At LF and MF there is a distance from the transmitter at which the ground
wave and sky wave have roughly equal strengths. Distance varies throughout
darkness.

As the height of the reflecting layer varies the path length of the sky wave
varies and so the relative phases of the ground and sky wave changes with
time between being in-phase and out of phase with each other.

The relative phases of carrier and sidebands are affected differently
because of their different wavelengths. Carrier phase shift causes variation
in signal strength. Sideband phase shift causes severe audio distortion.
---
Reg.


"Dave Pitzer" wrote in message
...

"Dave Pitzer" wrote in message
...
I have a CC Radio Plus (Sangean) AM/FM/TV/WX radio (from C. Crane Co.) I
enjoy broadcasr band DX'ing and this radion does a super job with just
it's
built-in ferrite antenna. I have logged AM BC stations from practically
every state east of the Mississippi.

Best reception is, of course, at night. But.... for some reason WABC
(New
York City) comes in poorly at night even though it's xmitter is only 80
miles away. The signal fades to next to nothing and then increases to
very
loud but extremely distorted then will be loud and clear for a while.
(During the day this station's signal is fine.) On the same evening,
stations in Georgia (WSB, Atlanta), Illonois (WGN, Chicago), Michigan
(WJR,
Detroit), etc., etc. come in fine 90% of the time.

Do I need an external antenna for the closer WABC?????

Thanks,

Dave Pitzer
Pocono Lake, PA
========================


Thanks guys.

All of these ideas make sense. It appears that I am just too *close* to
this
station to get decent nighttime reception --- just the opposite of the
normal situation. There seems to be a relatively small band of distances
within the xmitter's night pattern where the ground and sky signals
alternately cancel and re-enforce each other on a random basis after local
sunset.

Thanks,

Dave Pitzer
===========================