Uniden Pro510XL actual power

True. Except we were talking about the real-world issue of cranking up the output level of a radio. The 2SC2166 used as a final in the Pro 510XL has a maximum output power of 12.5 watts; that's its clipping level. Its linear region probably tops out somewhere around 7-8 watts; above that, it starts compressing. You start compressing a sine wave, it starts looking more and more like a square wave. As in f + (3f/3) + (5f/5) + (7f/7) + (9f/9) + ...

Just science. Not rocket science.

 

If only rocket science was applied by looking at the curves instead of specifications which is what you are going by. You are not correct to say "maximum output power of 12.5 watts; that's its clipping level", because it is not it's clipping level.

You are using 12.5 watts at 60 percent collector efficiency to give 7.5 watts power out with about a quarter watt of input drive. This is the standard specification. However a look at the curves yields the fact that this is at 1.2 amps collector current. Go look it up but please use the curves not the ratings. You will see this is exactly midpoint in the linear portion of the curve, or the horizontal valley on that particular curve. Clipping is closer to 2 amps collector current on the top end (upwards of 20 volts V-CE) and around 200 ma collector current close to the bottom of the curve. I will avoid discussing but will mention the actual RF output is from ringing in the tank circuit, noted only if power rises so high the magnetic field is clipped from saturation, not applicable for this discussion.

The reason these ratings you are using are given in spec sheets is quite simply we want to be in the middle so there is room on either side for linear excursion for clean power output when modulating the final. What must have been done in the radio quoted as keying 10 watts however was the value in pF of the coupling cap between the driver collector and final base was increased raising the drive. In his case assuming a 14 volt rail, 1.6 amps collector current, 400 milliwatts drive, hfe 83, efficiency 78 % (remember this is base-resistor to ground so effectively nearly class C), 10 watts out. Being 75-ish percent to the end of the curve is still below the clipping threshold. Also look at the curves for the variance in hFE given the other conditions.

Remember we are talking about a dead key so the need to be closer to the center need not apply because we are not driving it with modulation which would drive it past the saturation region. The fact is a member here was saying he saw 10 watts dead key, not telling us how he sounded to nearby people if he were actually modulating the thing with the limiter clipped and probably also using a power mike. I am just doing the math from the full set of curves for the 2SC2166.

Edit to add: I should point out this is all moot since no one in their right mind would try to get this radio to dead key 10 watts anyway. Any more than the too much modding to a 29 with a 9 watt dead key. They do not take so much into account including the total audio watts the audio section can do. It's all madness.

 

I carry one of those radios (the Pro 510XL) in each car in a zippered tool bag with a cigar lighter plug as a spare in the trunk, just in case everything else in my vehicles goes belly-up or if I find myself caravanning with someone unexpectedly who doesn't have a radio, etc. I've also got a couple as loaners in case someone has to get on the road before I've got time to troubleshoot and repair a radio properly, or if a radio needs parts I don't have on hand.
When I benched the ones I've got here, but without doing anything to them except restoring the clipped limiter I found on one, all of them were dead keying between 2.8 and 3.3 watts on a Bird with a low range slug. I double-checked them with a scope, using the P=E^2 /R (using 50 for the dummy load's "R" in the formula) and fed in a two-tone signal at fixed level into the mic input, so I wasn't trying to follow a cheesy meter's bouncing meter as an unstable whistle's level was changing as it was going into the microphone at a varying distance. (I still think a awful lot of "swing" can be attributed to the mechanical momentum of a needle's mechanism that can't stop moving up as quickly as the level that was driving it that way stops; that's why I like a scope, and a fixed tone to give me an average level.) At 100% modulation they all sound good and put out from 3.9 to 4.4 watts. I challenge any indifferent, critical listener to detect a difference on the air between any of these and one that's putting out 8 to 10 watts of "swing".
FWIW, I've got a spectrum analyzer on my bench, along with a tracking generator that I use to tune duplexers, not that the latter matters here, but certainly the former does when it comes to the classic "tuning for maximim smoke" like so many shops seem to do, the ones with nothing more than a $30 SWR meter and a diddle stick. My station rigs all have low pass filters that I have inline all the time, just on good engineering principles. But when I make a "house call" (or "cab call") to see someone's Cobra 29 that's "putting out 35 watts" but a bad SWR per the driver, I put a low pass filter inline and see how much difference it makes, let him/her see it, and offer them a chance to get it fixed correctly.
73,
Handlebar

 

" My station rigs all have low pass filters that I have inline all the time, just on good engineering principles " YEP

EVEN with a good radio ....

View attachment 36931

 

LPF always a good idea. I do not think anyone should want over 3.5 watts deadkey on the 510 but that's just me.