[time-nuts] Re: James Miller/Brooks Shera 10 MHz GPSDO

[Mervyn Thomas]

David,

Brooks Shera's only schematic for his GPSDO shows the DAC as a PCM61P 
but when I purchased the partial kit back some 15+years ago he supplied 
the AD1861.  I've got some Burr Brown PCM61P's coming from an eBay 
supplier and I will see if using one makes any difference.  The general 
consensus is that it will not.

Merv

On 2/09/2022 5:52 am, David G. McGaw via time-nuts wrote:
> I have one of the double oven 10811s and there is no tuning hole in 
> the inner case.  One would have to remove the flex-circuit outer oven 
> heating element and open the inner case to get to the tuning cap.
>
> I do not find a schematic of the Brooks Shera board that uses an 
> AD1861.  If there is one, perhaps we could rework the circuit to have 
> bipolar output.
>
> David N1HAC
>
> On 9/1/22 3:36 AM, Mervyn Thomas via time-nuts wrote:
>> Dan,
>>
>> As a last resort I would attempt to disassemble the osc.  What 
>> concerns me is the picture of the osc. shown in the article you gave 
>> is not my version osc. so I'm pretty sure there would be no tuneable 
>> cap inside mine??  Will keep the group posted on results.
>>
>> Merv
>>
>> On 30/08/2022 8:25 pm, Dan Kemppainen via time-nuts wrote:
>>> I found this helpful long ago...
>>> https://nam12.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.realhamradio.com%2FGPS-oven-journey.htm&data=05%7C01%7Cdavid.g.mcgaw%40dartmouth.edu%7C4cec14fbc44e4985d4c608da8c548d5d%7C995b093648d640e5a31ebf689ec9446f%7C0%7C0%7C637976592033788783%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=atgiKtTy8I1x3y5Lm71YavmLdGeQ84dBgfyi1%2FCXjwM%3D&reserved=0 
>>>
>>>
>>> I think you would only need to go part way in to get to the 
>>> adjustment screw.
>>>
>>> The double oven was used in some equipment spec'd for cold climate 
>>> operation. It helped speed warmup or some such issue. People have 
>>> used the outer oven to help stabilize the temperature, although from 
>>> what I understand that was not the original intention.
>>>
>>> Let us know what you find!
>>>
>>> Dan
>>>
>>>
>>> On 8/30/2022 3:31 AM, time-nuts-request at lists.febo.com wrote:
>>>> Unfortunately the HP 10811's I have are in a completely enclosed 
>>>> can - no holes to poke anything through. To get at any tuning 
>>>> capacitor would probably entail taking the insides out of the can.
>>>>
>>>> The oscillators like mine must have been fairly rare as I am unable 
>>>> to find anything via Google.  They have 2 main power leads coming 
>>>> out of the can with 6 pin female connectors to connect to the power 
>>>> Power Board which is out of an HP Z3801 GPSDO and 2 thin coaxes 
>>>> with SMB connectors on the end - one marked as 10MHz and the other 
>>>> as EFC.
>>>>
>>>> Regards,  Merv
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