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AM CB Myths???

Differences among 2 radio's

I also noticed on my base, people say it sounds better turned down (More swing) when I turn it up the deadkey is 100 and people say it sounds better down (Variable)... However with the 25, it sounds better maxed out... 50W DK and swinging to max.. So yea this was my original intention of the research on the truths of am... I believe this info is based on a barefoot radio, not with an "Illegal Amp" Lmao!
 
BOOTY MONSTER said:
"Adjusting for 1/4 of deadkey might be too little as you need some bias for the amp the follow as long as you do not overdrive"

hey mechanic , are you talking about amplifier bias class as in A , B , AB etc. ? if so can you explain why a amp needs more than %25 dead key to for the amp to bias itself ? or any dead key at all since SSB is all modulated/pep power ?
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Rf amps are usually class A as they are simpler and cheaper to build. They are inefficient, say 10 to 25% and they usually run hotter. They are linear to a degree and when they are over driven they distort or clip.
Class B amps are very efficient but can be very distorted in the audio range.
AB class amps are more than 35% efficient but cost is going up.
Negative feedback in audio amps can increase efficiency but when it comes to RF it is like balancing a pencil on it's point.
So most simple RF amps are class A and one just has to work with it's limitations. These multiple PILL amps are simply an amp after an amp and so forth.
Not all amp designs need 25% dead key but this helps with the negative feed back if it is in the design. SSB are switched into that mode with a built in feed back or bias so it can operate. Amps with out a SSB setting had to be excited with a monotone style of modulation to keep the amp running, ie: humming between words!Kinda rare nowadays! BTW tube amps do this in a simpler way! I am not all that much into amps and that is why I do not use them all that much.
I do know that good designed amps like my Texas Star DX667 are somewhat "Plug and Play" as long as the exciter (radio) is not to over revved! :whistle:

73erds! mechanic Hmmmmm.... :confused1:
 
i wasn't aware there were any class A biased cb amps .
all amps regardless of bias class will distort when overdriven .
what cb/rf amps use negative feedback ?

did i miss the answer to my question ?
 
mechanic said:
Rf amps are usually class A as they are simpler and cheaper to build. They are inefficient, say 10 to 25% and they usually run hotter. They are linear to a degree and when they are over driven they distort or clip.
Class B amps are very efficient but can be very distorted in the audio range.
AB class amps are more than 35% efficient but cost is going up.
Negative feedback in audio amps can increase efficiency but when it comes to RF it is like balancing a pencil on it's point.
So most simple RF amps are class A and one just has to work with it's limitations. These multiple PILL amps are simply an amp after an amp and so forth.
Not all amp designs need 25% dead key but this helps with the negative feed back if it is in the design. SSB are switched into that mode with a built in feed back or bias so it can operate. Amps with out a SSB setting had to be excited with a monotone style of modulation to keep the amp running, ie: humming between words!Kinda rare nowadays! BTW tube amps do this in a simpler way! I am not all that much into amps and that is why I do not use them all that much.
I do know that good designed amps like my Texas Star DX667 are somewhat "Plug and Play" as long as the exciter (radio) is not to over revved! :whistle:

73erds! mechanic Hmmmmm.... :confused1:
Click to expand...

Most CB rf amps are class C,which gives highest efficiency and lowest linearity,with high distortion,which is usually of no significance to those who are power crazy as they don't care if they splatter over other spectrum users.

SSB amps are generally class AB which gives higher efficiency than class A but with almost as good linearity.

Class B amplifiers have higher efficiency than class A but have higher distortion.

Class A amplifiers are rarely used in rf amps as they have very low efficiency but are very linear,more likely to be found in small signal amplifiers before the final rf amp.More common in high end hifi amps where linearity is far more important than efficiency.

Negative feedback is used to reduce gain and stabilise amplifiers which are unstable.If gain s reduced then it follows that efficiency is also reduced,not increased.

Not sure where you got your amplifier theory from but its back to front.I ain't no specialist in amplifiers myself,but very few amps sold to cb'ers are suitable for SSB use,and most suck even on AM/FM use mostly due to the demand for more power by purchasers that don't understand how power actually works.
 
BOOTY MONSTER said:
without an amp how are you getting a 50 watt deadkey ?
Click to expand...

with the 25 connected to an amp it reads 50w deadkey, swing up to around 200.. I dont plan on keeping that amp on it as I use that on my base.. the radio does under 1w swinging to around 10 or so.. So its perfect for the amp, but I will need to make it work to its peek without one (higher deadkey) unti l I get one :) I dont want to destroy the mod that is inplace making this low dk, however want to add a switch or something to keep it as an option.. Someone said around 3w barefoot, so well see what happens when I bypass the swing kit
 
jazzsinger said:
very few amps sold to cb'ers are suitable for SSB use,and most suck even on AM/FM use mostly due to the demand for more power by purchasers that don't understand how power actually works.
Click to expand...

what class is mine (texas star 250HDV)>>??? its got the SSB switch on it, so its suited for sideband right?
 
packrat said:
Simbalage22 said:
Thanks mechanic.. You've got me on the right track.. I was just on 19 and they too say depending on the amp, lower deadkey is better,

One piece of advice, stay off of 19 and 6 if you want good advice on radio tuning. :lol:
Click to expand...

Now why you want to go and give him bad advice like that?
TT Man on da bowl will teach him how to set his rig up to cover all 40 channels at the same time. :D
Click to expand...
 
BOOTY MONSTER said:
"Adjusting for 1/4 of deadkey might be too little as you need some bias for the amp the follow as long as you do not overdrive"

hey mechanic , are you talking about amplifier bias class as in A , B , AB etc. ? if so can you explain why a amp needs more than %25 dead key to for the amp to bias itself ? or any dead key at all since SSB is all modulated/pep power ?
Click to expand...

Just in case you wanted some info on this, it is the class C amplifier that will use a small portion of the drive power to turn the transistor on. The standard bipolar transistor takes at least .6 volts on the base before it's on and FET's take more. Since there is no DC bias in class C the transistor simply waits until there is .6 volts of RF drive before it starts to work.

This creates a unique distortion on SSB since it's most noticeable at the lowest output levels rather then the highest. All of the lowest points in the SSB modulation are clipped off before the transistor turns on. Some try to cover this up with more mic gain but that creates it's own problems. On AM the power in the carrier is used as bias and makes the distortion less noticeable.

It is true that class C amplifiers require more drive then class AB. However, once we are talking about stages that require several watts or more of drive, that .6 volts of RF used for forward bias becomes a much smaller percentage of the overall drive. Meaning the affect on drive is only significant when we are talking about stages much smaller then the typical final power amplifier.
 

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