"Mike Coslo" wrote in message
6
wrote:

If the only antennas we have are trapped verticals,
tribanders or dipoles/inverted vees cut for the band to
be used, we might get away with not having to use a
tuner at all. Still there are likely to be frequencies
significantly removed from the antenna's resonant
frequency where one might need a tuner to enable the
transmitter to make full power. We aren't likely to
need a wide range tuner for those times. A simple
T-match will likely enable us to find a combination of
settings which will present a low VSWR to the
transmitter. The main alternative is to have a variety
of antennas which present a VSWR of under 2:1 to a
transmitter.

That brings up a related issue. Lots of Hams today are
restricted to one antenna, yet they would like all band
operation. I think it would be a great idea for a
manufacturer to have a transciever that included a tuner
right in the rig itself.

- 73 de Mike KB3EIA -

They do exist, although being primarily interested in VHF/UHF operation
(we only recently had the morse requirement for HF dropped over here in
the UK, but that's another topic..!!) I've had little experience of them.

I do remember vividly using a Drake commercial HF transceiver (I think it
came out of a ship's radio room) back in the late 80's at a special event
station that had this feature, you could operate on any band without any
form of tuning at all, although of course how much power would get out on
a really bad antenna is debatable ;-)

Of course if you've enough money, there are those antennas that tune
themselves. A friend has a 3-element beam that is computer controlled; as
you tune across the bands, the elements automatically adjust themselves to
the correct length..! I don't recall the make/model, but it is of American
origin, does anyone know of it..?

73 Ivor G6URP

"Ivor Jones" wrote in message
...
"Mike Coslo" wrote in message
6
wrote:


[snip]


That brings up a related issue. Lots of Hams today are
restricted to one antenna, yet they would like all band
operation. I think it would be a great idea for a
manufacturer to have a transciever that included a tuner
right in the rig itself.

- 73 de Mike KB3EIA -

They do exist, although being primarily interested in VHF/UHF operation
(we only recently had the morse requirement for HF dropped over here in
the UK, but that's another topic..!!) I've had little experience of them.


My main HF rig and my husband's main HF rig both have built in tuners. Both
work pretty well. However they do not have the range of outboard tuners.

I do remember vividly using a Drake commercial HF transceiver (I think it
came out of a ship's radio room) back in the late 80's at a special event
station that had this feature, you could operate on any band without any
form of tuning at all, although of course how much power would get out on
a really bad antenna is debatable ;-)


A lot of commericial and military equipment have built in tuners with quite
significant tuning ranges. Of course this comes at a price so amateur gear
doesn't have as much range in their tuning capacity on the built in tuners.

Of course if you've enough money, there are those antennas that tune
themselves. A friend has a 3-element beam that is computer controlled; as
you tune across the bands, the elements automatically adjust themselves to
the correct length..! I don't recall the make/model, but it is of American
origin, does anyone know of it..?

73 Ivor G6URP

I think it is called the SteppIR. Too rich for my pocket book.

Dee, N8UZE

"Dee Flint" wrote in
:


My main HF rig and my husband's main HF rig both have built in tuners.
Both work pretty well. However they do not have the range of
outboard tuners.

I should have noted large range and balanced/unbalanced output. My
IC-761 has an autotuner on it that works pretty well with my vertical
antenna. The dipole is run with balanced line, and needs a different
tuner.


A lot of commericial and military equipment have built in tuners with
quite significant tuning ranges. Of course this comes at a price so
amateur gear doesn't have as much range in their tuning capacity on
the built in tuners.

Size can be an issue too. The IC 761's tuner is a pretty tiny
thing. I had to take an IC 765's autotuner 9 (very similar) apart once to
repair it, and it was around the size of one of the mfj tiny tuners.

A little bigger components, plus a 4:1 balun, and they would have
it.

- 73 de Mike KB3EIA -

On Mar 4, 10:23�pm, Mike Coslo wrote:
* * * * I should have noted large range and balanced/unbalanced output. My
IC-761 has an autotuner on it that works pretty well with my vertical
antenna. The dipole is run with balanced line, and needs a different
tuner.

---

* * * * A little bigger components, plus a 4:1 balun, and they would have
it.

Well, sort of.

The Ancient Ones used antenna matching
devices to feed balanced lines. The Johnson
Matchboxes are one example of a commercial
version. Most Handbooks have examples of
link-coupled balanced wide-range tuners.

The problem was that such link-coupled tuners are large
and not easy to bandswitch.

About 1970, a new idea in tuners appeared: Use an
unbalanced matching network such as a T or L
network with a roller inductor or tapped inductor, with a
balun if balanced output was wanted. 4:1 iron-core toroid
baluns were compact and broadband, the T or L tuner
could be made wide-range without complex bandswitching,
and the whole works seemed an improvement on the old
link-coupled balanced tuner.

The problem was that baluns aren't magic devices. The
system works well if the shack-end of the transmission line
is around 200 ohms impedance and not too reactive. But in
many cases the shack-end impedance with balanced line
is very high or very low, and/or very reactive. Under such
conditions the balun may not do a very good job because it is
being asked to work far outside its design parameters.

Also, if the shack-end impedance is low (say, 12 ohms), the
use of a 4:1 balun will make it so low (3 ohms) that it may be outside
the efficient matching range of the T or L network.

These conditions may be partially remedied by use of a balun
that can be switched to either 4:1 or 1:1 ratio, and by choosing
antenna and feedline combinations that don't result in extreme
values of shack-end impedance/reactance. But that reduces
the flexibility of the system.

The "unbalanced tuner followed by a balun" idea is clearly
one where "newer" wasn't necessarily "better" in all cases.
Yet it became very popular because it usually worked.
But in many cases the balanced line was actually
doing a lot of radiating and there was considerable loss in the
system.

Back in 1990, AG6K came up with an answer to the
shortcomings of that method. He put a 1:1 balun between the
rig and a simple balanced tuner, so the balun only has to
deal with a pure 50 ohm load once the tuner is adjusted.
Although AG6K favors baluns made from coax wound on
PVC pipe, other forms of balun such as ferrite-bead and
wound-toroid can be used if preferred.

You can read AG6K's article he

http://www.somis.org/bbat.html

and judge for yourself.

AG6K's approach used two ganged roller inductors and
a single variable capacitor, compared to most commercial
manual tuners that use two variable caps and a single variable
inductor. Because there are only two controls, remoting the
tuner is made easier.

73 de Jim, N2EY

wrote:


These conditions may be partially remedied by use of a balun
that can be switched to either 4:1 or 1:1 ratio, and by choosing
antenna and feedline combinations that don't result in extreme
values of shack-end impedance/reactance. But that reduces
the flexibility of the system.

True enough.

snip



You can read AG6K's article he

http://www.somis.org/bbat.html

and judge for yourself.

I have gathered the parts to make just that!. I'd have it up now, but I
switched to a coax fed antenna for a while, and built a more traditional
tuner. In the interim I went back to balanced line.


AG6K's approach used two ganged roller inductors and
a single variable capacitor, compared to most commercial
manual tuners that use two variable caps and a single variable
inductor. Because there are only two controls, remoting the
tuner is made easier.

Some day I'll report on how mine is doing. In the present situation I
don't need remote tuning, but will probably motorize the unit anyway.

- 73 de Mike KB3EIA -

On Mar 6, 4:30?pm, Michael Coslo wrote:
wrote:

You can read AG6K's article he

http://www.somis.org/bbat.html

and judge for yourself.

I have gathered the parts to make just that!. I'd have it up now, but I
switched to a coax fed antenna for a while, and built a more traditional
tuner. In the interim I went back to balanced line.

The AG6K tuner can be used with balanced or unbalanced
line.

All you have to do to use it with an unbalanced line is to ground the
coax shield at the tuner end of the coax balun,
and use the "other side" to feed the ungrounded line. A
simple SPST switch of adequate ratings can do the job.

The AG6K tuner, as described, has adequate matching
range for most dipole-fed-with-balanced-line amateur
antennas. A little care in choosing the antenna and
feedline length can make the tuner's job a lot easier.

Reg Edwards' DIPOLE3 program can be a big help in
figuring out the shack-end impedance of various
antenna/transmission line combinations.

AG6K's approach used two ganged roller inductors and
a single variable capacitor, compared to most commercial
manual tuners that use two variable caps and a single variable
inductor. Because there are only two controls, remoting the
tuner is made easier.

Some day I'll report on how mine is doing. In the present situation I
don't need remote tuning, but will probably motorize the unit anyway.

Although not mentioned in the article, the roller inductors
could be replaced by a pair of tapped coils and a double-pole switch.
The tap positions would have to be found by
experiment, but could be made permanent once they were found. Tuner
adjustment could then consist of simply selecting the correct tap
postion with the switch, and
adjusting the variable capacitor for minimum SWR.

Automatic tuners are not new to amateur radio, btw.
An automatic balanced tuner was described in QST for July, 1952. It
would automatically retune itself within
an amateur band. Changing bands meant changing coils, but once that
was done the tuner would do the rest automatically.

73 de Jim, N2EY

wrote:
On Mar 6, 4:30?pm, Michael Coslo wrote:



I have gathered the parts to make just that!. I'd have it up now, but I
switched to a coax fed antenna for a while, and built a more traditional
tuner. In the interim I went back to balanced line.

The AG6K tuner can be used with balanced or unbalanced
line.

I should have been more clear about the reasons. The tuner that I made
is a massively retro unit that is kinda pretty. Cherry finished wood
face, with real old time knobs and cranks. If I went to the balanced one
now, I'd need to start over again. I will eventually build the AG6K type
balanced tuner of course, but want to enjoy this one for a while.



Reg Edwards' DIPOLE3 program can be a big help in
figuring out the shack-end impedance of various
antenna/transmission line combinations.

I have all his programs. Upon his demise, his family and a number of
interested amateurs made sure to archive and distribute them. We miss
Reg over on rraa.



Although not mentioned in the article, the roller inductors
could be replaced by a pair of tapped coils and a double-pole switch.

The tuner can be hot switched, I assume?

Automatic tuners are not new to amateur radio, btw.
An automatic balanced tuner was described in QST for July, 1952. It
would automatically retune itself within
an amateur band. Changing bands meant changing coils, but once that
was done the tuner would do the rest automatically.

Thanks for the reference, Jim. It should be interesting to see how they
did it then.

- 73 de Mike KB3EIA -

wrote:
[snip]
The "unbalanced tuner followed by a balun" idea is clearly
one where "newer" wasn't necessarily "better" in all cases.
Yet it became very popular because it usually worked.
But in many cases the balanced line was actually
doing a lot of radiating and there was considerable loss in the
system.

Back in 1990, AG6K came up with an answer to the
shortcomings of that method. He put a 1:1 balun between the
rig and a simple balanced tuner, so the balun only has to
deal with a pure 50 ohm load once the tuner is adjusted.
Although AG6K favors baluns made from coax wound on
PVC pipe, other forms of balun such as ferrite-bead and
wound-toroid can be used if preferred.
[snip]

I'm not sure a "balanced" tuner is required. I have an off-center-fed
dipole I use with 600 ohm ladder line, and I'd like to try it with an
Ultimate Transmatch. If I put AG6K's coax balun on the input and isolate
the chasis from ground, wouldn't that achieve the same result?

Bill


--
73,

Bill W1AC

(Remove "73" and change top level domain for direct replies)

Mike Coslo wrote:

A little bigger components, plus a 4:1 balun, and they would have
it.

I wish that the manufacturers would include the provision for balanced
feedline. The random-length dipole, fed with balanced line, is an ideal
antenna in many cases. It's especially appropriate for disaster
situations (and simulated disasters, like Field Day). Find the two
highest supports that are available, as far apart as possible, measure
the distance, cut the wire and install the middle insulator and
feedline, hoist each end, and you're done. Now you've got a reasonably
efficient radiator (especially if there's enough distance between those
two supports) that you can use on any band, and the length of the
feedline isn't particularly critical. But it takes a tuner and balun to
make it work, and if this was included in the rig and was automatic, it
would be ideal.

73, Steve KB9X