Tuner efficiency question

[Parker Buckley]

I've been using my QRP K2 for the last 2-3 years with a "full sized" Palstar
tuner.  I use a variety of antennas from 160 to 10 meters, fed with coax,
ladder line, choke baluns, the Elecraft balun, etc.  I'm thinking about
going to an auto tuner (Dayton Hamvention coming).  Has anyone compared the
efficiencies of the very small tuner like the T1, the KAT2, and larger
tuners like the Palstar?  (I've been the Johnson KW Matchbox route as well.)
Intuition tells me there is something lost when going to very small
components packed into a tiny space compared to large air variables, big
roller inductors, etc., but I don't have anything to back up that gut feel.
Anyone make any measurements?  

 

Parker  K2 2636

WD8JOL

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[Don Ehrlich-2]

Parker et al,

QST did a review and test of a bunch of balanced tuners a year or so back.
I don't remember too much of it now but remember being shocked at how high
the losses typically were.  As I recall efficiency ran in the 65 to 75
percent range for many of them.  The Johnson matchbox was the most efficient
by far (90% or more??) but did not cover all bands.

I have not really studied this issue but have always been interested.  My
gut feel is that often much of the loss in these tuners (when driving a
balanced line) is in the internal balun which is at the output of typical
tuners and is driving a balanced line to the antenna which often has a
horrendous SWR.  The high SWR on the balanced line is not itself a problem
because balanced twin line or ladder line feeders can easily handle the high
currents and voltages with low losses but the poor balun can quickly get too
hot to touch because of the high circulating currents within the balun.

Don K7FJ  K2 4438

> I've been using my QRP K2 for the last 2-3 years with a "full sized"
> Palstar
> tuner.  I use a variety of antennas from 160 to 10 meters, fed with coax,
> ladder line, choke baluns, the Elecraft balun, etc.  I'm thinking about
> going to an auto tuner (Dayton Hamvention coming).  Has anyone compared
> the
> efficiencies of the very small tuner like the T1, the KAT2, and larger
> tuners like the Palstar?  (I've been the Johnson KW Matchbox route as
> well.)
> Intuition tells me there is something lost when going to very small
> components packed into a tiny space compared to large air variables, big
> roller inductors, etc., but I don't have anything to back up that gut
> feel.
> Anyone make any measurements?
>
>
>
> Parker  K2 2636
>
> WD8JOL
>
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[John, KI6WX]

Parker & Don;
I haven't tried to measure the efficiency of the Elecraft tuners.  It is a
fairly difficult measurement to make correctly when the input and output
impedance are significantly different.  However, there are two effects to
consider in tuner efficiency.

At high power, an inefficient tuner can generate significant amounts of
heat, which can destroy components.  A 1kW transmitter into a 70% efficient
tuner will generate 300 watts of heat in the tuner.

The second effect is the loss of signal at the receive station.  A 90%
efficient tuner will lose 0.5 dB; a 70% efficient tuner will lose 1.5 dB.
The 1 dB difference will not have any noticeable effect on the ability to
receive CW.  Even on digital modes, it will only have a minor effect on the
received error rate.  Other factors, such as QSB, QRM, or QRN, will have a
bigger effect.

As long as the Elecraft tuners are reasonably efficient, they shouldn't have
any significant effect on your ability to communicate.
-John
 KI6WX

> Parker et al,
>
> QST did a review and test of a bunch of balanced tuners a year or so back.
> I don't remember too much of it now but remember being shocked at how high
> the losses typically were.  As I recall efficiency ran in the 65 to 75
> percent range for many of them.  The Johnson matchbox was the most
> efficient by far (90% or more??) but did not cover all bands.
>
> I have not really studied this issue but have always been interested.  My
> gut feel is that often much of the loss in these tuners (when driving a
> balanced line) is in the internal balun which is at the output of typical
> tuners and is driving a balanced line to the antenna which often has a
> horrendous SWR.  The high SWR on the balanced line is not itself a problem
> because balanced twin line or ladder line feeders can easily handle the
> high currents and voltages with low losses but the poor balun can quickly
> get too hot to touch because of the high circulating currents within the
> balun.
>
> Don K7FJ  K2 4438
>
>
>
>> I've been using my QRP K2 for the last 2-3 years with a "full sized"
>> Palstar
>> tuner.  I use a variety of antennas from 160 to 10 meters, fed with coax,
>> ladder line, choke baluns, the Elecraft balun, etc.  I'm thinking about
>> going to an auto tuner (Dayton Hamvention coming).  Has anyone compared
>> the
>> efficiencies of the very small tuner like the T1, the KAT2, and larger
>> tuners like the Palstar?  (I've been the Johnson KW Matchbox route as
>> well.)
>> Intuition tells me there is something lost when going to very small
>> components packed into a tiny space compared to large air variables, big
>> roller inductors, etc., but I don't have anything to back up that gut
>> feel.
>> Anyone make any measurements?
>>
>>
>>
>> Parker  K2 2636
>>
>> WD8JOL
>>

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[Mark J. Schreiner]

I haven't had lots of different tuners to compare myself, but I do have
a Johnson KW Matchbox tuner.  It does a great job on Balanced lines.  I
didn't really know about the Palastar but just checked it out on the
website.  Looked like an interesting tuner.  But to me the downside of
it was that there is a balun on the output, which of course as Don
stated is a dominating factor in losses in a tuner (at least maybe that
is what I took away from his comments as well as other discussions on
this subject in the past).  Is there a modern tuner out there for
balanced lines that doesn't use a balun?

Maybe the proper comparison for more apples to apples comparison should
be made for tuners that are designed for type of feedline output or
maybe Hi-Z vs Lo-Z, as most today, including the Elecraft, are likely
moreso designed not for balanced line output and Hi-Z but coaxial output
and Lo-Z.  Sure, many tuners may also have a balanced line output
option, but that is likely there as a convenience or for marketing or
whatever but is really just added on as compared to the overall tuner
being designed for Hi-Z and balanced output.  While I like my Johnson KW
tuner for certain antennas I may opt for some other tuner for other
types of antennas.  The type of tuner should be considered as a whole in
the antenna system, not as a one size fits all solution (unless there is
a tuner out there that really can do both ends of the spectrum equally
well).

When I first started getting back into QRP just over one year ago I had
my RockMite-40 sitting on top of the Johnson KW Matchbox.  It was going
to a resonant antenna and didn't go through the tuner.  Even though the
Matchbox is supposedly a low loss antenna tuner it did seem like there
was something just wrong about using it with a QRP rig, maybe like some
sort of sacralidge in its own way, but maybe that is just me.

Maybe the purist would say that only resonant antennas should be used so
a tuner is not needed.  Okay, that makes some sense, but maybe I can get
an antenna with better overall performance than the extra losses
involved when using a tuner.  Again, the whole systems needs to be
evaluated an not just individual parts of a system.  If individual parts
are selected because they are the best but when put together they don't
work so well collectively it doesn't seem like a good solution. Maybe a
tuner with more versatility even if it has slightly higher losses is a
better solution for the next ham who doesn't use just one antenna at a
fixed location all the time.  Certainly as QRPers we are all aware that
antenna systems are quite important and band conditions really dominate
how well we can communicate.  But really, given good band conditions and
being able to somehow get some signal to something to radiate things
will result in being able to communicate.

I just installed the KAT2 in my K2 and am amazed at how fast it tunes.  
I haven't tried it with a variety of different antenna configurations,
so I can't comment much on its verstatility.  Unfortunately I'm not
currently using my balanced feedline antenna anymore due to a change in
QTH and a temporary hamshack setup, but the KAT2 seems to suit my needs
for now.  If anything, at this time the Matchbox at least still looks
quite respectable sitting on the bench (farther away from the K2 than
when I had the RockMite sitting on top of the Matchbox, HI! HI!).

I hope my late night ramblings make some sense.  Sorry if they don't.

Mark, NK8Q
K2 4876

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[Benny Aumala]

Palstar BT1500A is fully balanced tuner with
balun in INPUT, and tuning elements work balanced.
Here balun works properly.
The same applies to e.g. MFJ976.

World seems to wake up again for lattice feeders.
Most welcome.

--
Benny AUMALA         OH9NB
 

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[Parker Buckley]

Hi guys.  I certainly appreciate your quick responses.  Like everything
else, I guess the answer to a certain extent is "It depends".  I probably
should have sidestepped the balanced tuner vs tuner/balun part of the
question.  I've tried all kinds of combinations along those lines, probably
guided more by practicality for the particular installation than efficiency.
So maybe I should have started with "Assuming a coax-fed antenna......"  It
sounds like the decision still comes back to (given a reasonably efficient
design), what's most practical for the need.  The KAT2 integrates directly
into the K2 and the T1 offers flexibility for use with other rigs.  Looking
forward to Dayton!

73,
Parker
WD8JOL

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[Don Wilhelm-3]

Folks,

I recall comparisons and analysis of different tuner types done several
years ago by ARRL.  The conclusion was that the inductor Q was the major
determining factor for tuner efficiency of any one type of tuner.  The T
match circuit can match a large range but at some settings can produce high
circulating currents leading to very high losses, the PI network is
generally low loss but at the expense of failing to match very low impedance
loads with reasonable value capacitors, the L network is quite efficient,
but the lowest loss is a link coupled tuned tank circuit type tuner with a
high Q inductor (i.e. Johnson Matchbox type).

IMHO, compact designs have produced more tuner losses than any other
contributing factor - Hi-Q inductors are generally large airwound fixed
coils spaced far away from conducting surfaces.  I look at my Johnsom
Matchbox and see an air-wound coil supported in the center of a large box
(the coil has lots of surrounding empty space), quite in contrast to my MFJ
T match circuit tuner with the roller inductor placed less than an inch from
the side, bottom and top of the enclosure - the front panel appearance of
that tuner was judged more important than minimizing the inductor loss - and
we call it progress!!!

Contrary to popular belief, balun loss is not the largest contributing
factor, and if properly designed, makes little difference whether it is
placed on the input or the output.  Charles Green W1CG has done a lot of
work on balun loss and reports that the loss is actually quite low (even
when their design impedance is severly mismatched).

My bottom line conclusion here is that we pay a price in efficiency for the
convenience of compactness and a large matching range.  While I have not
seen efficiency tests of the Elecraft tuners, I would venture to guess that
their L network design with switched toroid inductors would show a
relatively low loss compared to many other designs.

73,
Don W3FPR

> -----Original Message-----
>
> I haven't had lots of different tuners to compare myself, but I do have
> a Johnson KW Matchbox tuner.  It does a great job on Balanced lines.  I
> didn't really know about the Palastar but just checked it out on the
> website.  Looked like an interesting tuner.  But to me the downside of
> it was that there is a balun on the output, which of course as Don
> stated is a dominating factor in losses in a tuner (at least maybe that
> is what I took away from his comments as well as other discussions on
> this subject in the past).  Is there a modern tuner out there for
> balanced lines that doesn't use a balun?
>
> Maybe the proper comparison for more apples to apples comparison should
> be made for tuners that are designed for type of feedline output or
> maybe Hi-Z vs Lo-Z, as most today, including the Elecraft, are likely
> ...

--
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[Stephen W. Kercel]

The comparison of balanced tuners is in the September 2004 QST.

It is worth mentioning that there is a strong correlation between tuner
efficiency and money. According to the ARRL lab data, a $900 Palstar is
substantially more efficient (Surprised?) than a $200 MFJ.

Side note: I dimly recall that there is an outfit in Germany that has been
making balanced tuners since before balanced became cool. They are very
expensive ($1.5 K - $2K), but I suspect that they are much more efficient
than the specimens tested in the ARRL lab.

A comparison of unbalanced tuners is in the February 2003 QST.

Again, it is worth mentioning that there is a strong correlation between
tuner efficiency and cost. According to the ARRL lab data, a $600 Ameritron
is substantially more efficient than a $330 MFJ. (All the more remarkable,
seeing that apparently the same people make both.)

Comparing the two different reviews reveals another detail. Commercially
available balanced tuners, as a class appear to be lossier than unbalanced
tuners. (Speculation: Since both the loss and cost are dominated by the
inductor quality, and the balanced tuner needs two of them, I expect that
the manufacturers are tempted to cut corners on the inductor quality for
the balanced tuner.)

Other point worth noting: Losses are much more severe when the load
resistance is substantially lower than 50 ohms. All the tuners show their
worst performance at R = 6.25. With R = 400 all the tuners do much better,
despite the fact that the SWR is 8:1 in both cases. (Almost certainly this
is caused by the resistive voltage divider effect. The resistance in the
tuner inductor is in series with the load impedance.)

Comment on baluns: If you drive a ferrite core to saturation, it will
overheat. It doesn't really take much to do it; a few minutes of normal CW
operating with 100 watts into a 5:1 SWR on 20 meters will do the trick for
me. Once the core overheats, the inductance changes and you lose your match
(quite severely, in my experience). You are much more likely to drive a
balun core into saturation on the high SWR output of a tuner than on the
low SWR input of the tuner.

73,

Steve Kercel
AA4AK


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[David A. Belsley]

> Side note: I dimly recall that there is an outfit in Germany that has
> been making balanced tuners since before balanced became cool.

Balanced didn't become cool; balanced always was cool.  Balanced is
only being rediscovered by the generation (or two (or three)) that
thought that coax was the only means for feeding a wire.


best wishes,

dave belsley, w1euy
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[Stephen W. Kercel]

Dave:

Personally, I've always thought that balanced was cool. I was using
balanced lines 20+ years ago. The sense that I had from my fellow hams at
the time was that practically everybody else thought that they were
decidedly uncool.

It is only in the last year or so that I've noticed them becoming rediscovered.

73,

Steve
AA4AK


At 09:41 AM 5/13/2005 -0400, you wrote:

>>Side note: I dimly recall that there is an outfit in Germany that has
>>been making balanced tuners since before balanced became cool.
>
>Balanced didn't become cool; balanced always was cool.  Balanced is only
>being rediscovered by the generation (or two (or three)) that thought that
>coax was the only means for feeding a wire.
>
>
>best wishes,
>
>dave belsley, w1euy

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[al_lorona]

> ...
> Contrary to popular belief, balun loss is not the largest
> contributing factor, and if properly designed, makes
> little difference whether it is placed on the input or the
> output.  Charles Green W1CG has done a lot of work
> on balun loss and reports that the loss is actually
> quite low (even when their design impedance is
> severly mismatched).
>
> My bottom line conclusion here is that we pay a price
> in efficiency for the convenience of compactness and
> a large matching range.

Yes, we most certainly do. Too many of us care only about the automatic aspect of these compact tuners, and we give up really efficient tuner operation. Tuners have to be really large to be really good. The components have to be large and the enclosures have to be large. But because many people don't like large boxes on their operating tables, and because they would rather not twiddle knobs, they go to these small, sometimes lossy autotuners. As long as they understand what they are giving up by doing this, it's cool.

However, balun loss isn't the only important factor and may not even be the most important factor. The balun's primary purpose is to convert to a balanced two-wire system, and in order to preserve the antenna pattern and keep the feedline from radiating, it has to provide equal currents in each leg of the feedline. In order to be effective at this, the balun's impedance has to be large compared to the antenna's input impedance. When baluns in tuners have to look into very high impedances, they stop acting as baluns. You may be happy that a particular balun doesn't have a lot of loss, but you would be very unhappy to learn that that same balun isn't doing it's job as a balun anymore. Under these conditions, who knows what the antenna pattern is.

Using a balanced tuner gets you part of the way to a highly efficient antenna system; the other half of the journey is to use a balun-less design that attains true balance no matter what the antenna/feedline conditions are. I have found this possible only by homebrewing such a tuner.

I don't know if you've ever seen the Annecke tuner on L. B. Cebik's web site:  http://www.cebik.com/link/link.html . It was the best hope we've had to seeing a link-coupled tuner like the old Johnson Matchbox, and many folks were expecting it to go back into production, but the person who bought the rights to the design has decided not to pursue the manufacture of the tuner at this time. Too bad. We'll just have to keep building them ourselves.

Al  W6LX







 
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[Don Ehrlich-2]

>I haven't had lots of different tuners to compare myself, but I do have
> a Johnson KW Matchbox tuner.  It does a great job on Balanced lines.  I
> didn't really know about the Palastar but just checked it out on the
> website.  Looked like an interesting tuner.  But to me the downside of it
> was that there is a balun on the output, which of course as Don stated is
> a dominating factor in losses in a tuner (at least maybe that is what I
> took away from his comments as well as other discussions on this subject
> in the past).  Is there a modern tuner out there for balanced lines that
> doesn't use a balun?

I don't know of any.  There is nothing wrong with using a balun as long as
the balun is looking into a relatively low SWR .  The  baluns we are all
familiar with only work well when feeding a balanced load that is fairly
flat.   In other words the balun ought to be at the INPUT of the tuner
instead of the OUTPUT.  This makes the tuner electrically and mechanically
much more complex and expensive and that is why you don't see it done very
often.  As John said .. half a db or so does not matter as far as signal
strength at the receiving station  is concerned.  The only problem is that
the power dissipation could damage the tuner or balun itself at the
transmitting station.

As a purist with lots of time on my hands I am trying for the best of all
worlds by building a true balanced L-C-L tuner with a balun at the input.
It is an auto tuner with all of the bells and whistles and will (probably ..
I think) handle up to 500 watts into my big wire antenna (but probably not
into shorter antennas).  I am going to put it into a K2 case with matching
button switches and a similar LCD.  It is working now on the benchtop at low
power levels but it remains to be seen if, when packed tightly into a small
case, I can keep the PIC controller circuits sufficiently free of rf
interference at high power levels.

Don  K7FJ

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[Vic K2VCO]

[hidden email] wrote:

> Yes, we most certainly do. Too many of us care only about the automatic
> aspect of these compact tuners, and we give up really efficient tuner
> operation. Tuners have to be really large to be really good. The components
> have to be large and the enclosures have to be large.

This is a good point.  Many QRP operators assume that a tuner used for QRP can
be small because one doesn't need the power-handling capability of a larger
tuner.  However, if a tuner has x db loss, then that loss will reduce the
strength of a received signal by x db whether the signal is transmitted at 5 or
500 watts!

So if I were building a QRP-only tuner, I would use a big silver-plated inductor
in a big box (although the capacitors could be smaller, since the voltage
requirement would be less).

--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco

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[Mike Morrow-3]

>> Is there a modern tuner out there for balanced lines that
>> doesn't use a balun?


>I don't know of any.  There is nothing wrong with using a balun
>as long as the balun is looking into a relatively low SWR .

Even the MFJ-974, 974H, and 976 balanced line tuners use a 1:1 current balun
on the input (http://www.mfjenterprises.com/man/pdf/MFJ-974.pdf ).  I don't
suppose that's all that bad a design compromise, though when these MFJ
tuners were first announced I had hoped that we would see a modernized
Matchbox design.

There are plenty of the Johnson Matchboxes to be found at hamfests and on
ebay.  I found mine (the version rated for about 300 watts) at a small local
hamfest a few years ago for $50.  I wouldn't even consider trading or
selling it.

73,
Mike / KK5F

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[Stuart Rohre]

Google the name Frank Witt, and you will find the tuner studies he did.
Also in archives of QRP-L reflector where he posted them, and maybe on
www.arrl.org technical topics links.

72,
Stuart
K5KVH



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[Stuart Rohre]

My understanding, from L. B. Cebik, was the German balanced tuners were
discontinued.  I could not find them by Google search.
-Stuart
K5KVH



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[Stuart Rohre]

The MFJ balanced tuner has a double tee network to give the most range of
adjustment.

Note even the vaunted Johnson Matchbox did not cover all of today's bands
and impedances.

-Stuart
K5KVH



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[Mark J. Schreiner]

You are correct, Stuart.  But, while lacking 160m, it did cover 80 to 10m.  Okay, so the bandswitch was discrete in the bands available at the time, but it I have used it on the other bands we have now and it still worked there, at least with my 340' double extended Zepp.  I didn't measure the efficiency though.  

Again, from my rambling comments last night, possibly the correct solution for one person is a tuner that covers the widest range of impedances while another that may not be the case.  Maybe one person has no need for balanced lines and is only interested in coaxial fed antennas and a tuner that does well with those (and that person has probably deleted all of these emails).  Like many topics, this one has many possible "correct" answers.  As somebody else said "It depends" is the right answer.

Mark, NK8Q
 

>The MFJ balanced tuner has a double tee network to give the most range of
>adjustment.
>
>Note even the vaunted Johnson Matchbox did not cover all of today's bands
>and impedances.
>
>-Stuart
>K5KVH
>
>

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[Stephen W. Kercel]

Stuart

It was a year or two back that I saw them. It may well be the case that
they are discontinued. They were way out of the price range of the typical ham.

However, these Web pages still work.

http://www.hewezi.com/bal_tuner.html

http://www.dj2hz.de/

If you're really curious, get in touch with DJ2HZ

73,

Steve
AA4AK

At 01:59 PM 5/13/2005 -0500, you wrote:
>My understanding, from L. B. Cebik, was the German balanced tuners were
>discontinued.  I could not find them by Google search.
>-Stuart
>K5KVH


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[Stephen W. Kercel]

Stuart:

The Johnson differs from modern balanced tuners in that it used link
coupling (a tuned transformer with inductive coupling) rather than a
matching network.

It also had the advantage over home brew link couplers that you tuned it
with knobs instead of moving little clips around on the big coil.

73,

Steve
AA4AK



At 02:14 PM 5/13/2005 -0500, you wrote:

>The MFJ balanced tuner has a double tee network to give the most range of
>adjustment.
>
>Note even the vaunted Johnson Matchbox did not cover all of today's bands
>and impedances.
>
>-Stuart
>K5KVH
>
>
>
>_______________________________________________
>Elecraft mailing list
>Post to: [hidden email]
>You must be a subscriber to post to the list.
>Subscriber Info (Addr. Change, sub, unsub etc.):
>  http://mailman.qth.net/mailman/listinfo/elecraft
>
>Help: http://mailman.qth.net/subscribers.htm
>Elecraft web page: http://www.elecraft.com

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