new-to-me Function Gen -- tips/help? - Page 1
Forum section: electronics / beginners

author: outofstepper
author_rank: Contributor
timestamp: August 31, 2012, 02:15:45 pm
content: Didn't take long to get fed up with the electronics-diy FG kit.stumbled across this thing in a 2nd hand shop (though it still cost me $100!):Unaohm EM136 Function GeneratorI've got the basics down (and probably more than I'll need).. but I'd really like to get up tosnuff on what this thing can do. Can't find any references to "Unaohm" or EM136 but i'm wonderingif someone could point me to some documentation for an FG of this age / type.. or.. if its not toomuch.. give me a run down of what some of the options are for? (like Sweep, VCF in, Counter.. andthat Gate led that keeps blinking?) etc..Here are some gratuituous scope shots of a 1k sine and square. The square wave has overshoot(looks like all frequencies).. its not the squarest thing I've ever seen either.But as I say, probably still more than enough for my skill level.here's a detail:Thanks!

author: Rerouter
author_rank: Super Contributor
timestamp: August 31, 2012, 02:21:48 pm
content: the counter input is if you feed in an external frequency, its a combination FG and counter,the gate led thats flashing is the counter display updating, depeding on your frequency each time it updates will give you a new reading

author: T4P
author_rank: Super Contributor
timestamp: August 31, 2012, 03:08:48 pm
content: Did you really pay 100$ for itI can like find function gens from GW-Instek that costs half that and are more recent

author: outofstepper
author_rank: Contributor
timestamp: August 31, 2012, 03:19:54 pm
content: Rerouter, thanks!t4p: unfortunately its true. I'm in europe.. at least where I am, I'm even lucky to have found that one.The one I was about to pull the trigger on was this (for comparison), at $250.. its also used:http://www.subito.it/attrezzature/generatore-di-funzioni-hung-chang-come-nuovo-olbia-tempio-33043129.htmany thoughts on that square wave?

author: ProBang
author_rank: Contributor
timestamp: August 31, 2012, 03:23:31 pm
content: Quote from: T4P on August 31, 2012, 03:08:48 pmCool... - where? Links?

author: JuiceKing
author_rank: Regular Contributor
timestamp: August 31, 2012, 03:59:29 pm
content: There's a lot of functionality in that little box and $100 is OK if it all works.The rise time on the square wave you show is about 40ns. My 15Mhz FG has a rise time of 20ns, so I'd guess yours will have an output limit in the 7-8Mhz range. Don't worry if the square wave isn't square at that level--its bandwidth is likely to be 5x less than the sine wave. I'd also expect the FG to have a 50-ohm output impedance, so you should use a 50-ohm passthrough terminator on your scope or a "T" with a 50-ohm terminator at the scope end in order to get the expected overshoot.The numbered buttons across the top set your scale for the counter and presumably the oscillator, too. Somewhere you will be able to toggle between frequency and time, which are just reciprocals. Looks like the "EXT" yellow button determines whether the counter is taking the COUNTER BNC input or the internal FG oscillator as its source. Be careful not to put in too much voltage to that BNC. I'd expect that the 150V max applies only when the -20db attenuator is depressed.For sweep, somehow you will need to set the start and stop frequencies, plus I'd expect a time constant for how long the sweep takes. I can see that you get a choice of linear vs. log on the frequency sweep. It looks like your knobs have at least two controls each, with the skirt being a separate knob from the center, but it's really hard to tell. It looks like you can pull them to get into another mode. The bottom right knob is blocking the legend. I just can't figure it out, sorry. You'll have to play with it.My guess is that the "SWP OUT" BNC will be a ramp waveform from 0-10V which corresponds to the frequency you are at in the sweep. It's convenient to put this into your scope's second channel so that you can see where the sweep starts and stops. I g guess you'll want to trigger your scope off the negative slope (end) of the sweep--...I don't see a trigger out BNC so that would be my guess. Are there any more connections on the back of the unit?- Ken

author: T4P
author_rank: Super Contributor
timestamp: August 31, 2012, 04:59:38 pm
content: Quote from: ProBang on August 31, 2012, 03:23:31 pmI don't know how fast can his FG go but the ones i saw ishttp://www.ebay.com.sg/itm/MATRIX-MFG-8216A-FUNCTION-GENERATOR-/310427330686?pt=BI_Signal_Sources&hash=item4846e9287e#shIdhttp://www.ebay.com.sg/itm/GW-INSTEK-GFG-8216A-FUNCTION-GENERATOR-/170872504925?pt=BI_Signal_Sources&hash=item27c8cb825d#ht_2865wt_905

author: w2aew
author_rank: Super Contributor
timestamp: August 31, 2012, 05:38:42 pm
content: Quote from: outofstepper on August 31, 2012, 02:15:45 pmLooks like a decent function generator. The Sweep can be very useful to do RF circuit alignments, filter response checking, etc. Looks like the upper two knobs on the left are used to set the Start and Stop frequencies for the sweep. You may want to look at my video on Sweep Generator basics and Receiver Alignment. I start talking about the sweep generator at about 4:30 in the video. It talks a bit about the Sweep voltage output too.The VCF input allows you to use the box as a voltage controlled oscillator, where the voltage applied to this input will determine the frequency of the output. Others have described the Counter function and the meaning of the Gate LED.Here's my video that I mentioned:

author: outofstepper
author_rank: Contributor
timestamp: August 31, 2012, 06:14:57 pm
content: This thing goes to 2Mhz.Well I started *some* kind of sweep.. how excitingonly the 2nd 'column' of knobs pull out. They are one piece knobs.. ie either they are in or they are out.The labels are (in ascii art):Freq WidthO Olog/lnrSWP STR SET pull only SWP STP SETO Ofine off/ Run RateSo I think when I pull the 2nd column knobs it goes into Sweep.I can't quite figure how to set anything though.. other than the top freq it sweeps to maybe.I get log/lnr.The knobs don't click anywhere.. continuous from, say, 7 oclock to 5 oclock.Instict says I'd put it on a "start" position, dial in a start freq, then put the knob in a stop positionand dial in a stop frequency.But this thing is older than me.

author: Monkeh
author_rank: Super Contributor
timestamp: August 31, 2012, 07:35:32 pm
content: Quote from: T4P on August 31, 2012, 04:59:38 pmAh, good, you can find a load of stuff from the US which has no relevance whatsoever to the rest of the world.

author: T4P
author_rank: Super Contributor
timestamp: September 01, 2012, 03:31:05 am
content: No not US it's from ... Singapore

author: Monkeh
author_rank: Super Contributor
timestamp: September 01, 2012, 03:25:36 pm
content: Quote from: T4P on September 01, 2012, 03:31:05 amOkay.. same difference. Price stupidly cheap, in US dollars, impossibly expensive to ship, and bearing no relevance to prices and availability in other countries.

author: ProBang
author_rank: Contributor
timestamp: September 02, 2012, 03:38:55 am
content: Quote from: Monkeh on September 01, 2012, 03:25:36 pmFull agree. Yeah, nothing else I have expected. My opinion:The TO made a good deal, he has no reason to think only one second about too much paying.So let him having his fun with the function- generator.Back to topic:Rebadging is a nice thing, isn't it?This device was sold in Germany as "Voltcraft FG 1617".So I can find something about it. I've attached that as Pdf´s."FG_1617-Part1" and "FG_1617-Part2" are containing the technical manual."FG1617" contains a short manual for students of a university - special to activate the "Sweep- Mode".Unfortunately all in german...(Perhaps you understand german. I have no idea where you come from,because there isn't a country- flag beside your name. But I guess: Not from Singapore...)I hope, the Pdf´s are at least a little bit useful for you.If there is a part that needs translation, please write it.About your last posting (to start "Sweep- Mode"):1. Set Start- FrequencyLike in normal use (Waveform, Attenuation, Range,Frequency...).2. Set theWidthof the Sweep- Steps.Left: Minimum increasing.Right: Maximum increasing.Button pull: Increasing is linear to time.Button push: Increasing is logarithmic.3.Runsweeping and set Sweep-RateButton push: Sweep off.Button pull: Sweep on.Button left: Sweep- Frequency minimum.Button right: Sweep- Frequency maximum.That's it.Greetings,Hartmut

author: outofstepper
author_rank: Contributor
timestamp: September 02, 2012, 07:20:28 am
content: Thanks! that makes more sense now.. and seems easier that I was making it.I assume it will only sweep within one range? Meaning if my scale is set to 1K, I couldonly sweep in that range: 1k-10k ... I could not sweep, for example, from 100 hz to 100k hz.

author: ciccio
author_rank: Frequent Contributor
timestamp: September 02, 2012, 02:12:27 pm
content: Quote from: outofstepper on August 31, 2012, 02:15:45 pmMaybe you were lazy when googling for UNAHOM.UNAOHM is an Italian Company that is still in existence (once they were manufacturers, now they are re-badgers for most of their catalog) and that is well know here in Italy.They have an Internet site:http://www.unaohm.it/unaohm_eng/index.phpand there I could find an address for technical assistance: "astec@unaohm.it".Write them and they will surely be of help.Best regards