Analogue Signal Generator (Kenwood AG-203) or Rigol DG811 - Page 1
Forum section: electronics / testgear

author: TheBay
author_rank: Unknown
timestamp: June 03, 2021, 11:20:21 am
content: I need to buy something to generate some audio signals in the Hz and KHz range, to feed some sinewave tones in to a Mic input on some amateur radioequipment to adjust/check modulation and deviation. It would also be useful to have a frequency/function generator in the workshop. So wondering about going for the DG811.I've seen a few Kenwood AG-203's for sale, in the frequency range I predominantly will use this has a distortion rating at 0.1% (or less) the reason I was looking at this particular model or similaris that it crops up quite a bit in various radio service manuals.I cannot seem to find a decent analogue audio signal generator new any more (maybe they have been discontinued in favour of more modern DDS function generators?) so have been looking at the used market.The majority of Mic inputs on amateur radio equipment is around 600r impedance and I need to generate a sinewave between 5mV - 100mv for various tests and adjustments.For what the price of a used AG-203 or equivalent from HP, Leader etc will be either a tiny bit less or sometimes more than a DG811.The question is, what do I go for, will the DG811 do everything I need and produce a nice sinewave in the Hz and KHz range and be able to go down as low as 5mV?We are not talking HiFi measurements for distortion here as it is low bandwidth radio I'm working with not high resolution high SNR audio.Or are there any other alternatives that would be suited, as it stands I don't have a function or signal generator but at times I would find one useful for various repairs and projectsso was looking at getting one anyway.

author: rvalente
author_rank: Frequent Contributor
timestamp: June 03, 2021, 11:30:59 am
content: Would not a sondcard do it? Perhaps a soundcard + 600ohm attenuator?

author: TheBay
author_rank: Unknown
timestamp: June 03, 2021, 11:33:31 am
content: Quote from: rvalente on June 03, 2021, 11:30:59 amThat's what I have been using but it is far from ideal and quite a pain to get the right output level.Plus the PC is the other end of the workbench.

author: rvalente
author_rank: Frequent Contributor
timestamp: June 03, 2021, 11:42:21 am
content: For low levels i would not trust the source to output 5mv without a good attenuator. Since THD is not your biggest concern, try a audio gen from android + attenuator and cal everything with a true rms meter

author: TheBay
author_rank: Unknown
timestamp: June 03, 2021, 12:32:42 pm
content: Quote from: rvalente on June 03, 2021, 11:42:21 amNone of my new Android devices have a headphone port now! I used to use an old Android tablet as a basic function generator, didn't work too bad and got me out of trouble a few times when I needed a signal.

author: Grandchuck
author_rank: Super Contributor
timestamp: June 03, 2021, 02:23:45 pm
content: Something like this?I don't own one but it seems as if it could work.

author: rvalente
author_rank: Frequent Contributor
timestamp: June 03, 2021, 02:39:44 pm
content: You could make a wien bridge oscillator as well.

author: TheBay
author_rank: Unknown
timestamp: June 04, 2021, 06:24:13 pm
content: The Kenwood is a wien bridge based oscillator.Does anyone have any opinions on the DG800 series generators by Rigol and whether it would be suitable for this task, can it produce a fairly clean stable sinewave at 1KHz and will it go down to low mV ranges on the output?Or shall I just go for an old used analogue frequency generator?

author: nctnico
author_rank: Super Contributor
timestamp: June 04, 2021, 07:48:11 pm
content: I'd go for one the Feeltech ones (FY6900 is the latest one) or the Uni-T one from this thread:https://www.eevblog.com/forum/testgear/uni-t-utg932utg962-200msas-function-arbitrary-waveform-generator-220394/msg2807932/#msg2807932For low amplitudes add an extra (external) attenuator so you keep the DAC's resolution.Analog function generators can not be set to precise frequencies and will drift away.

author: xmo
author_rank: Regular Contributor
timestamp: June 04, 2021, 08:04:01 pm
content: The modern waveform generators are very impressive.You get accurate, precise frequencies and levels and a lot more versatility than that Kenwood.For a few more dollars, something like the Siglent SG2042 will cover to 40 MHz, so for testing receivers through the HF bands you might not even need an RF generator.With these dual units, you can use one half as 'RF' and modulate that any way you want: AM, FM, PM.7.5 MHz RF at 50 millivolts - AM modulated with 400 Hz at 50% - just set it up with the push of a few keys.

author: TheBay
author_rank: Unknown
timestamp: June 04, 2021, 09:33:07 pm
content: Quote from: xmo on June 04, 2021, 08:04:01 pmI'm torn between the Rigol DG811/812 and the Siglent SDG 1032X if I go digital. The SDG20xx range is outside what I want to pay.The only reason I'm tempted by that Kenwood is it is a Wien bridge type oscillator and I can set it with a frequency counter and should produce a nice sinewave in the KHz range, but it will cost only a little bit more to get a brand new digital 14 or 16bit function generator that I can do so much more with.I already have a RF generator which will go from DC to over 1GHz which is perfect for checking SINAD and alignment, I just don't have anything to feed in to the mic/line to set the TX deviation.

author: thm_w
author_rank: Super Contributor
timestamp: June 04, 2021, 09:41:15 pm
content: Quote from: xmo on June 04, 2021, 08:04:01 pmDG811 goes to 100MHz, if you don't care about cal or can figure out how to cal it.https://www.eevblog.com/forum/testgear/new-rigol-16-bit-function-generators-dg800900-series/I assume you are talking about the SDG2042X?

author: tautech
author_rank: Super Contributor
timestamp: June 04, 2021, 09:51:00 pm
content: Quote from: TheBay on June 04, 2021, 09:33:07 pmSDG1032X can be improved to 60 MHz whereas SDG2042X to 120 MHz.SDG1000X models offer square waves to max frequency whereas SDG2000X models only to 25 MHz.SDG2000X has a touch screen but with the small display it's of limited convenience.https://www.eevblog.com/forum/testgear/siglent-sdg1000x-waveform-generators/https://www.eevblog.com/forum/testgear/the-siglent-sdg2042x-thread/

author: xmo
author_rank: Regular Contributor
timestamp: June 04, 2021, 10:25:25 pm
content: Yes, the Siglent SDG2000X seriesLook over the datasheets for the instruments you are considering.That Kenwood has a distortion spec of 0.1% or less from 400Hz to 20kHz whereas the Siglent SDG2000X series spec is Total Harmonic Distortion 0.075% 10 Hz to 20,000 HzIt's frequency accurate and level accurate so there's no guessing or needing three instruments to do the job of one.It's your budget but sometimes it pays to endure a little pain once in a while.The extra features and functions expand your capabilities and skills.

author: TurboTom
author_rank: Super Contributor
timestamp: June 04, 2021, 11:06:19 pm
content: Currently, I'ld go for the DG811 and hack it, lifting it almost to DG992 level. It "feels" much more modern than the competitors and it will get the job done. Despite its funny appearance, it's a solid piece of test gear.One important thing to consider when focusing on testing audio equipment is the low-level accuracy and common mode noise. Most of the these "universal" generators have their outputs earth-referenced which will almost certainly cause some coupled noise in the millivolt range. If you have to work with levels like these, you may want to assemble an isolator / attenuator box with maybe 0 - 20 - 40 - 60dB of switchable attenuation and an (audio) signal isolation transformer in-line (probably best before the attenuator) to eliminate the ground reference. With the mentioned AWG and this interface box, you'll be good to go...

author: TheBay
author_rank: Unknown
timestamp: June 04, 2021, 11:58:21 pm
content: Quote from: TurboTom on June 04, 2021, 11:06:19 pmYeah I'm going to order one when they come back in stock, the DG800 series looks pretty good for my needs. I can only find the DG812 available in the UK, the DG811 is out of stock (I wonder why) At least i'd get a sticker for the extra ££ that states 2 channels.Yes I will use a transformer (600R) for certain radios as some (Motorola are one) do not have the audio negative referenced to chassis ground. Although my TTI TSX3510 and all my linear 30/40amp PSU's do not reference negative to mains earth I could end up putting the radio chassis at mains earth potential if it happens to be plugged in to the PC for programming either serial or USB or it's connected to my RF generator and having it connected to the function generator will cause problems as that will also be referenced to mains earth.

author: nctnico
author_rank: Super Contributor
timestamp: June 05, 2021, 12:16:49 am
content: GW Instek has a function generator with isolated outputs.

author: TheBay
author_rank: Unknown
timestamp: June 05, 2021, 12:34:04 am
content: Just ordered the DG812, that GW Instek sounds interesting, what model is that?Quote from: nctnico on June 05, 2021, 12:16:49 am

author: rvalente
author_rank: Frequent Contributor
timestamp: June 05, 2021, 10:30:58 am
content: Get the dg811, not the dg812 and hack it to dg922. You can find how here

author: nctnico
author_rank: Super Contributor
timestamp: June 05, 2021, 10:49:56 am
content: Quote from: TheBay on June 05, 2021, 12:34:04 amIt is the MFG-2000 series.https://www.gwinstek.com/en-global/products/detail/MFG-2000

author: TheBay
author_rank: Unknown
timestamp: June 05, 2021, 11:07:01 am
content: Quote from: rvalente on June 05, 2021, 10:30:58 amThere is no stock for the DG811 in the UK, DG812 is only £20 more and can get it this week, plus if I ever sell it a 2 channel may sell easier (Some people don't like buying "Hacked" on the used market)10MHz is all I need really, maybe 24/25MHz for some things but I can use a GPSDO for that. So may hack it depending if I need above 10MHz.Though I'm still looking at the SDG1032X as I want to buy another scope and thinking of a Siglent this time and would be nice to have them both matching, but depends which generator is better really out of the DG812 or SDG1032X for my needs, really can't find a direct comparison of the twoInterestingly a friend bought a Rigol DS1202Z-E this week, I assumed this was a cut down version of the DS1054Z, but it must have a different front end as it seems to work well above it's specifications and far better than the DS1054Z.

author: TheBay
author_rank: Unknown
timestamp: June 05, 2021, 11:08:40 am
content: Just had a look at those, very expensive in the UKQuote from: nctnico on June 05, 2021, 10:49:56 am

author: tautech
author_rank: Super Contributor
timestamp: June 05, 2021, 11:27:31 am
content: Quote from: TheBay on June 05, 2021, 11:07:01 amDatasheets are your friend.If you pair a Siglent DSO with any of their AWG's you have seamless Bode plot functionality for the DSO's that support it and with the EasyWaveX SW utility the ability to capture waveforms from the scope and have the AWG reproduce them.QuoteOf course. 1202Z-E was released as direct competition to SDS1202X-E and they're both 200 MHz 2ch DSO's.Rigol were late to this market sector as SDS1202X-E had already been in the marketplace for some 3 years.

author: TheBay
author_rank: Unknown
timestamp: June 05, 2021, 11:33:42 am
content: I've studied the datasheets of both and the only 2 things that stand out on the Rigol are 1ppm and 16bit, where as the Siglent is 25ppm and 14bit.Regarding the scope, I'm trying to convince myself to go for a 4 channel, so most likely the SDS1104X-E or SDS1104X-E. The DS1054Z is not suitable, It is a big downgrade from my DS2072, especially with the offsets at lower voltage range and minimum V/div levels.Quote from: tautech on June 05, 2021, 11:27:31 am

author: tautech
author_rank: Super Contributor
timestamp: June 05, 2021, 11:43:59 am
content: Quote from: TheBay on June 05, 2021, 11:33:42 amYes for 16 bit only SDG2000X and SDG6000X models offer that.QuoteSDS1104/1204X-E have 2 ADC's so careful assignment of channels used will offer the same sampling rate as your DS2000 with 2 active channels but I can't remember the mem depth for those and things have moved on to where a comparably spec'ed DSO like SDS2104X Plus now offers 200 Mpts for each of its 2 GSa/s ADC's.Maybe consider getting the SDS2104X Plus as it has an inbuilt 50 MHz AWG so not needing to buy both and still have your RF gen for your HF work.

author: nctnico
author_rank: Super Contributor
timestamp: June 05, 2021, 12:16:24 pm
content: Quote from: TheBay on June 05, 2021, 11:07:01 amI strongly suggest to look at the function generators I suggested earlier. From a functional point of view the DG812 and SDG1000X don't add that much but are far more expensive.

author: TheBay
author_rank: Unknown
timestamp: June 05, 2021, 12:26:02 pm
content: Thanks for the suggestions, but the problem is the UTG962 costs the same price or more than the DG812 and the FY6900 is £120, DG811 is only £210 (If I could get stock) DG812 is only £235 delivered total cost. Also I do not trust the SMPSU in the FY6900 for RFI and also other components and the stability of it etc, I also heard that the FY6900 has a clone FPGA - It may be an okay device but it seems like a toy and also no warranty if it goes wrong.Quote from: nctnico on June 05, 2021, 12:16:24 pm