I was going to suggest Leo¡¯s GPSDO but you figured that out before I got ¡®round to typing. I know that the desire for high precision/high accuracy can be an obsession! For calibrating scopes, something less elaborate more than suffices. Even the cheapest CPU clock oscillators are good to 200ppm. You¡¯ll never see that error on a scope. But high accuracy clocks are now available for a song. I have a rubidium standard, and although I don¡¯t do any work requiring 10ppb accuracy, the fact that I have one caused me to check every frequency counter and every frequency source I own and tweak out whatever errors could be tweaked out. Ridiculous! But fun.
Enjoy the Quest For the Last Digit!
¡ª Cheers
Tom
Sent from my iThing, so please forgive typos and brevity.
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On Dec 3, 2021, at 3:35 PM, Dave Peterson via groups.io <davidpinsf@...> wrote:
? Thanks Jeff,
Michael pointed me to the appropriate section of the SM (RTFM Dave). I see there is an oscillator available on eBay. Not sure I feel the need to spend another $50 on eBay just today. I just bought an S-53 to enable viewing 1GHz signals. It was an impulse buy, sure, but this has been on my mind. And now I feel the need to have that capability. So I need to pace my spending. (Why start now!?)
Another intriguing possibility I've found in the SM is the possibility of using an external clock. So it seems I could pipe the Leo Bodnar GPSDO directly into the TG501. Now there's some time mark stability and accuracy! It should be easy to add a BNC to the back of a TM50x.
BTW, my homemade FR4 trimmer has set up nicely. I'm going to wait another day before trying it out on C515. I am looking forward to using it on the 2ns and 1ns Filter caps. I feel I've already tuned them well, but this all seems to require repeated fine tuning. And hopefully with the S-53 I'll be able to observe the 1ns signal at full BW (this will go in a 7S12 with S-6 sampler which is working quite well with my now working S-52).
Dave
On Friday, December 3, 2021, 03:21:58 PM PST, Jeff Dutky <jeff.dutky@...> wrote:
Dave,
I had thought that I had seen a video by either Jared Cabot (NFM) or Zen (Zenwizard) showing the addition of Option 01 to a TG 501, but I can't seem to find it now. I may have been thinking of Jared's video about adding a similar option to a DC503A.
The TG 501 Option 01 seems to consist of basically two components: U50 (a 7490 TTL decade counter) and Y50 (a 5MHz crystal oscillator, possibly ovenized?). The part numbers for Y50 are either Electronic Research Co. EROS-600-TK-9 (SN below B034510) or Bliley Electric Co. T15B141 (SN B034510 and above). I imagine that any 5 MHz TXCO or OCXO can be made to work, with effort.
The service manual has this to say about Option 1:
The TG 501 Option 01 is equipped with a temperature-compensated, 5 MHz crystal oscillator for a highly stable and precise internal clock. U50 provides countdown circuitry for the 5 MHz crystal.
Remove U100 and disconnect pin 3 of U350 before using external clocks. To disconnect pin 3 remove U350, bend pin 3 out then insert U350 back in tcurciut board.
The main circuit board jumpers that must be installed for Option 01 are: J3 and J7 (see. Fig. 5-2 for jumper location).
-- Jeff Dutky
