Re: DB6NT Xtal Oscillator


Robin Szemeti - G1YFG
 

I had the same issue with mine ... I found I could get it on frequency, but refusing to start up, or peaked, but miles off frequency. I  forget what I changed in the end, but there was some faffing before I got the specified power at the mixer. LO input and the right frequency and agreeing to start when powered up..

I am now distracted from whatever else it was I was supposed to be doing with rebuilding my transverters into unified 2U cases, with a unified interface back to a switcher, so I can just select the one I want at the push of a button ... well, that's the plan ... it will probably never happen.


On Mon, 4 Jul 2022 at 10:21, Andy G4JNT <andy.g4jnt@...> wrote:
Why did all the German designs  persist with that single FET crystal oscillator?  Getting the feedback optimised was so fussy.
The Butler used originally in the Microwave Committee "balloon board", then carried through into Sam's source modules was so much nicer,  reliable and easier to set up properly with its separated gain and limiter stages.



On Mon, 4 Jul 2022 at 10:16, geoffrey pike via groups.io <gi0gdp=yahoo.co.uk@groups.io> wrote:
After some time i finally built my 9cm DB6NT transverter, those filters needed some heat!. Anyway switch on time and i'am thinking will it be on frequency, low in power both or neither. Well it was way off frequency. I will later inject 407 MHz but the point of the story is the Fet. I have previously had problems with grounded gate SMD J310 Fets behaving badly. So rather than faff about playing with different feedback caps which would have likely only resulted in different positions of the brass slug in the coil and still ending up with the oscillator not starting up on frequency.
So in with a TO92 J310 Fet and bingo normal service resumed and i still got >200mW out. So are there different SMD versions of the SST310?. It's a pity you can't get these kits anymore
cheers
Geoff
GI0GDP


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Robin Szemeti - G1YFG

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