[time-nuts] Brooks Shera

EB4APL eb4apl at cembreros.jazztel.es
Sun Mar 24 22:34:15 EDT 2013

I wanted to build a GPSDO using the Brooks Shera design since I read the 
QST article.  I asked him in Jan 2009 about his source code, because I 
wanted to change the PIC to a more modern one and add some 
functionality, and his response was that he already had changed it to a 
16F876A and added a lot of improvements to the released code such as PC 
control of many parameters using a COM port and in his opinion it was 
better for me to order a pre-programmed PIC from him than trying to 
reinvent the wheel.
I did it and also he was kind enough to provide me with all the 
hard-to-obtain parts.
My chip has this last version (402NE is mentioned in the doc, but this 
is from 2007 and there is a later version), but probably it has the 
fuses set to avoid extracting the code.  Maybe somebody has the hex or 
the source of this improved version, in the documentation it is 
mentioned that Bob Leichner (WO6W) collaborated with Brooks in this 
version so he can be a source of more info.

Brooks also made a PC program for controlling the GPSDO and plotting its 
performance (EFC, ADEV, etc.).  The program can be downloaded from:
(you need both downloads).
I also have a description of the serial port commands accepted by the 
I have all parts and the PCB stored because I got a Trimble GPSDO, but I 
think this is the right time to assemble it, at least as a tribute to 
If anybody wants the files, just ask.

Best regards,
Ignacio EB4APL

On 24/03/2013 19:31, Chris Albertson wrote:
> On Sun, Mar 24, 2013 at 4:12 AM, Stephen Tompsett (G8LYB)
> <stephen at tompsett.net> wrote:
>> Here's a copy of the source package (that claims to be for version 1.28)
>> that he sent me when I enquired about it many years ago.
> That's great.  It needs to be some how linked to an archive of his
> article.  No better memorial to an engineer than to have is work
> preserved in a public place.   I read the assembly source code.  I'm
> not a PIC expert but I've been doing software for 25+ years I and see
> that it is well written and easy to understand.   Some day I'll
> transliterate this to run on a TI launchpad and will have to credit
> the author.

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