Quick Q...If an antenna is tuned, and then the CB is replaced, does the antenna need re-tuned?  I guess my question is ...is it the antenna that gets tuned or the CB/antenna combination?

Good question and I don't know the correct answer, although I would recheck my SWR and tune if necessary.  

No. Antennas are tuned for the operating frequencies, not for brand/model of radio.

You will need to redo your match,  new radio new match.  go to any truck stop and they will do it for 10 bucks.  I use to work on these alot.  an swr meter is a good investment.

HAHAHAHAHHAH!!!!

Quoted:
You will need to redo your match,  new radio new match.  go to any truck stop and they will do it for 10 bucks.  I use to work on these alot.  an swr meter is a good investment.

"No. Antennas are tuned for the operating frequencies, not for brand/model of radio".




These seem to conflict.....or do I misunderstand

The transmitter output circuit design varies from radio to radio and yes you will need to retune for optimum performance.

If you don't it probably won't hurt anything.

So the answer is somewhere in between!

Retuning is easy and you can pick up a R-S SWR meter on ebay for abt $10 and if you use CB you should have one anyway.

There is no need to retune, anything else is just bunk.

A resonant antenna is resonant regardless of the signal generator.

That's true to a point, and I presume you are assuming a 50 ohm output sig gen.

When you change the impedence the antenna looks into [various models of transmitters] you likely change the antenna's point of resonance.

Similarly to reactance modulation of an FM transmitter.

Attenuation in the feed line between the two will reduce any mismatch, but in the case of 10 feet of RG-58 at 27 mHz, not very much.

Short answer: No.

Long answer:

An ideal transmitter is matched to a 50 ohm load. This means that the radio is expecting the antenna to present a 50 ohm impedance.

Let's be honest here, CBs aren't exactly renowned for being high quality pieces of precision equipment. So chances are the SWR will be slightly different after changing radios.

Your SWR varies with frequency. Unless there's one channel (frequency) that you know you're going to be using exclusively, generally you tune for the lowest possible SWR in the middle of the band. In the case of CB, this will be channel 20. You'll have the lowest SWR right there and it will be higher closer to channels 1 and 40.

However, it's probably not going to make a whole lot of difference. The spread between channels 1 and 40 is only 440 kHz so the SWR difference from one end of the band to the other is probably going to be less than the error range of your SWR meter.

Assuming you're running the legal limit of 4W AM/12W SSB unless your antenna is WAY out of adjustment, you probably won't notice any difference after switching radios. The difference of 1.0:1 and 2.0:1 is .5 dB, which at CB limits is 4 watts vs 3.6 watts. 400 milliwatts is not a noticeable difference. Likewise, at 12 watts with a 2:1 SWR you're losing 1.2 watts - well below anything that's going to make any difference.

Most CBs should have a foldback circuit that will prevent any damage to the PA. Unless you're running an amplifier, just being in the ballpark is fine.

You are joking right?