy" is jsut the new language for low
VSWR.

You're missing the point. The "Holy Grail" is low VSWR at the antenna.
Obviously having the tuner present a nice resistive 50 ohm load to a
transmitter designed to be loaded with a resistive 50 ohm load is a
"Good thing(tm)".

But with a random length, i.e. non-resonant, antenna, VSWR at the
antenna is not a meaningful term.

... There
isn't room inside the case for a 4:1 current balun.

But there is probably room for an effective 1:1 Current Balun.

But my point was MFJ chose to use a voltage balun for two reasons.
They're cheaper and they still work to a fashion.

Ok, so in your experience, you haven't yet come across a load that could
be matched with the voltage balun, but not with an external current
balun.

Not yet. If it matches at all with one, it will match with the other.
The difference being that the current balun results in much less
erratic/sudden/critical tuning of the antenna tuner itself.

Due to the location of my station on the 2nd floor over looking a
covered porch, having a "good RF ground" is not going to happen.
The current balun forces the antenna and feed line into a truly
balanced condition.

Ideal conditions like "forces" and "truly balanced" don't often exist in
the real world. It would be of more interest if you had measured and
reported the differential and common mode current at various
frequencies.

Um, actually, yes they do. That's the whole point of a current mode
balun.

The whole purpose of the tuner is to allow the transmitter to see
a 50 ohm unbalanced load that it was designed for. Accomplishing
that, allows the most power to be transferred to the antenna. The

Yes. It is the meaning of "most" that is relevant. Most doesn't need to
mean 100%, or close to it, you make compromises for frequency agility
and multiband use, but "most" is often unknown. Perhaps some DX QSL
cards can substitute.

As an example then. How about working RA3DA in a pileup competing with
the "big guns" in New York running at or above the legal limit? Sure
I didn't get him on the first call, but I did it running under 100 watts
and into a $25 antenna.

102' doublet with open wire line seems to do a remarkable job at
radiating. (And equally well at receiving.)

Yes, they can be a good antenna, but it is not a no-brainer.

For example, a correspondent recently reported problems with just such a
thing on 40m. Turns out his feed line length was such that at 800W into
the feed line, the voltage between the wires was some 4000+V and was
causing flashovers in a 3kW rated ATU. In this case, I recommended that
since he could not lengthen or shorten the feed line enough, that he
shorten the antenna so solve the problem.

He had previously smoked up a CWS Bytemark 5kW rated current balun on
80m with another antenna, caused by unlucky feed line length.

See above. Why is it that hams seem to think they absolutely need to run
800 (or more) watts of power?

That leads into the question of whether a 4:1 balun is 'better'.

Better than what? A 1:1 balun or none at all,

1:1.

4:1 reduces the voltage impressed on the ATU components, which is good
for high impedance loads, and poor for low impedance loads.

There is no simple thing that always works best on a random set of loads
(which is the case for many multi band antennas).

All I've said is that this appears to work perfectly for me.
In the time honored tradition of Usenet "Your mileage may vary."

which seems to be
the selling point of the G5RV antenna and it's clones.

Perhaps to some. There is good argument for use of a balun with a G5RV
and not-balanced transmitter. Varney conceded that in one of his later
articles. Most people who are adament about what Varney did or did not
describe have not read his articles. Antenna manufacturers are not a
good source of factual information.

You're hear equally unsubstantiated claims about how well an off center
fed Windom antenna works with no tuner as well.

Jeff-1.0
wa6fwi

--
"Everything from Crackers to Coffins"

On Wed, 28 Sep 2011 21:22:55 -0500, Jeffrey Angus
wrote:

But my point was MFJ chose to use a voltage balun for two reasons.
They're cheaper

What is the price differential in winding one wire outside the core,
instead of winding it inside the core? Such "savings" accrue only in
the production run of millions of units.

and they still work to a fashion.

If both sides are unbalanced - you mean that fashion?

MFJ is not making a killing on this particular poor winding (OK, call
it historical inertia) practice, and their market for these internal
BalUns is dipoles, not monopoles.

73's
Richard Clark, KB7QHC