Re: Microwave Journal ... RF Engineering Education at University of Bristol
On Wednesday 21 May 2025 05:09:45 pm alan victor via groups.io wrote: From Microwave Journal May 2025. An very nice article addressing RF Microwave Design and Measurments
at the University of Bristol. A series of You Tube Videos located on the reference page, at the
end of the paper, are well worth the time to highlight (copy) and watch including building a homemade
cal kit, copper tape microstrip and more.
The PAPER:
A YOU TUBE VIDEO on cal kits and their construction and more...
youtube.com/watch?v=Ws1mIK-JIrg That video led me to another one which finally landed me on this one: That guy does some pretty interesting stuff... -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, ?a critter that can be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin
|
Re: [Ham-Antennas] FIXTURE for XMSN MEASUREMENATS 2.0
But in retirement the work IS play! My 8753C weighs nearly 100 lbs.! No way is it going to accompany me outside to make measurements of antennas. The NANOVNA certainly can and does go outside to make measurements. Further, the 8753C can not make direct measurements of my long doublet fed with open wire line as it is connected to the power grid and house wiring. The NANOVNA is small enough to make those measurements in the shack with nothing between it and the NANO. I just hope and pray that it will continue to be available to amateurs, professionals, and the schools in the future. It's indispensable for anything associated with RF! Dave - W?LEV <> Virus-free.www.avg.com <> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> On Wed, May 21, 2025 at 5:11?PM VE6LX via groups.io <dclarke2= [email protected]> wrote: I see another person who asks themselves where did I ever find time to
work. Retirement while every day "may" seem like Saturday there are days
when it feels more like the first day after after a long weekend and the
work is piled so high you can not see any daylight.
"The Golden Years, more like "Fools Gold" at times. "More Work and No Pay."
-- *Dave - W?LEV* -- Dave - W?LEV
|
Re: Microwave Journal ... RF Engineering Education at University of Bristol
You are welcome.
Since R&S was a partner in this education process, there are additional videos on more basic vna topics.
|
Re: Microwave Journal ... RF Engineering Education at University of Bristol
Thanks a lot Alan for sharing this article. Skimmed through it and bookmarked for detailed reading. 73 Jon, VU2JO On Thu, May 22, 2025 at 2:39?AM alan victor via groups.io <avictor73= [email protected]> wrote: From Microwave Journal May 2025. An very nice article addressing RF
Microwave Design and Measurments
at the University of Bristol. A series of You Tube Videos located on the
reference page, at the
end of the paper, are well worth the time to highlight (copy) and watch
including building a homemade
cal kit, copper tape microstrip and more.
The PAPER:
A YOU TUBE VIDEO on cal kits and their construction and more...
youtube.com/watch?v=Ws1mIK-JIrg
|
Re: Jittery , non steady readings
Same thing happens at the countryside
|
Microwave Journal ... RF Engineering Education at University of Bristol
From Microwave Journal May 2025. An very nice article addressing RF Microwave Design and Measurments
at the University of Bristol. A series of You Tube Videos located on the reference page, at the
end of the paper, are well worth the time to highlight (copy) and watch including building a homemade
cal kit, copper tape microstrip and more.
The PAPER:
A YOU TUBE VIDEO on cal kits and their construction and more...
youtube.com/watch?v=Ws1mIK-JIrg
|
Re: [Ham-Antennas] FIXTURE for XMSN MEASUREMENATS 2.0
I see another person who asks themselves where did I ever find time to work. Retirement while every day "may" seem like Saturday there are days when it feels more like the first day after after a long weekend and the work is piled so high you can not see any daylight.
"The Golden Years, more like "Fools Gold" at times. "More Work and No Pay."
|
Re: [Ham-Antennas] FIXTURE for XMSN MEASUREMENATS 2.0
finding anything like that in the dumpster. I am envious. I worked with Lab Grade VNA since 1979 and continued until I retired in 2001. I received a nanoVNA for Christmas 2024.
having a VNA which fits in my pocket and I can take anywhere I choose is amazing. I feel so spoiled now being able to test my antennas with a nanoVNA any time I choose. I can see the results of my calculations come to life one the screen on the VNA. Reminds me of college where the theory we studied in the morning was exercised in live applications in the afternoon.
|
Re: [Ham-Antennas] FIXTURE for XMSN MEASUREMENATS 2.0
Having the 8753C is a privilege of once having worked for HP. As you may
know, HP (before Carly - the wicked witch of the west) encouraged dumpster
dipping. There were two of these in the dumpster. I chose the one with
all the adaptors in place. All the cal kits were also there. So.......
the rest is history. My interests end when one has to involve waveguide.
Dave - W?LEV
toggle quoted message
Show quoted text
On Wed, May 21, 2025 at 12:03?AM Michael Carter <Mike.Carter@...> wrote: Thanks, Dave - the incremental improvements are less critical than the
final result, of course. I need to make up a similar test fixture and
assess its residual coupling with nothing on the alligator clips.
You're fortunate to have the HP 8753C to use at home. Had one at our
university lab, but I use a DG8SAQ VNWA at home, and the university got a
better Agilent VNA with wider frequency coverage beyond 6 GHz if I should
do more microwave work in the future.
73,
Mike, K8CN
------------------------------
*From:* David Eckhardt <davearea51a@...>
*Sent:* Tuesday, May 20, 2025 7:11 PM
*To:* Michael Carter <Mike.Carter@...>
*Cc:* NANO VNA <[email protected]>; Ham-Antennas <
[email protected]>; Ham Antennas <[email protected]>;
Kenneth Wyatt <emc.guru@...>; AA0RS@... <
AA0RS@...>; David Feldman <wb0gaz@...>
*Subject:* Re: [Ham-Antennas] FIXTURE for XMSN MEASUREMENATS 2.0
CAUTION: This email originated from outside of the University System. Do
not click links or open attachments unless you recognize the sender and
know the content is safe.
I can't give you numbers of improvement as I didn't record those. But I
can give you the order of additions.
1) Lengthened the shield between the ports. It was originally only the
width of the main board. supporting the BNCs.
2) Playing with a thin sheet of double sided board, I added the
additional orthogonal shields. I was going to enclose each port except for
the lond ends, but in "playing" with the essentially scalar network
analyzer, I discovered I gained just as much by shielding opposite sides of
each port.
3) That looked pretty good, but again playing with just a piece of AWG #18
stripped solid copper wire, I discovered the added wires on each side of
the alligator clips really bought me a lot. And, yes, I believe your
analysis that the wires form a transmission line which electrically looks
much like a trough line but allows access to the clips.
4) From there, I could make minor improvements in isolation, but all
those severely limited physical access to the alligator clips. The
additional improvements traded off against physical access was clear I'd
stop where I was. The 70 dB (somewhat +) isolation between ports was quite
satisfactory for me. I could dig deeper into the noise by increasing the
output of the source port on the 8753C, but, again, any additional physical
components would limit access to the clips. So I stopped with what you
see.
Now I gotta wonder how high in frequency it maintains the isolation and
good RF performance. Maybe tomorrow? I have too many projects lined up in
retirement. It's the satisfaction and joy of having good RF test equipment
in retirement!
Dave - W?LEV
On Tue, May 20, 2025 at 8:06?PM Michael Carter <Mike.Carter@...>
wrote:
Hi Dave (W0LEV),
Your measurements of your improved test fixture are impressive. I seem to
recall your original fixture had a single PCB shield between the alligator
clips? Now I'm curious about your thought process as you added bits and
pieces to that original fixture and found improved isolation between the
ports. While I understand adding more PCB walls, the addition of wire
bridges, and particularly the wires paralleling the alligator clips,
intrigues me. My sense is that you have created a transmission line on
each port comprising the alligator clip and its paralleled 'shield' wire,
and the shield wire helps terminate fields and weaken those fringing fields
that couple to the other port. Is this an accurate understanding of your
progression? Do you recall the order in which pieces were added and the
incremental improvement in port isolation you obtained at each step along
the way?
Thanks, and 73,
Mike, K8CN
------------------------------
*From:* [email protected] <[email protected]> on
behalf of W0LEV via groups.io <davearea51a@...>
*Sent:* Tuesday, May 20, 2025 3:38 PM
*To:* NANO VNA <[email protected]>; Ham-Antennas <
[email protected]>; Ham Antennas <[email protected]>
*Cc:* Kenneth Wyatt <emc.guru@...>; AA0RS@... <
AA0RS@...>; David Eckhardt <davearea51a@...>; David Feldman <
wb0gaz@...>
*Subject:* [Ham-Antennas] FIXTURE for XMSN MEASUREMENATS 2.0
CAUTION: This email originated from outside of the University System. Do
not click links or open attachments unless you recognize the sender and
know the content is safe.
As promised, I made some rigorous measurements of my home brew fixture for
making transmission measurements of various HF circuit elements using a
"professional" instrument. I could have used the NANOVNAs, but using HP
might add some credence to the results ????? Subjects for the fixture
might include common mode chokes, ugly baluns (which I do not use), current
baluns (which I use wound of RG-400 on toroids), filters, and other active
and passive circuits where a fixture is required.
I took the time to calibrate my HP8753C using HP standards with a full
2-port cal from 1 to 30 MHz to make these measurements of the fixture.
Please have a read of the attachment for the results. While the fixture is
essentially free for a few inexpensive components and my time (retired, so
that's free, too). While it's not up to the old HP standards, not bad for
a home baked project which will lead to other projects.
Oh, yes,..... any typos are also free.
If you attempt duplication based on the images, YMMV. Dimensions can be
scoped from the standard alligator clips which are 1.3-inches tip-to-tip (¡À
amateur measurement relying on a non-RF ruler).
Measure everything. Let the data speak for itself, *not *opinion, snake
oil, or sorcery.
Dave - W?LEV
--
*Dave - W?LEV *
-- *Dave - W?LEV*
--
Dave - W?LEV
|
Re: [Ham-Antennas] FIXTURE for XMSN MEASUREMENATS 2.0
I can't give you numbers of improvement as I didn't record those. But I
can give you the order of additions.
1) Lengthened the shield between the ports. It was originally only the
width of the main board. supporting the BNCs.
2) Playing with a thin sheet of double sided board, I added the additional
orthogonal shields. I was going to enclose each port except for the lond
ends, but in "playing" with the essentially scalar network analyzer, I
discovered I gained just as much by shielding opposite sides of each port.
3) That looked pretty good, but again playing with just a piece of AWG #18
stripped solid copper wire, I discovered the added wires on each side of
the alligator clips really bought me a lot. And, yes, I believe your
analysis that the wires form a transmission line which electrically looks
much like a trough line but allows access to the clips.
4) From there, I could make minor improvements in isolation, but all those
severely limited physical access to the alligator clips. The additional
improvements traded off against physical access was clear I'd stop where I
was. The 70 dB (somewhat +) isolation between ports was quite satisfactory
for me. I could dig deeper into the noise by increasing the output of the
source port on the 8753C, but, again, any additional physical components
would limit access to the clips. So I stopped with what you see.
Now I gotta wonder how high in frequency it maintains the isolation and
good RF performance. Maybe tomorrow? I have too many projects lined up in
retirement. It's the satisfaction and joy of having good RF test equipment
in retirement!
Dave - W?LEV
toggle quoted message
Show quoted text
On Tue, May 20, 2025 at 8:06?PM Michael Carter <Mike.Carter@...> wrote: Hi Dave (W0LEV),
Your measurements of your improved test fixture are impressive. I seem to
recall your original fixture had a single PCB shield between the alligator
clips? Now I'm curious about your thought process as you added bits and
pieces to that original fixture and found improved isolation between the
ports. While I understand adding more PCB walls, the addition of wire
bridges, and particularly the wires paralleling the alligator clips,
intrigues me. My sense is that you have created a transmission line on
each port comprising the alligator clip and its paralleled 'shield' wire,
and the shield wire helps terminate fields and weaken those fringing fields
that couple to the other port. Is this an accurate understanding of your
progression? Do you recall the order in which pieces were added and the
incremental improvement in port isolation you obtained at each step along
the way?
Thanks, and 73,
Mike, K8CN
------------------------------
*From:* [email protected] <[email protected]> on
behalf of W0LEV via groups.io <davearea51a@...>
*Sent:* Tuesday, May 20, 2025 3:38 PM
*To:* NANO VNA <[email protected]>; Ham-Antennas <
[email protected]>; Ham Antennas <[email protected]>
*Cc:* Kenneth Wyatt <emc.guru@...>; AA0RS@... <
AA0RS@...>; David Eckhardt <davearea51a@...>; David Feldman <
wb0gaz@...>
*Subject:* [Ham-Antennas] FIXTURE for XMSN MEASUREMENATS 2.0
CAUTION: This email originated from outside of the University System. Do
not click links or open attachments unless you recognize the sender and
know the content is safe.
As promised, I made some rigorous measurements of my home brew fixture for
making transmission measurements of various HF circuit elements using a
"professional" instrument. I could have used the NANOVNAs, but using HP
might add some credence to the results ????? Subjects for the fixture
might include common mode chokes, ugly baluns (which I do not use), current
baluns (which I use wound of RG-400 on toroids), filters, and other active
and passive circuits where a fixture is required.
I took the time to calibrate my HP8753C using HP standards with a full
2-port cal from 1 to 30 MHz to make these measurements of the fixture.
Please have a read of the attachment for the results. While the fixture is
essentially free for a few inexpensive components and my time (retired, so
that's free, too). While it's not up to the old HP standards, not bad for
a home baked project which will lead to other projects.
Oh, yes,..... any typos are also free.
If you attempt duplication based on the images, YMMV. Dimensions can be
scoped from the standard alligator clips which are 1.3-inches tip-to-tip (¡À
amateur measurement relying on a non-RF ruler).
Measure everything. Let the data speak for itself, *not *opinion, snake
oil, or sorcery.
Dave - W?LEV
-- *Dave - W?LEV*
--
Dave - W?LEV
|
FIXTURE for XMSN MEASUREMENATS 2.0
As promised, I made some rigorous measurements of my home brew fixture for
making transmission measurements of various HF circuit elements using a
"professional" instrument. I could have used the NANOVNAs, but using HP
might add some credence to the results ????? Subjects for the fixture
might include common mode chokes, ugly baluns (which I do not use), current
baluns (which I use wound of RG-400 on toroids), filters, and other active
and passive circuits where a fixture is required.
I took the time to calibrate my HP8753C using HP standards with a full
2-port cal from 1 to 30 MHz to make these measurements of the fixture.
Please have a read of the attachment for the results. While the fixture is
essentially free for a few inexpensive components and my time (retired, so
that's free, too). While it's not up to the old HP standards, not bad for
a home baked project which will lead to other projects.
Oh, yes,..... any typos are also free.
If you attempt duplication based on the images, YMMV. Dimensions can be
scoped from the standard alligator clips which are 1.3-inches tip-to-tip (¡À
amateur measurement relying on a non-RF ruler).
Measure everything. Let the data speak for itself, *not *opinion, snake
oil, or sorcery.
Dave - W?LEV
--
Dave - W?LEV
|
Re: NanoVNA-F V3 from SysJoint firmware beep
If Sysjoint does not listen to customers and provide a firmware solution you have only three choices: live with it, muffle it or cut the beeper circuit.
|
Re: FIXTURE for XMSN MEASUREMENTS
On Tue, May 20, 2025 at 07:58 AM, W0LEV wrote:
the BNC connectors are part of the fixture and I can not eliminate
them.
Dave, the connector is part of the fixture, but since its impedance is 50 ohms, its capacitance does not contribute to the stray fixture capacitance. If you measure an uninstalled connector, you can subtract the capacitance reading from what you measure for the fixture, which includes connector capacitance. I'm glad you posted about your new fixture. I think I've been overly concerned about shunt capacitance at HF. I see lots of evidence of it in the .s2p files the commercial L and C manufacturers provide, but that's in the GHz range where tiny strays do matter. Brian
|
Re: FIXTURE for XMSN MEASUREMENTS
Broam, the BNC connectors are part of the fixture and I can not eliminate them. Yesterday, I even questioned my own measurement of 2.7 pF. I need to revisit that today as it was a hurried measurement. I will get back with you after I'm satisfied I made a rigorous measurement. Dave - W?LEV On Tue, May 20, 2025 at 12:30?AM Brian Beezley via groups.io <k6sti= [email protected]> wrote: Dave, out of curiosity I created a circuit model for a common-mode choke.
It has an inductance, capacitance, and resistance in parallel. I chose the
values to mimic attenuation results for a common-mode choke someone sent me
a couple years ago. It's shown below. The choke was measured with a DG8SAQ
VNA with all four S-parameters. The software that accompanies the VNA can
implement what they call scripts. He ran the Y21 script and sent the
results. One of the neat features of the Y21 method is that it can
calculate the shunt capacitance at each port as well as the DUT response
with the capacitance nulled mathematically. Calculated shunt C was 2.8 to
7.3 pF depending on port and frequency. (I don't know why it varies with
frequency.) I used his choke to create my choke model. When I added a shunt
2.7 pF to each side of the choke in the model, I saw no difference in choke
attenuation to 30 MHz. I thought at least it would be noticeable, but the
curves overlap. I tried 27 pF to make sure the model was working, and I
could then see a small difference. 2.7 pF is about 2k ohms at 30 MHz. This
is comparable to the usual several-k ohm CMC impedance so I expected some
effect. You can notice the Y21/S21 difference below for a shunt capacitance
roughly double what you measured. The effect isn't great and is of no
consequence for choke attenuation, but it would be measurable.
One thing I often forget is that measured capacitance for a test fixture
like yours includes the connector capacitance. It is not stray capacitance.
It matches the connector inductance to form a 50 ohm impedance. You should
subtract the capacitance of a bare connector from the 2.7 pF you measured
to get the stray fixture capacitance. There is also capacitive coupling
between the choke and the VNA enclosure if it is nearby. That will
contribute to shunt capacitance.
Based on my circuit model. I think the capacitance of your fixture should
have a negligible effect at HF. It would be a good idea to verify that
expectation by measurement.
Brian
-- *Dave - W?LEV* -- Dave - W?LEV
|
Re: NanoVNA-F V3 from SysJoint firmware beep
Ohhh, that's too bad. Is there really no software based solution?
I really don't like the idea of physically destroying something in a "brand new" (for me) device I just bought.
?
|
Re: FIXTURE for XMSN MEASUREMENTS
Dave, out of curiosity I created a circuit model for a common-mode choke. It has an inductance, capacitance, and resistance in parallel. I chose the values to mimic attenuation results for a common-mode choke someone sent me a couple years ago. It's shown below. The choke was measured with a DG8SAQ VNA with all four S-parameters. The software that accompanies the VNA can implement what they call scripts. He ran the Y21 script and sent the results. One of the neat features of the Y21 method is that it can calculate the shunt capacitance at each port as well as the DUT response with the capacitance nulled mathematically. Calculated shunt C was 2.8 to 7.3 pF depending on port and frequency. (I don't know why it varies with frequency.) I used his choke to create my choke model. When I added a shunt 2.7 pF to each side of the choke in the model, I saw no difference in choke attenuation to 30 MHz. I thought at least it would be noticeable, but the curves overlap. I tried 27 pF to make sure the model was working, and I could then see a small difference. 2.7 pF is about 2k ohms at 30 MHz. This is comparable to the usual several-k ohm CMC impedance so I expected some effect. You can notice the Y21/S21 difference below for a shunt capacitance roughly double what you measured. The effect isn't great and is of no consequence for choke attenuation, but it would be measurable.
One thing I often forget is that measured capacitance for a test fixture like yours includes the connector capacitance. It is not stray capacitance. It matches the connector inductance to form a 50 ohm impedance. You should subtract the capacitance of a bare connector from the 2.7 pF you measured to get the stray fixture capacitance. There is also capacitive coupling between the choke and the VNA enclosure if it is nearby. That will contribute to shunt capacitance.
Based on my circuit model. I think the capacitance of your fixture should have a negligible effect at HF. It would be a good idea to verify that expectation by measurement.
Brian
|
Re: NanoVNA-F V3 from SysJoint firmware beep
I have found that all beepers can be permanently silenced with a pair of diagonal cutters. ;-)
A less invasive method is to stuff the transducer full with putty, Blue Tac, epoxy or similar physical means.
73, Don N2VGU
|
Re: FIXTURE for XMSN MEASUREMENTS
On Mon, May 19, 2025 at 03:28 PM, W0LEV wrote:
That certainly is quite low especially for
HF frequencies.
Thanks for the info, Dave. Please measure a common-mode choke using the fixture with your HP VNA with S11, S21, S12, and S22 and post the .s2p. I'll see how the Y21 method compares with the usual S21 method. Any difference will be due to the shunt fixture capacitance. Brian
|
Re: FIXTURE for XMSN MEASUREMENTS
1) My take on dynamic range is the ratio between the fixture with nothing between the two ports to a fat and short as possible conductor between the ports. With the recent images and using the HP8753C, that measured 80 dB over the HF frequency range. 2) The capacitance at each port is 2.7 pF measured directly at each BNC connector. I just measured it. That certainly is quite low especially for HF frequencies. Dave - W?LEV On Mon, May 19, 2025 at 5:04?PM Brian Beezley via groups.io <k6sti= [email protected]> wrote: OK, after looking more carefully at the photos, I think you're referring
to the ratio of the desired signal through the device under test to the
residual feedthrough with the device absent. Correct me if I'm wrong.
Did you consider the effect of the increased capacitance to ground at each
port? It looks like it may be substantial. Easy to measure.
Brian
-- *Dave - W?LEV* -- Dave - W?LEV
|
Re: READING L AN C VALUES USING THE NANOVNAs and the SMITH CHART
And with HP test equipment now KeySight, I dub it KeyOutOfSight. On Mon, May 19, 2025 at 12:57?PM Clyde Spencer via groups.io <cftr01b= [email protected]> wrote: One of the definitions for HP is High Price!!
*Clyde K. Spencer*
On Sun, May 18, 2025, 11:17?PM Charles VK1CM via groups.io
<mrcharlesmuller=
[email protected]> wrote:
I nearly fell out of my chair when I saw the HP fixture prices. May I
suggest using these:
There is a lot of other goodies on his website, and I have found him very
easy to deal with.
Regards,
Charles.
VK1CM
|
VE6LX
Roger Need
Stefan Wolfrum
Donald S Brant Jr