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Radio Surfer 12th Jun 2019 9:05 am

Signal generator terminology query

Please forgive what may seem a simple and naive query, but could someone clarify the terminology used to desicribe what seems to be the same thing.

I often read articles including the use of, and see advertised, Signal Generators, Audio Generators, Frequency Generators and Function Generators and then combinations of all of these, i.e Audio Frequency Generators, etc. Is there any real or even subtle difference between these or are they just one and the same?

Many thanks,


Dickie 12th Jun 2019 9:15 am

Re: Signal generator terminology query
This might provide some clarity:

lesmw0sec 12th Jun 2019 9:35 am

Re: Signal generator terminology query
The only real difference is the frequency range, apart from function generators. The foregoing generally produce sine waves, whereas a function generator may be expected to provide sine/square/triangle/sawtooth waveforms.

David Simpson 12th Jun 2019 10:38 am

Re: Signal generator terminology query
Hello Richard,
Welcome to the Forum. There are a few of us in the north of Scotland, but not many.
I assume from your initial posts regarding a Hacker VHF that perhaps you are considering acquiring a signal generator? As a new guy to radio repair & restoration, you might consider thinking in a "left to right" manner when reading circuit diagrams, and subsequently setting up a testing & repair workbench. I.e. Most, if not all circuit diagrams, have the Aerial & RF input stages on the left, IF stages in the middle, and Audio stages on the right. So a AM/FM HF & VHF Sig Gen on the left, an Oscilloscope capable of VHF in the middle, and an Audio Sig Gen on the right, along with an Audio Wattmeter. Plus a decent AVO8 Multimeter & a decent Digital Multimerer for fault finding, etc.
Me - I'd recommend a Marconi TF995A RF Sig Gen or one of Marconi's later & smaller 2000 series S/G's. Audio-wise, maybe a Farnell Function Gen which produces a decent basic AF signal, plus the additional square & sawtooth signals. Hameg produce a decent range of reliable Oscilloscopes.
Hopefully some Forum folk, with more "Tranny" & domestic radio experience than me, can advise you in more depth. Unless you've got deep pockets, don't jump into eBay & other internet sites before seeking advice.
If you've got the time, a trip down to a Golborne BVWS Swapmeet, should enable you to chat to a heap of Forum & BVWS guys, and hopefully acquire some decent test equipment.
Pity you weren't on the go about 6 years ago, I could've given you the whole caboodle for nowt, to get you started.

Regards, David

paulsherwin 12th Jun 2019 10:51 am

Re: Signal generator terminology query
You don't really need a signal generator of any type to work on old radios, though a basic one does make realignment easier. For FM work you ideally need a wobbulator (sweep generator) and a scope, though again you can usually get by without.

Many forum members here have a *lot* of high end workshop kit, but this has usually been acquired over many years and often 'liberated' from day jobs in electronics.

David Simpson 12th Jun 2019 11:47 am

Re: Signal generator terminology query
As Richard says in his introductory post "New Member from Tiree", radio signals in the Western Isles & the Highlands of Scotland can be a bit unreliable. Skye & Torridon are awash with VHF unfriendly mountains.
Marconi's range of RF Sig Gens, like the 995A, not only sweep internally for FM operation, but can supply between 30 to 100V for externally triggering a scope. The Farnell FG2 can put out 5V.
As Paul says, some of us have acquired quite a few items of test equipment over the years. However, to help Richard start his Vintage Radio endeavours, perhaps other Forum folk, who have started out more recently, could share their experiences & offer advice regarding gig gens & basic line-up of test equipment. I guess there must be a few Forum guys in Strathclyde, and a handful further up the West Coast.
In general, being a Forum &/or vintage radio guy, doesn't mean you have to just communicate solely online from your lonely workshop. Get out & about, meet folk, and like Bonny Prince Charlie - take a trip "Over the sea to Skye", as the song goes.

Regards, David

Radio Wrangler 12th Jun 2019 12:35 pm

Re: Signal generator terminology query
There are real differences, some are subtle.

A 'signal generator' is all-encompassing and therefore almost meaningless unless you know the context it was written/spoken in.

A function generator is usually found in a general purpose electronics lab. Their super power is that they can make various waveforms. Sine, square, triangular, ramps up and down and maybe some pulses. These things are relatively low in frequency, so not good for radio work. Their sinewave distortion is poor because of the way it is formed by distorting a triangle, so they're not good for audio work beyond finding gross faults. There are fancy digital versions where you create ANY waveform as a file and it 'plays' it. These are called arbitrary waveform generators. All of these are usually fairly noisy and impure on their output.

RF sig gens make sines only and cover the tuning ranges of various radios. Expect the facility to put AM on it and perhaps FM as well as a basic audio output. Good ones can go to very low levels... less than a microvolt.

Then there are 'Frequency Synthesisers' machines for making accurate and stable frequencies. They may lack modulation facilities, they may lack good attenuators. With them, they are modern RF sig gens.

Pulse generators do what they say on the can. Usually they go a lot faster than func gens can.

Not all RF sig gens cover all frequency ranges used by radios.

You can do a lot of fixing without one. But having one can make it easier and can make learning easier.


Radio Surfer 12th Jun 2019 1:57 pm

Re: Signal generator terminology query
Hello and thank you to all the responses so far from a beautiful, sunny and breezy Tiree.

Just to reassure everyone I'm not plannning buying any kit yet, just researching and getting confused (as usual). I'm sure most will agree the internet is great with plenty of excellent articles and videos, but you have to filter out the good from the misleading. Some clearly love their 5 minutes of fame on Youtube!

As far as the Hacker is concerned, that's up and running thanks to support of forum members and I'll post a comment in the relevant section in the next few weeks.

As many have said, when/if I decide to get some additional test kit (and I find my wallet) I'll take the advice of members first. The forum is really is very useful to me, particularly being so "cut-off" from the mainland it's not easy to get to various swapmeets etc. As my son says, we could be in the US quicker that getting to England. However, given the state of the world these days I wouldn't want to be anywhere else.

Keep the comments coming, it is much appreciated and gives me plenty to read through and undoubtedly I'll have many more questions.

Regards, Richard

Radio Wrangler 12th Jun 2019 2:06 pm

Re: Signal generator terminology query
Can you get yourself down to Glasgow on Sunday, Richard?

It's the Scottish amateur radio convention at the Braehead centre. There's usually plenty of test equipment, loads of components and loads of second-hand radio gear. It's the main event of the year north of the border... the only big radio event.


Radio Surfer 12th Jun 2019 8:20 pm

Re: Signal generator terminology query
Hi David,

Thanks for the details of the convention but a clash of dates I'm afraid as its Father's day and we're having a "Clan gathering". I don't think I'd be too popular if I disappeared on the Friday ferry and didn't reappear until Monday. I'll have a search around and see what other events are on this year. If I get enough warning we can combine other visits etc. to help justify the ferry costs, hotels etc. Otherwise auction sites, although more expensive than a swap-meet, can actually look very cheap!

Regards, Richard

Radio Wrangler 12th Jun 2019 9:02 pm

Re: Signal generator terminology query
I know what you mean. I'm on a foray down to see my family in Yorkshire, but with the dates chosen to allow me to get to the auction which was held a few days ago near Preston. The art is in combining excus.. er, sorry, reasons :-)


Diabolical Artificer 13th Jun 2019 6:14 am

Re: Signal generator terminology query
"I don't think I'd be too popular if I disappeared on the Friday ferry and didn't reappear until Monday. " Perhaps you can make a paper mache head a la prisoner of Alcatraz scrunch up a few pillows and escape with a spoon : )

There is a lot of software online and on modern smart phones that'll do sinewave's and whatnot. Audacity is one and Soundcard scope is worth a look at, it's a simple PC scope, spectrum analyser, sig gen and it's free. A bit limited for RF work perhaps but useful non the less.


Radio Wrangler 13th Jun 2019 6:23 am

Re: Signal generator terminology query
I thought you were about to suggest audacity for making snoring noises, Andy....


Radio Surfer 13th Jun 2019 10:34 am

Re: Signal generator terminology query

Thanks Andy, but I can see a problem with the papier-mache approach. By the time I got back my wife might prefer that to me on the basis she got more interesting conversation out of it..........!

On a more serious note, I'll have a look at the software approach as well.

All the best Richard

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