Avo RF Signal Generator HF 134

[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.
Alan

That is a good set of criteria to determine what to buy - along with what you want to use it for - and how deep your pocket is. I'll expand on that: depending on what you want to use it for, the following factors are relevant.

1. Accuracy & resolution of frequency indication.
2. Purity of waveform and freq. stability.
3. Frequency range.
4. Modulation facilities.
5. Range of the attenuator (dB), its accuracy & its resolution.

Of those, 1,2 and 3 don't really require any comment: it is almost sufficient to say "the more & the bigger, the better".
4. In addition to A.M., #4 includes the ability for F.M. and if it will handle an external input signal that will sweep the frequency over a substantial range - say, adequate sweep for nominal 465 kHz and 10.7 MHz IFs.
5. This is probably one of the most difficult specs. for any manufacturer to achieve, especially if an output down to the µV level is required. The main reason for that is screening: substantial screening and filtering. It can be very difficult at high frequencies to avoid a substantial part of the signal that is entering the attenuator to by-pass that attenuator and arrive at the output socket. It can also be difficult to arrange matters so that the output impedance of that attenuator remains substantially constant over the freq. range of the generator - especially if that freq. range is a substantial one.

In conclusion, they are the main reasons why lab. standard sig. gens. are so expensive. But as I said, it depends what you want to use your sig. gen. for. For example, if you wish to use it for reliable, repeatable and meaningful sensitivity tests on comms.-type radios and measure S/N ratios, then a lab. standard sig. gen. is required. However, for most domestic radio service, a basic (and much cheaper) type of sig. gen. will be perfectly adequate.

On a general note, when it comes to buying any item of test gear, by using the adage "buy the best (= most expensive) that you can afford", you usually won't go far wrong.

Al. / March 13, 2014 //