In article .com,
"Newbie" wrote:
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.
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 ?
The problem with your analogy is that there are no "Normal" conditions
when it come to RF Propagation. One could "Generalize" that Ground Wave
Communications in the 2-3 Mhz Marine Bands is 100-300 miles, for a 150
watt Transmit signal and no local Receiver noise. BUT that would be
a VERY BIG Generalization and your milage WILL vary with all the
previously posted conditional changes. Another generalization would be
that the higher the frequency the shorter the Ground Wave Propagation.
Again, that is a Gross Generalization, and if you used that to determine
what frequency to use for an y particular communications path, you will
not communicate 50% of the time. Modern MF/HF System use ALE to
determine what bands are open for any two stations. This is done by
having each radio send breif test transmissions on specific frequencies
in each Band at specific times, and allowing the ALE software to select
the best SNR for each band at the distance between the two stations.
This is very expensive equipment, and not common in Marine
Communications, but very common in Military Communications. After you
spend some time on the bands, communicating between specific locations,
at various times of the day, and year, and thru various SunSpot cycles,
you will get better at determining what will work and what is a waste of
time. This is where MF/HF Commincations is more an ART, and not a
Science.
Bruce in alaska Long time Marine Radioman, in the North Pacific.....
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add a 2 before @