HP 8558B Spectrum Analyzer - Page 1
Forum section: electronics / testgear

author: kc9qvl
author_rank: Regular Contributor
timestamp: January 13, 2014, 09:55:12 pm
content: Looking at an HP 8558B Spectrum Analyzer and am looking for some advice.Unit is in good condition. Appears to work. This model is very old 1973 and does have a tube in it. Price is $550.00.Should I get it or wait for something newer. What would be reasonable offer. I'm not sure I'm willing to pay 500 for such an old piece of equipment. It would suit my purposes though.More info:http://www.radiomuseum.org/r/hewlett_pa_spectrum_analyzer_hp8558b.htmlhttp://www.testequipmentdepot.com/usedequipment/hewlettpackard/spectrumanalyzers/8558b.htmhttp://www.testequipmentdepot.com/usedequipment/hewlettpackard/spectrumanalyzers/8558bspecs.htm

author: Mr Simpleton
author_rank: Unknown
timestamp: January 13, 2014, 10:42:34 pm
content: Not so sure it is worth 500 thoughIf you're lucky you may find a HP8590 for a few hundred more, that would be much better instrument.Still if money is thight and you need a spec... go for it, it's lots of fun!But try get it cheaper... try a low ball offer

author: G0HZU
author_rank: Super Contributor
timestamp: January 13, 2014, 10:58:49 pm
content: If you just want to use it for basic ham radio and homebrew testing then it would be a useful bit of test gear.The plus points are that it doesn't take up much bench space and it is a plug in type so even if one part of it fails you can swap out the mainframe or the plugin if it proves difficult to repair.The negatives are that it is a very basic instrument with fairly modest RF performance and is very old and $400 is probably closer to its true value so it definitely isn't a bargain at $500.Also, the lower the RF performance at the front end, the harder you have to work the instrument to get a valid measurement (i.e. one with minimal uncertainty)For example, to measure harmonics reliably at -50dBc would require quite careful use of the instrument to minimise uncertainty (due to the relatively poor linearity of the receiver front end)But go back 25 years and that analyser would have been a serious bit of kit to have at home even for a semi pro designer of ham homebrew stuff. However, these days you can buy an HP8568 for a similar amount if you are patient and this is a fabulous analyser. But it's also very big and heavy and noisy and could be costly to maintain.

author: pomonabill221
author_rank: Frequent Contributor
timestamp: January 14, 2014, 06:44:54 am
content: Also, doesn't seem to have a tracking generator which can be very useful but not necessary.I am not familiar with this model, but that is the first thing that came to mind.

author: nctnico
author_rank: Super Contributor
timestamp: January 14, 2014, 09:07:31 am
content: I wouldn't pay that much either. It looks pretty clean though. A problem with this old equipment is that the switches can be worn making it useless (no contact spray won't help because the contact material is gone). If it smells like contact spray just walk away.

author: kc9qvl
author_rank: Regular Contributor
timestamp: January 15, 2014, 11:28:50 pm
content: I think I will hold off on it. If I offer the guy what its worth I'll probably just upset him.

author: G0HZU
author_rank: Super Contributor
timestamp: January 16, 2014, 12:15:31 am
content: It's a difficult one to call really...If it wasn't for the fact that the used test gear market is now being flooded from industry with unwanted HP8568 and HP859x analysers at ever tumbling prices then that analyser would easily be worth the money today.If you only want it for basic homebrew design testing plus ham related transmitter verification then it has a lot of plus points against the big old flagship analysers like the HP8568. (these can be bought from $500 to $1500 on ebay if you are very, VERY brave)If it only has to do the above ham tasks then what really matters for your 500 bucks is if it keeps working OK for a few years. I would expect it will prove more reliable than an HP8568 over the course of 5 years assuming you don't abuse it or run it for many hours most days.Al lot of the mainstream big bucks analysers on ebay will have been run for several hours every working day for maybe 15-20 years and some even longer than this if they are on an ATE rack. So they are starting to become uneconomic to maintain and are being dumped on ebay.If the little 8558 has seen a fairly quiet life then it could prove far more reliable despite it age...

author: willb
author_rank: Regular Contributor
timestamp: January 16, 2014, 03:04:09 am
content: I paid slightly more than 500$ for a 8591A so I don't see this as being a good deal. If you are patient, better deals are to be had.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: January 16, 2014, 03:04:48 am
content: Hi,Correct me if I am wrong.This unit is not synthesized so the frequency accuracy is not that great, +/- 1 MHz below 195MHz and +/-5MHz for frequencies 195-1500 MHz. This is o.k if you know what frequency you are looking for.The HP8590A is also not synthesized and has similar frequency accuracy. Other members of the 859x family are synthesizer tuned. This makes them much easier to use.I am not sure about the amplitude accuracy of the unit in the picture. I can not read the ref level setting on the left hand knob. The signal from the calibrator is -30dBm. For the display to be correct the reference level would have to be +20dBm.This generation of equipment suffers from 'switch rot'. Each of the rotary switches are one more little contact attached the plastic part by melting the plastic. After 25 years or so the nylon dries out and the contact fall off. The symptoms are that some of the switch setting don't work. It is a lengthy job to disassemble the switches and fix these.Check it out carefully...Jay_Diddy_B

author: JoeyP
author_rank: Frequent Contributor
timestamp: January 16, 2014, 05:23:26 pm
content: In another life, I used to work on these (and many other instruments) for a living. The issue with the switch contacts can be permanently eliminated if you get to it before the contacts fall off. I used to drill out all of the plastic staking which held the contacts on, and replace them with 0-80 screws. Though it is a bit of work, this made them 100% reliable for years and years.It is true that these are not synthesized/phase-locked, which makes them not so useful for narrow bandwidth measurements. That's really the limiting factor with the RF performance. They have about the same front-end as much higher end HP units, but without being able to measure in narrow resolution BW's, the noise floor appears higher.$550 does sound high. They're very reliable and easy to use units once you do the contact mod (unlike Tek plug-in SA's which are total crap). However, that's a very early unit from the series. Newer units had multi-color screen printing on the knobs. I'd be thinking more like $300 for this one.

author: babysitter
author_rank: Frequent Contributor
timestamp: January 16, 2014, 09:29:17 pm
content: Talk about the price to the wannabe vendor; i find it a bit on the high end. This machine was my big dream as a young radioamateur, today it is a shiny Rigol youknowwhatmodel with TG. We should compare which machine is in which condition in 20 years, right ?If you are willing to play with it; dont be upset about the missing stuff. A comb generator will tell you more about the frequency to X-pos relation. A ham I know once said he made a TG with a surplus YIG oscillator, but never documented it, but you know it is possible with this machine.

author: G0HZU
author_rank: Super Contributor
timestamp: January 17, 2014, 12:26:00 am
content: For very basic ham stuff you don't really need a synthesised spectrum analyser so it could still be useful to the right buyer if it is in good working condition and the price is right. My first analyser was a Takeda (Advantest) TR4122 in the early 1990s. This covered up to 1500MHz with a tracking generator and a front panel build quality that put HP to shame.I found it very useful despite it not being synthesised. One bonus of the older type analysers is they can support very fast sweep speeds (should this ever be needed). I eventually upgraded it to another Advantest but this time the mighty TR4172.I didn't realise that the 8558 suffered with switch problems. HP seemed to drop the ball about 40 years ago because a lot of their test gear from the late 70s and the 1980s suffers from a feeble user interface with fragile controls. I kind of hoped the 8558 would be better built but it seems not...

author: kc9qvl
author_rank: Regular Contributor
timestamp: January 20, 2014, 10:41:19 pm
content: So actually took a look at the unit. yep bad switches. So the search goes on.

author: kc9qvl
author_rank: Regular Contributor
timestamp: February 03, 2014, 11:32:14 pm
content: Have an update and a new broken toy to play with.Dealer I've been slowly getting test gear from called me with a project.A slightly broken hp 8558b option 2. Option 2 is 75 ohm impedance not a deal breaker for me.Has a broken fine fequency control shaft. Just need to turn on the lathe.Broken shaft and a couple of money shoots.

author: kc9qvl
author_rank: Regular Contributor
timestamp: February 04, 2014, 11:46:11 am
content: I got the service manual for the unit. Looks like the gear driven dual shaft frequency control was an upgrade. Extracted image from manual. Broken part is part 116.Working on removing broken shaft to duplicate and repair.Also on the mainframe seems to be missing optical filters in front of the crt. Can anyone tell me about these filters. I've seen pictures blue black and maybe green?

author: kc9qvl
author_rank: Regular Contributor
timestamp: February 05, 2014, 01:16:14 am
content: Old broken brass shaft. New shaft in stainless steel and aluminum collar to accept normal 1/4" / 6mm knob

author: JoeyP
author_rank: Frequent Contributor
timestamp: February 05, 2014, 06:10:07 pm
content: Quote from: kc9qvl on February 04, 2014, 11:46:11 amThe filters just improve contrast. The very early ones were green. Later they went to blue. I've seen the smoked ones, but never found them to be much benefit.

author: kc9qvl
author_rank: Regular Contributor
timestamp: February 06, 2014, 11:17:24 pm
content: Got unit back together man does this thing drift. At 280 mhz calibration signal drifting 100 khz a minute. We'll let the analyzer warm up a bit see if it stabilizes.

author: JoeyP
author_rank: Frequent Contributor
timestamp: February 07, 2014, 12:19:43 am
content: From what I remember, 100KHz/minute sounds typical for that unit (especially during warm-up). Consider that the 1st LO is a YIG oscillator running in the GHz range, so 100KHz is <0.01% of the 1st LO frequency, which is pretty reasonable drift for an unstablized oscillator. That's why phase-locked/synthesized LO units are so much more desirable.

author: kc9qvl
author_rank: Regular Contributor
timestamp: February 07, 2014, 01:47:29 am
content: Well been 2 hours frequency is solid no drift at all.Time to calibrate

author: JoeyP
author_rank: Frequent Contributor
timestamp: February 07, 2014, 04:24:44 pm
content: So you just need a 2 hour warm-up, and then don't breath on it

author: kc9qvl
author_rank: Regular Contributor
timestamp: February 08, 2014, 01:40:41 am
content: hehehe The house furnace turning on and off you can see the calibration signal going up and down with the temperature.

author: JoeyP
author_rank: Frequent Contributor
timestamp: February 10, 2014, 08:01:08 pm
content: Up and down only in frequency I hope. If it's going up and done in amplitude then there's a problem with the unit.

author: kc9qvl
author_rank: Regular Contributor
timestamp: February 11, 2014, 12:11:50 am
content: No just frequency. Am having much mechanical issues though. The combo attenuation/reference level is worn and some @$$ used a bucket of loctite on it. The push in/pull out is damaged and not repairable. Ended up revising the controls. Trashed the original knob removing it. Reworked the internals a bit. Fabbed new knobs. Bringing out the attenuation with a separate knob. The attenuation indicator will still function The gear will be reinstalled just driven from other knob. This turning into a project.

author: 440roadrunner
author_rank: Contributor
timestamp: February 14, 2014, 02:57:24 am
content: I cannot answer your question directly. However, there has been a LOT of HP literature written about these, evidently they were quite popular. Go to the Agilent site, and find and download the applicable application notes. You can also find these on Ebay. Also, if you feel rich, you can put those RF modules (I think there were 3) into different display mainframes, and there is a separate tracking gen. I have both.Agilent:http://www.home.agilent.com/agilent/facet.jspx?t=79831.g.1&cc=US&lc=eng&sm=gAnother site. Look for the 150 series notes, especially. "Economy Spectrum Analyzer"http://www.hpmemory.org/ressources/resrc_an_02.htmSome of my old junk:Top photo is an 853A series mainframe with one of these RF modules installedMiddle photo,The analyzer on the left is a very old and beat up 141T series, with tracking generator on top. The one at bottom center is the 853A, with an old HP signal generator on top, the tracking gen for the 853 on top of that, and a very nice frequency counter at very top. And on top of THAT is a couple of more RF modules for the 853 analyzerTo the far left of the photo are the covered fronts of an old IFR 1000S RF monitor, and below that, an old CT Systems 3000 series. Even THAT old girl has a very poor spectral display in it.Top left, an old Tektronix scope, sitting on top of a still very useful Motorola RF service monitor. Even this old girl has a rudimentary spectrum analyzer good to 1 ghz.To the right are various sweep generators, and out of the photo is yet another obsolete HP o'scope frame which as a TDR (time domain reflectometer) installed, with what are called "amplitude swept analyzer" modules." These are the fore-runnerOn the far right of the bottom photo, and on the far left of the middle photo are two 180 series HP mainframes similar to what you have. These accept a variety of modules, depending on the specific mainframe. One is used for low frequency jobs, has an old, analog vert / horiz modules to make an Oscope, and the other usually wears a TDR module. I believe either will accept the RF analyzer modules, but not really sure.

author: kc9qvl
author_rank: Regular Contributor
timestamp: February 14, 2014, 03:03:49 am
content: Thats a nice collection of toys there.