Bad CB shop/Good CB shop

Some are here only to criticize most everything except a stock CB and CBers who worship the ham operators and want to grow up and be a ham someday. This is not a very "truck driver/CBer" friendly site. But the mods allow it, so I guess that's the way it is.

 

I missed something

 

"THe coils are a lowpass filter and matching device why would you fool with them"

FM technicians deal with radios designed and operated within a narrow tolerance range. Matching sections are designed for a specific carrier level which does not change. High end gear with AM and/or SSB modes may have LPF's in the output section but in a cheap CB you are lucky to have loading, and a 54 MHZ (TVI) trap. You adjust FM gear to a very narrow set of tolerances so there is no comparison. An FM tech also deals with a radio which was very carefully aligned in manufacture. CB is a different game. Tuning one first entails going through all the adjustments since they were slopped through the assembly line. This is more important than 'tuning' the radio. Next, you are increasing the output power level and this is going to alter the collector load impedance as would be seen from a simple load line analysis. This is something an FM tech will never encounter so therefore has no work experience with. At best they will be replacing a mono block power stage which is little more than desoldering a row of pins, dealing with screws and thermal compound. After which an alignment procedure will be performed. At no time will they be altering anything outside of the narrow design range of the equipment. As far as the TV trap goes this should not be altered other than to verify it was set properly in manufacture and this can easily be done using an old analog portable TV. In the age of digital broadcast this is much of a problem. So we end up back at the loading coil. By cheap design the only way to adjust it is by spreading or compressing turns. The FM techs here are saying 'you should never touch it'. A real Engineer would say 'if you alter the collector load impedance you will need a different loading parameter to achieve a non reactive 50 ohms at the radio output connector'. So true, in effect you are creating a conjugate match using reactive inversion to cancel out the reactance in the output stage while at the same time needing an alteration of load matching to match the new collector load impedance to the 50 ohms desired at the output connector. This is the science behind it and as such is governed by a well defined set of mathematical equations, in short it is as simple as that.

Being able to only think in terms of bouncing between extremes of a stock CB and a splatter box negates an entire world in between of people out there who can increase a CB's power cleanly yielding a better more powerful station for the operator. Myself I would not waste time listening to anyone only capable of thinking in extremes. There are out there shops who use Specans and do quality CB work. I will even name a couple. 8541 Electronics back east (NC), and Fine Tune CB out west (NM).

 

OK ......

Maybe what you are saying is you would have to tune the radio for max at FULL output ( 100% modulation ) not a static level ....

That would make sence but what would you gain in the real world ......

 

If you had ever run a 100 thousand watt AM station you would know the broadcast standard is 125 percent modulation on AM. Go look it up. What do they gain in the real world. However the millions of drivers who have run tuned up CB's since the Smokey & the Bandit days already know what they gained in the real world. If you have to ask you do not live in the real world so answering the question is a complete waste of time. They know that once they only talked 5 or 6 miles down the road before, and after they did 20 in flat terrain quite easily. They know when they were asking directions before nobody would shut up and answer them. They know that after, more often than not they were the station being heard well enough to get an answer. Anyone who would ask this question with a pre conceived slant that they disagree with the answer does not rate one.

 

Very, Very True!

 

SO you can get 16 watts after a tune up ? I'll have to try that on one of the midlands..... AS for 125 percent POS modulation I could see that ....

 

Thank You AB7IF...........to those who trashed me without knowledge

 

We were talking about Corbra 29/25 or Uniden equivalent . I'm under the impression the Midlands aren't quite the same and won't tune up as well..........I could be wrong or partially wrong on this.

 

I have 2 old midlands I can play with