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Signal Generator Help - Printable Version

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Signal Generator Help - captainclock1988 - 04-16-2020

Hello everone I just put in an offer on fleabay for a Radio City Products Model 705A Signal Generator and it appears to have at least its RF Probe still the AF Probes don't appear to be present but look to be a standard banana plug style probes which would be fairly easy to acquire or make new ones. 

If they accept my offer I would be getting it for $25 plus $25 shipping, which is the cheapest I've seen them go for, as they seem to go for as much as a couple thousand for a high end Hewlett-Packard unit without its probes which I think seems a bit over priced for a piece of equipment that not many people use anymore, except radio repair hobbyists like us.

My question is, how does one work one of these, and can one find the manuals for these things online? I was thinking that the Boat Anchor Manual Archive would be one place that should have manuals for signal generators like this but I'm not sure.

Any help would be appreciated in this subject.

RE: Signal Generator Help - captainclock1988 - 04-16-2020

A link to the signal Generator in question is posted below.

Signal Generator Listing

RE: Signal Generator Help - morzh - 04-16-2020

Keep in mind you will have to recap it, plus the rest, same as you would any old radio.

RE: Signal Generator Help - captainclock1988 - 04-16-2020

Yes, I realize that, although the unit I was initially asking about in this post no longer applies because I ended up getting a Heathkit SG-8 Signal Generator that ended up costing me much less than what this one would of costed me. 
It doesn't have probes (it uses the large screw-on type probe connectors) but I figure since its a Heathkit finding some probes for it shouldn't be horribly hard, or making some even.

But I will still need information on how to use it the signal generator and how to find the manual for it.

RE: Signal Generator Help - morzh - 04-16-2020

I have an SG8. I think I just googled it.

Like so.

SG-8 Heathkit.

The very first pdf is it.

RE: Signal Generator Help - captainclock1988 - 04-16-2020

Found the manual.

What kind of cabling and connectors do you need to make the test probes, I saw in the manual that it originally used alligator clips for the ends that connect to the circuit, but the end that connects to the signal generator itself I'm not sure what kind of connector that is.

RE: Signal Generator Help - morzh - 04-16-2020

https://forums.qrz.com/index.php?threads/old-heathkit-rf-generator-connectors.310043/

There is one discussion about the connector.
Use 50 Ohm coaxial cable.

At swapmeets and shows there are always people selling cables.
Last thing: even if you grab the chassis and the center with a pair of wires, for a reasonably short distance of a few feet it will work just fine.

RE: Signal Generator Help - captainclock1988 - 04-16-2020

Well I ended up getting the signal generator that I originally posted about in this thread because they ended up accepting my offer so I will have 2 signal generators, but the amount I have into both of them as far as buying them is way less than I would of had by buying one of those higher end Hewlett-Packard units that were going for $300-$500 plus $50 shipping. Plus I can have a back up in case one gives me trouble.

RE: Signal Generator Help - morzh - 04-16-2020

I have 2 generators, SG8 and the LST-11 Leader.
They are essentially the same. I got the latter for $25 and two formers for $5, one of which I gave to Kirk.
Now.....these are unreliable, their waveform in many places is all but the si ewave and they might refuse to oscillate on a particular band or a part of it for no appatent reason.
They also do not lend thenselves to adjusting, so if a band is off, it is off.

I got tired of it, and bought me an HP, and...I should've done that from the start.
Yes, $200.
Precise, convenient, and up yo 1GHz.

I bought it 3 years ago and have not used my other two since.

RE: Signal Generator Help - captainclock1988 - 04-16-2020

yes, but for me who doesn't have thousands of dollars to throw at test gear this will do just fine for me because I don't make enough money where I work to go out and blow $500 on a fancy quartz tuned signal generator like the Hewlett-Packards. I barely make enough to be able to afford the essentials and to be able to keep my radio restoration hobby afloat let alone trying to buy test gear. 
I have Autism and other disabilities so I get SSDI which mostly goes towards rent and groceries, and then my paychecks from work have to go towards gas for my car, and getting parts for my radios and buying radios to fix up, and other stuff like that. 

So yeah with that in mind like I said a simple analog signal generator like the ones I bought are more than enough for what I need considering most of the radios I restore are usually AM Only, AM/FM, and AM/SW radios which don't need those fancy Hewlett-Packard Signal Generators because I'll only be going up to about 150 Mhz at the most I won't ever use anything going into the Ghz range.

RE: Signal Generator Help - morzh - 04-16-2020

It will do the job, yes.
However, with these what I used (before settling on an HP) was a counter. I bought a decent BK Precision counter for $25 and every time I set a frequency I first would feed it to counter to set it exactly to what I needed. Then use it to align the radio.
Cumbersom but not too bad.
Otherwise your ST dial could be off quite a bit and your radio will be misaligned.

Recently there was a thread about folks using a cheap front panel counters built in their cheap tube SGs.

Terry might be the initiator of one of them. I think it was in the year of 2019.

This would make it almost as good as an HP.

RE: Signal Generator Help - captainclock1988 - 04-16-2020

Well The Radio City Products Model 705A  Signal Generator from what I read in the manual (which I found in the Boat Anchor Manual Archive) is actually adjustable and can be calibrated to within 1% if need be.

So that one is a bit higher quality it seems.

RE: Signal Generator Help - morzh - 04-16-2020

Good then.
To calibrate you still need a counter (calibrated counter). Or send it to someone who has.
Using a counter rids you of the need of calibration. Panel counter is even better as it doesn't require switching between it and the radio. Or if it does, it can be arrnged by using a pushbutton, when you push it to set the frequency, and release to divert the output back to the connector.

RE: Signal Generator Help - 462ron - 04-17-2020

Hi Captain, I have a Heathkit SG that was missing the probes. What I did was replace those screw on connectors on the generator with BNC connectors which are more compatible with modern equipment. Very inexpensive to do. While I was at it, I put a capacitor in series with it, thus blocking any DC voltage from getting into the generator from a radio you are connecting it to and possibly burning out the attenuator. I also used the audio input jack to the generator, wiring it to the oscillator input to the attenuator through a cap also. Did that with a BNC connector also. The audio input for me is useless so I repurposed it to be able to connect the generator to a frequency counter. You can find inexpensive RF probes like the one I attached and it uses a BNC connector. Just a thought you might consider.

Ron

RE: Signal Generator Help - Eliot Ness - 04-17-2020

Captain, if you have a solid state short-wave radio with a digital frequency display you can use that as one way to check the accuracy of your new generators.

The RCP generator looks like a pretty nice vintage piece and with the existing RF lead might be the easiest to start with since the other leads are just banana Jack's.  Also, I'm not positive, but the modern banana plugs from China might be a tad smaller than the vintage ones, but I might be wrong about that.  Good luck.