Finding the right signal generator - Page 1
Forum section: electronics / beginners

author: mvno_subscriber
author_rank: Regular Contributor
timestamp: July 19, 2020, 10:10:15 am
content: Hi,I'm in need of a signal generator - never used one before, but I have a limited budget and certain requirements that may or may not be difficult to achieve. It may also be that my perceived requirements are not as strict in reality, so please do chime in if you disagree!Basically, I'll use it for testing and tuning analog sound equipment - tape heads, filters and amplification stages. In addition, I'll need it for vintage digital electronics - mostly as a clock.Based on that, I figured I need something that can provide a stable signal at 1-2mV (with 1mV resolution), and preferrably be able to generate an 8Mhz square pulse - but 3Mhz would also be very fine. Sweep function would be awesome, but not 100% necessary.I've singled out the following two generators:Uni-T UTG9005C-II (https://www.uni-trend.com/html/product/gongye/Waveform/UTG9000C-II/UTG9005C-II.html) - sells for around €100JDS6600 - (https://joy-it.net/en/products/JT-JDS6600) - has been discussed here previously, sells for about the sameWould any of these do? Or do you recommend something else? I might double the budget to about €200 if there are compelling reasons. I assume getting a good quality, low voltage signal would be the most difficult.

author: ledtester
author_rank: Super Contributor
timestamp: July 20, 2020, 04:46:36 am
content: For testing your analog sound equipment... do you only need audio frequency sine waves? If so, consider using your computer's sound card/output. Just search for "sound card signal generator". Some programs have sweep functionality.For the square waves... you can pair up an Arduino with a Si5351A module for a versatile clock generator:https://www.adafruit.com/product/2045

author: bdunham7
author_rank: Super Contributor
timestamp: July 20, 2020, 05:11:49 am
content: No idea on the Uni-T, but I have the FY versions of the 6600 and 6900.For a quality low-voltage signal like that consider getting a 10X (20db) or 100X (40db) external attenuator and then using the corresponding higher output setting. Using the 6600 directly at those levels is suboptimal.There's a lot of discussion already on the more popular Feeltech versions 6600/6800/6900 that you can read to help understand the issues. You might want to modify the unit slightly to match your needs and there's plenty of information on that.https://www.eevblog.com/forum/buysellwanted/re-feelelec-new-arrival-fy-6900-signal-generator/msg2564763/#msg2564763As far as a clock signal goes, the 6600 isn't such a wonderful clock, especially with square waves where 250/f (in MHz) is not an integer. The 6900 is better but still flawed. It may not matter in your use case.

author: mvno_subscriber
author_rank: Regular Contributor
timestamp: July 20, 2020, 01:20:22 pm
content: Very interesting, thanks!It seems to me the major difference between FY6900 and JDS6600 is internal vs external power supply? I assume using an external one is better and easier to replace. Or is there some other difference I didn't see?

author: paul8f
author_rank: Regular Contributor
timestamp: July 25, 2020, 07:59:22 pm
content: Do some reading into Arbitrary Waveform Generator (AWG).

author: robca
author_rank: Frequent Contributor
timestamp: July 25, 2020, 09:16:34 pm
content: If all you need are arbitrary waves at analog audio frequencies, and clocks for digital boards, there is a super-cheap way to achieve bothUse a free program like Daqartahttp://www.daqarta.com/dw_gen.htmto generate everything you need, plus either your PC/laptop soundcard, or an external USB audio device with a USB isolator if you have to worry about high voltage signals making it back to the PC or ground loops. If you don' have a PC, a smartphone with a earphone output would work, tooThen use a cheap STM32 board with just enough code to program a timer to generate pretty much any square wave you need. Even a lowly STM32F103 like the ubiquitous "Blue Pill" should be more than capable of generating square waves up to 8MHz (if not, most of the <$10 boards with a STM32F4 certainly will. If 3.3V is not enough, add a level shifter to generate any voltage level you needCertainly a good function generator is a better tool, but if "cheap" is your goal, the above is the cheapest option