Hi Mikek,
An ALC is not necessary if the high to low impedance converter has fixed
gain through applied load impedances.
Bottom of:
is schematic: "Q-Meter Prototype Schematic"
An AD8055 is used as very low impedance driver. If RF In is applied by a
calibrated signal generator, voltage to injection transformer will be known.
John KN5L
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On 10/4/22 7:51 AM, Mikek wrote: ?We have seen that the HP4342A Impedance converter transformer driver is
a simple two transistor circuit with low output impedance.
?Does anyone have an automatic Level Control circuit (ALC), we could
insert between a signal generator and the two transistor
Impedance converter transformer driver to keep the drive voltage
constant? I have setup a couple transformers and see the
input impedance seems to move around a lot. A lot of that is probably
that I'm driving from 50¦¸, but an ALC is still needed.
?The HP4342A has an ALC with 5 active devices including an N channel
dual fet. As I see it the ALC only develops the control
voltage, an addition of the level controller is needed, maybe a fet opto
isolator.
?So, a circuit to keep the signal generator output voltage constant.
(50¦¸ output to drive the two two transistor Impedance converter
transformer driver)
?????????????????????????????????????????? Mikek
|
?We have seen that the HP4342A Impedance converter transformer driver is a simple two transistor circuit with low output impedance.
?Does anyone have an automatic Level Control circuit (ALC), we could insert between a signal generator and the two transistor
Impedance converter transformer driver to keep the drive voltage constant? I have setup a couple transformers and see the
input impedance seems to move around a lot. A lot of that is probably that I'm driving from 50¦¸, but an ALC is still needed.
?The HP4342A has an ALC with 5 active devices including an N channel dual fet. As I see it the ALC only develops the control
voltage, an addition of the level controller is needed, maybe a fet opto isolator.
?So, a circuit to keep the signal generator output voltage constant. (50¦¸ output to drive the two two transistor Impedance converter transformer driver)
?????????????????????????????????????????? Mikek
|
Please repost with a sensible title. I am locking the topic?
Dave, group owner?
|
You might get more of a response with a better topic than "any interest?"
Steve
|
New Q measurements in:
Wanted to measure an Iron Powder Toroid with Q-Curve within nominal
Q-Meter, 400pF to 500pF, maximum resonating capacitor value. Selected
T80-2 80 turns #26
Several evaluations documented.
1. Evaluate S11 Q measurement range and process. As shown VNWA
resolution is insufficient at higher Q values. Low frequency Q, Wire Rs
region, appears to be valid. High frequency region follows bandwidth Q
measurement.
2. Evaluate Rs and Rp Q model. Series wire, square root frequency, Rs Q
is a good match. Using fixed parallel core Rp does not match well. Core
loss must increase as frequency increases.
3. Evaluate Series resistance for two different capacitors. Summary in
table "VNWA Bandwidth Q using 150pF Variable and 120pF C0G." 150pF
variable and 120pF C0G has higher Q than 400pF variable. If capacitor Rs
is constant, with respect to frequency, would expect "Rs Delta" column
to be a constant value.
John KN5L
|
Sure, I can do the 3db method. The idea is to compare to the known good cap in the 260A.
I can also do the 3db method on my 260A to get a Q number to compare to the other caps, but that not a direct comparison.?
?I have a Kleijer amp for 3db tests, it has a very high input impedance.
>>How do you set the Boonton drive level low enough to measure Q levels of 1000?<<
?By decreasing the drive voltage. I found this years ago, but a search didn't find it. My scanner is not working so I took pictures of
the print out, if they are unread able, let me know and I'll send a full size picture by email.
????????????????????????????????????????????? Mikek
|
Have any way to measure q other than the 260?
Perhaps:
Make a similar inductor with a tap at 1 or 2 turns to serve as a measurement point to prevent loading when measured with a HP 3400.
Use the 260 as a driving source by using the LO terminal.
Test by measuring the tap voltage while measuring Q with the 260.
Calculate Q = (Voltmeter * (total turns/tap turns))/260 drive voltage
Q calculated this way should be close to 260 reading.
Now test variable caps with one end of coil on 260 LO terminal other end on cap stator, and cap rotor on GND terminal.
It's good that the 260 cap is slightly better than the best of your collection, but with the extra path through binding posts and connecting wires, TRW might be better. I've a cubic foot of assorted variables, but not many that might be very high Q.
How do you set the Boonton drive level low enough to measure Q levels of 1000?
John KK6IL
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On 10/2/2022 12:40 PM, Mikek wrote: On Fri, Sep 30, 2022 at 05:35 AM, Mikek wrote:
?I have a 237uH coil with a Q over 1300 at 1MHz to use for the
comparison.
? Q is fun!
I decided to experiment with my personal air caps compared to the Boonton 260A air cap.
I looked into disconnecting the air caps in the 260A, it's more than I want to get involved with!
Sooo, setting the Boonton 260A to its minimum capacitance of 37pf I tried 3 different caps and
found Q using my 237uH high Q inductor.
? Meaning, this measurement, is a mix of 37pf minimum of the 260A and the capacitor I'm testing.
?I'm confused of how to think about two loss resistances in parallel, it seems like loss would go down.
But, is the loss R higher at minimum capacitance vs higher capacitance? Q is lower, but that is? mostly because
Xc is lower. (Q = Xc/R)
? The caps I measured are good air caps, as over the years I have tried to buy only the best caps I can find.
?Measurement with Boonton 260A only
Freq???????????????? Q
500kHz??? ? ? ? 1002
1000KHz?????? 1134??? Loss R of inductor + capacitor = 1.28¦¸
1200kHz??????? 1004
1500kHz???????? 942
Silver plated Cap 14pf to 500pf
? Freq??????????? ? ? Q
500kHz????? ? ?? 1002
1000kHz????? ? ?? 924 ? Loss R of inductor + capacitor =? 1.58¦¸
1200Khz?????????? 726? I had to stop there because of minimum 260A capacitance.
Cardwell capacitor 24pf to 475pf
Freq?????????????? Q
500kHz???????? 756
1000kHz?????? 606??? Loss R of inductor + capacitor = 2.46¦¸
1200kHz????? 540
TRW capacitor?? 17pf to 461pf
Freq????????????? Q
500kHz?????? 1008
1000khz????? 1062??? Loss R of inductor + capacitor = 1.4¦¸
1200kHz????? 954
Take another look at the Wes Hayward article and look at the capacitor Qs *at the very end*, they are much higher than the
previous numbers shown in John's post, the article was unclear and misleading, which Wes admits in an edit 2 months later.
<>
Using the math present in Wes's article, first, we know that QL is greater than Q at Resonance (Q Res). Therefore with an unknown QL,
we must make a guess of what QL might be. The formula is below.
Qc = (QRes x QL) / (Ql - QRes).
?Since I have QRes of 1134 1MHz on the Boonton 260A, I'll assume the Inductor QL is 1200.
Qc = 1134 x 1200 / 1200 - 1134 = 20,618 = Qc
This might be to high, as I recall reading somewhere the 260A cap Q was 20,000, no idea at what setting.
So, QL may be less than 1200.
The TRW cap is the best cap tested.
?Now the TRW cap with the loss of the 260A cap set at the minimum 37 pf in parallel.
Qc = 1062 x 1200 / 1200 - 1062 = 9,235 = Qc.
? Feedback is appreciated.
???????????????????????????? Mikek
|
On Sun, Oct 2, 2022 at 05:11 PM, Tom Lee wrote:
But the reactance is also halved, so the ratio remains constant, so Q does not change.
OK, good, got that.? Now, does the actual loss resistance of an air capacitor change from minimum capacitance to maximum. ?Would the actual RL of the 260A capacitor be more or less at 37pf vs 100pf. ?What I'm digging at is this, I resonate an LC on my 260A, my capacitor is about 106pf It has a loss x ohms. when I lower the the 106pf to 37pf ( and add 69pf from the cap under test), is the 37pf adding more or less RL than the original 106pf. I suspect RL will be about the same, the frequency has not changed so internal loss would be the same. ??????????????????????????????????????? Mikek
|
That's a different case than I was discussing -- I was talking
specifically about a situation where a loss resistance (and a loss
resistance alone) is placed in parallel with a lossy capacitance
(say).
But if I put two equally lossy capacitors in parallel, the Q does
not change. If you choose to model the source of that loss as an
ESR, then putting two such identical lossy capacitors certainly does
cause the net ESR to go down by 2x. But the reactance is also
halved, so the ratio remains constant, so Q does not change.
If you choose to model the loss as a parallel resistance, Q still
doesn't change. The choice of model doesn't change the physics. As
long as the models are equivalent, they'll necessarily give you the
same answer.
--Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
On 10/2/2022 16:57, Mikek wrote:
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On Sun, Oct 2, 2022 at 02:54 PM, Tom Lee wrote:
Parallelling two resistors certainly makes the resistance
go down, but that means that the loss goes up
(Q goes down).
If I have two capacitors with an ESR of 1¦¸ and I put those two
capacitors in parallel, wouldn't the ESR go down , thus losses go
down?
I know I'm missing something, I just don't now what.
?????????????????????????????????????? Mikek
|
On Sun, Oct 2, 2022 at 02:54 PM, Tom Lee wrote:
Parallelling two resistors certainly makes the resistance go down, but that means that the loss goes up (Q goes down).
If I have two capacitors with an ESR of 1¦¸ and I put those two capacitors in parallel, wouldn't the ESR go down , thus losses go down? I know I'm missing something, I just don't now what. ?????????????????????????????????????? Mikek
|
Parallelling two resistors certainly makes the resistance go
down, but that means that the loss goes up (Q goes
down).
Q is a measure of how much energy is stored, per energy dissipated.
Think of the limit as the parallel resistance goes to zero, and
you'll understand why a reduction in parallel resistance causes a
reduction in Q. As the parallel resistance goes down, the overall
element's behavior becomes progressively more dominated by the
resistance, and less by the reactance.
For a series loss, a lower resistance increases Q. Again,
considering the limit of zero series resistance helps you figure out
which way things go.
-- Cheers,
Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
On 10/2/2022 12:44, Mikek wrote:
toggle quoted message
Show quoted text
>>My plan for today is to get out my 260A and compare
several air caps I have to the air cap in the 260A.<<
I decided to experiment with my personal air caps compared to the
Boonton 260A air cap.
I looked into disconnecting the air caps in the 260A, it's more
than I want to get involved with!
Sooo, setting the Boonton 260A to its minimum capacitance of 37pf
I tried 3 different caps and
found Q using my 237uH high Q inductor.
? Meaning, this measurement, is a mix of 37pf minimum of the 260A
and the capacitor I'm testing.
?I'm confused of how to think about two loss resistances in
parallel, it seems like loss would go down.
But, is the loss R higher at minimum capacitance vs higher
capacitance? Q is lower, but that is? mostly because
Xc is lower. (Q = Xc/R)
? The caps I measured are good air caps, as over the years I have
tried to buy only the best caps I can find.
?Measurement with Boonton 260A only
Freq???????????????? Q
500kHz??? ? ? ? 1002 ?????
1000KHz?????? 1134??? Loss R of inductor + capacitor = 1.28¦¸
1200kHz??????? 1004
1500kHz???????? 942
Silver plated Cap 14pf to 500pf
? Freq??????????? ? ? Q
500kHz????? ? ?? 1002 ????
1000kHz????? ? ?? 924 ? Loss R of inductor + capacitor =? 1.58¦¸
1200Khz?????????? 726? I had to stop there because of minimum 260A
capacitance.
Cardwell capacitor 24pf to 475pf
Freq?????????????? Q
500kHz???????? 756
1000kHz?????? 606??? Loss R of inductor + capacitor = 2.46¦¸
1200kHz????? 540
TRW capacitor?? 17pf to 461pf
Freq????????????? Q
500kHz?????? 1008
1000khz????? 1062??? Loss R of inductor + capacitor = 1.4¦¸
1200kHz????? 954
Take another look at the Wes Hayward article and look at the
capacitor Qs at the very end, they are much
higher than the
previous numbers shown in John's post, the article was unclear and
misleading, which Wes admits in an edit 2 months later.
Using the math present in Wes's article, first, we know that QL is
greater than Q at Resonance (Q Res). Therefore with an unknown QL,
we must make a guess of what QL might be. The formula is below.
Qc = (QRes x QL) / (Ql - QRes).
?Since I have QRes of 1134 1MHz on the Boonton 260A, I'll assume
the Inductor QL is 1200.
Qc = 1134 x 1200 / 1200 - 1134 = 20,618 = Qc??
This might be to high, as I recall reading somewhere the 260A cap
Q was 20,000, no idea at what setting.
So, QL may be less than 1200.
The TRW cap is the best cap tested.
?Now the TRW cap with the loss of the 260A cap set at the minimum
37 pf in parallel.
Qc = 1062 x 1200 / 1200 - 1062 = 9,235 = Qc.?
? Feedback is appreciated.
???????????????????????????? Mikek
|
>> My plan for today is to get out my 260A and compare
several air caps I have to the air cap in the 260A.<<I decided to experiment with my personal air caps compared to the Boonton 260A air cap. I looked into disconnecting the air caps in the 260A, it's more than I want to get involved with! Sooo, setting the Boonton 260A to its minimum capacitance of 37pf I tried 3 different caps and found Q using my 237uH high Q inductor. ? Meaning, this measurement, is a mix of 37pf minimum of the 260A and the capacitor I'm testing. ?I'm confused of how to think about two loss resistances in parallel, it seems like loss would go down. But, is the loss R higher at minimum capacitance vs higher capacitance? Q is lower, but that is? mostly because Xc is lower. (Q = Xc/R) ? The caps I measured are good air caps, as over the years I have tried to buy only the best caps I can find. ?Measurement with Boonton 260A only Freq???????????????? Q 500kHz??? ? ? ? 1002 ????? 1000KHz?????? 1134??? Loss R of inductor + capacitor = 1.28¦¸ 1200kHz??????? 1004 1500kHz???????? 942 Silver plated Cap 14pf to 500pf ? Freq??????????? ? ? Q 500kHz????? ? ?? 1002 ???? 1000kHz????? ? ?? 924 ? Loss R of inductor + capacitor =? 1.58¦¸ 1200Khz?????????? 726? I had to stop there because of minimum 260A capacitance. Cardwell capacitor 24pf to 475pf Freq?????????????? Q 500kHz???????? 756 1000kHz?????? 606??? Loss R of inductor + capacitor = 2.46¦¸ 1200kHz????? 540 TRW capacitor?? 17pf to 461pf Freq????????????? Q 500kHz?????? 1008 1000khz????? 1062??? Loss R of inductor + capacitor = 1.4¦¸ 1200kHz????? 954 Take another look at the Wes Hayward article and look at the capacitor Qs at the very end, they are much higher than the previous numbers shown in John's post, the article was unclear and misleading, which Wes admits in an edit 2 months later. Using the math present in Wes's article, first, we know that QL is greater than Q at Resonance (Q Res). Therefore with an unknown QL, we must make a guess of what QL might be. The formula is below. Qc = (QRes x QL) / (Ql - QRes). ?Since I have QRes of 1134 1MHz on the Boonton 260A, I'll assume the Inductor QL is 1200. Qc = 1134 x 1200 / 1200 - 1134 = 20,618 = Qc?? This might be to high, as I recall reading somewhere the 260A cap Q was 20,000, no idea at what setting. So, QL may be less than 1200. The TRW cap is the best cap tested. ?Now the TRW cap with the loss of the 260A cap set at the minimum 37 pf in parallel. Qc = 1062 x 1200 / 1200 - 1062 = 9,235 = Qc.? ? Feedback is appreciated. ???????????????????????????? Mikek 
|
Very nicely done, Brooke! Thanks for putting in so much effort to
collect and present all of that terrific information.
-- Cheers,
Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
On 10/2/2022 09:38, Brooke Clarke via
groups.io wrote:
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Hi Mikek:
Here's a table where each column has the same Litz bundle size.
--
Have Fun,
Brooke Clarke
axioms:
1. The extent to which you can fix or improve something will be limited by how well you understand how it works.
2. Everybody, with no exceptions, holds false beliefs.
-------- Original Message --------
On Sun, Oct 2, 2022 at 05:38 AM, Adrian Godwin wrote:
I recall seeing some very heavy litz inductors
recovered from a scrap UPS. I don't have any expertise in this
sort of thing, but it's somewhere I'd look for examples.
Litz individual wire size is specific to frequency. The UPS is
probably operating at under 100kHz.
?Here's a page that shows a wire size to frequency chart.
?????????????????????????? Mikek
|
Hi Mikek:
Here's a table where each column has the same Litz bundle size.
--
Have Fun,
Brooke Clarke
axioms:
1. The extent to which you can fix or improve something will be limited by how well you understand how it works.
2. Everybody, with no exceptions, holds false beliefs.
-------- Original Message --------
toggle quoted message
Show quoted text
On Sun, Oct 2, 2022 at 05:38 AM, Adrian Godwin wrote:
I recall seeing some very heavy litz inductors
recovered from a scrap UPS. I don't have any expertise in this
sort of thing, but it's somewhere I'd look for examples.
Litz individual wire size is specific to frequency. The UPS is
probably operating at under 100kHz.
?Here's a page that shows a wire size to frequency chart.
?????????????????????????? Mikek
|
On Sun, Oct 2, 2022 at 05:38 AM, Adrian Godwin wrote:
I recall seeing some very heavy litz inductors recovered from a scrap UPS. I don't have any expertise in this sort of thing, but it's somewhere I'd look for examples.
Litz individual wire size is specific to frequency. The UPS is probably operating at under 100kHz. ?Here's a page that shows a wire size to frequency chart. ?????????????????????????? Mikek
|
I have ordered one Ducati capacitor. Will check its Q using the delta Q method with my 4342 Q meter. See my website ve2azx.net? The Ducati capacitor will be used to build a very simple Q meter using a variable cap And a BNC tee plus a VNA? (or spectrum analyzer and sig generator). Excel calculation file on my web site.
Jacques? ve2azx
|
In an effort to produce a wideband transformer 1.5MHz to 150MHz, I propose a multicore transformer. As I see it part of the problem is to avoid resonance of the primary caused by the self capacitance. ?I may be showing ignorance, please enlighten me if I have it wrong. Since the secondary reflects its impedance back to the primary by the turns ratio squared, (50 to 1 is a 2500 impedance ratio). Then say we had a 0.1¦¸ LC loss resistance (very high Q, I think). That 0.1¦¸ reflected back to the primary is 250¦¸, thus requiring about 1000¦¸ primary reactance for proper transformer operation. (its worth an experiment to see if lower will work) This 1000¦¸ reactance is 100uH at 1.5MHz.? So if you used 5 cores at 20uH each in series you have your 100uH, then 1 turn through each core wired in parallel would give a proper turns ratio and raise the resonance frequency of the primary. ?I have no low permeability cores or I would try it. I'm leaving to others to try, if you you think it has merit.? The core not only need low permeability it needs good high frequency characteristics. ???????????????????????????????????????????????????????????????????????????????? Mikek 
|
I recall seeing some very heavy litz inductors recovered from a scrap UPS. I don't have any expertise in this sort of thing, but it's somewhere I'd look for examples.
On Sun, Oct 2, 2022 at 1:34 PM John Kolb < jlkolb@...> wrote:
Those weren't my tests and results, but an article by Wes Haywood,
"Experiments with Coils and Q-Measurement".
<>
"To begin an evaluation, I took the highest Q toroid that I had built at
the time (38 turns of #18 enameled wire on a FT-114A-61 core)"
------------------------
I've also got a number of capacitors here to test, including a BC-221
but haven't been able to measure a Q much above 200, so either my coil
or methodology is not very good yet.? To? get meaningful results, the Q
of the coil needs to be as high as possible.? A basket weave coil with
litz wire and testing around 1 MHz should be a good approach, but I
can't see buying a whole spool of litz wire for only 1 or 2 coils.
I don't see BC-221 or other caps with a 50:1 gear reduction or vacuum
variable caps as being ideal for a Q meter. That's a lot of cranking if
used frequently.? Ideal would be direct 1:1 drive or 5:1 reduction or
perhaps 5:1 and 25:1 like the old Swan radios with their dual knobs.
John? ?KK6IL
On 10/2/2022 4:25 AM, John KN5L wrote:
> Hi John,
>
> Can you describe the inductor used for these measurements?
>
> John KN5L
>
> On 10/1/22 7:52 PM, John Kolb wrote:
>> Of the 8 caps tested, the best was a modern Jackson Bros dual 497 pF,
>> Q=383. Next was a ARC5/BC-454,3 section, 514 pF total, Q=378. Third was
>> a BC-221, 188 pF, Q=364.? 107 pF Silver Mica scored Q=341.
>
>
>
>
>
>
|
Those weren't my tests and results, but an article by Wes Haywood, "Experiments with Coils and Q-Measurement".
<>
"To begin an evaluation, I took the highest Q toroid that I had built at
the time (38 turns of #18 enameled wire on a FT-114A-61 core)"
------------------------
I've also got a number of capacitors here to test, including a BC-221 but haven't been able to measure a Q much above 200, so either my coil or methodology is not very good yet. To get meaningful results, the Q of the coil needs to be as high as possible. A basket weave coil with litz wire and testing around 1 MHz should be a good approach, but I can't see buying a whole spool of litz wire for only 1 or 2 coils.
I don't see BC-221 or other caps with a 50:1 gear reduction or vacuum variable caps as being ideal for a Q meter. That's a lot of cranking if used frequently. Ideal would be direct 1:1 drive or 5:1 reduction or perhaps 5:1 and 25:1 like the old Swan radios with their dual knobs.
John KK6IL
toggle quoted message
Show quoted text
On 10/2/2022 4:25 AM, John KN5L wrote: Hi John,
Can you describe the inductor used for these measurements?
John KN5L
On 10/1/22 7:52 PM, John Kolb wrote:
Of the 8 caps tested, the best was a modern Jackson Bros dual 497 pF,
Q=383. Next was a ARC5/BC-454,3 section, 514 pF total, Q=378. Third was
a BC-221, 188 pF, Q=364. 107 pF Silver Mica scored Q=341.
|
Hi Mikek, In post #799 /g/Test-Equipment-Design-Construction/message/799I evaluated EMRFD measurement scheme using 2-Port VNA. worked perfect. I was not able to replace measured Q using Gigol AWG and Oscilloscope. Q's were depressingly low! John KN5L
On 10/2/22 6:51 AM, Mikek wrote:
"To begin an evaluation, I took the highest Q toroid that I had built at
the time (38 turns of #18 enameled wire on a FT-114A-61 core) and
attached it to various variable and
fixed capacitors from my junk box.Measurements were done at or near 1
MHz using the EMRFD
measurement scheme."
????????????????????????????????????? Mikek
|
Dr. David Kirkby, Kirkby Microwave Ltd
John Kolb