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eHam Forums => Boat Anchors => Topic started by: K3STX on September 08, 2012, 08:53:29 AM



Title: Calibrating old signal generator with modern transceiver
Post by: K3STX on September 08, 2012, 08:53:29 AM
I am trying to calibrate my old Eico 324 signal generator so I can align some radios. But first I have to calibrate it. When I put a short wire "antenna" over my old Crosley AM radio tuned to AM630 I can get a nice signal when my signal generator dial is set to about 625 kc. OK. But when I put this SAME short wire antenna on top of my modern Kenwood TS-850S and tune it to AM630 I do not hear any of the RF coming out of the signal generator no matter how high the "gain". Is this because the Kenwood is so well shielded? How can I get the weak RF signal into the Kenwood, surely not directly hook to antenna input?

I also notice that when I tune my radio to AM630 and my signal generator to 625 kc I hear the signal. Great. But I ALSO hear a signal on the same AM630 station when the signal generator is tuned to about 750 kc. Why is that, it is not a harmonic.

paul


Title: RE: Calibrating old signal generator with modern transceiver
Post by: AC5UP on September 08, 2012, 09:41:12 AM
Is this because the Kenwood is so well shielded? How can I get the weak RF signal into the Kenwood, surely not directly hook to antenna input?

Yeah, it's because the Kenwood has a metal case and is better shielded than the Crosley. The signal generator has an output attenuator and level control which should provide an adequate level for receiver test & alignment. If the generator is still too hot at the lowest setting couple the output through a very small condenser, like 3-5 mikemike, or the highest value resistor in your junk box to the Kenwood antenna jack. Also wouldn't hurt if the generator output was terminated by 75 Ohms.

BTW: Broadcast stations are usually very close to spot-on frequency so if you have two good stations, one near the bottom of the band and the other near the top, your best accuracy should be in zero-beating the generator against those stations. Set the generator dial to exactly the same frequency then align the appropriate slug or trimmer to zero beat. If the Kenwood has an internal calibrator with 100 KC steps that's also good. Check the calibrator against WWV for the helluvit.

I also notice that when I tune my radio to AM630 and my signal generator to 625 kc I hear the signal. Great. But I ALSO hear a signal on the same AM630 station when the signal generator is tuned to about 750 kc. Why is that, it is not a harmonic.

This has the makings of a math problem. With a strong signal and a lo-tech superhet it is possible to hear a signal image 455 KC's (typical) above the actual frequency. In your case the differential is 125 KC's and that's an odd IF frequency. It's also possible your EICO needs a little TLC as a weak output tube is being overdriven and throwing spurs. Another possibility is signal overload, and that's why alignment work is always done at the lowest usable signal level. You do not not want the receiver AVC kicking in to mask a signal peak. Another thought involves an unterminated output jack being a bad idea. Your best bet is to consult the EICO user guide to refresh your signal generator-fu if you haven't done so recently.

Nostalgia Air has one here:  http://www.nostalgiaair.org/References/Manuals/EIC/EIC_10.zip (http://www.nostalgiaair.org/References/Manuals/EIC/EIC_10.zip)


Title: RE: Calibrating old signal generator with modern transceiver
Post by: G3RZP on September 08, 2012, 09:41:48 AM
If the '750' is actually 770, (we know already the calibration is a bit off) and the Crossley has a 455 IF, then twice 770 is 1540, minus 910 (twice the Crossley IF) gives 630. So the second harmonic of the generator is on the image frequency of the Crossley.


Title: RE: Calibrating old signal generator with modern transceiver
Post by: N4NYY on September 08, 2012, 09:43:42 AM
Should have gotten a Heathkit IG-42

LOL


Title: RE: Calibrating old signal generator with modern transceiver
Post by: AC5UP on September 08, 2012, 09:46:48 AM
What do you have against K3STX ?

It's not like he swapped out the selenium rectifier for silicon and is suffering from circuit ground disorientation........   ::)


Title: RE: Calibrating old signal generator with modern transceiver
Post by: N4NYY on September 08, 2012, 01:01:02 PM
What do you have against K3STX ?

It's not like he swapped out the selenium rectifier for silicon and is suffering from circuit ground disorientation........   ::)

I think the Igggggggggy is better than the Eico. It is shielded everywhere, including the attenuator.


Title: RE: Calibrating old signal generator with modern transceiver
Post by: G3RZP on September 08, 2012, 03:03:18 PM
Dunno about the US, but over here, the test gear wasn't in Benton Harbor green....


Title: RE: Calibrating old signal generator with modern transceiver
Post by: AC5UP on September 08, 2012, 04:31:56 PM
I think the Igggggggggy is better than the Eico.

Don't make me bring out an empty chair and pretend you're sitting in it........................
The EICO was made in Flushing (Queens), NY and and that's almost like New Jersey.    But with a GED.     :P

UPDATE: Holy Toto !!! Just heard the news a tornado touched down near Rockaway (Queens), NY this afternoon.
I'm visualizing a young girl and her little dog swept up by the tornado. They end up in New Jersey. Where they follow a yellow brick road to a crack house...


Title: RE: Calibrating old signal generator with modern transceiver
Post by: W8JI on September 08, 2012, 06:37:29 PM
I am trying to calibrate my old Eico 324 signal generator so I can align some radios. But first I have to calibrate it. When I put a short wire "antenna" over my old Crosley AM radio tuned to AM630 I can get a nice signal when my signal generator dial is set to about 625 kc. OK. But when I put this SAME short wire antenna on top of my modern Kenwood TS-850S and tune it to AM630 I do not hear any of the RF coming out of the signal generator no matter how high the "gain". Is this because the Kenwood is so well shielded? How can I get the weak RF signal into the Kenwood, surely not directly hook to antenna input?

I also notice that when I tune my radio to AM630 and my signal generator to 625 kc I hear the signal. Great. But I ALSO hear a signal on the same AM630 station when the signal generator is tuned to about 750 kc. Why is that, it is not a harmonic.

paul

Paul,

Modern radios are shielded pretty well inside, not so much the cabinets. The RF and IF sections are very immune to all sorts of leakage issues, partly because they are on a PC board with groundplane and also because of board level shielding.

It would not hurt a thing to couple directly into the RF port of the radio.

RZP answered most logically about the 750 signal. The 455 IF image is 910 above the tune frequency. So the radio's image would be 630+910 = 1540 and you have the generator on half of 1540.

You can confirm an image this way. If you reduce the generator level and get a beat tone on the AM radio station, the pitch you hear from an image will change as you tune the radio without tuning the generator. 



Title: RE: Calibrating old signal generator with modern transceiver
Post by: K3STX on September 08, 2012, 08:45:00 PM
Thanks to all. Lots to think about. My Eico "antenna" is alligator clips to a loop of wire, perhaps I should use shielded cable instead of jumpers. I will work on identifying the real signal from the many images. I think it will be a LONG time before I use this calibrator to align my recently fixed HQ-170A (that is working perfectly fine, could even hear NH8S tonight on a dipole).

Paul


Title: RE: Calibrating old signal generator with modern transceiver
Post by: W2RKJ on September 09, 2012, 07:20:08 AM
Hey AC5UP, did somebody from New Jersey pimp slap you or did you have a ex-wife from the Garden State? If it's the ex-wife, I can understand the thoughts.


Title: RE: Calibrating old signal generator with modern transceiver
Post by: N4NYY on September 09, 2012, 07:33:15 AM
Hey AC5UP, did somebody from New Jersey pimp slap you or did you have a ex-wife from the Garden State? If it's the ex-wife, I can understand the thoughts.

He lived here!


Title: RE: Calibrating old signal generator with modern transceiver
Post by: AC5UP on September 09, 2012, 07:38:08 AM
A few years back I caught Triumph The Insult Comic Dog on one of the NBC late night shows and he was doing interviews at some music festival or similar... Interviewee says he's from Long Island, and Triumph says "Oh, yeah, Long Island. That's like New Jersey... Except with a GED". That was my first clue that New Jersey might be good for a cheap laugh. Then I met N4NYY in this forum. Suspicions confirmed....................   ;D

http://triumphtheinsultcomicdog.com/ (http://triumphtheinsultcomicdog.com/)


Title: RE: Calibrating old signal generator with modern transceiver
Post by: W2RKJ on September 09, 2012, 08:15:00 AM
I didn't catch that but I wish I had. I love a good line especially when that door opens and a good one slides in there.  Thank you.


Title: RE: Calibrating old signal generator with modern transceiver
Post by: G3RZP on September 09, 2012, 09:03:27 AM
A guy I knew from North Carolina very unkindly called New Jersey the 'Garbage State'.


Title: RE: Calibrating old signal generator with modern transceiver
Post by: AC5UP 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.     :P


Title: RE: Calibrating old signal generator with modern transceiver
Post by: G3RZP 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.


Title: RE: Calibrating old signal generator with modern transceiver
Post by: AC5UP 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 (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 (http://farm3.staticflickr.com/2453/4038021092_8c2189ec80_z.jpg)

Gotta' admire a guy who always finished on a laugh.


Title: RE: Calibrating old signal generator with modern transceiver
Post by: N4NYY 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 !


Title: RE: Calibrating old signal generator with modern transceiver
Post by: WB2WIK 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.


Title: RE: Calibrating old signal generator with modern transceiver
Post by: K3STX 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


Title: RE: Calibrating old signal generator with modern transceiver
Post by: G3RZP 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.


Title: RE: Calibrating old signal generator with modern transceiver
Post by: N4NYY 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.


Title: RE: Calibrating old signal generator with modern transceiver
Post by: G3RZP 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.


Title: RE: Calibrating old signal generator with modern transceiver
Post by: AC5UP 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 (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 (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 (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.    ;D


Title: RE: Calibrating old signal generator with modern transceiver
Post by: K3STX 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


Title: RE: Calibrating old signal generator with modern transceiver
Post by: W2RKJ 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!


Title: RE: Calibrating old signal generator with modern transceiver
Post by: AC5UP 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".


Title: RE: Calibrating old signal generator with modern transceiver
Post by: AC5UP 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.......  :o


Title: RE: Calibrating old signal generator with modern transceiver
Post by: G3RZP 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.


Title: RE: Calibrating old signal generator with modern transceiver
Post by: N4OI on September 22, 2012, 06:31:08 AM
I just have to ask so I can perhaps learn something....   I have a basic LodeStar SG4060b RF signal generator with a very rough-cut analog frequency adjustment.  When I want to set it with any accuracy, I just zero beat with one of my nice digital receivers that is set to the desired frequency.  I then know that my signal generator is right-on frequency, regardless of its analog dial setting.  This approach is very quick and I think is providing the level of accuracy I need.  Please let me know if I am missing anything here.  Thanks!

73 ES GOD BLESS U ES URS DE KEN N4OI  ;D