With all this great talk about VNA's it reminds me¡ I have an extra 8753ES,? 50ohm,? internal s-para,? working and looking beautiful¡ 3ghz unit.? $3k and also an n8357a 6ghz pna for sale¡ same condition.? ?Will do pics and details direct.? ?This post was just an after thought.? ?I am on a cruise in the caribbean now and can't give pics and full details at this time.?
On Mon, Feb 11, 2019, 11:04 PM Reginald Beardsley via Groups.Io <pulaskite= [email protected] wrote: Thanks.? I've got a lead on an 8753B with a 50 ohm 3 GHz S parameter test set at a comfortable price.? Gedas gave me a very succinct explanation of why an eternal test set is preferable from a hobbyist self repair? perspective.
Having spent my career in reflection seismology,? I am all too acutely aware of the problems caused by impedance mismatches..? Gedas linked some very helpful papers.which made clear that impedance matching is a significant headache. So I've got some mathematical chores to deal with.
One question I have is how difficult is replacing the N connectors? on a 8753B with an external test set if they are worn out.? Part of what I'm trying to do is is acquire a self sustainable bench.? I want to have tools to fix things.? I can't do anything about the problem of sourcing parts? ?But first of all you have to have the tools to identify the fault.? I've done it with "flint knives and stone axes'" but that is *very* tedious.
I'd greatly prefer to be an actively employed scientist, but that''s not possible in my field, so playing with electronics is the best alternative I can think of.
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Re: HP34702A Ohms converter issues
Hello Greg,
I think we're getting close to the root cause... but I thhink I
need some more data.
First, temporarily unsolder the collector lead of Q12 and one lead
of CR13, which will disable the overvoltage protection.
Then, with a 1K
resistor across the Ohms input, and when switched on the 1K
range:
- We know that the voltages at both inputs of U3 are -6.3V,
which is OK.
- The output of U3 is -7.3V which is OK, too.
- If the two gates of Q15 are balanced at -6.3V, then there should
be a 1V drop across R55-R56.
- But you have measured the output current to be 2mA, whereas it
should be 1mA.
Then please let me know...
Also, I'd like to try a little bit of lateral thinking. Maybe
we're dealing with some spurious oscillation, could you connect a
1K resistor across the Ohms inputs, and look at the outputs of U3,
then of U2 with an oscilloscope ?
Joel
|
Dr. David Kirkby from Kirkby Microwave Ltd
Just to be certain things don't get crossed up, the 85046A is a 50 ohm, 300 kHz to 3 GHz test set, and uses APC 7 connectors to interface with the DUT.? The 85047A is similar, but goes up to 6 GHz.
The 85046B is the 75 ohm version; it goes from 300 kHz to 2 GHz and uses 75 ohm N female connectors to interface with the DUT.
Yes, my error. I got the 85046A and 85046B transposed! The A is the 50 ohm version with APC7 connectors.
I doubt the RF source, A, B or R receiver N connectors would get damaged as they are rarely used.? ?
Dave.?
On Tue, Feb 12, 2019 at 12:00 AM, Dr. David Kirkby from Kirkby Microwave Ltd wrote: On Tue, 12 Feb 2019, 04:04 Reginald Beardsley via Groups.Io <pulaskite= [email protected] wrote:
One question I have is how difficult is replacing the N connectors? on a 8753B with an external test set if they are worn out.? Part of what I'm trying to do is is acquire a self sustainable bench.? I want to have tools to fix things.? I can't do anything about the problem of sourcing parts? ?But first of all you have to have the tools to identify the fault.? I've done it with "flint knives and stone axes'" but that is *very* tedious.
To my knowledge all 50 ohm 3 GHz test sets (85046B) have APC7 connectors, not N connectors. If the test set has N connectors then it is almost certainly an 85046A which is a 75 ohm test set, and best avoided.?
Changing the connectors on the test set is unlikely to be practical without changing the complete bridge, although the collets in APC7 connectors can be easily changed if you get a collet extractor, which you could pick up cheaply. It is most unlikely the APC7 connectors are worn out. Most people put APC7 to N adapters and so the APC7 connectors are rarely used.?
Dave.?
|
Hi Tom,
At 4GHz, using my E4406 to measure its output from -90dBm to +13dBm, it appears to be within 0.5dBm of indicated.
Above 13dBm the power doesn't increase and the UNLEVELED indicator comes on at about 14dBm.
Using my HP438A and HP8481H to do the same test gives a similar result but with an additional -1dB offset.
So its "close" :) ... well at least at 4Ghz
None of this kit has been calibrated in years so take the result with a grain of salt!
Given a bit of time I could write a labview thing to make some nice measurements and plots some graphs
regards
Tim
toggle quoted message
Show quoted text
On 12/02/2019 2:37 pm, Tom B wrote: Hi Tim,
How accurate is the power output at 4GHz?
Tom Bryan
N3AJA
On 2/11/2019 7:05 PM, Tim Tuck wrote:
Hi Colby,
I can still change things via GPIB, no problem so far, my simple Labview(Student Edition) program still works :)
regards
Tim
de VK2XAX
|
Re: HP34702A Ohms converter issues
I see that the output of U3 is at -7.4V and the input is at -6.4V, so off from the specified value by 0.1 at each end.? The gate voltages of Q15 are finally balanced, which they weren't before, but the reading across R56-R55 remains at ~2V.? The voltage at the end of R52 starts to drop as you switch ranges, going from -5.4V to about -4.1V by the time you go to the 10M range; this agrees with the display error increasing at higher ranges.? That seems to point to U2, which I've already replaced.
R64 is fine - I tweaked it earlier to be sure that the value was in range since it's a 10K and there is no R69 on this board; it did change the displayed reading over a small set of values as you would expect.? Following the voltage from U3-6 back to U3-2 the voltage changes in steps as you check each resistor junction R58, R60, R61.? They don't seem to be a problem.
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Just to be certain things don't get crossed up, the 85046A is a 50 ohm, 300 kHz to 3 GHz test set, and uses APC 7 connectors to interface with the DUT.? The 85047A is similar, but goes up to 6 GHz.
The 85046B is the 75 ohm version; it goes from 300 kHz to 2 GHz and uses 75 ohm N female connectors to interface with the DUT.
All three use 50 ohm N female connectors for the RF in, R, A and B connections to the 8753x, and a 50 ohm BNC jack for the DC Bias input.
-Pat
On Tue, Feb 12, 2019 at 12:00 AM, Dr. David Kirkby from Kirkby Microwave Ltd wrote: On Tue, 12 Feb 2019, 04:04 Reginald Beardsley via Groups.Io <pulaskite= [email protected] wrote:
One question I have is how difficult is replacing the N connectors? on a 8753B with an external test set if they are worn out.? Part of what I'm trying to do is is acquire a self sustainable bench.? I want to have tools to fix things.? I can't do anything about the problem of sourcing parts? ?But first of all you have to have the tools to identify the fault.? I've done it with "flint knives and stone axes'" but that is *very* tedious.
To my knowledge all 50 ohm 3 GHz test sets (85046B) have APC7 connectors, not N connectors. If the test set has N connectors then it is almost certainly an 85046A which is a 75 ohm test set, and best avoided.?
Changing the connectors on the test set is unlikely to be practical without changing the complete bridge, although the collets in APC7 connectors can be easily changed if you get a collet extractor, which you could pick up cheaply. It is most unlikely the APC7 connectors are worn out. Most people put APC7 to N adapters and so the APC7 connectors are rarely used.?
Dave.?
|
Re: Test fixture for dielectric measurements
Dr. David Kirkby from Kirkby Microwave Ltd
On Mon, 11 Feb 2019, 06:50 John Lyles < jtml@... wrote:
One of the typical measurements we made was liquid dielectric measurements. We had a brass cell, with O rings, that looked like a vertical coaxial cylinder. It was filled a certain height with the liquid, and it fitted on top of the HP 4342A Q meter. We made empty and full measurements and plugged the dial setttings into a program that computers K' and K"".
That is similar to what I see at NPL.?
?Keysight and an aftermarket Swiss? company make a surface probe that can measure flat materials and liquids. Damaskos in Pennsylvania also makes some devices.
The coaxial probes can be made oneself, but I personally find the mathematics too hard to work out Er' and Er". But EM simulations are easy. I did do some EM simulations on one and convinced myself they would not work well at a manageable size at 3.5 MHz.?
I believe NPL have one 40 mm in diameter to go down to about 30 MHz. I have seen them advertised to go down to about 3.5 MHz, but I am skeptical of how well they work. The phase shift at a few MHz will be very small, making it impossible to measure with any sort of useful accuracy.?
So much depends on the frequency range of interest.?
Dave.?
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Dr. David Kirkby from Kirkby Microwave Ltd
On Tue, 12 Feb 2019, 04:04 Reginald Beardsley via Groups.Io <pulaskite= [email protected] wrote:
One question I have is how difficult is replacing the N connectors? on a 8753B with an external test set if they are worn out.? Part of what I'm trying to do is is acquire a self sustainable bench.? I want to have tools to fix things.? I can't do anything about the problem of sourcing parts? ?But first of all you have to have the tools to identify the fault.? I've done it with "flint knives and stone axes'" but that is *very* tedious.
To my knowledge all 50 ohm 3 GHz test sets (85046B) have APC7 connectors, not N connectors. If the test set has N connectors then it is almost certainly an 85046A which is a 75 ohm test set, and best avoided.?
Changing the connectors on the test set is unlikely to be practical without changing the complete bridge, although the collets in APC7 connectors can be easily changed if you get a collet extractor, which you could pick up cheaply. It is most unlikely the APC7 connectors are worn out. Most people put APC7 to N adapters and so the APC7 connectors are rarely used.?
Dave.?
|
Thanks. I've got a lead on an 8753B with a 50 ohm 3 GHz S parameter test set at a comfortable price. Gedas gave me a very succinct explanation of why an eternal test set is preferable from a hobbyist self repair perspective.
Having spent my career in reflection seismology, I am all too acutely aware of the problems caused by impedance mismatches.. Gedas linked some very helpful papers.which made clear that impedance matching is a significant headache. So I've got some mathematical chores to deal with.
One question I have is how difficult is replacing the N connectors on a 8753B with an external test set if they are worn out. Part of what I'm trying to do is is acquire a self sustainable bench. I want to have tools to fix things. I can't do anything about the problem of sourcing parts But first of all you have to have the tools to identify the fault. I've done it with "flint knives and stone axes'" but that is *very* tedious.
I'd greatly prefer to be an actively employed scientist, but that''s not possible in my field, so playing with electronics is the best alternative I can think of.
|
Hi Tim,
How accurate is the power output at 4GHz?
Tom Bryan
N3AJA
toggle quoted message
Show quoted text
On 2/11/2019 7:05 PM, Tim Tuck wrote: Hi Colby,
I can still change things via GPIB, no problem so far, my simple Labview(Student Edition) program still works :)
regards
Tim
de VK2XAX
|
Re: Test fixture for dielectric measurements
thanks Dave, I sent it on to Ron. Did you see his website? It turns out to be his old one and his new one is down which he did not know so he got after his IT guy. I will send an update when back up in a few days for anyone interested. Regards, PeterB
On Mon, Feb 11, 2019 at 5:01 PM Dr. David Kirkby from Kirkby Microwave Ltd < drkirkby@...> wrote: Has anyone made test fixtures for measuring liquids or solids (essentially a capacitor with the DUT as dielectric)
Attached is a booklet from NPL on dielectric measurements.?
Is is noteworthy they advise against the term "dielectric constant" as no dielectric has constant properties.?
Dave.?
|
Re: Test fixture for dielectric measurements
Connecting to the material is a problem, especially above 1000 deg C. Metals may react with fumes and change or melt. Many insulators and dielectrics certainly will. We are watching these exchanges with great interest. PeterB
On Mon, Feb 11, 2019 at 7:49 AM Dr. David Kirkby from Kirkby Microwave Ltd < drkirkby@...> wrote: At work we have the Agilent liquid test fixture, use together with a LCR meter to measure the permittivity of different oil's
Is there any chance you could take some detailed photographs and detailed dimensions? I have looked at the manual, but some more details would be nice.?
What of the BNCs connect to the guard ring?
Whilst I take your point one is making comparisons to air. There is some software from Keysight that supports that fixture, which might be tailored to it.?
I believe the electrodes are plated in platinum. I don't know if that's the best possible material to reduce the barrier layer problem. I know getting things gold plated is easy, but I am unsure about platinum.
I remember that my company didn't want to buy? more than one, due to price....
Yes, I can understand that!
Keysight also has one for solids as well
The price is way to high for these, but if you study the manuals, you will see that the construction isn't that advanced, so making one should not be a problem if you have access to some proper machining tools.
I managed to pick up one of those. I have often wondered if it could be used for liquids too, if one made a small tank to fit inside - like a small fish tank! Although it would make the maths tricky, if the properties of the tanks material were first measured, an analytical solution (excuse the pun) could be derived.?
As I write before I have reasonable results with using an air spaced capacitor, but the lack of a guard ring is going to reduce accuracy.?
And the dimensions isn't that critical as you compare the dialectic of what you want to measure against the dialectic of air.
But of course you will? need a instrument to connect to the test fixture.
I have a 4284A & 4285A, which were top of the line instruments in their day. Unfortunately the fixtures sell on the used market for more than the instruments do!
Dave
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Re: Test fixture for dielectric measurements
Thanks John, we appreciate any information we can get. Even the old stuff which has a lot of information. PeterB
On Mon, Feb 11, 2019 at 1:44 AM John Lyles < jtml@...> wrote: In the late 1980s I worked at E. I. DuPont Co at their Engineering Physics Lab in Delaware. We did a lot of dielectric measurements for the company, and also had an 8510 plus the 1970s 8409 automatic network analyzer, a two rack wide series of instruments controlled with a 9836 computer. The basis was the 8410 network analyzer.
One of the typical measurements we made was liquid dielectric measurements. We had a brass cell, with O rings, that looked like a vertical coaxial cylinder. It was filled a certain height with the liquid, and it fitted on top of the HP 4342A Q meter. We made empty and full measurements and plugged the dial setttings into a program that computers K' and K"". I think we had a heat tape around it, and could measure vs temperatur. Later I automated it with a swept measurement system and had the dielectric properties vs temperature.?
Keysight and an aftermarket Swiss? company make a surface probe that can measure flat materials and liquids. Damaskos in Pennsylvania also makes some devices.
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Hi Colby,
I can still change things via GPIB, no problem so far, my simple Labview(Student Edition) program still works :)
regards
Tim
de VK2XAX
|
Are you able to select those frequencies via GPIB? I am trying to decipher my 'work' notes to determine exactly why I determined the Model needed to be changed..... but... those software options are largely irrelevant when Python, MATLAB (Hobby license), and a 33522B are used. I know for sure that the Service Tool won't calibrate the new range because it identifies as a 3GHz machine.... but there might be a way to trick that too. Regardless - I am working on a Python calibration script too. I have one in shambles for an IFR2398 SA, but once I am done with it, I will move on to the 8468 & E443XB. The tool will backup the existing calibration data, restore the backed up calibration data, and do basic calibrations (Amplitude, etc.).
I'd love to decipher the 8665B calibration ROM and create a process to calibrate it too....
On Mon, Feb 11, 2019 at 2:43 PM Tim Tuck < timt@...> wrote:
Hi Colby,
Frequency changes works nicely :)
I haven't worked out the math for the host id either
regards
Tim
|
Hi Colby,
Frequency changes works nicely :)
I haven't worked out the math for the host id either
regards
Tim
|
Re: HP34702A Ohms converter issues
If you're measuring about 2 mA test current in the 1 K range, it's about twice what it should be, so focus on the opamp U3 circuit. The key is to have the 1 volt drop on the reference resistor string, indicated by U3's output being -7.3 V nominal, as shown on the schematic. If it isn't, then there's the problem. If you've already tried swapping all the active parts, then look at the resistors around U3. You may want to especially check the pot R64, and jiggle it around a bit and rotate the wiper a few times. Normally, it should have only a few percent total effect, but if it opens up, then U3's output should tend to stick at -6.3 V instead. Now, this condition should cause the current source to shut off or be a very low value instead - the opposite of what seems to be going on. But, perhaps if the string voltage is lost, it can cause something in the overall circuit to go out of its normal range and lock up or oscillate.
So, first make sure the -7.3 V voltage reference circuit is right, by measuring the voltages all around its feedback loop. U3's circuit operation is independent of the rest of the system, so should be straightforward to diagnose. The reason I always suspect trim pots is that they sometimes take a lot of abuse during their life, being over-torqued and such, even to the point of destruction. Small board mounted plastic ones especially can have their screwdriver slot (and wiper) mangled, or even have their leads broken loose from the board, by overzealous tweaking.
Once you get the right reference voltage, check it while operating through the various ranges and some unknown resistors, to make sure it stays put with different loads.
Ed
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I am definitely going to try this, again, myself. I swear that when I only changed the upper limit, I wasn't able to dial to the new upper limit until I changed the model. I hope I am mistaken. Looking forward to your results, Tim.
Colby
Hi Tim,
You can use:
| ?41310111.15332 to get: |
GB41310111 |
| ?41310111.525391 |
US41310111 |
| ?41310111.328125 |
MY41310111 |
But You do not need to change the serial to get the frequency update. Only change the upper frequency limit at 165,2.
hostid is calculated from Type (165,10) (first 4 digits) and serial (last four digits of hostid). I did not get the formula to
do calculate it on my own yet.
Peter
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FS Agilent HP 8656B GENERATOR 0.1-990MHz + Opt 001 recent Calib
For sale - HP 8656B signal generator, 100 KHz to 990 MHz, with HPIB interface and Option 001 High Stability.?
- Recent calibration up to 3-18-2017, kept indoors, non-smoking.
- Operates well, very clean unit.
- Has handles installed, power cord and rack ears also included.?
- Manuals on CD included.?
- Pics show limits at 990MHz and 10KHz at? full and minimum power.
$450 PayPal, free shipping / insured to CONUS [48 states] address. Photos at Contact me offlist with questions or to get photos directly. Thanks for looking.? Ron ww2cbi ? ARRL member
|
Re: Test fixture for dielectric measurements
Dr. David Kirkby from Kirkby Microwave Ltd
Has anyone made test fixtures for measuring liquids or solids (essentially a capacitor with the DUT as dielectric)
Attached is a booklet from NPL on dielectric measurements.?
Is is noteworthy they advise against the term "dielectric constant" as no dielectric has constant properties.?
Dave.?
|
Cubdriver