Rigol DG1022 timebase modification - Page 1
Forum section: electronics / testgear

author: Dragon88
author_rank: Regular Contributor
timestamp: June 08, 2015, 01:02:51 pm
content: I picked up a DG1022 recently. I am very happy with it, and I think it offers a lot for the price.The unit has a soft power button, and I had hoped that it would keep the timebase inside warmed up all the time for stability. This is NOT the case. At soft power on, the crystal in my unit is about 40 ppm high. It then goes into a typical crystal warm-up period, eventually reaching several PPM low. I have yet to see it fully stabilize, even after being on for a quite a while.Now this isn't really a problem, and there's always the External Reference in that I can feed from a GPSDO. However, I was thinking about doing a timebase modification. Probably add a TCXO for minimal extra power consumption and minimal/no warm-up time.Has anyone modified the timebase on a DG1022?Is the reference crystal for the synthesizer 100MHz?I have seen two separate sets of teardown photos on this forum, and in both sets the crystal is hard to make out. I think I can see 100.000 in one photo, but can anyone verify this?Thanks.

author: bingo600
author_rank: Super Contributor
timestamp: June 08, 2015, 03:10:57 pm
content: I'm running mine of a GPSDO.The only annoying thing is that it seems to forget my selection of (ext ref), when i power it off/Bingo

author: Dragon88
author_rank: Regular Contributor
timestamp: June 08, 2015, 04:49:12 pm
content: Quote from: bingo600 on June 08, 2015, 03:10:57 pmYup, very annoying.Not to mention the external ref option is buried under several layers of menus. One of the reasons I'm considering doing a mod.

author: bson
author_rank: Unknown
timestamp: June 08, 2015, 06:48:19 pm
content: I too would be interested in this, even though I have a GPSDO in transit I plan to use for reference for the DG1022 and a few more instruments.Do you know off-hand if the reference input on the 1022 is 50R terminated or if I can run the same clock to more instruments and terminate externally? Hoping not to have to buy or build a distributor... although that would be a good excuse to experiment with clock shaping circuits.

author: Dragon88
author_rank: Regular Contributor
timestamp: June 08, 2015, 08:01:54 pm
content: I don't know if the ref in is 50ohm. All it says on the back of the panel is +-5V. Though I just encountered a strange issue testing it out. I put the 10MHz out from one of my calibrated counters (OCXO) into the ref in, then sent a 10MHz sine wave back to the counter from the 1022. The frequency it was generating was 10.023 MHz!I verified the ref out from the counter, and the 1022 detected the clock when I switched it to external ref. SURELY it can't be using the external ref that poorly..... I need to play with this more.Bingo, have you encountered any problems like this?As to your GPSDO, eventually you'll want to build or buy a distributor. You might be able to get away with a two-way splitter, but for 3 or more instruments you really need a good distribution amp. Gerry Sweeney has a good video series on YT about this. He used a rubidium, but it's certainly applicable to a GPSDO.

author: Dragon88
author_rank: Regular Contributor
timestamp: June 09, 2015, 01:03:40 am
content: I thought the first reference signal I used might be a little anemic, so I tried another reference with a stronger buffered signal. No dice. The unit gives the same behavior, way off on the generated frequency while using an external reference. I suspect a firmware bug. Perhaps it keeps the cal constant for the internal reference applied even when switching to external? But surely something like this would have been seen by others by now.

author: c4757p
author_rank: Super Contributor
timestamp: June 09, 2015, 01:05:23 am
content: Mine has serious issues using an external reference, including vastly increased phase noise and software glitches.

author: Dragon88
author_rank: Regular Contributor
timestamp: June 09, 2015, 09:04:54 pm
content: Come on Rigol...

author: markce
author_rank: Regular Contributor
timestamp: June 10, 2015, 09:02:05 pm
content: I had the same issue of frequency offset and jitter with the DG1022 when I used it with a terminated 50 ohm external timing signal connected. Removing the terminator solved this. The DG1022 apparently needs true 5V cmos logic signal, not just TTL level.