[time-nuts] How can I generate a very clean 1 W signal @ 116 MHz ?

Bob Camp kb8tq at n1k.org
Tue May 31 11:43:57 UTC 2016


Hi


> On May 31, 2016, at 6:30 AM, Dr. David Kirkby (Kirkby Microwave Ltd) <drkirkby at kirkbymicrowave.co.uk> wrote:
> 
> On 30 May 2016 17:01, "Richard (Rick) Karlquist" <richard at karlquist.com>
> wrote:
>> 
>> On 5/30/2016 4:06 AM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote:
> 
>>> I'm wondering what's the best way to generate 116 MHz with very low phase
>>> noise. Phase noise at < 20 kHz offset is particularly important, but 200
>> 
>> The "best" way is clearly to use a 116 MHz 5th overtone crystal
>> oscillator, which can be locked to 10 MHz with no difficulty.
>> I designed hundreds of these sorts of things 40 years ago when
>> I worked for Zeta Labs.
> 
> Please excuse my ignorance,  but how would one lock a 116 MHz 5th overtone
> crystal oscillator to 10 MHz with no difficulty?  Do you have a circuit you
> share that would give low phase noise, and if so how low?

There are an enormous number of PLL chips that will do the trick for < $2 a pop. About 
the only external components are a couple of caps and resistors. 


> 
> From what I have read here before,  amplifiers degrade the phase noise if
> driven to near the 1 dB compression point. So would the final amplifier
> need to have a 1dB compression point of 33, 36, 40 dBm?

Indeed, no matter how you do it and no matter what your signal source, your amp
will be an issue. A +40 dbm amp is a good starting point. You may get away with
something a bit less. 


> 
> My next problem would be measuring the phase noise, but that's a different
> topic for another day.

Checking the phase noise will be part of the design no matter how you do it.

Bob

> 
> Dave.
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