[Elecraft] Installed K3EXREF

[Jack Smith]

On 3/19/2011 9:34 PM, Paul Christensen wrote:

<Major snip of excellent information>

At least some AM stations operating with digital subcarriers are GPS 
locked and can be extremely accurate. WMAL 630 KHz here in the 
Washington DC area is one example. It's as close to 630 KHz as I can 
measure (about 10 milli-Hz) and E-mail correspondence with the station's 
chief engineer confirmed the transmitter frequency is GPS locked.

I've measured other local AM stations as far as 16 Hz off - within the 
FCC's tolerance, but not of much use as a frequency standard.
> Commercial AM broadcast station
> frequencies are typically only accurate to about +/- 20 Hz although most are
> better than that.
>
>
Jack K8ZOA