So, I thought I'd start writing some articles on CB radio to help dis spell some of the "myths" that go along with them. I'll always advocate getting your Amateur Radio (HAM) ticket, but also support the use of CB radio on the trail and as a fun hobby.
So here we go!
Many times you hear about a "peak and tune" on a CB radio. (Which can actually be done on any type of transceiver) They are advertised on just about every CB radio repair shop wall and truck stops around the US.
What exactly is a peak and tune?
Your CB radio has two sections. The transmitter and the receiver. These sections are made up of various "stages" that are coupled together by various electronic components that are "tuned" to assure the electronic single is passed along at it's highest value. The best analogy that I can give mechanical folks is back in the day trying to get those multi-carb engines where all the carbs are tuned together.
All the little silver cans in this photo represent transformers connecting various stages of the radio. Please DO NOT start turning these with your screwdriver!
When a CB is set up at the factory, it is normally set up with 80% modulation and dead on 4 watts of transmit power to remain well below the FCC regulations.
So the first part of the peak and tune is checking to assure the radio is transmitting exactly on frequency. We connect a frequency counter and assure we're spot on frequency. We then adjust the modulation to 100% and check the output power, and align the stages to assure we're getting maximum transmit power while talking into the mic. (this is the peaking portion) One word of advice is that if you have a shop tell you that they are going to clip out the Modulation Limiter, RUN AWAY! This almost always ends badly with a radio that sounds like crap.
Next, we inject frequency from a calibrated transmitter into the radio and align all of the receiver stages to assure that the radio is receiving dead on frequency for the best performance. At this point, we'll also reduce the power from that calibrated source and adjust the squelch threshold and the S meter. This is the "Tune" portion of the job.
The very last thing that I do is an audio check of the transmitter to make sure that radio sounds like it should then we close it up, clean it up and your on your way.
I will state here that there is absolutely nothing illegal or against FCC regulations about peaking and tuning a CB radio.
Do you need a Peak and Tune?
For trail use, most radios, out of the box are great performers and acceptable for that usage. It isn't a necessity. Now, if you're dealing with a used radio, I'd say to get one done by a reputable shop. That's just to be sure you're getting the most out of your purchase. Many shops will do this for you as part of the purchase of a new radio.
Some words of warning:
Like any other business there are good and bad out there. I have seen shops that take radios in for a Peak and Tune and do nothing to it then charge the customer $40 for it! Some shops do these and make the radio worse than before. (like cutting out modulation limiters) There are some great shops out there that do great work. Shop around! Ask if you can watch them do the work.
What should it cost?
This is just my humble opinion. If you buy a new radio, the shop will normally do this for free. SWR checks are done for free. A P&T really should not cost over $40.
That's about it! Feel free to ask any questions if I left something murky.