Best Value Function Generator  - Page 1
Forum section: electronics / testgear

author: AustinTxBob
author_rank: Contributor
timestamp: March 08, 2016, 09:27:50 pm
content: I would like to buy a function generator to be used in my AC class for the lab assignments. In the future, I might need one for ham radio projects but that is just speculation and not a confirmed need right now. Any thoughts on something cheap from ebay? I see a lot of well known brands but don't have a clue if they would be any good or not. Alternatively, there are they cheap DDS ones. I cannot afford to buy a nice piece of equipment right now so something over $100 just isn't going to be an option right now.Thanks.Bob

author: ataradov
author_rank: Super Contributor
timestamp: March 08, 2016, 10:31:24 pm
content: This one is all over the placehttp://www.ebay.com/itm/6-25MHZ-DDS-Dual-Channel-waveform-signal-generator-frequency-meter-signal-source-/191620192470. It is functional and does the job, but the UI is just horrible. It is very irritating to set it up and change settings.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: March 08, 2016, 11:11:39 pm
content: Quote from: ataradov on March 08, 2016, 10:31:24 pmI've got one of those, had it for about 2 months. At first I did find the setting system cumbersome but now that I'm used to it, it's easy enough to use. I wouldn't describe it as "just horrible", it just takes a little practice. I have not tried the software for entering arbitrary waveforms, but I've saved a few custom settings to its memory without trouble.However... there are some real performance issues with the thing, such as phase jitter. Still, it's useful around the lab, especially for making pretty coloured lines on an oscilloscope. It's nice to be able to have two outputs that can be either independent or "tracking". But the phase jitter issue, and the phase measurements, are problematic.The quality of the build seems better than some others I've seen, and I like the fact that it's powered by a 5VDC "wall wart" SMPS rather than having a mains line cord coming into the box. The two cliplead cords seem to be OK quality as well. It also has a TTL-level breakout connector on the back and it comes with a little screw-terminal adapter for it.I thought about sending it back over the phase jitter issue... but decided to keep it... because....:After all, it's only 65 dollars, what did you expect:

author: gearhead
author_rank: Contributor
timestamp: March 08, 2016, 11:22:11 pm
content: You might check this thread:https://www.eevblog.com/forum/testgear/feeltech-fy3224s-24mhz-2-channel-dds-aw-function-signal-generator/I posted a link in Reply#138 to the FY3224S function generator.

author: AustinTxBob
author_rank: Contributor
timestamp: March 09, 2016, 01:21:34 pm
content: So a DDS or maybe an old HP like a 3312a will work for me. I think for any radio work, I would probably want a signal generator instead. With that in mind, I've dropped the idea of getting something useful for that as well.

author: NilByMouth
author_rank: Regular Contributor
timestamp: March 09, 2016, 01:40:33 pm
content: Tektronix TM50X plus FG504? You're in the right country for Tek kit.

author: AustinTxBob
author_rank: Contributor
timestamp: March 09, 2016, 03:08:11 pm
content: Quote from: NilByMouth on March 09, 2016, 01:40:33 pmThat would be nice if I could get a good deal on one.

author: NilByMouth
author_rank: Regular Contributor
timestamp: March 09, 2016, 03:13:51 pm
content: Quote from: AustinTxBob on March 09, 2016, 03:08:11 pmI've seen "working" ones go for $50-ish each.

author: AustinTxBob
author_rank: Contributor
timestamp: March 14, 2016, 02:24:16 am
content: Nothing at the swap fest so it looks like the "for sale" section here and ebay will be searched on a regular basis. Lot on ebay, just don't know about the brand/models.

author: mtdoc
author_rank: Super Contributor
timestamp: March 14, 2016, 02:39:13 am
content: What sort of bandwidth do you need?I have oneof these Leader2Mhz function generators. It's old school analog style but it has been rock solid (much more so than the old HP and Tek FGs I've had) and should be easy to repair if any issues come up.If you need higher bandwidth on a low budget, I'd go for one of the cheap Chinese DDS generators.

author: jeffsf
author_rank: Contributor
timestamp: March 15, 2016, 04:58:19 pm
content: If you just need a signal source and don't need calibrated output or modulation, you might look at one of the AD9851 modules available on eBay for under $15. They're DDS at 180 Msps and have a decent LPF on them. There look to be two variants, one with jumpers and one without. I have the one without the jumpers. I'mguessingthat the jumpers allow selection of the device boot up between serial- and parallel-input modes.http://www.analog.com/media/en/technical-documentation/data-sheets/AD9851.pdf-- 180 Mspshttp://www.analog.com/media/en/technical-documentation/data-sheets/AD9850.pdf-- 125 Msps"Any" simple DDS generator will drop off with increasing frequency due to the sin(x)/x related to the sampling rate. See page 12 of the AD9851 datasheet orhttps://www.ieee.li/pdf/essay/dds.pdf,for exampleThere are some good write-ups on packaging and using the AD9850 modules around as well. One I like ishttp://www.vwlowen.co.uk/arduino/AD9850-waveform-generator/AD9850-waveform-generator.htm

author: AustinTxBob
author_rank: Contributor
timestamp: March 17, 2016, 01:16:26 am
content: Quote from: jeffsf on March 15, 2016, 04:58:19 pmThanks. This one looks pretty good. I think my class might be over by the time I got it put together and working though.I actually have a 9850 that I am using for my class project to make an antenna analyzer with. Guess I should have ordered two.