[time-nuts] OT: xtal osc PN
francesco.messineo at gmail.com
Sun Sep 19 16:41:58 UTC 2010
sine oscillators like the AXLE184 series (which is one of my candidate
solutions so far) has around -110 dBc/Hz at 100 Hz offset and -160 dBc/Hz
at 100 KHz.
In the application I'm talking about, the use of 500 - 250 Hz crystal
filters at the IF is normal practice.
On 9/19/10, Bob Camp <lists at rtty.us> wrote:
> If it's a "reasonably priced" synthesized radio, -90 is probably better than
> anything you will find on VHF at 100 Hz offset. A lot of stuff out there is
> closer to -60 than it is to -100. 100 Hz doesn't mess up the adjacent
> channel rejection, so they don't worry a lot about it.
> On Sep 19, 2010, at 12:04 PM, francesco messineo wrote:
>> On 9/19/10, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:
>>> On 09/19/2010 09:35 AM, francesco messineo wrote:
>>>> On 9/19/10, Bob Camp<lists at rtty.us> wrote:
>>>>> 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
>>>>> 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.
>>> Do you *really* need -150 dBc/Hz? That is a hard requirement!
>>>> 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)
>>> I would need some more fundamental understanding of the system and needs
>>> to be able to understand how you come up with the above noise level at
>>> 100 Hz.
>> as I said, if it's not possible or not practical, of course I'll take
>> what I can get. The receiver will be limited by its phase noise and
>> not for example by its IMD3.
>> I think already -110 dBc/Hz at 100 Hz is better than any LO in
>> commercial receivers (for ham radio at least).
>> Best regards
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