Signal Generators

Hi  Everyone.

I am a New Member just getting into Radio Restorations.  I am no Stranger to Vaccum tube technology.   High school electronics and My first semester of College were 100% vacuum tubes. (I guess that Dates me a bit). 

I have a basic question about Signal Generators.

If I remembr back to my younger days, it seems the signal generators of the past used for radio repair had RF and Audio output.   You could swirch in /out the audio componet (Modulate) the RF Signal while trouble shooting. I would like to purchase a Signal Generator capable of these functions. Are there any currently produced signal generators that members are purchasing that will provide these functions?  Do I need this Function?   I see many old  signal Generatos for Sale. However, I want to spend time restoring Radios, not the test equipment. 

Thanks For the Help Team!

Bob

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Dear Bob,

I'm a beginner in the restoration of tube radios and just these days I'm setting up my little lab and I'm confronted with your own problems.

I purchased a Tektronix 453A oscilloscope and a vintage Unigor A43 multimeter, used, and they are wonderful instruments.

For the signal generator instead I bought an unprofessional one produced in China TSG-17 (Pls.find the attached manual)  inexpensive but that I think do just what you need; naturally it needs a frequency counter to align it if you want to generate very precise frequencies. I'm using it these days to calibrate an FM / AM radio and it seems to me that it does its job well.

I hope this indication is useful to you.

Best wishes

Roberto

• Signal Generator TSG-17 User Manual (214 KB)

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 areHi Robert

Most RF generators I have or used allow switching off the audio modulation but dont 'bring it out' as a separate useable audio signal.

But AF generators are around at low cost at swap meets and usually are working or need little fixing.  I use mine now and then for seeing what audio bandwidth is like.

The RF generators and I have AM and FM are more used (AM mostly) so go for that first.

You could put this question on the US Antique Radio Forum which is excellent particularly if you are US based.

Gary 

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Thanks for the Info Roberto and Gary

I will look into the TSG - 17

I also found B&K Precision 2005B RF Signal Generator, 150 MHz after hunting around.  It Seems you need to Verify with a scope or Frequency counter that you are right on the 455 KHZ  since the dial is analogue.

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I run a freq counter on a T switch from the generator.  Most decent gens are pretty close anyway but its nice to be sure.

See the TSG is AM only so do you need to have FM?  Must be ones out there with both modulations.

Looked at the manual and Yes! it does have a useable audio generator but only to 1 1/2 kHz ... not so good if checking amps.

Gary

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Hello everyone,

yes TFG-17 is a non-professional instrument but has a frequency range from 100KHz to 150MHz, and an adjustable 150 Hz to 1500 Hz AF output (in fact I have measured from 125Hz to about 1500 Hz), I am a beginner at the foot of the ladder and still studying a lot, but I do not understand what uses is not good for FM?

Thank you very much for your contribution

Roberto

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Well, I have two RF gens, one quite small for AM modulation which is primarily what suits most of my collection.  It is made by a Brit company called Advance and is Model SG62B.  Bought at a swap meet for a few pounds and its covers re-sprayed.  For the electronics just new electrolytics as far as I can remember.  Only 1 valve so neat circuitry.  A good thing is the attenuator which is a switch built into a die casting so little leakage.  Small 10" W, 10" D and 8" high.  

So this is another way.   Lots of people part with the hobby and there is always good test gear around if you look for it.  Go for valve stuff and any repairs are normally easy.

However, If you are going to work on radios with an FM band, say from the 60's on, then a gen with FM modulation is really needed.  I have another that has that but if I had thought about it at the start I might have tried to find one with both.

Gary

• Advance signal generator (279 KB)

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On the advice of a friend with many years experience, I purchased a Precision Apparatus model E-200-C on ebay for 75 bucks.  This is a tube type sig gen and does not do FM.  (There is one on ebay right now for 100 or best offer.)  I have a very expensive Motorola R2200 service monitor that can do transmit and receive from 10 khz to 1 ghz, but it generates so much digital noise it is useless on antique radios.  I have found that tube test equipment works best on tube sets.  I even use an analog voltmeter.  

Another note,  Setting your signal generator with a frequency counter is the best way to get accurate tuning, but many of the cheap little Chinese counters have input sensitivity of 300 mv or higher.  Many signal generators will not put out that much RF, especially at the short wave bands.  Something to keep in mind when purchasing a sig gen.  My little HP 5314A counter (85 bucks on ebay) has 100mv sensitivity and a trigger level control, sadly missing on almost all modern, cheap counters.

Good luck in your new hobby.  It will provide you with many challenges and much satisfaction.

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Actually, for aligning FM radios you use AM or none. Also automated or manual sweep to see IF bandwidth or align a discriminator.

I use a €6 FM transmitter for FM audio, the kind sold to connect an MP3 player or phone to an FM car Radio.

I have an old 1940s valve  generator (good attenuator) with counter connected direct to attenuator input. Also a cheap Chinese generator based on ADI DDS, which has two outputs. Does from a fraction of a Hz to about 15MHz as function generator, and up to about 50MHz sine output.

There is almost no need to have FM on a a signal generator. External sweep, (or sweep signal) to feed Scope X channel and then a diode detector on the Y channel (or discrimator DC output test point) is useful.

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