Koolertron JDS-8060 60MHz Sig Gen (eventual success)

edit: See update in post 2. Had to offset the reference and most of what follows cleared up. Leaving what I discovered along the way for the next person instead of deleting.

You get what you pay for

The external sync feature never worked. On top of that, there was extreme phase jitter and RF leakage with the outputs off. Lifting the power leg on that chip with the red dot (I added the dot) disabled the useless back ports and cleared up much of the phase jitter.

But I wanted to use an external reference, so I hot aired off the 50MHz oscillator chip (that outputs CMOS level RF) and injected the CMOS output from the Leo Bodnar GPSDO. I expected that to make this thing dead-on frequency, but it didn't. To get the outputs close, I have to set the fine tuning adjustment to 57.

Since that fine tune control is doing roughly 5Hz per step, getting it perfect is not possible.

And the frequency is still not super stable, its doing the same thing it did with the internal oscillator after being warmed up, bouncing around a couple Hz. The GPSDO outputs 10MHz on port 1 for my bench counter reference and 50MHz for the new signal gen reference. If I put the 50MHz from ch2 or the output of the rubidium into the FC, they are both dead on and rock solid, but this sig gen running off the confirmed-stable GPSDO is not outputting a stable signal. Set to 27.383996Hz and the fine tune at 57, the output bounces between 27.383999 and 27.384001 with an occasional small excursion beyond that. For comparison, with the fine tune at 50 (center) and the sig gen set to 27.385000, I get 27.384903-27.384905.

Update:
If I set the fine tune to 50 and set the GPSDO to 50000177.75Hz, the sig gen is dead on from 0-60MHz and the variation is within a tenth of a Hz (which is the resolution of my counter). This is odd, why would a little frequency offset change the stability?

So, after a whole day fighting with it, I think I have something usable.

Oh, and if you interrupt that 50MHz signal, even briefly, the output goes out. The controls, power button included, requires that 50MHz signal be present. A change in reference frequency requires a sig gen power cycle..

And I am extremely excited to report that with this funky reference frequency, the sig gens counter feature is also accurate. before it wasn't and it didn't matter what the fine tune was set at.

I think they have a hard-coded frequency adjustment (not menu accessible) somewhere to get it close to whatever run of crystals they had. And I assume the crystal they based that on ran at the frequency I currently have it set to. I think for this built in counter to be useful, an amp is needed. It takes logic level signals, it won't see small signals.

I started this thread fairly upset with this sig gen and now I am extremely happy with it.