Junctec?

[Terry Bites]

I'm not one to talk up cheap gear but....

I borrowed a Junctec signal generator to play with.
A JDS8060 8080 Dual Channel Function Generator 14bits 80MHz
Its just under £120 on Ali. It feels so light you think it must be crap but its surprisingly good for the price.

I checked it on my recently cal'd Racal Dana counter (still in love) and its not far off after 20min of warmup. I left it on overnight and it was still on frequency.
Maybe I got lucky. So not so Junk. I hate the lack of numeric key pad entry but you get what you pay for here. No external ref input sadly.
I think it wouldn't be too hard to modify that though. Must do a teardown. BTW, what's the best way to make an external ref automatically override the internal?

Its dual chanel and has all the usual waveforms, modulation types, arb, exteral mod input, burst (on external sync) DC offset, CV input etc.
You can even use one channel as a counter while the other output is a generator. Stores user presets. Thats great for low cost bench.

It can be mains or 5V adaptor powered. That might be handy if you want a floating source to drive balanced lines.

Remote control via PC, IOS or Andoid app. TTL GPIOs and I think RS232 coms too.

For a beginner on a budget I'd recomend it. https://video.aliexpress-media.com/play/u/ae_sg_item/2209337394332/p/1/e/6/t/10301/1100067032873.mp4?from=firefox

[mawyatt]

I think it wouldn't be too hard to modify that though. Must do a teardown. BTW, what's the best way to make an external ref automatically override the internal?

Recall someone utilized injection locking the Internal 10MHz Oscillator which effectively switched to the External Reference when available on one of the low cost AWGs. Inserting a small resistor or inductor in the Ground or VCC line and injecting the Ext Ref by means of a series RC into 10MHz oscillator might do the trick!! This couples the Ext Ref into the Internal Oscillator which "locks" to the external signal when the external signal is very close in frequency. The Ext Ref signal level as "seen" by the Internal Oscillator doesn't need to be large, just a few 10s of mv.

When no External Ref is present the 10MHz Oscillator determines the Internal Reference, when an External Ref is present then the Internal Reference becomes "Disciplined" by the Ext Ref.

Best

[Terry Bites]

Its a bugger because its ref osc is 50MHz.
I'll have to upscale and thats put me off messing with this thing.
I recently discovered that it has a lot of amplitude jitter at the top end.

I found the perfect ic for a 10MHz clock switch over. I think this might just work, I'd get 4x50R ref outputs too.
Cheap enough for a quick lash up. Simulates just fine.

[mawyatt]

It still might work with the 50MHz oscillator. We recently posted an article on EDN about Injection Locking Divider here:

https://www.edn.com/injection-locking-acts-as-a-frequency-divider-and-improves-oscillator-performance/

This might also work as a Multiplier altho we haven't tried, and since the 50MHz is the 5th harmonic of 10MHz this just might lock on!!

Worth a try anyway

Best

[BennoG]

I have the 80Mhz and the older 20Mhz. I love both of them.
You can do channel coupling in ways I have never seen on generators.

I used it once to generate a AB encoder signal that hat a sweep on the speed and worked like a charm (they were rock solid on a 90 degree angle, regarding the sweep)

[Terry Bites]

Ive seen this before but it doesnt say how to control the division ratio.
It just says you can. It doesnt say at what point in the circuit the external signal is applied either.
Any how, I wanted to go in the other direction. The 501 from Renasas seems to be an economical solution.
Its accademic. I'm intersted in acquiring something with more grunt. I'll give it back to the owner...

[mawyatt]

The 5th harmonic of the 10MHz external ref would allow the AWG internal 50MHz oscillator to lock-on if the ext ref frequency is close enough to 10MHz (like within <100ppm). You can try coupling to 50MHz oscillator Ground, Output or VCC pin at first without any changes to the 50MHz oscillator, try a series ~470pF and ~100Ω for coupling from the ext ref for starters. If this doesn't work you may need to create a reasonable impedance (2~5Ωs) in the Ground or VCC line to the 50MHz oscillator to "work" into from the ext reference.

The nice thing about this approach, besides simple, is the AWG 50MHz oscillator produces a 5X phase/frequency locked replica when the 10MHz ext ref is connected, and the oscillator free runs when the ext ref is not present.

Best

[antenna]

I recently connected my GPSDO to my 60MHz JDS-8060 sig gen.  The part on the board is an oscillator, not just a crystal.  I replaced my oscillator with a direct connection (with series resistor to be safe) to the top BNC port and that connects directly to the CMOS output of the Leo Bodnar GPSDO (thanks Leo!)

The trouble is that there are two frequency adjustments in this sig gen.  One way is in the menu, setting 1-99 for fine tune with 50 being the center (works in steps of about 10Hz IIRC, not fine enough).  The other adjustment I don't know how to access, but I do know how to work around it.  Apparently, there is a software adjustment for the crystal (oscillator) batch they used, similar to the adjustment in the Si5351 boards. 

Thanks to this GPSDO having two programmable outputs, I was able to connect one to the CMOS reference input, the other to the oscope, and an output from the sig gen to the other scope input.  With the GPSDO sending  50MHz into the sig gen reference, the other GPSDO output set to 60MHz fed into ch1 on my scope, and the output of the sig gen also set to 60MHz into ch2 of the scope.  With the scope in x-y mode (or not, both work), the 50MHz reference was adjusted until the sig gens 60MHz matched the 60MHz from the GPSDO.

At 50.000178009MHz into the sig gen reference, that apparently compensates for the "correction math" they programmed in.  At 60MHz and 10MHz, The sig gen and the GPSDO are rock solid.  Watching for a minute or two showed no movement between them.  The reference offset scales properly at all sig gen frequencies.

And that IC chip by the BNC jacks, the one they laser blasted the numbers off, I found I had to lift the power leg (pin 1), because with that chip powered, the sig gen output can be off and any radio tuned in within a mile would hear it.  At least with that chip dead, it barely disturbs my nearby radio unless the output is on.  Whatever that chip does, it is used with the useless ports on the back.

The only problem is that each time the GPSDO receives command to change frequency, the sig gen output dies.  The sig gen needs to be power cycled if the clock is interrupted.  This makes fine tuning the GPSDO a little bit of a chore.  Make adjustment, power cycle the sig gen, turn its output back on to compare.  Repeat.

If you are adding a OCXO or something, don't adjust it to exactly 50MHz, adjust it by counting what comes out of the sig gen output.