This morning I noticed that the field strength of my AM station was higher than usual as monitored by a receiver with a meter using an indoor antenna. The transmitter is ground mounted over radials and feeds 85 mW into a base coil loaded 3 meter antenna. Previously, the car radio range has been observed to be 1 mile listenable and 1.3 miles identifiable as my station by program content...
While out on an errand today I checked the range and it was 1.8 miles listenable and 2.4 miles identifiable.
It would be nice if this was the norm but I suspect it is an anomaly. My best guess is that the ground conductivity conditions are improved today.. I have noticed in the past that when the ground is frozen the range improves. Today, the ground is frozen, it is 41 degrees F, and we have had 1/10 inch of rain overnignt. This probably has raised the ground conductivity considerably and thereby improved the range. The transmitter power is the same as usual so it is most likely the change in ground conditions that is causing this.
Strange that frozen soil would give this result but considering that to be frozen there must be moisture present then it sort of makes sense.