In my opinion the VC2002 is the more functional of the two, although I have no experience with this specific model or brand. This an old analog function generator with low stability and moderate distortion, but it has a full complement of functions and full output amplitude control from 20 mV to 20 V.
The AD9851 board uses the much more modern DDS method and should deliver much better frequency stability and frequency range, but I wouldn't call it a function generator. Output amplitude is fixed to a not that useful 1 V. This won't be enough to drive a CMOS logic input, for example. No DC offset control either.
Popular choices on this forum appear to be the GW-Instek SFG-1003/1013, which is has similar features to the VC2002, but uses the superior DDS method to generate functions, and the Hantek DDS-3x25. The latter is somewhat between the stand-alone function gens and the AD9851. Its amplitude is a fixed 3.5 Vp-p, but can be reduced (at the cost of spectral purity and output resolution) in software. Advantages are bandwidth and arbitrary waveforms, disadvantages are lack of front panel, limited amplitude control, no DC offset and requirement for PC control (throw it away when Hantek stops updating the drivers for the next Windows version). Both will probably exceed the $100 budget.
thank you alm for reply
i've found the Hantek DDS-3x25 on ebay with a price 150$ and if you recommend me this one i can buy it.
Is it the good choice?
thank you
thank you guys
after a couple of hours searching on the net, my choice went to GW-Instek SFG-1003.The hantek USB function generator is good, but i look for something like a laboratory FG.
i just buy it on ebay for 150$ and in few days i will let you know my opinion about this function generator.
have a good day guys