[time-nuts] OT: xtal osc PN

francesco messineo francesco.messineo at gmail.com
Sun Sep 19 07:35:18 UTC 2010


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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