[hpsdr] VHF Clocks

[Chris Bartram]

Hello Phil

> I should have said that problem is generating a 160 or 180 MHz low
> noise clock without using custom low phase noise crystals that you
> have to buy in quantities of 100 or more with lead times of 3
> months...LOL...

Based on quite a lot of experience in the field, I can say that decent 
crystals in that context don't cost a huge amount of money - maybe USD40 for 
a single part and about USD5 at 100off. Because crystals are quite precise 
electro-mechanical components which need to be tested for ageing, they do 
take a little time to make, and typical lead times are of the order of three 
if or four weeks.

The problem comes if you try to buy these parts from commodity distributors 
and manufacturers. There are still manufacturers who will manufacture 
short-run custom crystals. Some of them are actually quite good!

A clock based on a 90MHz low-noise crystal oscillator, followed by a passive 
diode frequency doubler and output driver wouldn't be a complex project.

There is also another approach. Quite a few manufacturers make crystals and 
packaged oscillators for use as 155MHz clocks for SONET applications. Most of 
the packaged oscillators have voltage control inputs to allow locking to an 
external standard.

Vy 73

Chris
GW4DGU

 1203677688.0