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Reviews For: HP-8640B

Category: Tools & Test Equipment for the amateur radio work bench

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Review Summary For : HP-8640B
Reviews: 12MSRP: Available used.
This is a signal generator that covers 455kc to 510 mhz and is one of the best signal generator available on the used market from $400.00 to the $1000.00 range.
Product is in production
More Info: http://Sold use from
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
K8PD Rating: 2022-10-05
Versatile - Rugged - Accurate - Spectrally Pure Time Owned: more than 12 months.
I've used the HP-8640B professionally since the early 1980's in an engineering lab and consider it one of the best RF generators out there. The ruggedness allowed us to use it in the field as well as on the bench.

The 8640B was manufactured for nearly 20 years which is a testimony to customer demand, and it's still considered highly desirable. Parts, sub-assemblies, and repair and calibration are available at affordable prices.

The generator is easy to use, stable and very versitile. My 8640B supplements by HP-8921A service monitor when I need to do 2 generator tests. The manual is well written and complete including all the information needed to repair and calibrate the generator.

There are a couple of well known and documented mechanical weaknesses in the slide switches and range selection gear train. HP used nylon gears that crack over time, but replacement machined brass gears are available if a rebuild is needed. Given that most of the units are now 30-50 years old, it's not unreasonable to expect mechanical parts to wear out.

Overall ... The 8640B offers an affordable high performance RF generator option for hams and hobbyists at an affordable price. I wouldn't part with mine.
KB4RK Rating: 2022-04-28
AM/FM Alignment Workhorse Time Owned: more than 12 months.
I have been using the 8640B since the early 90s, first in the Navy then as an avionics technician. Now I own and use the 8640B to align shop equipment and radios. The unit is built like a tank, has easy to use and logical controls and has always been spot-on in terms of accuracy. I find the HP manual to be more than sufficient to do the job whether servicing or operating but do think the authors were paid by the word as the manual is as big and heavy as the unit; I’m exaggerating a little, although it’s the largest manual on the shelf. My unit came from Electronics Revisited out of Princeton, MA, with new gears, as the originals, nylon I think, are known to crack eventually. Besides the highly accurate and adjustable AM and FM modulated outputs (455 kHz to 512 mHz, option 2 to 1,024 mHz) the 8640B has a very accurate frequency counter. Lastly, because of the high quality construction and engineering you’ll find it straight forward and relatively inexpensive to service. Even if you don’t want to service it yourself, most shops charge a flat fee of about $250 to $300, as of this review, April 2022. There are still plenty of good working units on the market under $1,000 (which used to be a lot of money!?!) but in perspective if you purchased a new version today prices would start at $8,700 and probably not built half as well. Two thumbs up from me for the $8640b.
Note: these units are Not currently in production and the eHam link to landaircom is no longer valid…
G8DLH Rating: 2022-02-16
Big plusses & huge minuses! Time Owned: more than 12 months.
I'm a qualified & experienced electronics engineer, spent many years in Gov't. and industry, all disciplines and technologies; service, production and R&D; 50+ years; I have my own well-equipped electronics w/shop at home.

I've owned an HP 8640B for over 10 years and during that time it has worked flawlessly, except for the need to replace the Delrin bevel edge gears (I had custom ones made from brass). Recently, the gears for the fine tune modulation freq. broke up: had replacements made and fitted them. And this S.G. has never worked properly since: no F.M.; reason: cannot identify.

What I did discover, after many days of research, is that this S.G. was physically built with no thoughts of prospective maintenance whatsoever. And the manual is utterly terrible: full of errors and inconsistencies, very difficult to discover information, etc., etc.

Here, on this Web Site, K7LZR has stated:
"Easy to service and maintain".
Utter rubbish! Nothing, absolutely nothing, could be further from the truth.
In all my 50+ years of working with - and overhauling - electronics T & M equipment, HP's / Agilent's 8640B is the most nastily designed, built and documentated item I have ever met. I could easily add several pages here, listing all the defects that HP have clearly & deliberately put into this S.G. by design.
But to conclude: when it's working, it is a really useful piece of Test kit. But if it develops a fault (of which there are many opportunities for it to do that). don't waste time trying to repair it: just put it out with the trash.
W5CRY Rating: 2013-11-17
Great Generator Time Owned: more than 12 months.
I purchased an HP-8640B from an auction site some ten years ago and it has performed reliably, until recently, when the frequency display became erratic. Two known problems with this instrument is the little contacts on the Frequency/FM Selector Switch or cracked or broken gears in the assembly. After some research on the internet, I found Electronic Revisited. Bill the owner is an absolute encyclopedia of knowledge about the 8640. He was most helpful via email and offers an 8640B repair service. In the end he rebuilt my Switch Selector Assembly and my trusty 8640B is back to working great ! There is a gentlemen in Italy who is manufacturing new gears for the 8640B, I purchased a set just for future insurance and found them to appear to be very good quality.
AC5UP Rating: 2011-05-21
Built To Survive! Time Owned: more than 12 months.
I have the Navy version configured with Option 323. Once you get past the bright yellow find-me-under-water case (which I repainted with Krylon dove grey) it's an intuitive generator that's very easy to use.

Mine was an ePray bargain that arrived DOA. Opened it up to find the cable harness between the RF PA and output attenuator had been unplugged. There is no way this just happened. Best guess is that's how they're de-milled prior to auction. I re-attached the harness, added a Ty-Rap to keep it that way, and it hasn't missed a beat since.

HP built these like Steven Spielberg built Jessica Rabbit. Absolutely outstanding. Spot-on dead accurate and stable -after- it has achieved run temperature which takes 30-45 minutes. The mil version does not have the PLL frequency lock so there is a slight amount of drift, but I've learned that mine always drifts downward in frequency. So I set it a tad high then let it drift through the alignment frequency while I tweak. The unit was intended to run 24/7.

For all I know there's something newer, synthesized, digital and so near perfection that it's a better buy than the 8640B, but you won't find anything built better or likely to outlive one.

The full set of books are available on the Agilent web site as a free download.
WA4AOS Rating: 2010-08-28
EXCELLENT GEN Time Owned: more than 12 months.
I have a small business where I primarily restore R 390, R 390A and R 392 receivers. I own 3 of these generators, one for each bench and they are outstanding. There is a fellow out of TX named Gene who restores these beast and sells them on epray. His units sell for about $900 with 01, 02 and 03 options. The test equipment companies sell them for about the same but they are often dogs. Gene's units are clean and he does an excellent job getting them right.
These gens are rock solid and very clean. I have used them for experimental filter design work and could not be more pleased.
The one down side is many of the gears up front are special and made of plastic, It is common to find them cracked. I have a few parts queens on hand to rob from should I need to later.
I have worked on lots of very complex and well made electronic test gear, receivers and transmitters. The 8640B is probably the most well made piece of equipment that I have worked with. This unit was made for serious long term applications and will hopefully serve me for the duration.
W8AAZ Rating: 2009-03-19
Heavy but clean spectrum Time Owned: more than 12 months.
I have used or owned these in the past quite alot. Both the mil. version and the commercial. Of course the mil. version does not have the freq.lock feature and requires a long warm up. And it is built like a tank. Nothing flimsy. HP's golden age of hi grade test gear. The thing has a UHF cavity oscillator for tuning, and divides it down for the lower ranges, thus lower freq ranges have less and less drift. For testing bandpass of receivers, the clean carrier is a boon. Some of the synthesized generators are not as clean. SO if you are testing a rx. for the minus 60 selectivity response, the noisier synth. units will give a falsely broad skirt response. Downside is the weight and size. IF you got the room for it, you can't go wrong with a good HP. Somewhat outdated in appearance and controls.
N4UE Rating: 2008-10-24
A 'standard' Time Owned: 3 to 6 months.
Hi. I have a bunch of HP Signal Generators. Most are of the 606 and 608 vintage. Although excellent, the 608s lack coverage below 10 MHz. I came across my 8640B on ePay, er, eBay. The seller stated it was in good condition and "works as far as we can tell". What the heck, I did a 'Buy it Now', for pretty cheap. The unit was packed in spray in foam and arrived in perfect shape. The only thing wrong (!!!) was that the 'Fine Tune' control was not working. There was a label on the front stating so. I used it for a while in this state (which is not difficult) until I ran across an 8640B 'guru'. He told me that the 'fine tuning' was part of the cavity and was mechanical. Heck, I opened her up and lo and behold, there was NO shaft connecting the knob to the shaft on the cavity. There is an offset to these 2 shafts, which probably accounts for the broken/missing part. I found a short piece of vinyl tubing that was a press fit on both shafts and she's back in business.

The inside of these units are just scary - beautiful!!!
If I were to nit pick, I would rather have LCD display segments rather than those 'dots'.
Once you select your frequency and "Lock" it, it will stay there ALL week!!!

Wonderful! Wish I had bought one years ago!
By the way, ALL of it's Manuals are available FREE on Aligent's website. In PDF format, they are great. Just buy stock in a paper company first!!! ha ha


SV8YM Rating: 2008-09-24
A great classic Time Owned: more than 12 months.
The HP-8640(A or B) may be a bit old, but for amateur radio purposes it just can't be beat! Its phase noise performance is exceptional, enabling dynamic testing of even the best receivers. All it requires is a bit of infrequent basic maintenance, and it goes on ticking - but even in case of trouble, it can be (relatively) easily repaired. A great instrument to own and a joy to use.
WN5EGO Rating: 2008-01-27
Great tool! Time Owned: more than 12 months.
I use my HP-8640B (with options 001, 002, and 003)
to align my R-390 and R-390A receivers, among other duties. It's a fine gadget for that. It also has turned out to be useful in aligning more modern receivers, such as the Debeg E2000, with IFs up in the VHF.

One particularly useful dodge with the 8640B, when I want to get response curves for a device, is to
drive the 8640B's FM modulation input, in DC mode,
with a linear ramp, and use the same ramp as the X-axis drive on my 'scope.

The attenuator does down to tiny levels with great
accuracy, and the shielding is good enough that
the generator just doesn't leak.

One of the options takes my 8640B up to 1024 MHz
according to the specs and about 1200 MHz in practice; the bottom end is officially 500 KHz, and in practice about 440 KHz, which covers almost
all IF's I've ever had to deal with.

I wish I had another.