I’m not sure if I’m noticing over time, a steady decrease in the propagation characteristics of the AM radio band, particularly those frequencies above 1 Mhz, or a steady degradation of the performance of my AM receivers and a lack of quality in newer receivers.
I live in Shoreline, WA, just north of Seattle (about 13 miles north of downtown Seattle). I used to be able to receive CFUN in Vancouver, BC, Canada, about 100 miles to the north, at about S8 on my receivers that had an S-meter and strong enough, save for the occasional night time fade, to be listenable.
For the last few years though, CFUN barely comes in at all, not even S2 on the S-meter anymore and the noise level is too high to tolerate listening, even at times to be intelligible. Even many local stations which used to be solid are now marginal, particularly on the high end of the band.
At the same time AM propagation seems to have suffered, the higher shortwave bands seem to be alive at times of the year and times of the day that they wouldn’t have been in the past and sporadic E-skip on the low VHF TV channels has almost become so regular that calling it “sporadic” anymore seems inappropriate. It seems to occur more frequently now during the winter months during a solar minimum than it used to during a solar maximum in the summer. And during the last solar maximum, on one occasion I got skip all the way up to channel 10, and for all I know it may have gone past that but there are local stations on 11, 12, and 13 that would have required a very strong signal to overrun.
I’m wondering if this is the result of changing atmospheric chemistry, or a general increase in RF power levels causing an increase in ionization, or HAARP, or some other factor(s).