[BC] Skywave reception, big potential, under-utlized , was Re: Daylight Savings Time changes?

[Richard Fry]

Rich Wood:
>I really think the only way nighttime AM radio can continue to exist
>is to reduce skywave that's going to wipe out a lower powered local
>signal. IBOC stations have admitted anything beyond their protected
>contour isn't important. Let's take them at their word and reduce
>their interfering signal
__________________

Effectively reducing the skywave is much easier said than done.

Even radiation at low elevation angles (from just above zero to, say, +20 
degrees) eventually becomes a skywave, and can provide nighttime secondary 
service under the right conditions.  Nighttime radiation directed at +20 
degrees elevation returns to the earth after one reflection from the 
ionosphere at a point about 500 km from the transmit site.  Lower radiation 
angles serve greater distances, so it can be seen that the part of the 
radiation envelope most useful for generating usable secondary coverage is 
contained at these low elevation angles.

There is no practical way in the MF band to build an antenna system that can 
generate a groundwave of 100% relative field, and at the same time produce 
very low relative fields at all elevation angles that produce a useful 
nighttime skywave.

RF