How to use a HP8517 S parameter test set without a HP8510C?(Phase lock stage) - Page 1
Forum section: electronics / rf-microwave

author: Robert_Sky
author_rank: Contributor
timestamp: May 12, 2019, 04:04:45 am
content: I bought a parts only HP8517 S paramerter set recently. Is it possible to control the set using GPIB command. Look through the service manual of HP8510C and HP8517, but did not find the command about how to control it. Is it possible to using this metal box standalone.I see a similar thread at the HP yahoo group, No answer yetThanks.Robert

author: rastro
author_rank: Frequent Contributor
timestamp: May 12, 2019, 03:19:09 pm
content: The HP 8510B/C systems use a GPIB between the Display Section, Test-set, and the RF generator (source). I believe this is refered to as the internal bus. There is also another (external) GPIB located on the Display that is used to communicate to outside system controllers for ATE purposes. The 'external' GPIB commands is documented in the HP 8510 user/programmer manual - it is more of what you normally think of when referring to GPIB. The 'internal' GPIB which you are asking about is not documented in any user/service manuals, as far as I know. There is also a cable between the IF unit and the test-set.Are you looking to run the HP 8517 as a VNA or just trying to access the couplers to do simple transmit and reflection measurements?

author: Earendil
author_rank: Regular Contributor
timestamp: May 12, 2019, 06:08:32 pm
content: Well, if you need a 50 GHz test set then I'm pretty sure you have the tools to figure it rather quicklyI would take a look at the firmware of the VNAs that use it before start attaching any probes though...

author: Robert_Sky
author_rank: Contributor
timestamp: May 12, 2019, 11:48:01 pm
content: @rastro Thanks for the information.Yes, you are right. i would like to run the HP 8517 as a VNA or just trying to access the couplers to do simple transmit and reflection measurements. Agree with you, the HP do not pulish any document about how to control the "internal" GBIP. For now, the only way is to read the ROM on the CPU board of 8517 set. It is a MC68B00@Earendil, I am a poor man. i have nothing about the 50GHz,only one set.

author: KE5FX
author_rank: Super Contributor
timestamp: May 13, 2019, 12:47:35 am
content: Have a look at theUS patent for the original 8510A. The internal HPIB bus commands used to communicate with the test sets may well be in there somewhere. For whatever reason, HP basically just printed out the firmware source and mailed it to the patent office.

author: Earendil
author_rank: Regular Contributor
timestamp: May 13, 2019, 02:10:54 am
content: @Robert_Sky:I keep saying the same thing, yet nowadays I don't know where to put all my electronic "junk" as my parents call it.Those 50 Ghz ones are still quite expansive but anyway.Here you can find a firmware for the 8510, I'm not sure if it's complete:http://ftb.ko4bb.com/getsimple/index.php?id=download&file=HP_Agilent/HP_8510_Network_Analyzer/HP_8510C_85101C_firmware_U66/85101_80134_rev_3_04_U66_AM27C020-2000C.binI've seen some GPIB commands in it though the test set control commands are not obvious.Another option if you ask someone with a 8510A to tunnel GPIB over Internet and control your testset. Or you can take the test set apart, read the ROM (I'm not sure if this type has it but most ones has a small computer) and try to find the commands there.I'm interested in what'll you find because I considered this as well, and in fact I even did it as well, but with a newer and not so wideband VNA test set. That one was used by a PNA which is Windows based and I could find the necessary information in its firmware.You test set is much older and more specialized. Though the 50 GHz is very alluring but problem is that one needs very expensive cables and other stuff (calibration standards, anyone?) if one wants to fully utilize the 50 GHz. Another issue is unless one also a get a calibration and verification standard it is difficult to tell if the couplers work well. From what I heard the connectors on these can easily go out of spec and then it's almost impossible to fix them because the coupler and front panel connector are a single unit. The connectors are replaceable but I doubt you will manage to get replacements for them. Another issue is that these use custom cables though those can be obtained. So overall I would only buy such a test set if I wanted to use it with the VNA it was designed for or I only needed the internal components. Which are nice but it's mainly the couplers that are difficult to obtain.

author: hendorog
author_rank: Super Contributor
timestamp: May 13, 2019, 02:45:14 am
content: Much like the OP, I've got a parts only 8515 test set, and have been intending to hook it up to my 8753C (for a while)I didn't find anything on the GPIB commands so I gave up on that approach.So instead, I was going to bypass the micro in the test set and just drive the outputs directly. One day...

author: Robert_Sky
author_rank: Contributor
timestamp: May 13, 2019, 12:07:39 pm
content: @KE5FX Thanks for the link@Earendil Thanks. I was in the unconscious incompetence stage when i decided to buy the not cheap set. 50GHz is alluring and is very difficult after in the conscious incompetence stage.i believe the command is very simple. Four commands are enough, These four command are already printed on the CPU board of 8517. But we do not know the HP format for these command.i guess you are refering the N4420 set for PNA port extension. They are nice and expensive. i see the mixer is not in the set. So you need another signal generator and mixer to detect the reflective and through signal?@hendorog Yes, you just need four signal to control the two switch if you see the CPU board.Thanks a lot for everyone's input

author: rastro
author_rank: Frequent Contributor
timestamp: May 13, 2019, 01:51:20 pm
content: Quote from: Robert_Sky on May 12, 2019, 11:48:01 pmI commend you for wanting to get into the nuts and bolts of the system - there is certainly a good deal of knowledge/insight to gain from that endeavor.Here are some additional considerations beyond GPIB to achieve VNA or Simple Coupler(Xmit/Reflect) functionality.To make it work as a VNA you need to replace/emulate the functionally of the display and IF units. Just considering software/firmware it's a considerable reverse engineering task. There is also a signal cable between the IF and test set that have I believe has 20MHz IF signals and about 17 additional electrical control signals. Since there is an IF conversion in the test set there is probably some way to track the LO against the source like a PLL. At the very least your new IF section would need to measure phase and amplitude of the (5) 20MHz signals and probably compensate for inherent signal degradation across 50GHz bandwidth of the test sets RF path.For Simple Coupler(Xmit/Reflect) functionality you still have concerns with the 20MHz IF and control signals. Another possibility is to use some of the internal components prior to the IF conversion. This seems like a reasonable possibility if the hybrid RF components can separated from the IF signal path. At that point you would need to see if the couplers are passive components or if they need additional voltages for bias or internal amp. You would also need to determine the performance curve for each of the couplers ports. I suspect there is a lot of dynamic baseline compensation going on between the test set and the IF section even before the calibration standard procedure fine tunes the readings. Think about trying to create a flat response on an RF coupler with 50GHz bandwidth....I do not mean to sound discouraging but I think it's worthwhile to step back and look at the larger picture of requirements to accomplish your goal.rastro

author: Robert_Sky
author_rank: Contributor
timestamp: May 13, 2019, 11:52:14 pm
content: @rastro, Thanks for the reminder.Yes, it is too difficult for me now. I know the 50Ghz is impossible task if you do not have some 50GHz tool. If i get good results up to 20GHz, i will be very happy and satisfied.

author: KE5FX
author_rank: Super Contributor
timestamp: May 14, 2019, 02:12:38 am
content: Quote from: Robert_Sky on May 13, 2019, 11:52:14 pmThe big win with the 8517 test set is time domain. You don't need a perfect 2.4 mm calibration to get exceptional spatial resolution. With an 85134-60003 cable and a beat-up 85033C cal kit, I can resolve features in connectors, fittings, and PCB traces that would be much less distinct on a 20 GHz setup.E.g.:The main downside is the cost of the 50 GHz sweeper. It usually takes $8K or more to put your hands on a good, clean 83651B.

author: Robert_Sky
author_rank: Contributor
timestamp: May 14, 2019, 02:52:28 pm
content: it is 27ps rising time in your setup. the bandwidth is about 13GHz?

author: Robert_Sky
author_rank: Contributor
timestamp: May 14, 2019, 02:59:02 pm
content: Find some GBIP command related to test set work in the bin file of 8510. The command may be simple as ".PE1" to make port1 active.

author: KE5FX
author_rank: Super Contributor
timestamp: May 14, 2019, 11:00:23 pm
content: Quote from: Robert_Sky on May 14, 2019, 02:52:28 pmIt's not directly comparable to oscilloscope risetime. For low-pass step response with a normal window, the best achievable response resolution is about1/span, or 20 ps for 50 GHz. That's about 3 to 4 mm in FR-4 microstrip.

author: hendorog
author_rank: Super Contributor
timestamp: May 15, 2019, 01:34:55 am
content: Quote from: Robert_Sky on May 14, 2019, 02:59:02 pmGive it a try, you should see the LED's reflect the change.

author: hendorog
author_rank: Super Contributor
timestamp: May 15, 2019, 01:50:13 am
content: Quote from: hendorog on May 15, 2019, 01:34:55 amOK I couldn't wait so I tried itCode:Connection String: GPIB0::20::INSTRConnected to GPIB0::20::INSTR*IC0// Observed the Active light on the front go off*IC1// Active light on the front panel turns on.Well done Robert_Sky, you have cracked it

author: hendorog
author_rank: Super Contributor
timestamp: May 15, 2019, 02:48:27 am
content: Here are the things I have worked out:Code://Preset Test Set*IP1;// Turn off active light*IC0// Turn on active light*IC1//Turn off both port lights*PE0;//Turn on port 1 light/Enable Port 1*PE1;//Turn off port 2 light/Enable Port 2*PE2;//Turn on both Port lights*PE3;//Select Port 1 Attenuator*RA87 13;//Select Port 2 Attenuator*RA87 12;// Attenuation is set on the active attenuator// Set zero attenuation*RG00 0;// Set 10dB attenuation*RG00 1;// Set 20dB attenuation*RG00 4;// Set 30dB attenuation*RG00 2;// Or*RG00 8;// Set 40dB attenuation*RG00 3;// Set 50dB attenuation*RG00 6;// Set 60dB attenuation*RG00 7;// Set 70dB attenuation*RG00 11;// Set 80dB attenuation*RG00 14;// Set 90dB attenuation*RG00 15;Edited to fix error in Attenuator command. Confirmed activating port 2 also switches to port 2 and vice versa.These are probably useful for the full range of test sets, listing them for search engines: 8510, 8511, 8512, 8514, 8515, 8516, 8517

author: Robert_Sky
author_rank: Contributor
timestamp: May 16, 2019, 12:50:51 pm
content: @hendorog It is everyone's input to make this happenYou are really a quick hand. My GPIB adapter is still on the way

author: Robert_Sky
author_rank: Contributor
timestamp: May 16, 2019, 01:10:38 pm
content: The next step is how to lock the mixed down signal, amplitude and phase detector.

author: hendorog
author_rank: Super Contributor
timestamp: May 20, 2019, 12:15:04 am
content: Quote from: Robert_Sky on May 16, 2019, 12:50:51 pmThanksQuote from: Robert_Sky on May 16, 2019, 01:10:38 pmMy original plan was to remove the VTO and samplers from my test set (one of the samplers is marked as Bad anyway).I intended to replace them with a PLL board and some mixers and configure it to act as a transverter for my 8753C VNA.But your test set is much higher frequency than mine so keeping the original VTO & samplers makes more sense.There is a diagram in the 8510 service manual with a high level block diagram of the phase lock arrangement with the summing amp.I will have a play with mine - at this stage I am not confident the VTO is working at all in my unit.

author: Robert_Sky
author_rank: Contributor
timestamp: May 23, 2019, 03:16:05 pm
content: Hi hendorogDo you have an idea about the voltage level of Pretune and vtune for phase lock? for now, i do not dare to input some value to burn the set in case.Thanks

author: hendorog
author_rank: Super Contributor
timestamp: May 23, 2019, 06:49:48 pm
content: Quote from: Robert_Sky on May 23, 2019, 03:16:05 pmYes - in one of the service manuals I found a chart for testing the VTO. From memory it was -1V to -12V.There was also some information about testing the VTO with the test set disconnected from the 8510. I seem to remember it was supposed to be about 180 MHz.I will find the chart/info and post it.Edit: attached VTO test procedure found in the HP 8516 service manual, which is searchable.http://literature.cdn.keysight.com/litweb/pdf/08516-90069.pdfNote the warning, using a positive test voltage will damage the VTO!!

author: hendorog
author_rank: Super Contributor
timestamp: May 23, 2019, 07:51:20 pm
content: Also look here, which shows the relationship between the Tune signals from the IF box and the VTO in the test set.The summing amp sits in between and combines the pretune and the phase lock feedback to produce a drive for the VTOhttp://literature.cdn.keysight.com/litweb/pdf/08510-90282.pdf

author: Robert_Sky
author_rank: Contributor
timestamp: May 24, 2019, 12:54:41 pm
content: Hi HendorogThanks a lot for the information. it is really very very help.The scanned 8517A service manual do not mention how to test the VTO.Two loop need to be phase locked, it is not easy thing

author: SpencerTC
author_rank: Contributor
timestamp: May 31, 2019, 01:44:10 pm
content: Wow, good work so far guys. I don't currently have the test set mentioned, but I once had the chance to obtain one for free and I let the opportunity pass by as I didn't think I would have much use for it. I work with older gear regularly and will be following this thread to satisfy my curiosity on the subject (and in case I run into a similar need in the future).Best regards,Trent KM4YTU

author: IW1EPY
author_rank: Newbie
timestamp: January 27, 2020, 08:25:43 pm
content: do you still have the HP8517? I am interested of some parts of this test equipment.IW1EPY