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high-power tuner

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Ian Kahn, KM4IK

Re: high-power tuner

This probably shows my gross lack of knowledge of the physics involved
here, but what does the weight of the tuner have to do with its efficiency?

73,

--Ian

Ian Kahn, KM4IK
Roswell, GA
[hidden email]
K3 #281, P3 #688

On 3/9/2012 6:14 PM, Fred Jensen wrote:

> On 3/9/2012 2:24 PM, WILLIS COOKE wrote:
>
>> If you need a tuner, your
>> antenna does not meet this criteria so, what are you using to form
>> your opinion?
> Weigh the tuner, then transmit continuously, measure the temperature
> rise, and when it's stable, calculate the heat loss [something to do
> with Boltzman's Constant -- the tuner *is* painted black]. What doesn't
> leave as heat must leave as RF. Did it years ago on a 10 KW FM
> broadcast transmitter [4 ea 4-1000's], and it came within one percent of
> the efficiency measured with the water-cooled dummy load. YMMV however.
>
> 73,
>
> Fred K6DGW
> - Northern California Contest Club
> - CU in the 2012 Cal QSO Party 6-7 Oct 2012
> - www.cqp.org
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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Rick WA6NHC

Re: high-power tuner

I'll take a guess...

You have to know the mass to find the amount of energy converted into heat.
Like Ohm's law, given two values, you can figure out the third. If you know
the mass and know the temperature change, you can calculate the energy.

Ok Fred, am I close?

Rick wa6nhc

-----Original Message-----
From: Ian Kahn - Ham

This probably shows my gross lack of knowledge of the physics involved
here, but what does the weight of the tuner have to do with its efficiency?

73,

--Ian

Ian Kahn, KM4IK
Roswell, GA
[hidden email]
K3 #281, P3 #688

On 3/9/2012 6:14 PM, Fred Jensen wrote:

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Mike WA8BXN

Re: high-power tuner

In reply to this post by Ian Kahn, KM4IK

Ian,

Weight comes into play in two ways. A heavier tuner will likely have less
loss due to less resistive loss by using larger diameter wire etc. But that
s not the issue in measuring the loss.

As Fred mentions below, power fed into a tuner goes two places. One is out
to the load (antenna) and the other is heating the tuner (not a good thing).
One can measure how much a tuner warms up during use, that's due to loss in
the tuner. Just knowing the temperature change doesn't give the full answer
though. Lets say we measure an increased temperature of 10 degrees. Now if
we have a very heavy tuner, that would be more power lost in the tuner than
in a tuner that has the same 10 degree increase but is very small. Look at
it this way. It would take a lot more power to heat a gallon of water 10
degrees than to head a drop of water 10 degrees.

To calculate the actual power loss in the tuner you would have to use the
right degree units, the right weight (mass) units and constants. You would
also have to heat insulate the tuner from the room so it doesn't cool off
during your measurement period.

73 - Mike WA8BXN

-------Original Message-------

From: Ian Kahn - Ham
Date: 3/9/2012 6:31:37 PM
To: [hidden email]
Cc: [hidden email]
Subject: Re: [Elecraft] high-power tuner

This probably shows my gross lack of knowledge of the physics involved
Here, but what does the weight of the tuner have to do with its efficiency?

73,

--Ian

Ian Kahn, KM4IK
Roswell, GA
[hidden email]
K3 #281, P3 #688

On 3/9/2012 6:14 PM, Fred Jensen wrote:

Bob K6UJ

Re: high-power tuner

In reply to this post by W5RDW

QST had an article a while back comparing tuners, MFJ, Palomar, Drake and several others if I remember correctly.
They had a chart showing the loss per band per each tuner.
They included the old Johnson Viking matchbox in their ranking too. The old Johnson was right up there
in the top rankings, with very low loss. I wish I still had my old Johnson, sigh...............
Anyway a search on the ARRL webpage for QST articles about tuners should show the article.

Bob
K6UJ

On Mar 9, 2012, at 2:10 PM, W5RDW wrote:

> Never had any reason to wonder if my MFJ-998 has more than normal loss. It
> hasn't let any smoke out of the cabinet yet! I use to run a Drake L-7 thru
> it, but now use the KPA500 all the time and have retired the Drake.
>
>> /Most of the MFJ tuners tend to rank pretty low in that respect./
>
> Dave, I'd be interested in reading about the info you have on the MFJ tuner
> loss.
>
> -----
> Roger W5RDW
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/high-power-tuner-tp7314904p7359740.html
> Sent from the Elecraft mailing list archive at Nabble.com.
> ______________________________________________________________
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> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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k6dgw

Re: high-power tuner

In reply to this post by Ian Kahn, KM4IK

"The only thing that shows gross lack of knowledge is not asking the
question for which you need the answer." [Cal Poly Physics Professor
whose name escapes me but whose class I remember as a personal struggle].

To know the net rate of heat input [i.e. generation within the tuner]
from the temperature change, you need to know the mass of the tuner.
Weigh it and a little arithmetic and you have the mass. The RF that
doesn't heat the tuner must go up the coax. Weighing has nothing to do
with the efficiency itself, it is part of the
not-exactly-precise-measurement-method I suggested but don't recommend.

For the FM transmitter, we had temperature sensors in the grid
compartment on the bottom where the refrigerated air entered, and just
far enough above the chimneys where it came out hot. There was a water
manometer to measure the pressure difference between the air inlet and
the vent that took the hot air outside. The pressure differential was
very low so I assumed that the air got hot at a constant pressure. This
was an important assumption because at that time I didn't know enough
calculus for the alternative. I probably don't remember now either.

I got up very early one morning [was 17 and living at the TX], and
turned on the filaments. When the temperatures had stabilized, and
knowing the filaments were turning 600W of electricity into almost 600W
of heat, I could calculate the mass rate of the air flowing through the
chimneys. Sign on came, I let the temps stabilize at 5.3 KV and 3.5A
plate current, and calculated the heat input to give those temps. That
power blew out the vent, the rest went up the 3 1/8" rigid coax to the
antenna, I assumed. Turned out we were a little overpower, almost 12KW
for about 70% efficiency and the 4-1000 plates were fairly bright. OK,
really bright.

For the case of the tuner, it's not so simple and I skillfully tried to
skate past the effect of radiation from the "black body" [i.e. the
"black" tuner which, while black, probably isn't a real black body] as
the RF heats it. While I know the first six digits of Boltzmann's
Constant [138065 -- it used to be the master unlock password for a UHF
repeater I maintain], I've forgotten some of the physics and math I used
to know and it's guaranteed that, were I to attempt that calculation on
this list, a countable infinity of people would correct me and then each
other ... likely forever or until Eric stepped in.

It was a e-nerd semi-joke, which I've found are not often funny except
to other e-nerds. Undaunted however, I continued. Cookie's comment
about measuring the efficiency of tuners being hard is very true, and
you can't do it with a Micronta SWR meter from Radio Shack. It will
involve some math, maybe even calculus, and quite a bit of expensive
test equipment.

I would trust ARRL's numbers, and those of a few others like Sherwood,
I'll remain a little skeptical of the Mfr's numbers, if they even
publish them.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2012 Cal QSO Party 6-7 Oct 2012
- www.cqp.org

On 3/9/2012 3:30 PM, Ian Kahn - Ham wrote:
> This probably shows my gross lack of knowledge of the physics involved
> here, but what does the weight of the tuner have to do with its
efficiency?

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Tony Estep

Re: high-power tuner

In reply to this post by Ian Kahn, KM4IK

On Fri, Mar 9, 2012 at 5:30 PM, Ian Kahn - Ham <[hidden email]> wrote:
> This probably shows my gross lack of knowledge of the physics involved
> here, but what does the weight of the tuner have to do with its efficiency...
=============
Ian, the idea was to measure the power soaked up by the tuner by
measuring how fast it heats up. To turn degrees/second into a measure
of power, you gotta know how much mass was getting heated.

Tony KT0NY

--
http://www.isb.edu/faculty/facultydir.aspx?ddlFaculty=352
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Phil Salas

Re: high-power tuner

In reply to this post by Cookie

I've been making tuner loss measurements for an upcoming QST review of some
remote autotuners. My set-up is similar to the ARRL lab, but I've made a
few changes. I have two different load boxes. One is a resistive load box
that lets me measure loss with loads from 12-800 ohms. The second load box
simulates different types of electrically short end-fed antennas - like a 43
footer on lower frequency bands, or an 8-footer like you might have mobile,
and other combinations. I use Caddock thick-film 30-watt resistors for the
resistive portion of both test boxes. For the short antenna simulator, I
use series silver mica capacitors with shunt Caddock resistors.

Basically, I feed the 40 watt output of my test transceiver through a high
power 6dB pad, through an Array Solutions PowerMaster, then to the tuner.
So my test power is 10 watts. The 6dB pad helps keep the power relatively
constant, but primarily ensures that any reflected power from a non-perfect
tune (the tuners have a target of 1.5:1) is attenuated 12dB more if
re-reflected by the transmitter. The output of the tuner feeds the load
box. The load box has an output that feeds a 50 ohm attenuator/Minicircuits
PWR-6GHS+ power sensor (that output is shunted or seriesed with Caddock
resistors to give the required test impedance). So I start with no tuner
in-line and adjust the Minicircuits offset so it and the PowerMaster read
the same at 10 watts. They are both NIST-traceable cal'd, and were within
3% of each other, but I adjusted the offset so they are within 1%. Then I
insert the autotuner, hit it with RF and let it tune. When tuning is
complete I adjust the input drive so it is exactly 10 watts, read the output
on the PWR-6GHS+, and compare that to the expected power under lossless
conditions.

Phil - AD5X

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Ian Kahn, KM4IK

Re: high-power tuner

In reply to this post by Ian Kahn, KM4IK

All,

As I said, question shows my lack of knowledge of physics. :-)

Thanks, everyone, for the explanations!

73,

--Ian

Ian Kahn, KM4IK
Roswell, GA
[hidden email]
K3 #281, P3 #688

On 3/9/2012 6:30 PM, Ian Kahn - Ham wrote:

> This probably shows my gross lack of knowledge of the physics involved
> here, but what does the weight of the tuner have to do with its
> efficiency?
>
> 73,
>
> --Ian
>
> Ian Kahn, KM4IK
> Roswell, GA
> [hidden email]
> K3 #281, P3 #688
>
>
> On 3/9/2012 6:14 PM, Fred Jensen wrote:
>> On 3/9/2012 2:24 PM, WILLIS COOKE wrote:
>>
>>> If you need a tuner, your
>>> antenna does not meet this criteria so, what are you using to form
>>> your opinion?
>> Weigh the tuner, then transmit continuously, measure the temperature
>> rise, and when it's stable, calculate the heat loss [something to do
>> with Boltzman's Constant -- the tuner *is* painted black]. What doesn't
>> leave as heat must leave as RF. Did it years ago on a 10 KW FM
>> broadcast transmitter [4 ea 4-1000's], and it came within one percent of
>> the efficiency measured with the water-cooled dummy load. YMMV however.
>>
>> 73,
>>
>> Fred K6DGW
>> - Northern California Contest Club
>> - CU in the 2012 Cal QSO Party 6-7 Oct 2012
>> - www.cqp.org
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html

Don Wilhelm-4

Re: high-power tuner

In reply to this post by Bob K6UJ

Bob,

One can construct a link coupled tuner that will have even greater
efficiency than the venerable Johnson Matchbox. It will have plug-in
coils, and the antenna will connect to taps on the coil rather than
using a differential capacitor - that tuner will have a greater matching
range than the Matchbox as well as having less loss. The drawback is
that it does not lend itself well to bandswitching. OTOH, it does not
need to be in an enclosure, can be built on a piece of wood (yes, mine
is built on a wooden board), so the plug-in coil is easily accessed and
changed to whatever band one wants ot operate on. Once the settings for
any one antenna have been established and recorded, changing bands takes
less than 30 seconds.

As L.B.Cebik has stated many times, link coupled balanced tuners are the
most efficient. Their loss is close to zero.

73,
Don W3FPR

On 3/9/2012 7:56 PM, Bob K6UJ wrote:

> QST had an article a while back comparing tuners, MFJ, Palomar, Drake and several others if I remember correctly.
> They had a chart showing the loss per band per each tuner.
> They included the old Johnson Viking matchbox in their ranking too. The old Johnson was right up there
> in the top rankings, with very low loss. I wish I still had my old Johnson, sigh...............
> Anyway a search on the ARRL webpage for QST articles about tuners should show the article.
>
> Bob
> K6UJ
>
>
>
> On Mar 9, 2012, at 2:10 PM, W5RDW wrote:
>
>> Never had any reason to wonder if my MFJ-998 has more than normal loss. It
>> hasn't let any smoke out of the cabinet yet! I use to run a Drake L-7 thru
>> it, but now use the KPA500 all the time and have retired the Drake.
>>
>>> /Most of the MFJ tuners tend to rank pretty low in that respect./
>> Dave, I'd be interested in reading about the info you have on the MFJ tuner
>> loss.
>>
>> -----
>> Roger W5RDW
>> --
>> View this message in context: http://elecraft.365791.n2.nabble.com/high-power-tuner-tp7314904p7359740.html
>> Sent from the Elecraft mailing list archive at Nabble.com.
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

Re: high-power tuner

In reply to this post by Tony Estep

OK Guys, I have a Physics Degree too, but realistically, if the tuner uses real coils and air capacitors like the Matchbox it is really efficient. If it uses link coupling like we did in olden days it is probably a scotch (technical term meaning a little bit) better than the more common T network. If it uses toroids, small fixed capacitors and relay switching, it probably has even more loss. So, maybe the answer is to buy a tuner that is the same size as your amplifier. If you elect to run a KTA-500 you probably are not terribly concerned whether you get 475 watts to the antenna or 450 watts. If you need an Alpha 9500 to be sure that you get through then you need the Alpha 4040 so it will look great near your 9500 and the 3 grand price will seem cheap after paying 8 grand for the amp. You can always brag on your 75 meter net that of the 1499.9 watts out of the 9500 1499.8 watts get through the 4040 to melt the RG8X that feeds your Buddy Pole.
But, if the KTA-500 is your thing then a tuner that costs more than your amp and is the biggest thing in your shack (unless you have a left over BC-610) will look pretty silly.

If you must measure your temperatures to figure your efficiency down to the milliwatt, be sure and use RTDs for measurement because thermocouples are not nearly accurate enough for precision measurements.

Willis 'Cookie' Cooke
K5EWJ & Trustee N5BPS, USS Cavalla, USS Stewart

________________________________
From: Tony Estep <[hidden email]>
To: Elecraft <[hidden email]>
Sent: Friday, March 9, 2012 7:01 PM
Subject: Re: [Elecraft] high-power tuner

On Fri, Mar 9, 2012 at 5:30 PM, Ian Kahn - Ham <[hidden email]> wrote:
> This probably shows my gross lack of knowledge of the physics involved
> here, but what does the weight of the tuner have to do with its efficiency...
=============
Ian, the idea was to measure the power soaked up by the tuner by
measuring how fast it heats up. To turn degrees/second into a measure
of power, you gotta know how much mass was getting heated.

Tony KT0NY

--
http://www.isb.edu/faculty/facultydir.aspx?ddlFaculty=352
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Don Wilhelm-4

Re: high-power tuner

In reply to this post by Phil Salas

Phil,

My lab "simulated antenna" consists of a dummy load and a Johnson Matchbox.
I can connect a dummy load to the Matchbox and twist the dials to create
just about any reasonable impedance that you want. I set it up using my
MFJ259B if I am looking for something specific.

The helpful parameter is that it is frequency sensitive (just like an
antenna), while a resistive dummy load is not sensitive to frequency.

I do normally use Caddock Thick Film resistors to create dummy loads. I
have several 50 ohm loads, but also have a 25 ohm (2 50 ohm resistors in
parallel) and a 100 ohm (2 50 ohm resistors in series) that I use for
setting the 2:1 SWR point while I am calibrating wattmeters. These are
1% tolerance loads, and if mounted to the connector (and heat sink) with
short leads present a flat response up to 500 MHz.

Note well that the Caddock literature says only that the 50 ohm
resistors are non-reactive - that may be true for other values, but I
have taken that information at face value and use only the 50 om
resistors for dummy loads.

73,
Don W3FPR

On 3/9/2012 8:42 PM, Phil & Debbie Salas wrote:

> I've been making tuner loss measurements for an upcoming QST review of some
> remote autotuners. My set-up is similar to the ARRL lab, but I've made a
> few changes. I have two different load boxes. One is a resistive load box
> that lets me measure loss with loads from 12-800 ohms. The second load box
> simulates different types of electrically short end-fed antennas - like a 43
> footer on lower frequency bands, or an 8-footer like you might have mobile,
> and other combinations. I use Caddock thick-film 30-watt resistors for the
> resistive portion of both test boxes. For the short antenna simulator, I
> use series silver mica capacitors with shunt Caddock resistors.
>
> Basically, I feed the 40 watt output of my test transceiver through a high
> power 6dB pad, through an Array Solutions PowerMaster, then to the tuner.
> So my test power is 10 watts. The 6dB pad helps keep the power relatively
> constant, but primarily ensures that any reflected power from a non-perfect
> tune (the tuners have a target of 1.5:1) is attenuated 12dB more if
> re-reflected by the transmitter. The output of the tuner feeds the load
> box. The load box has an output that feeds a 50 ohm attenuator/Minicircuits
> PWR-6GHS+ power sensor (that output is shunted or seriesed with Caddock
> resistors to give the required test impedance). So I start with no tuner
> in-line and adjust the Minicircuits offset so it and the PowerMaster read
> the same at 10 watts. They are both NIST-traceable cal'd, and were within
> 3% of each other, but I adjusted the offset so they are within 1%. Then I
> insert the autotuner, hit it with RF and let it tune. When tuning is
> complete I adjust the input drive so it is exactly 10 watts, read the output
> on the PWR-6GHS+, and compare that to the expected power under lossless
> conditions.
>
> Phil - AD5X
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

Mike WA8BXN

Re: high-power tuner

In reply to this post by Cookie

I'm not convinced that toroids are inferior to air wound coils. There will
be some core loss but there will be less ohmic loss as well. I'm also not
sure that just getting a tuner rated at the same power level as an amplifier
is always going to be most efficient. If the marketing agency is doing the
tuner rating the rating may be suspect.

There are some tuners that can just about match anything for an antenna. If
it won't melt at a particular power level, is it the best tuner for that
power level? Matching a given load usually means giving the transmitter near
a 50 ohm load. If you have a tuner that does that with no antenna attached
it means the tuner must dissipate all the power.

Manual tuners often have some hints on how to get the best efficiency at a
good match, like try to find a match using maximum or minimum value for
control X. With automatic tuners, we often just let the tuner do its thing
and use the match it finds. Some tuners will have better algorithms than
others in picking the best match. The difference from one tuner to another
can be a lot more than milliwatts. So it can be a good idea to get good
evaluations of available tuners.

73 - Mike WA8BXN

-------Original Message-------

From: WILLIS COOKE
Date: 3/9/2012 9:47:31 PM
To: Elecraft
Subject: Re: [Elecraft] high-power tuner

OK Guys, I have a Physics Degree too, but realistically, if the tuner uses
real coils and air capacitors like the Matchbox it is really efficient. If
it uses link coupling like we did in olden days it is probably a scotch
(technical term meaning a little bit) better than the more common T network.
If it uses toroids, small fixed capacitors and relay switching, it probably
has even more loss. So, maybe the answer is to buy a tuner that is the same
size as your amplifier. If you elect to run a KTA-500 you probably are not
terribly concerned whether you get 475 watts to the antenna or 450 watts. If
you need an Alpha 9500 to be sure that you get through then you need the
Alpha 4040 so it will look great near your 9500 and the 3 grand price will
seem cheap after paying 8 grand for the amp. You can always brag on your 75
meter net that of the 1499.9 watts out of the 9500 1499.8 watts get through
the 4040 to melt the RG8X that feeds your Buddy Pole.
But, if the KTA-500 is your thing then a tuner that costs more than your amp
and is the biggest thing in your shack (unless you have a left over BC-610)
will look pretty silly.

If you must measure your temperatures to figure your efficiency down to the
milliwatt, be sure and use RTDs for measurement because thermocouples are
not nearly accurate enough for precision measurements.

Willis 'Cookie' Cooke
K5EWJ & Trustee N5BPS, USS Cavalla, USS Stewart

______________________________________________________________
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Don Wilhelm-4

Re: high-power tuner

Mike and all,

The T-Network tuners are problematic even though they can be quite
wide-range - they may show multiple tuning condition for any given
antenna/matching situation. They should always be adjusted for the
largest value of capacity that will tune properly.

Most automatic tuners are of the L network type which avoids the
ambiguous tuning spots of the T-network tuners.

73,
Don W3FPR

On 3/9/2012 10:22 PM, Mike WA8BXN wrote:

>
> I'm not convinced that toroids are inferior to air wound coils. There will
> be some core loss but there will be less ohmic loss as well. I'm also not
> sure that just getting a tuner rated at the same power level as an amplifier
> is always going to be most efficient. If the marketing agency is doing the
> tuner rating the rating may be suspect.
>
> There are some tuners that can just about match anything for an antenna. If
> it won't melt at a particular power level, is it the best tuner for that
> power level? Matching a given load usually means giving the transmitter near
> a 50 ohm load. If you have a tuner that does that with no antenna attached
> it means the tuner must dissipate all the power.
>
> Manual tuners often have some hints on how to get the best efficiency at a
> good match, like try to find a match using maximum or minimum value for
> control X. With automatic tuners, we often just let the tuner do its thing
> and use the match it finds. Some tuners will have better algorithms than
> others in picking the best match. The difference from one tuner to another
> can be a lot more than milliwatts. So it can be a good idea to get good
> evaluations of available tuners.
>
> 73 - Mike WA8BXN
>
>
>
>
> -------Original Message-------
>
> From: WILLIS COOKE
> Date: 3/9/2012 9:47:31 PM
> To: Elecraft
> Subject: Re: [Elecraft] high-power tuner
>
> OK Guys, I have a Physics Degree too, but realistically, if the tuner uses
> real coils and air capacitors like the Matchbox it is really efficient. If
> it uses link coupling like we did in olden days it is probably a scotch
> (technical term meaning a little bit) better than the more common T network.
> If it uses toroids, small fixed capacitors and relay switching, it probably
> has even more loss. So, maybe the answer is to buy a tuner that is the same
> size as your amplifier. If you elect to run a KTA-500 you probably are not
> terribly concerned whether you get 475 watts to the antenna or 450 watts. If
> you need an Alpha 9500 to be sure that you get through then you need the
> Alpha 4040 so it will look great near your 9500 and the 3 grand price will
> seem cheap after paying 8 grand for the amp. You can always brag on your 75
> meter net that of the 1499.9 watts out of the 9500 1499.8 watts get through
> the 4040 to melt the RG8X that feeds your Buddy Pole.
> But, if the KTA-500 is your thing then a tuner that costs more than your amp
> and is the biggest thing in your shack (unless you have a left over BC-610)
> will look pretty silly.
>
> If you must measure your temperatures to figure your efficiency down to the
> milliwatt, be sure and use RTDs for measurement because thermocouples are
> not nearly accurate enough for precision measurements.
>
> Willis 'Cookie' Cooke
> K5EWJ& Trustee N5BPS, USS Cavalla, USS Stewart
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html
>

David Gilbert

Re: high-power tuner

A T-Network tuner with a large enough capacitor in one leg set to full
capacity is essentially an L-network tuner.

73,
Dave AB7E

On 3/9/2012 9:55 PM, Don Wilhelm wrote:

> Mike and all,
>
> The T-Network tuners are problematic even though they can be quite
> wide-range - they may show multiple tuning condition for any given
> antenna/matching situation. They should always be adjusted for the
> largest value of capacity that will tune properly.
>
> Most automatic tuners are of the L network type which avoids the
> ambiguous tuning spots of the T-network tuners.
>
> 73,
> Don W3FPR
>
> On 3/9/2012 10:22 PM, Mike WA8BXN wrote:
>> I'm not convinced that toroids are inferior to air wound coils. There will
>> be some core loss but there will be less ohmic loss as well. I'm also not
>> sure that just getting a tuner rated at the same power level as an amplifier
>> is always going to be most efficient. If the marketing agency is doing the
>> tuner rating the rating may be suspect.
>>
>> There are some tuners that can just about match anything for an antenna. If
>> it won't melt at a particular power level, is it the best tuner for that
>> power level? Matching a given load usually means giving the transmitter near
>> a 50 ohm load. If you have a tuner that does that with no antenna attached
>> it means the tuner must dissipate all the power.
>>
>> Manual tuners often have some hints on how to get the best efficiency at a
>> good match, like try to find a match using maximum or minimum value for
>> control X. With automatic tuners, we often just let the tuner do its thing
>> and use the match it finds. Some tuners will have better algorithms than
>> others in picking the best match. The difference from one tuner to another
>> can be a lot more than milliwatts. So it can be a good idea to get good
>> evaluations of available tuners.
>>
>> 73 - Mike WA8BXN
>>
>>
>>
>>
>> -------Original Message-------
>>
>> From: WILLIS COOKE
>> Date: 3/9/2012 9:47:31 PM
>> To: Elecraft
>> Subject: Re: [Elecraft] high-power tuner
>>
>> OK Guys, I have a Physics Degree too, but realistically, if the tuner uses
>> real coils and air capacitors like the Matchbox it is really efficient. If
>> it uses link coupling like we did in olden days it is probably a scotch
>> (technical term meaning a little bit) better than the more common T network.
>> If it uses toroids, small fixed capacitors and relay switching, it probably
>> has even more loss. So, maybe the answer is to buy a tuner that is the same
>> size as your amplifier. If you elect to run a KTA-500 you probably are not
>> terribly concerned whether you get 475 watts to the antenna or 450 watts. If
>> you need an Alpha 9500 to be sure that you get through then you need the
>> Alpha 4040 so it will look great near your 9500 and the 3 grand price will
>> seem cheap after paying 8 grand for the amp. You can always brag on your 75
>> meter net that of the 1499.9 watts out of the 9500 1499.8 watts get through
>> the 4040 to melt the RG8X that feeds your Buddy Pole.
>> But, if the KTA-500 is your thing then a tuner that costs more than your amp
>> and is the biggest thing in your shack (unless you have a left over BC-610)
>> will look pretty silly.
>>
>> If you must measure your temperatures to figure your efficiency down to the
>> milliwatt, be sure and use RTDs for measurement because thermocouples are
>> not nearly accurate enough for precision measurements.
>>
>> Willis 'Cookie' Cooke
>> K5EWJ& Trustee N5BPS, USS Cavalla, USS Stewart
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

Rick Stealey

Re: high-power tuner

There seems to have been no answer as to how to accurately measure the loss in a tuner.
Here is a solution but requires two tuners or at least one calibrated one that could be
used to measure others.
Take first tuner and tune it into the mismatch, say 600 ohms. Use an antenna analyzer.
Then remove the load, and connect another tuner to the output of the first (back-
to-back - antenna port on first to antenna port on second tuner.) Then put a 50 ohm
load on the second tuner where the transceiver would be connected, and tune the second
tuner to a match. It will have the same settings as the first tuner, complete symmetry.
Then measure the power in the 50 ohm load to get the loss.

Since both tuners are matching the same load, and the system is symmetrical the
loss contribution by each tuner is half. Repeat for other types of loads, and now
you have a calibrated tuner to use with any tuner you want to test.

Rick K2XT

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Tim Heasman

Re: high-power tuner

In reply to this post by k6dgw

Hi All,

What you really need to do is to put the whole tuner inside a calorimeter
and measure the rate of temperature change to determine the the dissipated
wattage.

Tim
gm4lmh

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K7TV

Re: high-power tuner

In reply to this post by Rick Stealey

As has been clearly demonstrated in this thread, there are multiple methods
of measurement. The one that gets my vote for elegance is the one with two
tuners back-to-back. With respect to the method that measures temperature
rise, taking into account the mass of the tuner, one also needs to take into
account the specific heat capacity of the tuner. One kilo of material x
doesn't heat up at the same rate as one kilo of material y when the same
heating power is applied. The tuner will of course be a mix of materials, so
one would have to measure the rate at which the tuner heats up when heat is
applied through a know heating source rather than TX power. If it is done
that way, one needs to know neither the mass nor the specific heat capacity,
since what one is measuring is essentially the mass times the specific heat
capacity.

73, Erik K7TV

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Ron D'Eau Claire
Sent: Saturday, March 10, 2012 11:47 AM
To: 'Rick Stealey'; [hidden email]
Subject: Re: [Elecraft] high-power tuner

I was investigating tuner losses a few years ago and ran into many of these
same questions.

A physicist buddy pointed out to me that the normal approach to measure loss
in something like a tuner is to put it in a well-insulated chamber and
measure the rise in temperature over time while transmitting. From there on
can calculate the energy required to cause the temperature rise which can be
used to calculate the number of watts of RF that never make it through the
box.

73, Ron AC7AC

-----Original Message-----

There seems to have been no answer as to how to accurately measure the loss
in a tuner.
Here is a solution but requires two tuners or at least one calibrated one
that could be used to measure others.
Take first tuner and tune it into the mismatch, say 600 ohms. Use an
antenna analyzer.
Then remove the load, and connect another tuner to the output of the first
(back- to-back - antenna port on first to antenna port on second tuner.)
Then put a 50 ohm load on the second tuner where the transceiver would be
connected, and tune the second tuner to a match. It will have the same
settings as the first tuner, complete symmetry.
Then measure the power in the 50 ohm load to get the loss.

Since both tuners are matching the same load, and the system is symmetrical
the loss contribution by each tuner is half. Repeat for other types of
loads, and now you have a calibrated tuner to use with any tuner you want to
test.

Rick K2XT

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David Gilbert

Re: high-power tuner

In reply to this post by Rick Stealey

I haven't dug it up , but QST April 1995 pp. 30-34 and QST May 1995 pp.
33-37 describes how the QST lab does it.

Dave AB7E

On 3/10/2012 6:17 AM, Rick Stealey wrote:
> There seems to have been no answer as to how to accurately measure the loss in a tuner.
>
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Vic Rosenthal

Re: high-power tuner

In reply to this post by K7TV

I've recently been experimenting with tuners. I have a "275 watt" Johnson Matchbox (which
is actually good for more than a kW on CW in most cases) and a huge T network that I just
built with a massive edge-wound rotary inductor and capacitors with air gaps of about 3/8"
(near 10mm). The T network has a DX Engineering "5 kW" rated 1:1 balun on the output.

The antenna is an 88-foot dipole fed with 500 ohm open-wire line and some 450-ohm ladder line.

I can switch between these tuners instantly. On 40 meter received signals I can detect
absolutely no difference in signal strength. The T network is adjusted for the least
possible inductance that gives a 1:1 SWR, and the output capacitor is at maximum (300 pf
air plus 300 pf ceramic padder)..

There is also no difference in noise level. If one of the tuners provided better balance,
one would expect that there would be less noise pickup on the feedline. But I don't see this.

One anomalous result: there is a weak unstable carrier that I can hear on the Matchbox but
not on the T network. I have verified that this is not a birdie, but an actual signal. It
could be attributed to feedline pickup -- but wouldn't you expect the matchbox to be
better in this regard? I'm investigating further.

On 3/10/2012 12:31 PM, Erik Basilier wrote:

> As has been clearly demonstrated in this thread, there are multiple methods
> of measurement. The one that gets my vote for elegance is the one with two
> tuners back-to-back. With respect to the method that measures temperature
> rise, taking into account the mass of the tuner, one also needs to take into
> account the specific heat capacity of the tuner. One kilo of material x
> doesn't heat up at the same rate as one kilo of material y when the same
> heating power is applied. The tuner will of course be a mix of materials, so
> one would have to measure the rate at which the tuner heats up when heat is
> applied through a know heating source rather than TX power. If it is done
> that way, one needs to know neither the mass nor the specific heat capacity,
> since what one is measuring is essentially the mass times the specific heat
> capacity.
>
> 73, Erik K7TV

l

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

Re: high-power tuner

I just did the following experiment: I coupled a grid-dip oscillator to my feed line far
from the tuners and switching relays. I put it a few inches from the feedline equidistant
from the conductors. I found that the T network plus DXE balun reduced the signal pickup
by about 15 dB over the Matchbox!

That means that both radiation and noise pickup on the feedline are much less with the T
than with the Matchbox. At the same time I verified that there was no detectable
difference between the strength of received signals coming from the antenna.

This is amazing! It means that the T network and balun is significantly better than the
Matchbox in this important respect. So much for mythology.

On 3/10/2012 1:11 PM, Vic K2VCO wrote:

> I've recently been experimenting with tuners. I have a "275 watt" Johnson Matchbox
> (which is actually good for more than a kW on CW in most cases) and a huge T network
> that I just built with a massive edge-wound rotary inductor and capacitors with air gaps
> of about 3/8" (near 10mm). The T network has a DX Engineering "5 kW" rated 1:1 balun on
> the output.
>
> The antenna is an 88-foot dipole fed with 500 ohm open-wire line and some 450-ohm ladder
> line.
>
> I can switch between these tuners instantly. On 40 meter received signals I can detect
> absolutely no difference in signal strength. The T network is adjusted for the least
> possible inductance that gives a 1:1 SWR, and the output capacitor is at maximum (300 pf
> air plus 300 pf ceramic padder)..
>
> There is also no difference in noise level. If one of the tuners provided better
> balance, one would expect that there would be less noise pickup on the feedline. But I
> don't see this.
>
> One anomalous result: there is a weak unstable carrier that I can hear on the Matchbox
> but not on the T network. I have verified that this is not a birdie, but an actual
> signal. It could be attributed to feedline pickup -- but wouldn't you expect the
> matchbox to be better in this regard? I'm investigating further.
>
> --
> Vic, K2VCO
> Fresno CA
> http://www.qsl.net/k2vco/

123