HP10811 single/double oven? - Page 1
Forum section: electronics / general

author: tkamiya
author_rank: Super Contributor
timestamp: July 04, 2019, 02:54:10 pm
content: I need a confirmation on something I read:Some web articles I read mentioned single oven version of HP10811 and double oven version of HP10811.To my knowledge,all HP10811 is double oven'ed. The only difference between suffix is that they have different specs.What's correct?

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: July 04, 2019, 03:35:41 pm
content: The only double oven 10811 versions were the ones used in the Z3801A GPSDO.Check this page out for details.https://www.realhamradio.com/GPS-oven-journey.htmThis also has excellent teardown pictures of the 10811 hidden inside!It's kind of a misnomer as it really should be called an augmented warmup 10811 as the outer oven cuts out completely once the unit is up to temperature.It was made to meet some telecomm spec. for starting up at some subfreezing temperature.You could engineer your own outer oven controller to make it a real double oven but I would not bother.If it's one you picked up to play with just leave the outer oven disconnected and it will work fine.Cheers,Corby

author: tkamiya
author_rank: Super Contributor
timestamp: July 04, 2019, 04:02:23 pm
content: I knew that page but I was a bit confused why pictures seem to appear out-of-order. Now, I understand. There is a complete product inside a complete product!I had a crazy idea of buying a thermos (the drink thing) with wide mouth and put 10811 inside. Sort of create a chamber but without any additional heat.

author: edpalmer42
author_rank: Super Contributor
timestamp: July 04, 2019, 05:50:59 pm
content: Quote from: tkamiya on July 04, 2019, 04:02:23 pmThat's not a good idea. An OCXO is designed so that it's internal heat can escape in a controlled manner. If you reduce the rate at which heat can escape, you risk instability in the temperature control circuit or, worst case, the temperature will just keep increasing due to the oscillator's own power dissipation until the circuit cooks. Your idea of using a Thermos / vacuum bottle / Dewar flask is a worst-case scenario because they're about the best thermal insulators available.It's one thing for the manufacturer to make this kind of change like HP did for the double-oven 10811. It's not something for a user to mess with.The only time you should put an oscillator in a Dewar flask is if the original Dewar flask was broken. Guess how I know this.Ed

author: texaspyro
author_rank: Super Contributor
timestamp: July 05, 2019, 03:38:21 am
content: I did an outer oven controller board for the HP-10811. It is based upon a design by Warren Sarkison:https://oshpark.com/shared_projects/yliVG3SZ

author: tkamiya
author_rank: Super Contributor
timestamp: July 05, 2019, 03:05:36 pm
content: Wow....

author: edpalmer42
author_rank: Super Contributor
timestamp: July 05, 2019, 05:10:01 pm
content: Quote from: texaspyro on July 05, 2019, 03:38:21 amIs there a document package for that? Schematic, parts list, etc.Ed

author: texaspyro
author_rank: Super Contributor
timestamp: July 05, 2019, 05:36:34 pm
content: Quote from: edpalmer42 on July 05, 2019, 05:10:01 pmNot really, but all parts values are shown on the silkscreen. There is also some info on the OSHPARK page for it.

author: texaspyro
author_rank: Super Contributor
timestamp: July 05, 2019, 05:43:06 pm
content: Outer oven controller for the HP10811 double oven oscillator based upon a design by Warren Sarkison.The darlington power transistor should have a high beta at the oven current. I used a house-numbered part with a beta of around 1000.IC1 is a dual op amp like a TL082.C8 and C9 should be quality, low leakage caps.R7/R8/R9 (as marked on the PCB and NOT the schematic) can be adjusted for different input voltages and oven currents.The three pads on the right end of the board are for monitoring test points.Schematic attached:

author: texaspyro
author_rank: Super Contributor
timestamp: July 06, 2019, 03:57:08 pm
content: I also posted the board on DirtyPcbs.com I just got an email from them that somebody just bought some! Note that the silkscreen for those boards might have different reference designators (check R1, one of the resistors for setting the oven temperature). On both the OSHPARK and DIRTYPCBS versions, you should check for differences between the silkscreen and schematic.The two main adjustment devices are the two paralleled power resistors that set the oven current and the resistor marked TADJ near the upper right corner of the board that sets the oven temperature.https://dirtypcbs.com/store/user/preview/975

author: tggzzz
author_rank: Super Contributor
timestamp: July 06, 2019, 04:10:10 pm
content: When I found myself in possession of an 10811-60111, I needed to build a PSU.My approach was to use a "capacitor multiplier" to derive the non-critical 20V oven PSU, then use the datasheet's LM723-based "Fig 2.1 Single Source Regulated Power Supply" for the 12V, with a little extra RF filtering at the input.Why? Because I had a 723 available, the 12V should be low noise, and, as TAoE III puts itQuote

author: tkamiya
author_rank: Super Contributor
timestamp: July 06, 2019, 04:30:05 pm
content: Also, don't forget a +/-5V EFC power supplies. Trimmer on top of the case is too touchy with lots of backlash. I'm thinking just using +5 and cut the adjustment range in half. I have a similar project in planning stage.

author: texaspyro
author_rank: Super Contributor
timestamp: July 06, 2019, 04:47:24 pm
content: Note that the HP schematic uses the 723 in the TO5 can, not the DIP package... pinouts are different.

author: tggzzz
author_rank: Super Contributor
timestamp: July 06, 2019, 07:26:30 pm
content: Quote from: texaspyro on July 06, 2019, 04:47:24 pmI'd forgotten that important detail. Fortunately I spotted it before I started wiring it up!

author: texaspyro
author_rank: Super Contributor
timestamp: July 06, 2019, 11:59:15 pm
content: Long ago, I started a layout with a 723 regulator / EFC pot on it, but never finished laying out the PCB. I used the DIP packaged part.

author: tkamiya
author_rank: Super Contributor
timestamp: July 07, 2019, 11:55:44 pm
content: I have a little board made by HP. I believe it came out of one of my trashed spectrum analyzers. It's a board 10811 would sit. It has EFC port grounded and +12V is provided by a 3 terminal device that look like 78L12. It's been renamed by HP so I am not 100% sure what it is.