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HP 8901A modulation analyzer




 
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Author Topic: HP 8901A modulation analyzer  (Read 5977 times)
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w3jn
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« on: March 27, 2006, 10:10:23 AM »

Scored one of these on eBay last week - anyone here used one?  Looks pretty cool, peak/average mod percentages, demodulated audio output with .1% distortion, frequency counter, etc all in one package.
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VE7 Kilohertz
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« Reply #1 on: March 27, 2006, 11:46:14 AM »

Hi John,

Great units!  Very useful for analyzing anything RF in your shack. You will need some good attenuators to go with it as it will only take 1W input. Did you get the manual? I can email you one I think, when I go to town next time. I'm on dial up here in the sticks. Yes, the demod is awesome quality. You will definately need the manual though as there is so much in setup that needs to be preset.

Let me know.

Cheers

Paul
VE7KHz
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Tom WA3KLR
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« Reply #2 on: March 27, 2006, 11:51:52 AM »

I have one here in the shack John.  I pointed it out to the Timtron when he was here a few weeks ago.  I used one at an engineering job about 10 years ago where we needed to develop some frequency modulators.  At the time, I thought it was a great piece of gear for the money, so I eventually acquired one for myself a couple years ago off of ebay.  I'll be using it with the Class E project for sure.  Get the manuals if you don't already have them.

Did you get the version with the r.f. and audio connectors out the front or unfortunately like mine where they come out the back?  Not a big deal though.  Mine is in near new condition though.  I think they were about $11,000 at the end of their production as I recall.  Good bargain today for the price they go for, kind of big, but I bought a wooden kitchen cart at WalMart and it sits in the lower space of the cart.  My HP spectrum analyzer sits on the top of the cart.


* hp8901a_hp8568B.JPG (126.13 KB, 640x480 - viewed 465 times.)
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73 de Tom WA3KLR  AMI # 77   Amplitude Modulation - a force Now and for the Future!
w3jn
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« Reply #3 on: March 27, 2006, 12:07:23 PM »

Thanks for the responses, guys.   Most of the manuals are available on the Agilent website, plus, the Timonium hamfest coughed up a service manual for all of $10.  Curiously the Agilent website has the service manual, all kinds of application notes, etc., but no operator's manual  Huh

Tom, I think the connectors go out the back, the photos in the auction weren't the greatest, and I haven't received it yet.  Is that a 8566 or an 8568 specan?  *Still* the best specans ever made, IMHO.

I would have rather had the 8901B which apparently is already set up for SSB phase noise measurements (THAT would be a cool capability to have in a single instrument) but for the price I paid for the 8901A I can't complain.

73 John
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Tom WA3KLR
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« Reply #4 on: March 27, 2006, 03:28:20 PM »

John,

I have the 8568B Opt E96 version, spec'ed at 1 kHz. to 1.5 GHz.  There is only one r.f. input BNC connector, whereas the full 8568B has 2 BNC's - one for down to 100 Hz. dc coupled and one for 100 kHz. on up to 1.5 GHz. ac coupled.

I have found that my unit is just useable down to 100 Hz.  I think the 1st l.o. phase noise may be a hair more too, as the lowest resolution bandwidth is 30 Hz.  It is 10 Hz. on the full 8568B.  I think these units were for a government surveillance contract, is my guess.  They are very sensitive as is.  Nevertheless, a great acquisition.

I bought a bare bones tracking generator off of ebay also to go with the analyzer.  It is the 8444A Opt 059.  As I recall, I paid about $150 for it; works great.

The 8901B can measure the distortion of the demodulated 400 Hz. and 1000 Hz. audio tones also.
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73 de Tom WA3KLR  AMI # 77   Amplitude Modulation - a force Now and for the Future!
John K5PRO
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« Reply #5 on: March 27, 2006, 04:38:40 PM »

We just scrapped our favorite Hp 8568B S/A at work, as it finally died after 20 years of use. Still have the books for it sitting in a box. Picture went blank, HV was OK though. Appears to be a controller problem, as it won't start up without having the cable between the two units unplugged, then it lights up CRT, but none of the buttons responds.
Agilent won't touch it now. Only option would be for some non-Agilent repair/cal depot to take a look, but it could be costly to fix that. I was told by an old friend who worked for HP in Loveland, that a lot of the old instruments had very obsolete parts in them, esp the controllers, ROMs, could not be found anymore. We loved that box despite the size and two men needed to haul it around. None of the newer HP units touched it in RF performance, although many had more digital whiz bang features.

I am looking to replace it, actually with something digital, the new Tektronix RSA series of real time DSP analyzers looks like it is quite useful. It is the result of a Sony/Tek venture.

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w3jn
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« Reply #6 on: March 27, 2006, 07:37:11 PM »

The HP 859x series are Fine Business specans and damn near bulletproof.  We've shipped these things all the way round the world countless times - some are now nearing 20 years old - and I cna think of only a couple failures out of the 50 or so we have in that time.

I don't like Tektronix specans, nor do I like their digital scopes.  The analog ones were teh shitz, though  Grin
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WA1GFZ
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« Reply #7 on: March 27, 2006, 07:52:26 PM »

the guys I work with love Lecroy with opposite controls as the tek scope.
Don't ever get on their mailing list they never go away.
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w8khk
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« Reply #8 on: May 25, 2022, 04:21:27 PM »

Scored one of these on eBay last week - anyone here used one?  Looks pretty cool, peak/average mod percentages, demodulated audio output with .1% distortion, frequency counter, etc all in one package.

The good deals are still out there.  But it took lots of patience to wait for one to come along with my name on it!  Winning bid only $78.00  Total cost $121.21 including tax and shipping.  John, thank you for the suggestion!

The seller has a good track record; I have purchased from him previously.  His products are packaged well.  Now we just have to trust FedWrecks.


* PayNow.JPG (97.63 KB, 1240x640 - viewed 36 times.)
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Rick / W8KHK  ex WB2HKX, WB4GNR
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w3jn
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« Reply #9 on: May 25, 2022, 06:59:59 PM »

Great score!  These things are really great - one of the best things about them is they have a very low distortion AM detector.  You can feed the IF of your RXer to this end enjoy FB audio.
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w8khk
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« Reply #10 on: May 27, 2022, 08:57:56 PM »

Thanks, John.  I have the QIX mod monitor, and just today I received the K7DYY mod monitor from Bruce.  It will be interesting to see how the three devices correlate.

I know the HP 8901A will make an excellent detector for AM, but there are also many other applications for the instrument.  They have some resources and app notes on the Agilent / Keysight web, all free downloads.  One is targeted to field engineers (sales reps) but they encouraged sharing it with customers as well.  After working for HP for many years, I later retired from Agilent Colorado Springs in 2006.  I drooled over so many of their instruments, never imagining I would ever afford any for myself!  And yet Fed-X will deliver my new toy tomorrow!  It is great that Keysight still makes these resources available!
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Rick / W8KHK  ex WB2HKX, WB4GNR
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« Reply #11 on: June 01, 2022, 08:27:57 PM »

One thing that many receivers, even good communication receivers and thiose considered 'hi fi' need is a better demodulator or detector. Maybe not the 8901 but something that has cleaner audio.
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