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Suggestions for a good digital signal/function generator? - Printable Version

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Suggestions for a good digital signal/function generator? - Ron Ramirez - 09-27-2019

I want to get away from the old Clough-Brengle signal generator I've been using for a few decades now and get something where I can punch in the desired output frequency and know it will be accurate. It needs to have internal modulation, cover frequencies from longwave up to at least 30 MHz or so (60 MHz would be better), and have a sweep function.

And I don't want to spend thousand$ of dollar$ to get this.

I began to see the need for something like this when attempting to align my RCA C15-3 and my Hammarlund HQ-129-X, both of which want a sweep generator for IF alignment. Plus, both needed something more accurate than that old Clough-Brengle. Even running the C-B through a frequency counter, it is not possible for me to get, say, 455 kHz dead on at 455.000 kHz.

I've been looking at these two:

https://www.amazon.com/Koolertron-Generator-Precision-Dual-channel-Arbitrary/dp/B073P6TKQC/ref=zg_bs_5011665011_5?_encoding=UTF8&psc=1&refRID=XZ9M2CXK4NJ8BZB0BHS1

https://www.amazon.com/Generator-KKmoon-Dual-Channel-819214bits-Modulation/dp/B0779V9VR2/ref=sr_1_fkmr0_1?keywords=kkmoon+fy6800+60mhz+generator&qid=1569605150&sr=8-1-fkmr0

Advice, people, please...

and thanks in advance.

RE: Suggestions for a good digital signal/function generator? - EdHolland - 09-27-2019

Hi Ron,

Those both look good - I have used this (slightly simpler) unit quite successfully, priced around $66:

https://www.amazon.com/Generator-KKmoon-Precision-Dual-Channel-Arbitrary/dp/B071HJ31WN/ref=sr_1_2?qid=1569606101&refinements=p_89%3AKKmoon&s=industrial&sr=1-2

A warning though: the output does require some protection, as I managed to zap one channel connecting to a radio before thinking.... That warning would apply to any of these modern inexpensive generators. For IF and other alignment work, it is easy to use, and spot-on in frequency. I've used it on AM and FM circuits with good results, and the low frequency range allows for 19 kHz injection for stereo multiplex circuit alignments.

I bought a second unit, and use the first as the master oscillator for my SW beacon. It allows me to fine tune within 10's of Hertz and stays there.

Cheers,

Ed

RE: Suggestions for a good digital signal/function generator? - morzh - 09-27-2019

Yes, digital generator is way more convenient.

Ever since I bought an HP (forgot which one....something like this one

https://www.ebay.com/itm/Hewlett-Packard-HP-8643A-Synthesized-Signal-Generator-0-26-1-03GHz-w-Opt-009/274023798555?epid=1623881977&hash=item3fcd17571b:g:CYwAAOSwJwVdio6z

) I never got back to the analog Leader I used before. In fact I should probably sell it.

One single piece of advice for using SS generator: I made a limiter, two small value Zeners serialized in opposite to each other and then soldered into a barrel of two BNCs, then the output is plugged through it. It will prevent spurious charges from tubes' grids from destroying the output of your generator.

I have the thread somewhere here.

   

or

   

RE: Suggestions for a good digital signal/function generator? - morzh - 09-27-2019

Either one will work.

RE: Suggestions for a good digital signal/function generator? - rfeenstra - 09-27-2019

I have been using the KKmoon 6600 unit for some time.  I used to monitor the out put with a freq counter but don't any more.  Seems to be plenty accurate and stable for my use.  It is not always the most convenient to use, but then I have little experience with signal generators in general.  Changing frequencies and output involves using the arrows to select the the decimal range, then dialing it in.  If you are modulating the channel 1 output with the channel 2 frequency, and then want to change the channel 1 frequency, you have to select channel 1 which then cancels the modulation, change the channel 1 frequency, and then press the MOD button to start the modulation again.  A little inconvenient.

I have not used the sweep function as I usually use a spectrum analyzer where I need that.  I would like to learn to use it, however, to get the FM discriminator waveform they always show in FM alignment data.  Nor have I tied into a PC, which probably would make use easier, as I don't have room for a PC on my bench.  Another function I would like to play with some day.

The unit is inexpensive and has done what I need it to do.  But, like I said, I have no basis of comparison.

RE: Suggestions for a good digital signal/function generator? - rfeenstra - 09-27-2019

I better make one of those protectors!.  Thanks.


Edit: is this the thread? https://philcoradio.com/phorum/showthread.php?tid=19209

RE: Suggestions for a good digital signal/function generator? - morzh - 09-27-2019

Yes this is the one.
I forgot I put a small resistor in there, it is optional as the current is limited. And if you touch a real high voltage (not a grid capacirance charged to it) the resistor won't help.
This jig is to take care of smaller charges with self limited discharge. Transorbs for Telecom signals could be used also. Otherwise a real serious protection device is needed.

RE: Suggestions for a good digital signal/function generator? - John Bartley - 09-28-2019

I have one of these and have been using it for about fifteen years. It works well for me ::

https://www.bkprecision.com/products/signal-generators/4040A-20-mhz-sweep-function-generator.html

I also have a couple of old analogue units that I can set using a digital radio if I need more than 20MC.

RE: Suggestions for a good digital signal/function generator? - Radioroslyn - 09-28-2019

Don't have any suggestions for the moderately priced generator but there is one feature that I'm not seeing on the mentioned units. Could be I 'm not seeing it? That would be an attenuater calibrated (in microvolts). This would go along w/a very low leakage factor. That meaning how much of the rf signal escape the generator from other sources than the shielded output cable. Leakage from the plastic cabinet and radiation from the ac cord. The reason I mention this is that w/o a calibrated output it's difficult to determine the sensitivity of a set.

With my old cheap SG-7 it leaks terrible! When I was aligning the HRO senior I had to put the generator a couple of rooms away so it would overload the receiver. With a calibrated attenuater you can get a definitive measurement of the sensitivity. This may not matter if you are working on the run of the mill home/entertainment sets but if you work on any higher end or communications sets it's pretty handy.

RE: Suggestions for a good digital signal/function generator? - rfeenstra - 09-28-2019

The output attenuator on these units goes from .0001 to 20 Volts. At higher frequencies, to 5 volts. I really don't know how much leakage there is. I can seem to be able to turn the output down to a very low signal with a direct connection to the antenna so as not to activate AVC.

RE: Suggestions for a good digital signal/function generator? - W8ZV - 09-28-2019

Hi Ron!!

I've replied to this on ARF.  I use a pair of HP 8640B's and I also have an HP3312A function generator.  In addition I've got the Berkeley Nucleonics 625A, which is an Arbitrary Waveform Generator.  It's basically the same generator that you've sited in your original post here.  It's what I use for FM alignment.   Berkeley is building B&K AWG's that go for about $1300.  Mike on AFR is right, that if you look at E-Bay long enough, or travel to the Dayton Hamvention, you'll find REALLY GOOD stuff cheap.  That said, you need to be able to fix some of that stuff too.  That's what usually fouls up many folks.  They don't have the ability to fix something that needs fixed.  I have NOT used any of the new Chinese gear, but both pieces you site can be had for less that $100 and I've seen the 40 Mhz version for $88.  I'm fairly sure, after reading several posts here on the same generator, that you're going to be happy with one of them.  I will say this:  NONE of the new digital generators are that user friendly.  They are all a computer, in a test equipment box.  So you have a learning curve.  The shielding issue mentioned on ARF is probably not an issue.  You could internally shield the RF generation portion and have no leakage out of the box.  For the price, I'd try it.  You have a warranty and if you buy it from a reputable dealer and you don't like it or it doesn't work, you can send it back.

RE: Suggestions for a good digital signal/function generator? - W8ZV - 09-28-2019

Something else that I should've mentioned:  You should NEVER connect any of the newer generators to any radio directly.  You need at LEAST a capacitor between the generator output and the device under test.  I have HP11509A fuses which connect to the output of the generators so that IF anything get reverse applied to the output, the fuse blows.  These things take a 60 milliamp fuse and it's inside of a barrel that's tested flat to 1 Ghz.  That's not necessary for what we do here.  You could do the same thing in a shielded box with two BNC connectors and the fuse in a fuseholder inside.  You get the same protection, it's just not flat impedance wise.  Again, no big deal here. 

The other thing to keep in mind is that an isolation transformer is a must for AA5 radios.  You'll kill a generator REAL QUICK if you don't have one.  Don't ask how I know Icon_thumbdown .

RE: Suggestions for a good digital signal/function generator? - Ron Ramirez - 09-29-2019

Hey Kim! Good to hear from you. Icon_smile

Acked re: never connecting a new generator to an old radio, especially an AC/DC unit. Mike (morzh) posted a protective circuit earlier in this thread, and I don't think an additional capacitor would hurt, either.

I asked this same question at ARF. Rob almost had me steered toward the KKmoon 6600. But now thanks to the ARF guys, I'm taking a second look at a unit I hadn't mentioned here previously - a Siglent SDG1025:

https://www.amazon.com/Siglent-SDG1025-Function-Arbitrary-Generator/dp/B01LECZU98?pf_rd_p=27933938-66d5-4a49-965b-3c0c25216562&pd_rd_wg=MyXVl&pf_rd_r=D9WT8D517WBTSWP6QT5W&ref_=pd_gw_cr_simh&pd_rd_w=sKMal&pd_rd_r=3c454937-4e1d-4014-b5a8-55dded9a397e&th=1

Which leaves me at this point, which Vinny Barbarino (John Travolta) said best back in the 1970s:

[Video: https://youtu.be/qnVrjFSE1hA]

Icon_crazy

And John B., I had said I didn't want used, but I will look into the B+K Precision 4040A. Does it do everything I need to do (save for going to 20 MHz instead of 30)?

Along those lines, here are the main things I'm looking for:

* No analog dials. Punch in a frequency and it will be on that frequency. I'm frankly tired of the constant drift, drift, drift of my Clough-Brengle OC-A plus the inability to set 455 kHz right on 455 kHz. It has served its purpose over several decades, but it is time to retire this unit.
* Audio modulation of AM signals.
* Sweep function for various AM IF frequencies.
* If I need to add an external unit to turn down the output into the mV or uV range, I'm naturally willing to add that.
* Needs to cover fairly low longwave (say, around 100-150 kHz) to upper SW - 30 MHz.
* New - not used. (although as I said, I would consider the B+K unit)
* A price that will not break the bank.

I don't need square or triangular waves, but understand they come as part of the package of the newer generators.

I have a Sencore SG165 to take care of my FM/FM Stereo needs. Yes, its dials are analog, but it does well for what it is.

Again, I do sincerely appreciate the help from everyone who has posted in this thread...sometimes a guy who's been in the hobby for 45 years finds he needs some upgrades...

RE: Suggestions for a good digital signal/function generator? - rfeenstra - 09-29-2019

Good luck! On the one I have, you can't punch in a freq. You have to select a range and dial it in. I realigned my 41-295 tonight before I store it away ( the 41-295 is decidedly lacking in its tracking across the bands!) using the 6600. It certainly works ok. I often get confused in my button punching and wind up turning off the channel and then wonder why I don't have a signal, but I figure it out! Again, I have no basis of comparison. But, it does what I need it to do for now. And it's cheap! Plus it goes up to 60 mHz allowing you to use the harmonic to get into the FM band.

RE: Suggestions for a good digital signal/function generator? - EdHolland - 10-05-2019

One important consideration - the unit I suggested (and use) doesn't have a straighforward means to modulate the output. Sometimes I fall back on the old Heathkit...