Handheld signal generators? - Page 1
Forum section: electronics / testgear

author: David Aurora
author_rank: Frequent Contributor
timestamp: August 28, 2025, 02:50:33 am
content: Anybody know of anything out there besides those clunky looking $20 eBay ones?I used to have a Velleman HPG1 that was great for the tool bag but I lent it out ages ago and never saw it again, and they don't seem to be on the market anymore. Similar story with the Tenma 72-505/Iso-tech IFG100, I can see plenty of places that used to sell them but can't find them in stock.I basically just want to replace the old one I had as it was super handy on jobs to be able to patch in without a power cable (both for simplicity and also as it takes ground loops out of the equation). I only need sine waves in the audio range, ideally with level control from a few mV to a couple volts RMS

author: KungFuJosh
author_rank: Super Contributor
timestamp: August 28, 2025, 03:37:32 am
content: I still have one of those Tenma 72-505 in one of my meter totes.If high quality isn't a concern, there are lots of portable signal generators including Fnirsi TC3 or TC4, or stuff from other less annoying brands.Something like the Uni-T UTG932 could probably be powered off a USB power bank. That's a decent gen, and it's small.Thanks,Josh

author: David Aurora
author_rank: Frequent Contributor
timestamp: August 28, 2025, 04:22:50 am
content: I had considered one of those handheld scopes with a signal generator (and I may still go that way), but I should have specified that I meant a dedicated signal generator with as few bells and whistles as possible. If I can avoid fucking around with buttons and menus that's ideal, because by the time I do that I feel like I could just plug in one of the billion bench signal generators I already have

author: Aldo22
author_rank: Super Contributor
timestamp: August 28, 2025, 05:47:50 am
content: Quote from: KungFuJosh on August 28, 2025, 05:27:00 amThe Fnirsi SG-003A is a very useful tool, but not a signal generator in this sense.It cannot generate sine waves.It is a process calibrator.https://www.elektormagazine.com/review/fnirsi-sg-003a-signal-generator

author: David Aurora
author_rank: Frequent Contributor
timestamp: August 28, 2025, 06:14:55 am
content: Yeah, that Fnirsi thing isn't what I'm talking about, and that Amazon thing is exactly what I was talking about not wanting

author: David Aurora
author_rank: Frequent Contributor
timestamp: August 28, 2025, 06:20:24 am
content: Just to be clear, these are the kinds of things I'm talking about, neither of which appear to be available anymore:https://www.velleman.eu/products/view/1-mhz-pocket-function-generator-hpg1/?id=398568&lang=enhttps://us.amazon.com/Tenma-72-505-Hand-Audio-Generator/dp/B008DJS2GY

author: armandine2
author_rank: Frequent Contributor
timestamp: August 28, 2025, 07:44:37 am
content: ..not inexpensive but has a interesting looking AWG included, RS Pro 133.I order an unused one for less than half price from ebay - but the vendor couldn't supply"inventory" error.

author: themadhippy
author_rank: Super Contributor
timestamp: August 28, 2025, 10:40:23 am
content: Quotecant get much simplerhttps://www.canford.co.uk/Products/25-065_CANFORD-TONE-GENERATOR-Analogue-audio-balanced-battery-powered

author: David Aurora
author_rank: Frequent Contributor
timestamp: August 28, 2025, 11:49:34 am
content: Quote from: themadhippy on August 28, 2025, 10:40:23 amThat's more along the lines of what I'm after

author: themadhippy
author_rank: Super Contributor
timestamp: August 28, 2025, 12:11:52 pm
content: Theres also the minarator ,https://www.nti-audio.com/en/products/minirator-mr-pro-mr2 but it comes with a lot more whistles and bells along with a heftier price tag

author: David Aurora
author_rank: Frequent Contributor
timestamp: August 28, 2025, 12:19:01 pm
content: Quote from: themadhippy on August 28, 2025, 12:11:52 pmYeah they look handy but massively overkill for my needs. I've got better sig gens if I need them, I just want something quick and easy for the tool bag for basic signal checks.

author: DaneLaw
author_rank: Frequent Contributor
timestamp: August 28, 2025, 01:49:57 pm
content: An old phone/tablet with a free app would likely be the cheapest option. (picure below)Or use your work phone with TypeC splitter if you just need crude signals in the audio range.Otherwise, if you need it to be ruggerized and be able to just drop in a toolbag, then get one of these small 40 to 70 dollar multimeters with scope.. many of those tend to have a signal generator built-in that can deliver your sine.Usually called 3-1, and simply write of the secondary DMM/Scope aspects... Gochifix, Fnirsi, Owon, and likely also Zotek and Aneng got a few models with a built-in sig-gens.fxhttps://m.media-amazon.com/images/I/71jj2aVnfHL._SL1500_.jpgJust make up your mind, what sig-gen connector you want, as they do vary.. mcx, bnc or simply crude hook-on points..

author: hfleming
author_rank: Regular Contributor
timestamp: August 28, 2025, 07:13:27 pm
content: If you need a handheld signal-generator, why not go for one of those hand-held DSO/signal generator combo’s instead? Plenty of those around. zoyi, Fnirsi, Owon, etc, etc…

author: danno_cj
author_rank: Contributor
timestamp: August 28, 2025, 09:37:50 pm
content: Some of these 3:1 devices have fixed output or limited range adjustment. With these 3:1 devices the upper and the lower limit can be the issue.Owon hand-held DSO/signal generator combo’s can supply voltage from 10mV to 2.5 Vpp. Not all of them have generator inside. Models with generator have S at the end of name.

author: David Aurora
author_rank: Frequent Contributor
timestamp: August 28, 2025, 10:54:28 pm
content: Yeah, nah, like I said- I'm looking for a handheld signal generator like the ones I linked to. I know there are all in one devices, apps, DIY options etc, but I'm specifically looking for a standalone hand held signal generator. Really looks like slim pickings out there these days though

author: KungFuJosh
author_rank: Super Contributor
timestamp: August 28, 2025, 11:18:50 pm
content: Here ya go, have some fun with a project:https://www.jameco.com/z/WSAH105-Velleman-Velleman-Signal-Generator-Kit-1kHz-Fixed-Frequency-by-Whadda_2136930.html

author: David Aurora
author_rank: Frequent Contributor
timestamp: August 28, 2025, 11:43:02 pm
content: Or... I could not. Again, not looking for alternative ideas, just trying to see if there's still an off the shelf solution on the market similar to the ones I linked.

author: DaneLaw
author_rank: Frequent Contributor
timestamp: August 29, 2025, 12:20:04 am
content: Quote from: David Aurora on August 28, 2025, 11:43:02 pmPeople are trying to help you... tone down the attitude.

author: David Aurora
author_rank: Frequent Contributor
timestamp: August 29, 2025, 05:23:36 am
content: Quote from: DaneLaw on August 29, 2025, 12:20:04 amIf you ask for suggestions on a framing hammer and people keep recommending their favourite rubber mallet it gets old quick. I definitely appreciate the people who chimed in with relevant suggestions, but just randomly recommending shit without actually looking at the examples isn't helpful.

author: David Aurora
author_rank: Frequent Contributor
timestamp: August 29, 2025, 05:34:15 am
content: Quote from: KungFuJosh on August 29, 2025, 02:54:32 amApparently there is. I just managed to find a supplier with those Tenma/Iso-tech ones in stock under yet another name (which makes at least 3 rebadges of the same item that I've found so far)

author: Aldo22
author_rank: Super Contributor
timestamp: August 29, 2025, 08:27:16 am
content: I also have a silly suggestion. Not for the OP, who has now found what he is looking for, but for others.The $20 LCR Tweezers are quite handy for giving a quick signal.You can choose between 100Hz, 1kHz, and 10kHz, as well as 100mVrms, 300mVrms, and 600mVrms (ZT-MD1).This sine wave is quite clean.Often that's all you need.

author: David Aurora
author_rank: Frequent Contributor
timestamp: August 29, 2025, 08:29:56 am
content: Quote from: Aldo22 on August 29, 2025, 08:27:16 amThat actually just made me realise my DE-5000 can do the same, though not with adjustable level. Handy in a pinch for sure though!

author: themadhippy
author_rank: Super Contributor
timestamp: August 29, 2025, 12:14:06 pm
content: QuoteGonna share that name? Not that i need another signal generator, but others may find it useful.

author: David Aurora
author_rank: Frequent Contributor
timestamp: August 29, 2025, 02:30:18 pm
content: Quote from: themadhippy on August 29, 2025, 12:14:06 pmThere are a few! So far I've found it as the following:- Tenma 72-505- Iso-tech IFG100- B&K Precision 3001- Chung Instrument Electronics 555 RC Oscillators (yes, with an "s" at the end)- Scope RC-555 RC Oscillators (again with an "s" at the end)I sort of get the vibe that Chung Instrument Electronics might be the OEM because that's the only version I can find in stock anywhere, they're in Taiwan and all versions I've seen say made in Taiwan and they list themselves as an OEM manufacturer for other brands but who knows. I've emailed them to check if they're actually still producing them or if the ones I've found are just the last of some stock kicking around.

author: Aldo22
author_rank: Super Contributor
timestamp: August 29, 2025, 02:42:40 pm
content: This model is more than forty years old.https://www.radiomuseum.org/r/cie_chung_rc_oscillators_555.html#

author: themadhippy
author_rank: Super Contributor
timestamp: August 29, 2025, 03:46:42 pm
content: Quoteskoda or lamborghiniQuoteso's my soldering iron ,but it still do's wot i wants it to so why change just because something newer is available

author: David Aurora
author_rank: Frequent Contributor
timestamp: August 29, 2025, 11:44:58 pm
content: Quote from: Aldo22 on August 29, 2025, 02:42:40 pmSo am I but I still get the job done.

author: Aldo22
author_rank: Super Contributor
timestamp: August 30, 2025, 06:12:31 am
content: Quote from: themadhippy on August 29, 2025, 03:46:42 pmMy HM203-4 is also that old and still works.But nobody is surprised that this CRO is no longer manufactured. Its technology is outdated.What is astonishing in the case of the 555 RC, however, is that something newer and comparable is apparentlynotavailable.

author: KungFuJosh
author_rank: Super Contributor
timestamp: August 30, 2025, 06:20:03 am
content: Quote from: Aldo22 on August 30, 2025, 06:12:31 amAstonishing is a strong word. It's not a great product by any means. It's just okay at what it does. You can make something better yourself without any significant investment.For anybody that needs better signal quality, or lower noise, it's junk. For a basic audio signal to test a circuit at 1kHz, it's passable but certainly nothing special.

author: David Aurora
author_rank: Frequent Contributor
timestamp: August 30, 2025, 08:25:30 am
content: Quote from: KungFuJosh on August 30, 2025, 06:20:03 amI don't think anybody would expect these things to be a high quality source though? It's a basic tool for audio work when you're out and about on a job. There's only so much gear I want to drag to a studio or venue calloutYeah, you can DIY all sorts of great things if you have time. But I work about a billion hours a week though so given the choice between spending a pile of time designing something, ordering parts, assembling and testing it or just clicking "Buy" it's a no brainer. And being a simple unit if something fails it's probably a 10 cent fix, and battery life is going to be worlds better than an all in one scope/function generator/toaster/cappuccino maker.

author: Aldo22
author_rank: Super Contributor
timestamp: August 30, 2025, 09:07:07 am
content: Quote from: KungFuJosh on August 30, 2025, 06:20:03 amIt's not that bad.THD looks pretty good:https://www.farnell.com/datasheets/1992833.pdf

author: nfmax
author_rank: Super Contributor
timestamp: August 30, 2025, 01:16:44 pm
content: Here’s a lateral thought: eBay yourself an iPod Nano or similar; use Audacity or whatever to create some sound files with sinewaves of various frequencies; convert to Apple Lossless, name them appropriately & download to your pocket signal generator. Won’t suit everyone, might suit you?

author: KungFuJosh
author_rank: Super Contributor
timestamp: August 30, 2025, 04:38:10 pm
content: Here's a few screenshots of the Tenma 72-505. Relatively stable but ugly waveforms at 100kHz. At 1kHz it's still ugly, and not stable.I previously used it for testing guitar amps, so 300mVpp is a decent average for relatively hot passive pickups. Higher voltage cleans the signal a little bit, but still nothing special. Whether using the amplitude knob or -20dB attenuator to get the lower voltage doesn't make any noticeable difference on the quality of the output.This is great for simulating crap quality signal from a mediocre guitar, but it's terrible for troubleshooting the amp itself since it's introducing its own noise and maybe some oscillations. I'd say unusable for HiFi.

author: KungFuJosh
author_rank: Super Contributor
timestamp: August 30, 2025, 05:33:56 pm
content: 199, 200, and 201 are from the Fnirsi DSO-TC3. Not capable of a 100kHz square, so set to 1kHz. No voltage control except for sinewave. Amazing quality signals in those captures, right?202 is the Tenma 72-505. At 3.33Vpp, the signal quality is good enough to compete with the Fnirsi. That's nothing to brag about.Thanks,Josh

author: David Aurora
author_rank: Frequent Contributor
timestamp: August 31, 2025, 12:33:27 am
content: Not sure what you're trying to demonstrate with all the 100kHz tones as they're not really relevant to basic audio circuit testing, but if your unit is unstable at 1kHz are you sure it's even working correctly?I should have one in the next few days to test myself and see if I get the same issues, but if it produces a basic sine wave at various audio frequencies it's gonna do the job just fine out in the field. If I need ultra low distortion etc I've got proper signal generators for that

author: KungFuJosh
author_rank: Super Contributor
timestamp: August 31, 2025, 01:45:10 am
content: It works as well as it works.Higher frequencies were both looking for stability and range of application for other people curious about these devices. Not everybody will be content at 1kHz.I'm curious to see if the one you receive is any better.

author: David Aurora
author_rank: Frequent Contributor
timestamp: August 31, 2025, 01:54:20 am
content: Murphy's Law says it'll be DOA and the last one they hadI'll report back though either way once it shows up

author: themadhippy
author_rank: Super Contributor
timestamp: August 31, 2025, 02:39:29 am
content: Quoteyea but it still beats shouting " testing 1 2 1 2" into a mic hour after hour

author: David Aurora
author_rank: Frequent Contributor
timestamp: September 03, 2025, 04:01:09 am
content: So it just arrived and mine works fineNo stability issues, signal is clean and THD is actually lower than the published spec. Maybe yours needs a tune up? I did find calibration instructions somewhere, I'll try to dig them up

author: David Aurora
author_rank: Frequent Contributor
timestamp: September 03, 2025, 04:01:50 am
content: Oh, one thing that DOES suck though is the banana spacing not being standard. What a pain in the ass.

author: KungFuJosh
author_rank: Super Contributor
timestamp: September 03, 2025, 04:12:32 pm
content: Weird spacing, and shallow.Can you post a screenshot of a 1kHz sinewave at 300mVpp?Mine is old so it might need a tune up. Most of these things can be improved if you're inclined to spend time on them.

author: Aldo22
author_rank: Super Contributor
timestamp: September 03, 2025, 04:26:09 pm
content: Quote from: David Aurora on September 03, 2025, 04:01:50 amWith Fnirsi, the spacing is also systematically wrong.Zoyi, Aneng, Owon, Uni-T etc. get it right.

author: David Aurora
author_rank: Frequent Contributor
timestamp: September 04, 2025, 12:54:39 am
content: https://www.alfaelectronics.com/manuals/RC-555.pdfThese were the schematics/cal instructions I found the other day300mV 1kHz measurement attached, looks good enough for rock and roll to me

author: KungFuJosh
author_rank: Super Contributor
timestamp: September 04, 2025, 03:10:27 am
content: Forgive me if I don't have faith in an analog scope to tell the whole story in a single image.That said, your sig gen might be fine. Try max output amplitude, square wave, and step through from 800Hz to 1.5kHz and see if it's still stable.I cleaned the contacts on my 72-505, and it did help, but it still has issues. I did the cal stuff in that doc (thanks), and that improved the accuracy. It didn't do anything for the stability or noise (the cleaning and better cables did help with the noise).After I adjusted the 640Hz range on my CNT-90XL (GPSDO ext ref), I connected to my Magnova scope to set the duty cycle.In screenshot 235, you can see the square jumps, and the duty cycle was 49%.In 236, duty cycle is corrected.In 237 duty cycle is still correct, and the wave still jumps.I cleaned the contacts and it was more stable, so I went up to 1kHz.In 240 duty and freq still look good, but the Mask captured the square. It's perfectly offset, so I wonder if it was jumping, or inverting.BTW- the mask test fail rate right now is a little over 1% (screenshot 243). It's not terrible, but I would prefer...0.Thanks,Josh

author: tautech
author_rank: Super Contributor
timestamp: September 04, 2025, 03:38:51 am
content: Quote from: KungFuJosh on September 04, 2025, 03:10:27 am100% truth right there.

author: David Aurora
author_rank: Frequent Contributor
timestamp: September 04, 2025, 04:53:32 am
content: Just to make sure I've got this right- you said yours had contacts so dirty they were causing issues, it worked better after adjustments meaning it hasn't even been working right for all your other tests, but you can't believe the one I just pulled new out of a box works fine because I tested it on an analog scope? Riiiiight...I don't have all day (nor the interest) to flesh out a detailed report on this thing, but I did spend 20 minutes when it showed up testing at various frequencies/levels and it's perfectly fine. Frequency is stable, THD is actually lower than a few other random Tek/HP function gens I have laying around (though not as low as the ones I use for actual THD measurements, but who would expect it to be?).Aside from the 7603 the signal is also clean on Siglent/Picoscope DSO's as well as an 339A and a 35665A.Not sure what else to tell you. Sorry yours is broken, I guess?

author: Aldo22
author_rank: Super Contributor
timestamp: September 04, 2025, 09:01:20 am
content: Here is a short video about it.Demo starting at 7:15I don't know how helpful it is.

author: KungFuJosh
author_rank: Super Contributor
timestamp: September 04, 2025, 02:57:23 pm
content: Quote from: David Aurora on September 04, 2025, 04:53:32 amWow, that was,something. Minor issues and contacts needing to be cleaned over time is normal. The difference wasn't as great as you imply; it was a minor improvement. The end result was still not impressive. Being 1 point off on duty cycle, and 3Hz off on cal is also nothing special, and doesn't have any implication on the other tests as I was not testingbasic accuracy. Calibrating thefrequencyandduty cycledid not magically repair theinstabilityorsignal quality.If you have a digital scope capable of pass/fail testing, then a 5 or 10 minute test is plenty. Exaggerating the time involved is silly. Anyway, whatever, if you're happy with it,be happy with it. I'm not trying to convince you not to be happy with it. I'm simply curious if a new unit does better on a pass/fail test than my old unit.

author: David Aurora
author_rank: Frequent Contributor
timestamp: September 04, 2025, 11:37:48 pm
content: Quote from: KungFuJosh on September 04, 2025, 02:57:23 pmIt's a cheap, basic handheld audio signal generator.It's something to throw in a tool bag for when it's impractical to carry a proper one. Same as how I have a handheld air blower in the tool bag because it's more practical than throwing my big ass air compressor in the car in the off chance something is a bit dusty when I get to a job. This is gonna blow your mind, but I actually sometimes just take a shifter spanner too instead of a full set of spanners, crazy right?Why are you expecting these things to be "impressive" or something "special"? Literally in post #1 on page one I explained I just needed something portable for the tool bag to plug in and make some basic tones in the audio range and you've been banging on for 3 pages about it's square wave/100kHz performance and other irrelevant information about your busted one.Let's even say I waste my time doing a pass/fail test and it DOES move a couple Hz at some point- who gives a shit?It's a cheap, basic handheld audio signal generator..Of course cleaning and maintenance needs to be done from time to time. My point wasn't that it doesn't, my point was that you apparently didn't have the common sense to try any of that stuff before spending god knows how much time taking measurements and posting screenshots about the issues you were having with it. You even said changing cables made a difference, meaning you hadn't even tried the most basic of troubleshooting techniques.

author: KungFuJosh
author_rank: Super Contributor
timestamp: September 05, 2025, 01:23:24 am
content: Geez, guy, have a Snickers.Cheap piece of crap or not, I'm not the problem with my cheap piece of crap signal generator. Even when it was new, it introduced its own signal problems. You were whiney about other modern devices not being good enough, and many of them are better than this. If you're not interested in checking on it further, then don't bother. No reason to get your panties in a twist.

author: David Aurora
author_rank: Frequent Contributor
timestamp: September 05, 2025, 01:50:50 am
content: Quote from: KungFuJosh on September 05, 2025, 01:23:24 amMate, get a life. You started off pushing process calibrators, then literally the $20 eBay ones I said in the first post I was avoiding, then you were getting pissy because I didn't want to build one, then banged on posting page after page of screenshots that say absolutely nothing about audio signals, then you got butthurt when it became clear you didn't even know your unit wasn't working right.I don't know whether the issue is that you can't read, you want to be a hero or if it's simply that you don't know your ass from your elbow, but either way you're just wasting screen space here. Jog on.