[time-nuts] precision frequency/time/amplitude reference

jimlux jimlux at earthlink.net
Mon Oct 9 20:49:21 EDT 2017

On 10/9/17 8:02 AM, Bob kb8tq wrote:
> Hi
> Pick a couple of local broadcast stations and record them. That will give you a baseline
> for each of the parameters you are after in real time. They *will* drift.
> Past that, I’d go with a sweep of each node before installation. That will give you the
> frequency response and (to some degree) a guess for noise and spurs.

The RTL-SDR has only about 2 MHz BW, so you'd have to be lucky to have a 
broadcast station in the band (and if I'm looking at trying to image 
Jupiter with an interferometer, at 20.1 MHz, I'm not sure that the SW 
broadcast bands cover within 2MHz - and you'd be subject to the vagaries 
of propagation.. low sunspots = low critical frequency = not much 
skywave propagation for WWV).

So a local reference would be nice.  Originally, I thought about just 
radiating a CW tone (perhaps modulated with timecode), but then, I 
realized I'd also like to calibrate the RF chain in the receiver, so 
feeding a calibrated pulse that has spurs (hey, a "marker beacon" in old 
school radios with a analog dial)

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