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Author Topic: Calibrating old signal generator with modern transceiver  (Read 6673 times)
AC5UP
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« Reply #15 on: September 09, 2012, 10:21:57 AM »

A guy I knew from North Carolina very unkindly called New Jersey the 'Garbage State'.

Nahhhhhhhhhhhhhhhhhhhhh................... The official motto is " The Garden State ".

New Jersey only smells like the garbage state.     Tongue
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G3RZP
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« Reply #16 on: September 09, 2012, 10:33:29 AM »

Go down to the south west corner, and New Jersey is quite pretty. More than I can say about the parts of Delaware that I've seen.
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AC5UP
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« Reply #17 on: September 09, 2012, 11:19:49 AM »


What a coincidence!  That's approximately where Vinnie lives...  http://files.qrz.com/y/n4nyy/N4NYYqrz.jpg

Or, as they said in Cape May when he moved in:  " There Goes The Neighborhood "



BTW:  " There Goes The Neighborhood "  is also the epitaph on Rodney Dangerfield's headstone.

http://farm3.staticflickr.com/2453/4038021092_8c2189ec80_z.jpg

Gotta' admire a guy who always finished on a laugh.
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N4NYY
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« Reply #18 on: September 09, 2012, 12:13:10 PM »

Quote
Go down to the south west corner, and New Jersey is quite pretty. More than I can say about the parts of Delaware that I've seen.

Yep! Exactly where I live. Gorgeous down here !
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WB2WIK
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« Reply #19 on: September 09, 2012, 06:50:54 PM »

Problem with a lot of those low-end "signal generators" (which are really just tunable oscillators) is they leak, they drift, they have harmonics...I never found any of them to be particularly useful for anything relating to ham radio.

A 55 year-old Measurements model 80 or 45 year-old HP 608 is a much better standard, although they build strong muscles in more ways than Wonder Bread.

I've seen 1976-vintage HP 8640Bs on the market for a few hundred dollars, and if they work, that's an amazing deal.
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K3STX
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« Reply #20 on: September 09, 2012, 07:01:32 PM »

I never found any of them to be particularly useful for anything relating to ham radio.

Steve, with all my futzin' around with this thing I am thinking you are right.

paul
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G3RZP
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« Reply #21 on: September 10, 2012, 12:20:10 AM »

Heathkit AF generators are fine: the RF ones, like most cheap RF generators, are just toys, hardly capable of doing service work on BC radios.

With the HP606, make sure you have spare tubes: from memory there's a compactron in there that's not so easy to find. HP8640s have a transistor in the oscillator made of unobtainium: there is a way of fixing that - the article is in an old edition of QEX.

With sig gens, because of the shielding that's needed to be any good, you can almost say that if you can lift it with one hand, there's not enough shielding.
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N4NYY
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« Reply #22 on: September 10, 2012, 03:35:40 AM »

Quote
I've seen 1976-vintage HP 8640Bs on the market for a few hundred dollars, and if they work, that's an amazing deal.

Well, I had a Wavetek 3000 crap out on me that I paid $225 for. The HP8640 will run about $400 in known working and calibrated order.
That is not cheap. These are better if you are tuning a high end PLL unit like a modern ham rig or receiver. However, for a boat anchor or old BCB radio, these should work fine.
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G3RZP
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« Reply #23 on: September 10, 2012, 04:23:35 AM »

I got  a pair of UK 1960s made ones, 30kHz to 30MHz, metered,  well double shielded, with a good  attenuator manufactured in a custom  diecast block, for $50 - second hand of course... 6J6 RF oscillator, 6SN7 AF osc and modulator, 6X4 rectifier. Extremely accurate frequency calibration, too.

This is the difference between the very cheap, and the next level up. The level up after that is the HP606 or the Marconi TF144H, after which we start seeing the solid state ones. One point about the tubed generators as opposed to the early SS ones, is that they are generally much better on phase noise.
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AC5UP
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« Reply #24 on: September 10, 2012, 06:59:58 AM »

However, for a boat anchor or old BCB radio, these should work fine.

Up to a point........... As long as you give the generator adequate warm up time, can check it against a frequency counter, and it does not have the word "Heathshkit" anywhere on the cabinet. That's the Chippewa word for "throw in dumpster". An All American Five with a 455 KC IF will play perfectly well aligned to 456 KC's (Ooops!) and the local oscillator can be adjusted against local radio stations. I have enough stations at both ends of the dial that I don't need a signal generator for the RF side.

BUT.......... Try aligning a CB or anything SSB and there's a real good chance you'll do worse than the two minute tweak it got at the factory. Low-end generators do not have adequate tuning accuracy at the higher frequencies. In some cases the backlash in the dial makes them near worthless, in others the highest band covers 13 to 30 MC's in less than one turn of the big knob. Then you realize why the F band is called the F band. Either way, on a dual conversion or SSB radio the IF at 6950 KC's had better be aligned to 6950 KC's or you'll be talking to yourself at the truckstop.

FWIW: My first signal generator was an RCA that looked like this: http://www.jollinger.com/radio/images/other/RCA-WV-49A.jpg I spent many an evening doing craptastic alignment work with that generator. This was in the late 60's when a good used car cost less than a frequency counter and I was foolish enough to assume the dial was accurate. After all, it's precision test equipment like an Iggy-42. The I/O jacks accept a car radio antenna plug which is better than a one button mic connector, but not by much.

Then I stepped up to one of these in the late 70's: http://www.radiomuseum.org/forumdata/users/6435/articles/service/URM25.JPG More than adequate for 90% of what I wanted although it's not uncommon for them to need re-capping at this stage of their life cycle. Not the easiest piece to work on, but beautifully built and when working as God and the DoD intended is a very fine piece of test gear. One nice feature is that it covers 10 KC to 52 MC. Which means you can plug it into an audio amplifier and piss off dogs...........

Currently on the bench is one of these: http://pictures1.kyozou.com/pictures/_15/14127/14126752.jpg

That's what an HP 8640B looks like when option 323 is specified by the US Navy. An hour or so of sanding followed by two coats of Krylon dove gray can address the yellow case issue. Some of you may choose hammertone green instead. As much as I like the URM-25D after it was recapped, the HP is Da'Bomb. Takes up half an acre on the bench but it's worth it. AM & FM from 500 KC to 256 MC with enough slack at the bottom end to reach 455 KC. When mine arrived from eBay it was DOA. The interconnect harness between the PA and attenuator had been unplugged. In some cases mil equipment has to be de-functionalized (is that a word?) before it can be auctioned as "parts". Maybe that's why the cable was pulled, or maybe someone wanted a newer generator so this one "broke" at a convenient time. Either way, plays great, very stable, looks muy macho but has a slow drift that's easy to deal with unless it's warmed up for three hours. Apparently there's enough mass in the aluminum castings that the internal heater needs time to reach equilibrium. Book says run it 24/7. Nope, not gonna' do that. The consumer version has a PLL to compensate.

One thing I get a kick from is the dot-matrix LED display for the counter... Dial up any frequency in CW mode, flip it to FM and watch the display blur.

As it should.    Grin
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K3STX
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« Reply #25 on: September 10, 2012, 07:19:24 AM »

This is the difference between the very cheap, and the next level up.

In all seriousness, if units like this cheap Eico 324 are "pretty" useless, who was buying them and for what purpose?

My goal is not to align an All-American Five, it is for an HQ-170A or an SX-71 or NC-300. I think I will leave these alone: if I REALLY want them aligned I would be better off finding a friend who has some time and an interest in Scotch.

paul
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W2RKJ
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« Reply #26 on: September 10, 2012, 07:40:40 AM »

Well, I hope all of you posters are getting a good laugh today. Check the following link: http://content.usatoday.com/communities/ondeadline/post/2012/09/10/trenton-mayor-corruption-fbi-tony-mack/70000032/1

Man, are all of the politicians corrupt in this state. Me thinks AC5UP had a valid point!
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AC5UP
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« Reply #27 on: September 10, 2012, 08:10:34 AM »

In all seriousness, if units like this cheap Eico 324 are "pretty" useless, who was buying them and for what purpose?

In the 60's they were bought for exactly the same reason you bought yours..... Small, cheap, and probably close enough for casual use with old radios. And don't forget that back in the day when 10% carbon comp resistors were typical a VTVM within 2% on DC volts was perfectly acceptable. Today that's 10x worse than the cheapest DMM from Harbor Freight.

Your expectations are much higher because 60 years and the transition from analog to digital made a huge difference in what's considered "normal".
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AC5UP
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« Reply #28 on: September 10, 2012, 08:13:34 AM »

Me thinks AC5UP had a valid point!

First time this year..... Thanks for noticing!

BTW: There's a rumor floating around the internet that says the reason Mitt Romney refuses to release more than two years of tax returns is because the numbers show he's doing better today than he was four years ago.......  Shocked
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G3RZP
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« Reply #29 on: September 10, 2012, 08:28:20 AM »

There's a lot of 8640Bs around, and I really loved them, essecially if you have the LF extension unit. You needed a good strong bench, though when you had three of them stacked up with a 8568 spectrum analyser alongside! The only thing that would make me cautious about them these days is the amount of unobtainium in them: you can spend a lot of time getting around that if you get a failure.
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