Function Generator

[s.mosfet]

hello
i would buy a function generator, (300-400$)
Which is the best choice, DDS or analog?

i've seen:
isotech gfg-2120 (DDS)
tti tg330 (analog)

..

 

[Reloadron]

To my way of thinking buying a function generator is like buying any other piece of test, measurement or diagnostic equipment. You generally select it based on your needs and budget. With for example a function generator do I want or need sweep functions? How much amplitude do I need. Sometimes the basic features are fine but sometimes we need additional features.

Also, depending on your location frequently a good deal can be had on used test equipment. I got the old Wavetek Model 145 pictured in the attached for $5 (USD) at a yard sale. That thing has to be 25 or 30 years old and works just fine for many applications.

Ron

 

[s.mosfet]

1) Do analog generators have more distortion?
2) In which application is a >3MHz generator useful?

 

[Reloadron]

My experience has been that analog function generators produce a signal with less distortion and distortion being harmonics hum, and noise. So do you get better spectral purity with a non-synthesized unit? Yes, in my opinion you do.

What is the merit to > 3MHz? You tell me. For someone who works with audio frequencies nothing but for someone who wants 5MHz or 10MHz the less than 3 MHz would not be a wise move would it.

If I am looking for a frequency counter and I am never going to measure over 50 MHz I sure don't need a 1 GHz mainframe do I? You buy TMDE for its intended application. I have no clue what you want a function generator for or what applications you have for a function generator so how can I possibly tell you what would be a good function generator for whatever you want one for. You buy what you need for what you want to do with it.

Ron

 

[s.mosfet]

Ok,
now i'm making audio projects, but i don't know which projects i'll make in the future...
so, what do you do with a 5MHz generator? digital projects? what in particular?

 

[flat5]

For audio you can buy something inexpensive. Even make your own.
If in the future you need something (and I mean IF) expensive then look around.

I would buy a cheap analog FG that goes above 20khz, maybe 50khz.
Mark a few freqs. of interest on the dial.
and keep my eye open for a used Tektronix or HP or Wavtech or ? FG for a good price.

 

[Reloadron]

I think analog generators is best option for distortion point of view because analog generators have more distortion than digital generators.

Not sure what you are saying there? I tend to agree for audio applications an older analog signal generator is good choice because they offer less distortion for sine wave applications. Newer DDS (Direct Digital Synthesis) generators have a higher level of distortion.

This is a good overall read on function generators.

Anyway the options are build or buy and as to buying with a little luck you can snag an old Wavetek like the 142 model or similar or as flat5 mentions:

Tektronix or HP or Wavtech or ? FG for a good price.

I paid $5 for the old Wavetek I posted a picture of earlier in the thread. There must be a few million of them out there. If you just want sine wave even an old HP 200CD or like would be a good choice. I would look to buy used.

Ron

 

[audioguru]

An XR2206 function generator IC has "low distortion" of as high as 1.5% which is horrible for audio. It can be heard and can be seen on a 'scope. An audio generator has distortion as low as good amplifiers, about 0.05% or less.
Buy both generators if you need both.