Yeah, I mentioned the TF930 in my initial posting. Problem is that I couldn't find anything cheap yet. Actually the few ones sold on eBay are much more expensive than a new unit from RS (including VAT) which is around 420€ and a bit more than I'd like to spend.
Besides, I don't think I like the external reference input on the front and I guess some thinks like Phase A/B are missing (which I don't really need though) compared to the 6010.
Then there's the issue that there are two inputs, but the B input is only for >80MHz. So I couldn't even use stuff like Ratio A/B with a 10MHz OCXO vs. GPSDO.
Again, not a total showstopper. It's just that this makes the 2nd channel more or less useless for me.
The only measurements that the TF930 has but the 6010 doesn't are pulse width and duty cycle measurement. Dunno how much sense these make though as they depend on rise/fall times and threshold.
About the old HPs: my impression is that these are at least 10 years older than the Tabor 6010 and the ones that are in the <200€ range don't seem to have a TCXO.
Anyway my chances to get a mint unit for a good price are better for a less known brand like Tabor.
Wow, thanks, how could I overlook the schematics in the manual? I actually searched for the Jumper 4 layout in the manual but didn't consider that the schematics were only graphics.
Anyway, I tend to think that the manual mixes up U56 and U58. While U58 is used in the analog output option, U56 is the 74F132 (Quad 2-input NAND Schmitt trigger) used in the 5ppm Oscillator. It's socketed as all the other ICs and I guess it would make perfect sense that the 5ppm oscillator isn't connected to the device anymore if it's removed.
I originally planned to use one of the 10MHz OCXOs I bought some time ago and I guess I could build some PLL circuit to crank it up to 100Mhz.
The benefit of this approach would be that I could also still use an external 10MHz (keeping the 10x multiplier) reference with an internal jumper.
But it's certainly much easier to try to get a 100Mhz TCXO (or OCXO) with <=1ppm.
Now this really looks like it could be a piece of cake to build myself a fake option 1...
[EDIT]
On a 2nd thought, I guess using some off-the-shelf clock multiplier like the IDT ICS601M-01 I could actually re-use my 10MHz OCXO and keep the possibility to use an external 10MHz Reference.
https://www.idt.com/document/dst/601-01-datasheet
You might want to be careful with that chip - it seems to be designed for direct crystal driving.
It also states that the jitter and phase between the reference and output are not specified.
The external input is really useful I think and it is something I'd try to incorporate, but I'd be looking for a higher spec design. The problem is going to be the accuracy of your measurements will be directly affected by the jitter.
Quote from: AshThe external input is really useful I think and it is something I'd try to incorporate, but I'd be looking for a higher spec design. The problem is going to be the accuracy of your measurements will be directly affected by the jitter.The typical output jitter (one sigma) is defined as 12ps for the ICS601 which is probably >100 times less than the time resolution of the counter. Actually I couldn't find any specification for the single shot interval resolution only the 10ps resolution for averaged (!) measurement with option 1 (TCXO). So probably even with the TCXO the single shot resolution is 500ps or more. Actually I think it could be as bad as 2ns.
I don't think a typical OCXO or TCXOs will have much better values regarding phase noise. E.g. I looked up a 100MHz VCTCXO from Abracon (ASGTX-D-100.000MHz-1 for 51,36€) and my understanding is that it has a phase noise specification of -116dBc/Hz at 10KHz for a 120MHz carrier.
So I'm not sure that an affordable TCXO or OCXO will have a much better phase noise or jitter than this multiplier solution.
Yeah, I'm like 95% percent sure I will do this sooner or later. It's just that I guess I want to design a PCB for this and even if I should do this in the next days it will take >6 weeks or so until I get the PCBs from China. And well, you know if I'm ordering parts it usually ends with days checking what I could order additionally now that I'm ordering anyway.
So don't expect an update on this too soon
Side note: I looked a bit more into the schematic and it looks like simply connecting a 100MHz oscillator won't do the job.
There seems to be some +/-5V level shifting going on at the output So I guess I will replicate that circuit.
While I'm at it, I guess I will also replicate the 10MHz external reference input/output circuit using the 74F132 NAND-Schmitt-Triggers (funnily they are called Schmidt-Triggers in the manual which is actually the more common German spelling).
Well, the output of the normal 5ppm oscillator and the external reference is definitely created vby a TTL NAND gate (74F132). When I follow this signal into the "Measurement Logic circuit", it's simply connected to the ECL NOR gate through a series 820Ohm resistor and 100nF capacitor. So I guess this is exactly what I need to connect my TCXO/OCXO output to the 100MHz input.
Quickly checked this with LTSpice and it looks somewhat promising: