[time-nuts] low power, but quiet, oscillators
alexpcs at ieee.org
Mon Feb 6 21:24:12 EST 2017
hi Magnus, how about the effect of that cheap 2,7K on the active device
if it is bipolar?
On 2/6/2017 4:35 PM, Magnus Danielson wrote:
> On 02/07/2017 12:36 AM, jimlux wrote:
>> On 2/6/17 2:37 PM, Bob Camp wrote:
>>> One of the most basic reasons for putting out > +20 dbm is that you
>>> had a spec of -195 dbc / Hz for the noise floor :)
>>> Some of these specs *are* a bit mutually exclusive.
>> Sure.. And to be honest, I'm not sure that some of the folks coming up
>> with paper requirements for these speculative low power transmitters are
>> aware of that. They take dBc values from 1 Watt transmitters and assume
>> you can meet that with your 1 mW transmitter.
>> Then again couldn't you cool your oscillator.. that gets the T part of
>> the kT down lower <grin>
>> Cool that puppy down to <1K and get 25dB noise improvement, eh?
> Your 50 ohm termination resistor will be a great source of that noise.
> For a narrow-band fixed signal you can terminate with whatever
> reactive network you feel confident with instead. If you match
> impedance well enough it will work fairly well. Some oscillators have
> far-out impedances far from 50 Ohm anyway so impedance matching is
> so-so and most of the noise comes from the termination resistor.
> Besides, for the deep space stuff you have cheap access to 2.7 K or so
> anyway, right? :)
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