[time-nuts] OT: xtal osc PN

[Bob Camp]

Hi

Ok, you have just ruled out all of the silicon oscillators and by similarity ruled out a DDS. That narrows things down quite a bit. 

You will indeed need to shop around for low noise VHF crystals. Since you are in Europe, talking to KVG probably is your best bet.

Bob


On Sep 19, 2010, at 3:35 AM, francesco messineo wrote:

> Hi
> 
> On 9/19/10, Bob Camp <lists at rtty.us> wrote:
>> Hi
>> 
>> Is -195 dbc/Hz floor good enough or is it overkill?
> 
> I'd say this is obviously overkill, -160 dBc/Hz could be a good compromise.
> 
>> 
>> Is -155 dbc/Hz at 100 Hz offset a requirement or is -40 dbc ok?
> 
> -40 dBc/Hz at 100 Hz is about useless, -150 dBc/Hz at 100 Hz is again
> a good compromise, the lower (practically) the better.
> 
> It's hard to explain why to ones not familiar with weak signal
> operation between broadcasting signals, but really the noise floor
> raise a lot when you have some 5 or 6 broadcasts signals in 500 KHz of
> band (all with power levels of at least 10 dB more than the levels
> used in amateur radio, often +20 dB more)
> 
>> You need to quantify what you are after before deciding on an approach. Low
>> noise means many different things to each of us.
> 
> it's a compromise, of course I can't spend years or thousand dollars
> on the LO part of the setup. In the first case I'd not use it very
> much (so would be useless) and in the second case I could probably pay
> me a trip at the other side of the world far away from broadcasts :-)
> As good as it can gets within few months and a hundred dollars (maybe
> more if for useful test equipment). The rest of the parts are going to
> cost less than $300 total.
> 
> Best regards
> 
> Frank  IZ8DWF
> 
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