Re: 11801 question (+GPSDO vs OXCO)


Hi Reginald,

There are sophisticated ways to increase the time resolution of timebases which I first discovered while reading the Tek DC5010 service manual. It was many years ago so I no longer remember the details, but what I do remember is thinking at the time that it was an electronic equivalent to how a Vernier Caliper works to get an additional digit of resolution out of a measurement scale.

It is unfortunate that Tek no longer provides technical details and a detailed Theory of Operation the way they once did. I always wonder if this was done in a vain attempt to turn a profit for the support their manuals used to provide because they were losing money, or if this was a decision that backfired on them and caused them to lose even more money that they might have otherwise.

Either way it was coincident with Tek beginning a deep slide they never recovered from.

Dennis Tillman W7PF

-----Original Message-----
From: [] On Behalf Of
Reginald Beardsley via Groups.Io
Sent: Friday, March 29, 2019 6:13 PM
Subject: Re: [TekScopes] 11801 question (+GPSDO vs OXCO)


The SD-22, 24 & 26 use 3.5 mm connectors. The SD-30 & 32 use 2.4 mm
connectors. Having been infected with a severe case of "Test
Equipment Acquisition" syndrome, I'm trying to cope as best I can.
I'm also trying to avoid doing something stupid. I'm playing with
things I never even dreamed I could have. And measuring the air gap
in an SMA to 3.5 mm connection completely blows my mind!

I'm seeing a slow, persistent 5 ps variation in trace timing even
after running for hours. The 11801 uses a 200 MHz OCXO. Even if it
is good to 1e-8, 5 ps is 2e-11. But the scanty service data make it
hard to know how the horizontal sweep clock is being generated.

Has anyone replaced the OCXO with a GPDSO. Leo Bodnar is of the
opinion that the periodic drift is the sampling head.

I plan to test that tomorrow by locking my LeCroy DDA-125 to a 10 MHz
reference and then comparing the OCXO output to a 200 MHz signal from
the other port on Leo's GPSDO. At least if I can figure out the
correct settings for Leo's dual GPSDO for 200 MHz output.

Have Fun!

Dennis Tillman W7PF
TekScopes Moderator

Join to automatically receive all group messages.