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nice little box for sure

A blast from the past for you:

http://web.archive.org/web/200102021...iers/index.htm

I've got one of those silver streak 150s right here, that I fixed for a local girl (needed a new so-239). It seems like I can set up the radio to run it on either low or high. If I set the dk to run the box on low, then I get 120 watt dk on high. If I set the dk low enough, to run on high, then I get almost nothing on low. I got the best results on low, so I might just tell her to run it on low only. (still does over 100 on low)

I still say 1 watt drive on these is best to go . Isn't a linear more linear when they key higher on high with less swing from there ? I was always under the impression that anything keying lower then 1/2 watt on AM could mess with the radios audio quality ? even still , cap/resistors will do that scope wise anyway , IM thinking class C AM is what it is ? You can run your amp any way you please (I prefer to run them lightly rather then hard) , My numbers with a 1 watt to 4 drive from radio looked very comfortable as far as longavity might be concerned in numbers given ? 1 watt to 20 pep was pushing 80 to 200 on high audio were the low side was doing 20 to 80 on audio. But I can understand where Gearhead is coming from by saying running it on low looked best , let me guess GH ? was that with about a 2 to 3 watt drive on the low side ? I can't believe they put 4 watt max input on the back of these . What's really going on here Freecell ?

A Class C amplifier is not linear regardless of how much or how little drive, or how much or how little swing. By definition, Class C (and Class B) amplifiers are NOT linear.

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73 de K7KBN

That may be easy for you to say Beetle , but by all means you might want to explain why for those of us that don't have a clue on the differents ?

I've posted this same answer to this same question many times.

http://www.tpub.com/neets/book7/25e.htm

Where the article states that Class C amplifiers are used for broadcast transmitters, what it fails to point out is that these are FM transmitters, not AM (and certainly not SSB). In order for an amplifier to be "linear", the output has to look like the input, just larger. No portions cut off, no distortion because of overdriving. Class B and C aren't linear, period.

Nor is Class AB, but if a Class AB amplifier is operated intelligently, it will be almost as linear as Class A, but a bit more efficient.

__________________
If you're like everybody else,
you're about average.
73 de K7KBN

the portion of the input signal for which there is an output produced (measured in degrees) determines the class of operation of the amplifier. the larger the portion of the input signal is that produces an output the less distortion and the higher the linearity when the devices are operated along the flat portion of the transistor gain curve.

Class A: output which is a replica of the input. (minimum distortion)
collector output current flows for the complete (360 degree) duration of the input. the dc operating point is between cutoff and saturation

Class AB: crossover distortion attenuated, linearity improved.
collector output current will flow for more than 180 degrees but less than 360 degrees of the input signal. the dc operating point is such that collector current is zero for a portion of one alternation of the input signal.



Class B: crossover distortion is present.
collector current will flow for approximately 180 degrees (half) of the input signal. the dc operating point for this class of amplifier is set up so that base current is zero with no input signal.

Class C: output not a replica of the input. (maximum distortion)
collector output current flows for less than one half cycle (<180 degrees) of the input signal. the dc operating point is below cutoff and allows only the portion of the input signal that overcomes the reverse bias to cause collector current flow.

OK , very good. For me , there's alot more to it then just reading it , it's like math of any kind , you have to understand it to get it, other then just reading it. Beings that IM a simple minded cb radio / amp user , if AM is all that I use ? class c will fill the bill ? . If IM more into sideband ? AB will be a cleaner situation then C although C will work on SSB to a degree of cleanliness.

(You should be familiar with two terms used in conjunction with amplifiers - FIDELITY and EFFICIENCY. Fidelity is the faithful reproduction of a signal. In other words, if the output of an amplifier is just like the input except in amplitude, the amplifier has a high degree of fidelity. The opposite of fidelity is a term we mentioned earlier - distortion. Therefore, a circuit that has high fidelity has low distortion. In conclusion, a class A amplifier has a high degree of fidelity. A class AB amplifier has less fidelity, and class B and class C amplifiers have low or "poor" fidelity. )

That part I do understand. It's the "why" part that tends to avail me , but does somebody like me really need to understand it in the first place ? I don't think so , but I also don't want to be a poupous ass either. (although it can happen from time to time) It's obvious I didn't get it when Freecell tried to explain it (thanks Freecell for trying) So I was wrong to say that a amplifier with a more so high dead key from a lower drive in with less swing but with a higher power reading was more Linear , I stand corrected.

It just goes back to the beginning for me , and I know Freecell mentioned the MRF455s were why this little amp keyed so high with such a low DK into it. The only other amps I've seen simlar to this one over the years were the older original Palomar mobile transistored amps that usually only needed about 1 watt input on the AM sides of those. Freecell said it was all in the spec's of the transistors. Like all that has been said up to this point , there's a lot more that I would need to understand concerning those spec's.

I truly appreciate the time taken here by those that do understand these formulas and "why". IM just a simple minded guy when it comes to all of this and I often look for simple answers to what I don't understand. IM either teachable or not and the flip side of the coin of that is .....will it benifit me ? I try and keep it as simple minded as I can , I still appreciate the truth and know how on all of this , weather it computes in my mind or not. I tend to get by on the basics. Every now and then , I tend to wonder why and how things work.(weather I understand it or not) Thank you gentleman.

Exactly right. And the most important factor in establishing this is the amplifier's bias.

Neither the amount of "dead key" nor the amount of "swing" has anything to do with the class of amplifier. If the amplifier is used for any amplitude modulation scheme (including SSB in any of its forms), Class C will distort the signal that goes on the air. "Loud"? Probably. Clean? No.

__________________
If you're like everybody else,
you're about average.
73 de K7KBN