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On Wed, Mar 20, 2019 at 04:52 AM, amirb wrote:
yes, it seems the SA is having an issue.?Yes, I'm quite certain now that the displayed problem above is due to the SA and not the 8664. I was able to flatten out the response shown in the upper band by (1) reducing the SA sweep time (to give things more time to settle and (2) playing with the preselector peak. The response still isn't perfect as far as absolute amplitude, but there's some adjustments that I can do to fix that. I also showed a picture of a much narrower sweep right around the area of that bad dip in the pic above. As you can see, it's about as flat as you like. With the flatness of the response seen from 10 kHz to 2.5 GHz, I seriously doubt that the final 500 MHz is as bad as that original photo showed. Honestly, after doing much testing yesterday looking at CW from the 8664 in narrow spans, I can't really find any faults with how it is functioning. I'd say I agree with the others above that it's worth keeping and repairing (and adjusting as needed). Sean |
开云体育Dear All,Measuring signal generator output accuracy with a spectrum analyser, even as nice a one as the 8566B, does not make a lot of sense since the amplitude accuracy is limited. The 8566B flatness is +/- 2.2 dB to which has to be added the calibrator accuracy of +/- 0.3 dB. A good signal generator has much better accuracy.? What you need for the job is a decent RF power meter, which will give you a total measurement uncertainty of about +/- 0.4 dB. Regards, Alwyn ? _____________________________________________________ Alwyn Seeds, Director 114 Beaufort Street (Management) Company Ltd., 114 Beaufort Street, London, SW3 6BU +44 020 7376 4110 114 Beaufort Street (Management) Company Ltd., Registered in England and Wales: No. 02797775 Registered Office Address: 114 Beaufort Street, London, SW3 6BU ______________________________________________________ |
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On Wed, Mar 20, 2019 at 03:03 PM, alwyn.seeds1 wrote:
Dear All,Hi, I am looking into getting one. The purpose of the above exercise is simply to make sure there are no gross problems with the 8664. Of that I am quite sure now, so I am keeping the instrument and getting a bit of a refund from the seller. Sean |
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Bob Albert
For a decent power meter you do NOT want a Bird.? They are pretty sloppy. I use my HP410B for example.? I calibrate it with my HP 3456A in the audio range and then it's good up to at least 500 MHz.? My HP 8657B isn't all that accurate and I have to use the Offset to get more accurate readings.? The spectrum analyzers are, as you say, not too accurate. On the other hand, I don't need precision amplitude.? All I do is calibrate S meters and you can barely see 1 dB on them, and most aren't too accurate over the range.? So as long as I have 50 microvolts I am happy.? Flatness is another issue but then the SA does a good job. Bob
On Wednesday, March 20, 2019, 3:43:53 PM PDT, <[email protected]> wrote:
On Wed, Mar 20, 2019 at 03:03 PM, alwyn.seeds1 wrote: Dear All,Hi, I am looking into getting one. The purpose of the above exercise is simply to make sure there are no gross problems with the 8664. Of that I am quite sure now, so I am keeping the instrument and getting a bit of a refund from the seller. Sean |
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Agreed on the Bird reference. They're great inline watt meters for high power needs, but not for fine performance verification. I use the E4418B and E4419B w/8482A and E9300A heads, or a U2001H USB Power Meter - depending on where I am.... Colby On Wed, Mar 20, 2019 at 5:28 PM Bob Albert via Groups.Io <bob91343=[email protected]> wrote:
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Colby |
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On Wed, Mar 20, 2019 at 05:28 PM, Bob Albert wrote:
Thanks for the pointers on power meters. Needed one eventually anyway (isn't that the best excuse for buying more test gear!) Sean |
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On Wed, Mar 20, 2019 at 05:38 PM, Colby Burkett wrote:
Agreed on the Bird reference. They're great inline watt meters for high power needs, but not for fine performance verification. I use the E4418B and E4419B w/8482A and E9300A heads, or a U2001H USB Power Meter - depending on where I am....Thanks as well...good stuff to start watching for. Sean |
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On Mon, Mar 18, 2019 at 07:41 PM, Colby Burkett wrote:
Would you happen to have the bit of hardline coax that connects the front panel RF out to the inside? I'm worried that might have been damaged. Sean |
开云体育Dear All,"From:?Bob Albert Date: Wed, 20 Mar 2019 17:28:34 PDT? For a decent power meter you do NOT want a Bird.? They are pretty sloppy." Sorry for using the vague term “decent power meter”. I meant something like an HP 435/436 with an 8481A measurement head. The Bird instruments are intended for measuring rather larger RF powers and, as Bob says, do not offer the accuracy required for testing a signal generator. While writing, a tip to avoid the mistake I once made. Power meters are, of course, broadband. Therefore if the signal to be measured has significant harmonic content an error in measuring the fundamental power will result. Forgetting about this, I was puzzling why the Cal. outputs of my 8560 series and 8590 series spectrum analysers measured differently. Then I realised that the 8590 Cal. source has strong harmonic output, whereas the 8560 series source does not. Similarly, some signal generators that use frequency doublers produce strong half-frequency outputs which would cause an error when checking output power on the highest frequency range with a power meter. Regards, Alwyn _____________________________________________________ Alwyn Seeds, Director SynOptika Ltd., 114 Beaufort Street, London, SW3 6BU, England. Tel.: +44 (0) 20 7376 4110 SynOptika Ltd., Registered in England and Wales: No. 04606737 Registered Office: 114 Beaufort Street, London, SW3 6BU, United Kingdom. _____________________________________________________
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开云体育Seconded,? I have gotten bit by the 2nd or 3rd harmonic even on a good meter.? Bird is considered a 5 or 10% meter at best great for tuning bad for accuracy ? Regards, ? Stephen Hanselman Datagate Systems, LLC 3107 North Deer Run Road #24 Carson City, Nevada, 89701 (775) 882-5117 office (775) 720-6020 mobile a Service Disabled, Veteran Owned Small Business DISCLAIMER: This e-mail and any attachments are intended only for use by the addressee(s) named herein and may contain legally privileged and/or proprietary information. If you are not the intended recipient, any dissemination, distribution or copying of this e-mail and any attachments is strictly prohibited. If you have received this e-mail in error, please immediately notify me and permanently delete the original and all copies and printouts of this e-mail and any attachments. ? ? ? From: [email protected] <[email protected]> On Behalf Of alwyn.seeds1
Sent: Thursday, March 21, 2019 3:35 AM To: [email protected] Subject: Re: [HP-Agilent-Keysight-equipment] HP 8664A signal generator repairability ? Dear All, ? "From:?Bob Albert ? For a decent power meter you do NOT want a Bird.? They are pretty sloppy." ? Sorry for using the vague term “decent power meter”. I meant something like an HP 435/436 with an 8481A measurement head. ? The Bird instruments are intended for measuring rather larger RF powers and, as Bob says, do not offer the accuracy required for testing a signal generator. ? While writing, a tip to avoid the mistake I once made. Power meters are, of course, broadband. Therefore if the signal to be measured has significant harmonic content an error in measuring the fundamental power will result. Forgetting about this, I was puzzling why the Cal. outputs of my 8560 series and 8590 series spectrum analysers measured differently. Then I realised that the 8590 Cal. source has strong harmonic output, whereas the 8560 series source does not. ? Similarly, some signal generators that use frequency doublers produce strong half-frequency outputs which would cause an error when checking output power on the highest frequency range with a power meter. ? Regards, ? Alwyn ? _____________________________________________________ ? Alwyn Seeds, Director _____________________________________________________ ? |
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Thanks for all the hints on power meters! Duly noted.
As for the 8664, it passes all self tests. I also re-ran self cal now that the frequency reference is good and warm and everything seems to be working absolutely great. I negotiated a bit of refund back from the seller for the pain and suffering, and I have an order of rack handles on the way 2 4U sets (so I can put some handles on my 8569B microwave SA as well), and some extra 3U handles. Sean |
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Got a new set of 4U rack handles today, so that issue is fixed! Also called up Keysight and they were able to send me the cal report from the last time it was seen by them (Agilent at the time) in 2013. Please excuse the temporary (and heavy) stack. Moving relatively soon, so hopefully this will all go into my new and bigger lab. :o)
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Another update, today I received a nice box of goodies from Mini-Circuits, including some 18 GHz semirigid coax with stainless SMAs as well as matching type N to female SMA adapters. While the flatness in the upper band of the 8566A still isn't perfect, it's a LOT better with good quality connectors and cabling.
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开云体育By mechanical attenuator, I assume you mean one that you physically have to switch to change the level of attenuation. ?If so then changing frequency should have NO effect on attenuation, for that matter it shouldn’t effect the electrically switched ones either. ?What I suspect you are really seeing is a change in level to the attenuators from the output module(and/or others) as you change frequency. I’d check the input to the attenuators for that problem instead. I don’t have a 8664 but my 8665 has an essentially constant output level that only varies a few dB electronically, the rest is a pair of attenuator that adjust in 5dB steps that work in conjunction with an “AGC” like variable to give the output from the generator.? Regards, ? Stephen Hanselman Datagate Systems, LLC On May 26, 2020, at 11:51, John Perlick <jperlick@...> wrote:
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What i mean by mechanical attenuator is this:? The 8644/45 cam with a PIN diode attenuator or, if you have a -002, like mine, you get a mechanical, solenoid driven attenuator.? I've checked the attenuators and yeah all steps work fine. I am checking the drive circuits next.But good point I will check the input.? Like other HP sig gens, the RF power is leveled at the input to the ATTN with an ALC loop. I assume there might be a Cal setting involved.? But running the internal cal should fix that.?
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开云体育I understand although all of the ones I have are thick (thin???) film resistors. ?While it would not be as precise if you need some resistor segments I have about 25 units of various dash numbers I can pull them from.?Regards, ? Stephen Hanselman Datagate Systems, LLC On May 28, 2020, at 11:54, John Perlick <jperlick@...> wrote:
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