K5CM Dual Carrier Frequency Measurement Test Phase Plot: May 20, 2012

On May 20, 2012, Connie, K5CM, made a Frequency Measurement Test (FMT) transmission consisting of two carrier frequencies, each referenced to a GPS-disciplined frequency standard, and spaced approximately 2 kHz apart.

The frequency of the lower carrier was published prior to transmission. Observers were asked to determine the frequency of the higher carrier, using the lower carrier as a reference.

The transmission was received over a distance of 1200 miles in New Jersey using a receiver whose AM detector was used to heterodyne the two carriers together, thereby producing an audio tone equal to the frequency difference between the individual carriers.

This video plots demodulated audio voltage as a function of time, and illustrates the phase variability of the recovered audio tone, which was bandpass filtered to a 50 Hz bandwidth, and plotted against a local standard.

Frequency stability of the received signal was not as good as the FMT transmission made several days prior. Some interesting phase shifting takes place during the transmission period due to propagation effects, but there appears to be an area of "equilibrium" throughout the transmission that accurately represents the frequency difference between the two carriers.

RF frequencies employed during this transmission were as follows:

Carrier #1: 14120000.000 Hz
Carrier #2: 14122002.327 Hz

Delta = 2002.327 Hz

Видео K5CM Dual Carrier Frequency Measurement Test Phase Plot: May 20, 2012 канала 5UP7