Why do truckers use linear amplilfiers with their CB radios?

Be careful around those with high top rubber boots

 

i have a general lee and a tx300 in my pickup with a 102" i have no trouble getting out 35 to 50 miles.. my question is the fm switch on my radio.... i know i have a radio that i don't know how to halfway use but i have never seen one on a radio before and i really just wanna know what its for? also what is the 10k switch for and why will it make you talk a channel lower? someone told me its for talking between channels..

 

also on the skip issue i have had a 10 minute conversation with a guy who claimed to be from great lakes MI, and i live in virginia. he was on a base i was on my old setup, (a cobra 29 with a wilson 2000 trucker in the daytime. but he could of been lying.
with my general lee i pickup stuff from all over the country... but i can only seem to be able to talk local with it about 50 60 miles max

 

That's the beauty of skip. It lets you talk all over the country. Doesn't matter what radio you have either. I have personally talked to Florida from Missouri on a Uniden PC68LTW. On channel 40 AM.

 

The "FM" bands are a whole other set of frequencies. It is completely different than the "AM" bands. I have never heard anybody on the FM bands, and also they are restricted for use with a ham operators license. The +/- 10khz switch changes your frequency and those frequencies are also ham bands.

 

FM has been pretty dead IMO. We used it briefly for a while (seeing as nobody else was) and found it to be completely clear, devoid of ground noise, some cb toys won't work on it (good thing), and everyone you know suddenly sound different, like you're talking on the phone, since there's no overmodulation; just volume.
It sort of takes some of the fun out of radio; you'd just want to call their phone and talk. We seemed to have no fadeouts, range was pretty good.

 

It is NOT "a whole other set of frequencies". FM is another mode of operation. The frequencies are the very same as those on AM. AM, Sideband, both upper and lower, are, again, a mode of projecting and decoding a frequency. "FM" is frequency modulation as opposed to amplitude modulation where the frequency remains the same and the amplitude or loudness superimposed on the carrier increases and decreases with the mike. Hence, the "swing" that so many CBers are so "het up" about. In FM, the amplitude of the signal remains the same and it is the frequency that is varied within a specified width. All signals have what is called a "bandwidth"--the space, or elbow room, in which the signal can work. The advantage of FM is a smoothe, constant signal, and it is why music up on the higher frequencies sounds better using FM. The DIS-advantage of FM is it requires a larger bandwidth and allows for fewer users at a time. Contrary to CB myth and legend *(of which there is much), FM will "skip" just as far as AM.

Single Sideband is yet another method of projecting and decoding radio signals. The frequencies, again, are the same as AM or FM; it is simply another mode of operation. In a nutshell, the little radio midgets down inside your radio "saw" your signal in half and eliminate the carrier ( or most of it) and uses the upper or lower "half" of the signal to "throw" your signal. To decode sideband, when the signal "arrives" at a receiver, an internal decoder, or detector, grabs the signal, re-inserts the carrier, so to speak, so that the audio can be heard correctly. But that is also why a non-ssb radio sounds like Donald Duck or can't be translated. The advantage of SSB is that, because the carrier is eliminated, most of what is projected is pure audio resulting in more punch and, sometimes a perceived increase in distance (actually it may not be farther, but what you hear is heard LOUDER. Both AM (of course) and SSB are LEGAL for CB radio, but FM is not. Basically it is the wider bandwidth that FCC does not want because it creates WAY more interference than the other two. And because it "skips" just like the other two modes, the interference to other stations can be horrific! It also has another downside; it tends to try to "capture" the strongest signal it "hears" (if that is a good word to use). The result is, when two FM signals arrive at the same time, if they are equal in strength, the noise it generates can be awful to listen to! This can be seen if you visit the ham 10 Meter repeaters up on 29.620 FM. Its OK to listen to these, and you can hear stations coming in from New York, Boston, NC, and the midwest. Do NOT transmit on these (they are on split frequencies and many have tone encoders anyway) as the General Amateur license is required. But this will show how FM behaves on low frequencies AND the noise that can result. I can only "play" with these machines for a few minutes before I get tired of the racket (when they are busy) and move on!
The purpose of them, of course, is experimentation, and there aren't that many of them.

I hope this explains some of the quirks of FM. I tried to keep it simple, and while it is not dead-on technically accurate, it might help you see how modes work. And, BTW, the next time some truckstop guru tries to tell you the sideband radio he's trying to sell you "has 120 channels", tell him he's full of it! There are only 40 channels, SSB, AM, and FM are only modes of operation!!!!


Gadfly

 

Gadfly .....

The reason FM is quite on CB is no CB RADIO BY LAW can have FM in it .
So that means what ever radio they are using is not a CB set.
The FCC HAD NO CHOICE but to ban FM it is far too wide for 10khz spacing. Fm is way better than AM in a car and is much more likely to be heard when the signal is right at the background noise ... THIS IS WHY ALL SERVICES USE IT ...... EXCEPT CB and HAM.

I run FM on 10, 6, 2, 220 and 440 as well as MURS which is a cb band and FM IS LEAGAL on MURS.

29.600 mhz is the FM calling frequency on 10 meters and run one of these

http://www.universal-radio.com/catalog/fm_txvrs/2607.html

Bruce

 

I'm just trying to KISS--keep it simple. I know it's illegal, but since when did it stop CBers from violating the rules?

Gadfly

 

It actually depends on which country you are in. E.g. in Germany FM is an approved modulation mode for CB radio (80 channels for FM, digital modes and SSB, as opposed to 12 channels for AM. Also, in FM, SSB and digital modes you can transmit with 4 Watts as opposed to 1 Watt for AM). Since last year directional antennas are permitted as well.
This is also why you have those "export"c radios, which have been manufactured with other country´s regulations in mind.

Jan, DL1JRK