cascadia cb power

In case you're not able to come up with an answer from someone who's familiar with the wiring in that truck, there's an easy way to find out -- but only if you know where the truck's fuse for that line lives. A quick check of the fuse will reveal the amount of current the line is supposed to carry. Fuse values are set to be between 25% and 50% higher than the load they're protecting, to give a little leeway. If the truck's fuse is 3 amps, the circuit is probably rated at 2.25 or 2.5 amps. At that point, your test is over, as you already know that fuse will blow when you transmit on your radio. At that point, you should figure on running the radio's power leads to the battery, which also complies with best engineering practice for a long term happy radio.

It's probably simpler than you'd think. Since your radio has a factory specified 10 amp fuse in its power harness, you now the radio is protected. Just plug it in to the wiring you want to use. Turn it on on receive and make it "blow squelch" -- disable the squelch and turn up the volume to max. When someone talks, the radio might draw a half-amp to one amp. It probably will stay OK. Now, with your antenna (if it's tuned) or a dummy load attached, put it into transmit. If the truck's fuse blows, then it's obviously not rated for a current draw as large as your radio.

And simply upping the fuse size on the truck's fuse panel may be dangerous if the wiring that supplies the radio terminals is only large enough to carry current consistent with the truck's fuse. Fusing it larger and then drawing 8 amps through it may end up burning down the truck, in what best exemplifies having the radio and its wiring "blow" to save the fuse. Not the ideal solution

Another reason for keeping with the idea of running your power leads directly to the battery is because you don't know how many junctions, fuse panels, relays, and crimp connectors to get to where its voltage source is. At every connection along the way, a little resistance from a loose or corroded conductor will induce a voltage drop downstream (towards the load -- the radio) AND reduce the effectiveness of the battery as a noise filter.

But I'd start out by locating the truck's fuse that feeds that built-in CB connection point and see how big it is. A typical CB comes with a 2.5 or 3 amp fuse, and it may be that that's all the truck manufacturer would spring for to save money.

 

Nope; SWR is a function of the antenna system, and is independent of the radio driving it.
That said, it's important to note the SWR of the first radio you hook to the coax; literally, write it down in your vehicle maintenance log or someplace where it'll be somewhat permanent. I write a short note and email them to myself, so they're always on the email server, besides whatever paper notes I write. The reason for this is that a wildly different SWR with a new/different radio may show a hack tuning job on the new radio. Your antenna system serves as a bandpass filter, albeit a crude one. It's made to radiate only the frequencies around 11 Meters, where CB lies. Taller antennas, ones with less coil to make up for missing physical length, will have a relatively wider bandwidth. My 102" whip on the side of the maintenance shop's first floor roof, with aluminum fascia behind it for a counterpoise, shows an acceptable SWR for 10 Meters all the way down to 12 Meters. The PCTel base loaded whip on the base adapter is only good for a little extension in both directions from the legal 40 CB channels.
If I did a Golden Screwdriver "tune" (I hesitate to use the term "tune", but unfortunately it's widely known) so that coils are spread, slugs removed, limiter clipped, etc., so that the radio now puts out measurable harmonics on 54 and 81 MHz (they show up on my spectrum analyzer), they hit that ~nominal 27 MHz antenna and see a huge impedance, so they get reflected, and show up as increased reflected voltage on the SWR bridge. (81 MHz, being an odd multiple of the fundamental of 27, will actually radiate somewhat better than 54 MHz.)

So if you change radios on an installation that was showing good SWR before and now it's suddenly gone nuts, you may safely assume that something has gone awry inside the new radio. It *could* have happened at the factory, I suppose, slipping by QC after someone on the production line broke protocol or substituted wrong parts on assembly, but it's pretty unlikely. It's much more likely to happen if one pays a vendor to do some sort of "super peak and tune" (ever notice how "peak" and "tune" are used together? Kinda like "kit and kaboodle". Ever see just a kaboodle for sale?) If a vendor tells you that a Cobra 29 will put out 28 watts after their super duper diddlestick orgy inside your radio, run -- fast -- the other way, or just buy it "stock", and see how it does for you. There's really not much you can do to a stock radio to markedly (definition: noticeably) improve anything about its on-air performance. And don't even think about sending it to the factory for warranty service when it fails.

So, back to your original question: indicated SWR for a given frequency range will not show a change if you change radios to another unbutchered radio made for the same frequency range. If it does, your radio is at fault.

Hope that helps, and that I didn't overstate the theory behind my explanation.

73