"Newbie" wrote in message
oups.com...

Caveat Lector wrote:
From the ICOM website -- the IC-M710
a.. Covers all allowed bands between 1.6 and 27.5 MHz
a.. But propagation varies on each band depending on night or day, time
of
year, time in the sunspot cycle, solar storms, ground wave propagation,
etc.

Suggest you read about propagation.
See URL:
http://www.ae4rv.com/tn/propflash.htm

Hope that helps.

CL

Thank you Caveat.

When VOA or BBC plan to build a radio station, they must be able to
calculate the coverage of their station in 'normal' conditions.

The VOA and BBC transmit on several frequencies to have coverage because of
the varing propagation.

When we talk about cars, you may say a Mercedes C200 speed depends on
road conditions, tires pressure, gas, temperature, etc... but surely
people can say it can do 100km/hr.

Don't we have something similar when talking about radios ?

Not really, take AM Broadcast stations. During the day they cover a small
area. At night, this area is increased quite a bit. From wikipedia
http://en.wikipedia.org/wiki/AM_radi...ns_of_AM_radio
Medium wave and short wave radio signals act differently during daytime and
nighttime. During the day, AM signals travel by groundwave, diffracting
around the curve of the earth over a distance up to a few hundred miles (or
kilometers) from the signal transmitter. However, after sunset, changes in
the ionosphere cause AM signals to travel by skywave, enabling AM radio
stations to be heard much farther from their point of origin than is normal
during the day. This phenomenon can be easily observed by scanning an AM
radio dial at night. As a result, many broadcast stations are required as a
condition of license to reduce their broadcasting power significantly (or
use directional antennas) after sunset, or even to suspend broadcasting
entirely during nighttime hours. (Such stations are commonly referred to as
daytimers.)

In fact, at night during the winter time, big AM stations can be heard clear
across the USA. Not so during the day.

CL