[time-nuts] 75Z vs 50Z for GPS receivers

[Didier Juges]

Hi Brooke,

I am familiar with the Jim Williams app note, but I felt the pulse shape 
was somewhat lousy (based on the pictures that came with the article) 
due to the very small cap on the collector, OK to calibrate or evaluate 
a fast scope, I guess, but too far from a square wave to be able to 
visually observe and analyze reflections (at least from my perspective). 
Due to my ignorance of the avalanche effect, I did not think of mating 
this with a delay line. It seems the Zetex app note with a delay line 
can make decent square pulses, I have to try that. I have made high 
power pulse generators with delay lines a long time ago (radar 
modulators), it's been so long I had forgotten...

Didier

Brooke Clarke wrote:
> Hi Didiere:
>
> There's also an app note at Linear Technology for making pulses so fast 
> they are used to calibrate sampling scopes.
>
> Some years ago I made a very simple circuit that pulses a LED with many 
> amps (very short time) based on a transistor going into avalanche.
>
> Have Fun,
>
> Brooke Clarke
>