[Elecraft] OT: K3 timekeeping

[Fred Jensen]

On 11/26/2014 10:11 PM, Jim Brown wrote:

> How far down were the harmonics? -40 is 1% distortion, -50 is 0.32%. 5%
> is widely considered to be "communications quality."

The tones [500 and 600 Hz on alternate minutes] are transmitted at 50% 
modulation.  The second harmonic of the tone on 10 MHz is about 15 to 18 
dB below the fundamental tone on my P3 using the dBm scale.  There is 
selective fading visible on the tones.  The third harmonic is roughly 
another 15 dB below the second harmonic, and it fades more.  At times, I 
can discern the fourth harmonic on the waterfall in monochrome mode, but 
can't see it on the spectrum display.

The tone fundamental and each of the harmonics are surrounded by the 
sidebands of the 100 Hz sub-carrier and the IRIG-H time code.

The striking part for me is the difference between 2.5/20 MHz and the 
other three.  2.5/20 are very clean, no tone harmonics, and the 100 Hz 
sub-carrier is where it should be and nowhere else.
>
> When I've listened to WWV (not often), I hear distortion. They're a
> Standard for Frequency and Time, not high futility. :)

The modulation that is generated at Ft. Collins [tones, ticks, time 
announcements] appears to be very high quality and exact. The weather, 
GPS status, and propagation announcements seem to come from other places 
and are of highly variable quality, mostly unintelligible for me.

The WWV time announcements are rumored to be the voice of San Francisco 
area radio announcer.  This may be an urban legend however. :-)

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 50th Running of the Cal QSO Party 3-4 Oct 2015
- www.cqp.org