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Switch Kit · #21 04-11-2008, 06:11 PM

Well Beetle , I think I've understood what Class C has meant over the years , LOUD ? sure why not , Dirty ? You bet'cha ! this part about Class C reminds me of Pyscho's analogy which others tend to think he's crazy about when it comes to class C amplifiers on the 11 meter band. I personally think his analogy hasn't been that far off. CB radio is what it is , it's almost as if your DAMNED if you do or your DAMNED if you don't know matter what class amplifier you use . Although , it is nice to have a decent amplifier ,especially if SSB is your thing ? AM ? it's almost why have a cleaner box if it's DIRT IN AND DIRT OUT anyways ? I have a nice Cobra XL 450 , I seldom use SSB until DX picks up and becomes strong again ,so AM has always more so been my way of life on the 11 meter band. I still use a cap resistor mod for this perpous into my amp , IM just back to dirt in and dirt out , but I seldom get any complaints from anybody nor do I want any. Is this a "truly" clean amp ? would a (qoute on quote) perfectly tuned radio into this thing "truly" going to make that much differance on the other end ? If class C is dirty from the get go ? What does it truly matter ? in other words , can class C ever be clean ? Thanks Beetle , you have always been a great help around here and else where. Peace

Beetle · #22 04-12-2008, 09:48 AM

Quote:

Originally Posted by Switch Kit

in other words , can class C ever be clean ?

Class C can never be LINEAR. If you're feeding an FM signal to the input, the Class C amplifier will work just fine; this is what it is born to do. The amplitude of the input is virtually constant so there are no modulation transients to cause problems.

If you're feeding an AM signal (full carrier, no sideband suppression) to the input, and you're careful to have only a minimum of "swing", you probably won't have technical problems with a Class C amplifier. Again, you're keeping the mod transients to a minimum.

For SSB, however, the input signal is ALL "mod transients". The signal will splatter all over, and sound ungood.

Switch Kit · #23 04-12-2008, 10:12 AM

I thought I heard that mentioned about Class C as far as FM is concerned , again , whom uses FM on the 11 meter band in America ?

( If you're feeding an AM signal (full carrier, no sideband suppression) to the input, and you're careful to have only a minimum of "swing", you probably won't have technical problems with a Class C amplifier. Again, you're keeping the mod transients to a minimum. )

You probably won't ? in other words you will , but your just making it as clean as clean can be concerning class C as far as AM is concerned ? Still far from the best ? or does this mean you can utilize more power from the class C amp with "less" distortion ? Would this mean the more so cleanly tuned radio into the class C
application and this would all show up clean on the testing machines ?

Beetle · #24 04-12-2008, 10:31 AM

Quote:

Originally Posted by Switch Kit

I thought I heard that mentioned about Class C as far as FM is concerned , again , whom uses FM on the 11 meter band in America ?

>>I wasn't referring to using FM for CB/11 meters specifically. Class C amplifiers are great for FM, regardless of what band or frequency is being used. You, as the operator, have to know what's legal in that regard.

( If you're feeding an AM signal (full carrier, no sideband suppression) to the input, and you're careful to have only a minimum of "swing", you probably won't have technical problems with a Class C amplifier. Again, you're keeping the mod transients to a minimum. )

You probably won't ? in other words you will , but your just making it as clean as clean can be concerning class C as far as AM is concerned ?

>> Right.

Still far from the best ? or does this mean you can utilize more power from the class C amp with "less" distortion ?

>> A Class C amplifier on AM will ALWAYS, by design, produce a signal that's a distorted parody of the input. The higher the drive (and the mod transients), the greater the distortion. More power? Maybe, but very little of it, if any, will be on the frequency you think it is.

Would this mean the more so cleanly tuned radio into the class C application and this would all show up clean on the testing machines ?

>> The spectrum analyzer will reveal all: harmonics, spurs, IMD and all the junk. And the more you overdrive the amplifier, the worse it gets.

.

Captain Kilowatt · #25 04-12-2008, 07:14 PM

Quote:

Originally Posted by Beetle

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).

Just to be picky here and slightly off topic but class C amplifiers are used in AM broadcast transmitters because of the higher efficiency.The catch is that they are plate modulated.The RF amps run class C whereas the audio amp is class B or maybe class AB. In no way is the modulated signal amplified by a class C amplifier however. IMHO an amplitude modulated signal should NEVER be amplified by a class C amp. I prefer to keep all my dirt in the back yard and not on the airwaves.

Beetle · #26 04-12-2008, 10:53 PM

Thanks for the clarification, QRN. I was in a hurry when I wrote that and didn't convey all I was thinking. Plate modulation is a great way to go, but for every 100 watts of input you need right around 50 watts of audio, I believe. I remember the modulation transformer on my old DX-100B weighed as much as the power transformer!

Captain Kilowatt · #27 04-13-2008, 04:24 AM

That's correct Beetle. Plate modulation requires that the audio amp provide 1/2 the DC input to the finals for 100% modulation. A typical 1 Kw (output) plate modulated class C amp requires nearly 750 watts of audio. Plate modulation (or high level) is the only time a class C amp should be used in AM service.

Stevenp55 · #28 06-29-2009, 07:33 PM

The data sheet shows that 1 watt at 13.6 vdc produces 55watts, and at 12 vdc only 50. So, 5 watts at 13.6 produces 80 watts. In ideal conditions it would stand to reason that your Silver Streak should be capable of 160 watts!

Conversely, my Palomar "Elite" 400 with 4 MRF455s doesn't seem to be doing any better than 150 W DK at full voltage.

: I noticed that one of the caps has that "pregnant" look at the top. Naturally it will be replaced, but would the storage in the cap affect my dead key? Nice AB1 class amp if I can get it to perform.

psycho · #29 06-30-2009, 01:41 PM

That SS-150 looks like a nice clean well built light duty amp. Looks much better than a crappy texas Star or palomar. Previous owner must have had a problem with the high/low resistors buring out and went with the 2 watters.

mackmobile43 · #30 07-04-2009, 09:52 AM

Quote:

Originally Posted by Switch Kit

My question is why the high DKs on these with only 1 watt , the many I've had over the years all acted that way. Your data sheet means nothing to me unless you explain it ? why the high DK's on these little boxes at 1 watt compared to many others is the question. As far as fluff goes , I already said that didn't count. No offence to you Mack , but folks tend to ask simple questions (or look for simple answers) and I could drop a data sheet on somebody any day of the week weather i understood it or not ....kind of like this past thread ......"Pill" questions... Thanks for the reply all the same Mack , the data sheet doesn't tell me why these little amps key higher then I personally would think they would on the high side of a 2 x 455 amp. I can believe the low side at 20 to 60 but 80 to 120 audio pep seems strange to me ? Is when a radio is perfectly tuned at 1 to 4 into this box , what happens to the 4 to 1 ratio from the box , this is why I "think" 80 watt DK would be high on this one ? NO ?

It's very simple, the turns ratio of the transformers is how you determine the transistor's resting carrier and ramping up.

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SILVER STREAK 150 (2 X MRF455) ?