Avo RF Signal Generator HF 134

[tim.54]

Have been looking for a reasonably priced rf sig generator , has anyone any experience of the above ? or should i go for something more modern and expensive ! all advice appreciated ,
regards, tim

[pwdrive]

No experience of that one, there was a thread on UKVRR on the Avo HF 135. Possibly similar to a Taylor sig gen.

Whatever you get make sure you can get the manual or at least the schematic.

Lawrence.

[Yorkie]

The only downside to Avo equipment (or Taylor, or Advance etc) is its age, but that's almost certainly going to be the situation whatever you go for, and to get it into good working order will usually need a little bit of work and TLC, but not too daunting. Generally, (assuming the phantom fiddler hasn't been at it!), the only work needed whatever the model - be it Avo, or later (Taylor) tends to be the need to replace smoothing caps in the power supply. The tuned circuits usually had high stability components such as silver mica caps. Allegedly the HF134 is almost identical to the 135, and looking at the circuit for the 135 it uses 3 x 10uF/450V smoothing caps quite possibly in one can. (8uF would be fine as replacements if need be). The might well be OK if re-formed, but it's handy if you can check if their ESR has gone high and if they measure reasonably close to 10uF. If they're not OK, there are physically small modern replacements which would fit inside the can. There may also be one or two 'waxy' paper caps which would benefit from replacement.

The AVO uses a metal rectifier, and given its age that's quite possibly a contact-cooled selenium one which may be OK, but if not, 4 x 1N4007 silicon diodes would be fine in its place, possibly with a series resistor to lower the higher voltage which silicon diodes would produce. In line with many signal generators of that era including Heathkit designs such as the RF1U, The AVO uses two twin triodes - a 12AT7 and a 12AU7.

Whatever make or model of signal generator you obtain, ideally a frequency counter is useful to check the calibration, and a scope to observe the output waveform with the internal modulation switched in/out. The good thing about signal generators is that unlike old valve radios, few of them had a lot of use and spent more time on the shelf than on the bench so usually, the valves are fine, leastways in my experience.

Just my thoughts - others may have a different take on things.

Avo were of course designed for use by professionals, but there are others to look out for, notably the Heathkit RF1U and the Tech TE20D, aimed more at hobbyists, though perfectly adequate. I've attached a pic of a Heathkit RF1U which I use, standing on top of my homebrew nixie frequency counter (1976 vintage), showing a 100MHz signal.

Rob Vine, who goes by the name of 'Bushbaby' on this forum, and 'Guitarist28' on the other side of the wall put a query out on that forum in Feb 2011 about the HF134 - I don't know if he still has that equipment. He was seeking a manual, and someone came up with the circuit of the HF135. I think it's considered discourteous to 'lift' attachments from other forums, but you'll find the circuit at this link:

http://www.vintage-radio.net/forum/showt...hp?t=66016

If Rob doesn't spot this post you might like to drop him a PM on here to see if he can help further Tim.

Hope that helps a bit Tim.

[Joe]

To save AlanBeckett the trouble of saying it: "Proper signal generators say 'Advance' on them." I'm extremely satisfied with my E2.

- Joe

[pwdrive]

When I was in the trade the Advance E2 was the most popular, room on top for a cup o' tea and a sticky bun and a good handle to hook the soldering iron on....

The only Avo I really liked was their original All Wave Oscillator, had one of them for years.

My favourite was the original Marconi TF144, solid to say the least.

Lawrence.

[AlanBeckett]

Well said young Joe.
Seriously, it all depends on what you want to do with it and what you expect from it by way of accuracy, purity and facilities.
There are all sorts of Generators about which are entirely adequate for general Servicing, and as David says, a Counter/Frequency Meter solves the accuracy problem.
I've got an hp 8640B and an Anritsu Spectrum analyser if required, but it ain't very often.

Alan

[Skywave]

Seriously, it all depends on what you want to do with it and what you expect from it by way of accuracy, purity and facilities.

I've got an hp 8640B and an Anritsu Spectrum analyser if required, but it ain't very often.
Alan

I'd be seriously restricted in my interests if I lost my HP 8640B. But then I am a 'dyed-in-the-wool' R.F. man.
As far as reliability (etc.) of the 8640B is concerned, the one area that does cause headaches is the nylon gearing that is used between some of the front panel rotary switches and the internal controls: the bushes that secure the gears to their respective shafts have a nasty habit of fracturing. Yes, repairs to those are possible, but that is not an easy or a quick job! I have also had one example of failure of the extractor fan at the rear. But it wasn't the fan, per se, rather the 2-phase control board, one transistor on it: that was a much easier repair.
Overall, the HP 8640B is a fine piece of kit - and for serious and accurate measurements, (between 400 kHz and 500 MHz), it takes a lot of beating.

For those who are curious - there's are photos of mine in the Gallery.

Al.

[AlanBeckett]

Of course, if you have a problem, you take it to Al, as I did
It really is a splendid piece of kit.

Alan

[Radio Fixer]

Look out for an Advance SG62B, it is an excellent genie. I like it better than other advance models as it has a smaller footprint that suits my tiny workbench.

Mine cost £10 to £20 at a swap and the repairs were mainly mechanical apart from changing the electros.

Yes! a freq counter is most useful and I use most of the time although the SG62B is pretty accurate for L and M wavebands.

   

Gary

[AlanBeckett]

That's the modern version!
Shock, horror
This is a real one:

   

For reasons which are too long winded to go in to I have 2.

The P is another small one.

   

If you want fm then go for a 63.

   

I've never discovered why they made similar Generators in different cases.

Alan