Sunday, May 18, 2014 at 09:31
as I originall said...all radio reception is limited by signal to noise considerations.
As we use more advanced methods of modulation the point where loss of service occurs becomes more dramatic.
with crude old "continuous wave" modulation...just turning the carrier on and off...( morse code)...the signal can be very noisy and still be read for a very wide margin near the limits of range.....except in very short range conditions the signal will always be read thru fairly obvious noise.
AM...amplitude modulation where we vary the size of the carrier ( as we use in AM radio and old 27Mhz CB radio gives us a clearer in range reception...but there is still a wide margin where the signal is read thru fairly obvious noise near the margins of reception.
FM..Frequency modulation....where we vary the frequency of the carrier while keeping its size constant has far better in range noise performance and noise immunity...but the margin of readbility thru obvious noise is considerably narrower.
When we get into the current digital modulation methods like are used in digital television and mobile phones......the in range readbility is near perfect...but there is very little margin at the limits of readbility thru noise...it will be near perfect..suddenly become unreliable and then its gone.
what the OP and other will be experiencing with the new 80 channel CB is a combination of factors.
Starting with a radio system that is intentionally range limited.
A combination of the frequencies used, the modulation system, and power restrictions very effectivly limits the range of UHF CB.
It is intended to be pretty
well line of sight and only a few Km.
A hell of a lot of what is done with UHF CB is pushing it right in to that bleeding edge where the signal is read thru the fairly narrow noise tolerance margin.
Reducing the signal to noise ratio by only a few db will mean that margin of readability thru noise will be dramaticall reduced.
the regulators will have known damn
well that this will occur, and they will have considered that the range reduction is a positive result.
because it will allow the system to carry more users over a wider area.
some of us argued that this would not benifit anybody outside of a few very busy locations and would in general be not worth the trouble....but the regulators did not care.
SO...with 80 channel UHF CB is is even more important to understand that it is line of sight and good antenna positioning is imperative.
Selecing a good aerial with a reasonable amount of gain and having it
well located will predominate ove all other considerations.
there have been some..."spirited" discussions about the near fradulent marketing that goes on with CB radio aerials..and a number of things people believe that simply are not true....like the "gain for terain" idea and the notion that a big white (or black) stick mounted on the bull bar is a good choice.
The difference between what actually works and that that does not will become more obvious with this chnage to an 80 channel system.
Persnally I'll be hanging onto my 40 channel radios as long as I can....even if I do buy 80 channel.
cheers
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