Afternoon all!
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I've had this HP 3585A for a few weeks now and it's been working great. Tonight I noticed that the CRT is, for lack of a better term, twitching. I took a video and you can see it more clearly once I turn down the CRT intensity later in the video. Also note the reference line is not as pure as it once was. It's almost striped looking now.?
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Any idea what could be causing this? I would assume a power supply issue.
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Thanks. Looking at your other plot, I think your spectrum analyser plot is a plot of noise output vs frequency. It looks like your noise source has a steeper noise reduction than mine as the frequency is reduced. It may be that your noise source has a different capacitance value for the dc blocking cap inside it?
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I can try and come up with a better way of measuring mine to try and characterise it better. I didn't spend much time on this last time. I don't think it will reduce by 2dB by 2MHz and by 4dB at 1MHz though.?
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I've also got a couple of homebrew noise sources here. One contains a decent Noisecom noise diode and the other uses a high frequency diode. I think it's a Schottky diode but I can't remember now. It works very well up to several GHz. The Noisecom source is only really good to about 1300MHz although it is supposed to work down to 200kHz according to the datasheet.
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Re: HP 182T Power Supply Troubleshooting
Typo in R11B formula in the previous message, correct formula is below. It was missing a parenthesis although LTspice didn't mind it.
Ozan
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R11A N014 N012 {1000*R11setting}
R11B N012 N017 {1000*(1-R11setting)}
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On Wed, Oct 16, 2024 at 11:03 AM, Ozan wrote:
I usually parameterize trimpots like the example below. Then you can use e.g. (0,1) range to try 0%-100% trimpot settings or change the formula to R11setting/100.0 if you like (0,100) range better. LTspice doesn't like 0-ohm resistors, R11setting of exactly 0.0 and 1.0 won't work in the example below. ?
Ozan
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R11A N014 N012 {1000*R11setting}
R11B N012 N017 {1000*(1-R11setting}
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On Wed, Oct 16, 2024 at 06:48 AM, Frank Mashockie wrote:
I'm looking to go back to school to get a degree in EE and I'm previewing some courses.? Needed to familarize myself with LTSpice.? So I created the 100V from the 182T just to mess around.? Of course I also put a few of the transistors in backwards just like I did in reality a few weeks ago! lol.? But after fixing that, it works!? Unfortunately I don't think you can add trimpots, so you have to adjust the value of R12 to adjust the voltage.? Right now it is dialed in at 100.3V.? I created a folder called 'LTSpice' so people can add files for any simulation related to HP equipment.? I added this file to that folder.? I figured it could come in handy for troubleshooting purposes.
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Re: HP 182T Power Supply Troubleshooting
I usually parameterize trimpots like the example below. Then you can use e.g. (0,1) range to try 0%-100% trimpot settings or change the formula to R11setting/100.0 if you like (0,100) range better. LTspice doesn't like 0-ohm resistors, R11setting of exactly 0.0 and 1.0 won't work in the example below. ?
Ozan
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R11A N014 N012 {1000*R11setting}
R11B N012 N017 {1000*(1-R11setting}
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On Wed, Oct 16, 2024 at 06:48 AM, Frank Mashockie wrote:
I'm looking to go back to school to get a degree in EE and I'm previewing some courses.? Needed to familarize myself with LTSpice.? So I created the 100V from the 182T just to mess around.? Of course I also put a few of the transistors in backwards just like I did in reality a few weeks ago! lol.? But after fixing that, it works!? Unfortunately I don't think you can add trimpots, so you have to adjust the value of R12 to adjust the voltage.? Right now it is dialed in at 100.3V.? I created a folder called 'LTSpice' so people can add files for any simulation related to HP equipment.? I added this file to that folder.? I figured it could come in handy for troubleshooting purposes.
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You are correct, JMR. The 346A is a lot better below 10 MHz than the 346B.
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Vladan
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Just to clarify, the thread title does ask about the HP 346A and so I gave estimated VSWR data for the HP 346A. The 346A has much lower VSWR than the 346B. You can typically expect to see less than 1.02:1 VSWR at 10MHz with the 346A and this will degrade to about 1.05:1 by about 300kHz. It might degrade to 1.06:1 by 100kHz.
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I did also say I couldn't remember how much worse the 346B VSWR was. I would guess that the 346B has maybe 9dB less attenuation after the diode because it has a higher ENR at its output. So the VSWR will obviously be worse than the 346A in this respect.
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Hi Tom,
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Correct, things become unpredictable at lower frequencies. The original 346 diode was a special design in that, among other things, it had a p-doped guard ring to control the avalanche area as tightly as possible. The diode is in a hermetically sealed assembly and it was eutectically attached to the package to stabilize the temperature. Later, when HP obsoleted the Si process, the diodes came from Metelics, which unfortunately went downhill after being purchased by a conglomerate. I am not sure about the differences between old HP and Metelics diodes.
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Vladan
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JMR, your numbers didn't sound right to me, so I made the following measurements on a 346B. The OP is curiously absent, so we may never know what he wants to do.
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Vladan
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I was not looking for images to create thumbnails. I have two aims
1) Expand the files area, so we have more information about more instruments.
so that looking at any type of instrument, you can see a list of model numbers. Clicking a model number will take you for the directory containing user manuals, service manuals, or anything else of use.
So the directory for the 204D now exists
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Thanks, though I'd still appreciate some guidance on sizes for images and PDFs. I've just scanned the 213B Manual at 300dpi which gives 2.2MB for 23 pages, will try to upload it when we have a folder for it. This size seems to be in line with other manuals we have here. What about images?
?- Julian
Those sizes don¡¯t seem unreasonable.?
You can create the folder yourself. I will explain the steps in a way that will work for any instrument, rather than something specific to that instrument.
1) First go to the main files area
2) Select the directory that has instruments by model number?
3) Since the model number has 213, which is between 0 and 999, select the directory for instruments in range 000 to 999.?
4) Click New/Upload at the top and select ¡°New Folder¡±?
5) Create a folder, using a Folder Name of the instrument, followed by a brief description.
If you want, put a longer description in the area marked ¡°Description¡±. You could put information such as pulse width, risetime, or anything else that you think is relevant.?
6) Once the folder is created, go into the folder and upload the manual. We would prefer filenames without spaces in them - use underscores or hyphens. The filename should indicate whether it¡¯s a user manual, service manual or combined manual.?
You get the option to edit things, so if you made a mess of the filename or directory name, or description, don¡¯t worry.?
Dave (admin)
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On 10/16/24 09:41, saipan59 (Pete) wrote: Dave's HPwiki has many more models listed:
should also work. -Dave -- Dave McGuire, AK4HZ New Kensington, PA
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I was not looking for images to create thumbnails. I have two aims
1) Expand the files area, so we have more information about more instruments.
so that looking at any type of instrument, you can see a list of model numbers. Clicking a model number will take you for the directory containing user manuals, service manuals, or anything else of use.
So the directory for the 204D now exists
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Thanks, though I'd still appreciate some guidance on sizes for images and PDFs. I've just scanned the 213B Manual at 300dpi which gives 2.2MB for 23 pages, will try to upload it when we have a folder for it. This size seems to be in line with other manuals we have here. What about images?
?- Julian
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Re: HP 182T Power Supply Troubleshooting
I'm looking to go back to school to get a degree in EE and I'm previewing some courses.? Needed to familarize myself with LTSpice.? So I created the 100V from the 182T just to mess around.? Of course I also put a few of the transistors in backwards just like I did in reality a few weeks ago! lol.? But after fixing that, it works!? Unfortunately I don't think you can add trimpots, so you have to adjust the value of R12 to adjust the voltage.? Right now it is dialed in at 100.3V.? I created a folder called 'LTSpice' so people can add files for any simulation related to HP equipment.? I added this file to that folder.? I figured it could come in handy for troubleshooting purposes.
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Dave's HPwiki has many more models listed:
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Pete
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I have a 202J Telemetering Signal Generator, and an original manual.
[Early versions of the 202J are marked Boonton.]
Will make a PDF scan in the next few days.
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Pete
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For the 892x series the Wiki line item or category could be called? "Mobile Station Test Sets"
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The Wiki is looking great!
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Jim
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Looking back through my old notes, the ENR at 1MHz was lower than 5.20dB so this may be a typo on my ENR table stored in the analyser. However, I possibly boosted it to prevent 'pulling' of the NF results when operating just below 2MHz. My notes suggest that the ENR drops quite rapidly below about 1.5MHz. I should probably have added an extra ENR table entry at 1.5MHz because of this.
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I wouldn't trust it below about 2MHz anyway. There are too many contributors to overall uncertainty. The analyser uncertainty will be quite significant here although the use of an external LNA helps in this respect. Not many modern analysers from HPAK are going to be usable below 10MHz unless an external LNA is used. The noise floor and VSWR is going to degrade below 10MHz with the internal factory preamp enabled. My analyser manages a noise floor of about -170dBm/Hz down to a few MHz with my external preamp fitted and the preamp input VSWR is about the same or better than the 346A noise source VSWR at these sub 10MHz frequencies.
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Re: HP83651B troubleshooting
Hello,
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Just thinking, can't it be something in A28 AMP/MULTIPLIER or A29 AMP/FILTER?
Can you break out the signal before A32 AMP/DOUBLER to see if you get the same behaviour earlier in the path?
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Regards,
? Staffan
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I've never attempted to use one at the bottom end of the spec'd frequency range, but based on my (limited) experience with homebrew noise sources, I'd question the stability of the ENR down there. Avalanching gets you a high ENR without operating at incandescent temperatures, but it is flaky. The 1/f corners are high and not particularly stable. I assume that the 346x uses buried devices to moderate the instability, but there's only so much that one can do.
Whether any of that matters depends, of course, on what you need out of the NF measurement. How accurately, and over what frequency range, do you want to measure NF? For terrestrial wireless, for instance, ambient noise typically sdominate over intrinsic thermal noise below about 20-30 MHz. Making accurate NF measurements at 1 MHz, say, isn't particularly important if the idea is to infer the sensitivity of AM radios, for example.
And if you only want to measure NF below tens of MHz, there are several other options for doing so.
-- Cheers
Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070
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On 10/13/2024 4:46 PM, WReeve wrote: Has anyone investigated the ENR and ENR uncertainty of the HP 346A noise source at frequencies below 10 MHz? Same question for the HP 346B?
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I do not know the specific application, or I missed something, but below 10 MHz noise figures are generally spoken not so crytical an usually quite high. Couldn¡¯t you just go for the 3dB method? As said above the HP346A/B/C needs dedicated equipment that normally does not operate below 10 MHz.? Best regards, Harke
(Send from my iPad4)
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Op 15 okt 2024 om 18:21 heeft jmr via groups.io <jmrhzu@...> het volgende geschreven:
? Over my career, I've used a lot of HP 346A noise sources (5.5dB ENR) but only a few examples of the 346B (15dB ENR).
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In my experience, the input VSWR of the 346A (in both hot and cold states) is usually very low across 10MHz to a couple of GHz. A typical VSWR figure might be 1.02:1 across this frequency range. A good example might achieve a VSWR of < 1.01:1 at 10MHz. At frequencies below 10MHz, the VSWR will gradually degrade, but I don't think it will get much worse than about 1.06:1 even below 1MHz.?
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Probably the biggest issue with the 346A will be finding an instrument that formally supports it below 10MHz. In terms of noise figure measuring performance, the performance of a typical analyser will degrade quite a bit below 10MHz in various ways. This makes it difficult to support a noise source with a low (5.5dB) ENR like the 346A. You may be better off using a 346B with (say) a 6dB attenuator fitted to it to lower the 15dB ENR a bit and also improve the source match. This might achieve a better compromise for use below 10MHz.
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It's a while since I used a 346B so I've forgotten the typical input VSWR vs frequency. The VSWR will be higher for the 346B because it has less internal attenuation after the noise diode. One option is to fit a low Q matching network at the input of the 346B as well as an external attenuator. This would hopefully deliver a decent ENR of maybe 9dB as well as providing a good source match below 10MHz. This should improve the overall uncertainty when using the noise source although you would have to find a way to determine the ENR of such a setup when used below 10MHz.
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Over my career, I've used a lot of HP 346A noise sources (5.5dB ENR) but only a few examples of the 346B (15dB ENR).
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In my experience, the input VSWR of the 346A (in both hot and cold states) is usually very low across 10MHz to a couple of GHz. A typical VSWR figure might be 1.02:1 across this frequency range. A good example might achieve a VSWR of < 1.01:1 at 10MHz. At frequencies below 10MHz, the VSWR will gradually degrade, but I don't think it will get much worse than about 1.06:1 even below 1MHz.?
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Probably the biggest issue with the 346A will be finding an instrument that formally supports it below 10MHz. In terms of noise figure measuring performance, the performance of a typical analyser will degrade quite a bit below 10MHz in various ways. This makes it difficult to support a noise source with a low (5.5dB) ENR like the 346A. You may be better off using a 346B with (say) a 6dB attenuator fitted to it to lower the 15dB ENR a bit and also improve the source match. This might achieve a better compromise for use below 10MHz.
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It's a while since I used a 346B so I've forgotten the typical input VSWR vs frequency. The VSWR will be higher for the 346B because it has less internal attenuation after the noise diode. One option is to fit a low Q matching network at the input of the 346B as well as an external attenuator. This would hopefully deliver a decent ENR of maybe 9dB as well as providing a good source match below 10MHz. This should improve the overall uncertainty when using the noise source although you would have to find a way to determine the ENR of such a setup when used below 10MHz.
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Brad Jackson
Dr. David Kirkby, Kirkby Microwave Ltd
Dave McGuire
Julian_Hardstone
Frank Mashockie
saipan59 (Pete)