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Silicon Chip Mag (UK EPE) GPS-synced Frequency Reference
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g0mgx:
Hi All

I have built myself the GPS synced frequency reference that was featured in Silicon Chip Magazine back in Oct 2018 and also more recently in Practical Electronics Oct 2019:

http://www.siliconchip.com.au/Issue/2018/October/GPS-synched+Frequency+Reference+Pt.1?res=nonflash

There are some useful files here which I hope you will be able to access:

https://drive.google.com/drive/folders/1ytFVLRi3dYImGWtByd7xdfiFW5mCnu4B?usp=sharing

I **think** I have a problem with PSU filtering/decoupling (I've spent many a happy hour watching Daves videos on this subject) as the problem with the build is that the main oscillator looks very noisy and also the output signal has a lot of "interference" (dont know the correct technical term) in the signal.

If you look at the video file at the link above, you will see that when the output is set to 10MHz there is a log of steady change in the signal, the "interference" coincides with the data burst from the GPS.

There is also a video in the link above showing the "debug" point of the circuit - which is the clock output from the PLL and is a 40MHz signal - again this doesnt look very clean. I've tried (rather randomly) adding additional caps to the circuit - I've also done something the article suggests "the stability of the reference may be improved by reducing the impedence of ground tracks on the PCB" - smells rather fishy to me  |O but this is basically adding wire connections between a number of ground points. This mod improved the problem dramaticallty, but hasnt cured it.

is anyone clever than I willing to take a look at the files in the link above and offer any suggestions (other than throw it in the bin) over what I might try to get this thing to function correctly.

Thanks muchness  :-+

Mark
g0mgx:
In case the info isn't visible I've posted details here:

https://g0mgx.blogspot.com/2019/12/practical-electronics-really.html

Grateful for any help.

Mark
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