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Old 10th December 2012, 04:59 PM   #1
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Default Do You Have An HP 8640B... ?

And do you love it?

I want one.

I already have a Wavetek 184 that covers 0.0001Hz to 5MHz and I'm looking at the HP 8640B to replace my Eico 315.

Tell me all about the goods and bads of this cool critter.
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Old 10th December 2012, 08:34 PM   #2
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No, I don't have one but I used one quite often many incarnations ago. At the time - and even after it had been superseded by "more modern" designs - it was perhaps the cleanest VHF generator in the galaxy. I don't blame you for lusting after that signal generator!

Dale
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Old 12th December 2012, 02:17 PM   #3
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The 8640B is meant for narrow bandwidth communications type equipment and has very low residuals. That's the good part. Now the bad, plastic gears falling apart is the common issue and its not PLL locked. A more modern replacement for it albeit more expensive is the Fluke 6071A.

Now my question to you is, what is the application you are planning to use the 8640B for? There are plenty of signal and RF generators out there but no box can do all things.
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Old 13th December 2012, 12:08 AM   #4
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Quote:
Originally Posted by hitachi_nut View Post
The 8640B is meant for narrow bandwidth communications type equipment and has very low residuals. That's the good part. Now the bad, plastic gears falling apart is the common issue and its not PLL locked. A more modern replacement for it albeit more expensive is the Fluke 6071A.

Now my question to you is, what is the application you are planning to use the 8640B for? There are plenty of signal and RF generators out there but no box can do all things.
Yes, I have read about how time affects this thing, and have been suggested the Fluke 6070A on another site (oddly enough!).

Application? Not sure. My mantra has just been to buy the best I can within my limited budget and grow my skills with the tool at hand vs. upgrading.

There's a Wavetek 2001 that I've been eyeing all week... at $10 + $28 shipping, I'm thinking that might be fun to play with for a bit, but I keep reading that it's a piece of garbage...


Building robots and general electronic projects as a kid led me into the world of vintage audio gear (dad's old receiver broke, and I fixed it at 12 y/o) and that led me into the DIY audio scene, so if I could coax it from a general tool to one that I might be able to align a tuner with (for example), that would be cool.

Last edited by thefragger; 13th December 2012 at 12:11 AM.
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Old 13th December 2012, 02:14 AM   #5
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Quote:
Originally Posted by thefragger View Post
. . . if I could coax it from a general tool to one that I might be able to align a tuner with (for example), that would be cool.
It's been over 30 years since I used an '8640 so memory is a bit hazy.

As a signal generator for development, performance evaluation, or general alignment and repair of anything used in the FM broadcast band I suspect a fully functional '8640 would be excellent. I seem to recall that it had near-PLL stability without the PLL. I believe some versions had a built-in frequency counter with 6 digits (or more?) of readout, allowing you to set the output frequency with acceptable precision. Today, stand-alone VHF and UHF counters are inexpensive and common, and could help you set an output frequency to the necessary precision.

I don't recall if the '8640 has a DC-coupled FM-modulation input or not. If it does, an external counter that provides a "discriminator" or "tracking signal" output can be used to complete the loop and provide PLL stability.

Dale
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Old 13th December 2012, 02:56 AM   #6
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The 8640A had a tuning scale with a needle (I think) and the 8640B has the built-in counter. I've also got a Philips counter that's good to 1GHz and I've got a 10MHz oven-controlled ref that I'm working on.

Sounds like an awesome endorsement, Dale--thanks!


I won the Wavetek 2001... $33 to my door. Might be useful for something... I figure what the heck.
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Old 13th December 2012, 03:13 AM   #7
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For tuner alignment specifically high end FM tuners, there are plenty of better digital display PLL-based generators from Japan that are now ~5% the original cost, i.e. $100-$300. In contrast, HP made only one low THD FM/AM bare bones generator (HP 11715A) that was meant for calibrating their other test equipments.

Most of the FM generators out there are meant for 2-way communications testing including the Wavetek you mentioned (bought in this case, too slow typing). Key specification on an FM generator is THD/distortion/linearity, the lower the number the better (best THD<0.01%/-80dB). Don't fall into the trap of buying the overpriced Sound Technology 1000A, you'll end up buying more test equipment so you can calibrate it or pay someone else to do it for you.
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Old 20th December 2012, 07:10 PM   #8
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No 8640, but I do have a HP 8656B or actually two of them. I use it for broadcast receiver design/service work.
When I worked at Motorola, in the 80's, HP8640B was used by the development engineers because it is cavity tuned and not PLL. These cavity tuned genarators had much lower SSB phase noise compared with PLL types such as 8656B. Been a long time, but I can atest to that they (8640B) were no fun to repair. I remember that the upgraded model was 8642A with an orange backlit LCD display. Still expessive as I see on ebay even today.
We used a HP 11715A test set to test out 8901A/B,8902 Modulation Analyzers for performance and calibration requirements.
Since many of these old HP pieces of equipment are dirt cheap these days, I usually have two of each, one for spare parts, since many parts are obsolete, having spares is the only option for parts.
Cheers
Rick
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