Ok I've read numerous times that it is better to have your equipment/radio set up at a 1 to 4 ratio.on output to have a clean signal without distortation.. I have seen where there can be a higher ratio n still sound real good (not on a meter). So if a 1 to 8/10 ration be loud n sound good to some then wouldn't a deadkey of 1 swing to 30 after tuned be more like a "splatter box" & if not then why? Would it be because of the negative peak. I know it may be a dumb? ?? But I am just getting into the hobby n trying to understand
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??? about the NPC MOD!!!
- Thread starter doc919
- Start date
Just because a radio might swing a bunch means little. A good number of exports can be made to swing a huge amount but their audio still could be flat as a pancake.
If your radio starts to swing way too much....such as 1/2 watt key swinging to 30, it might sound distorted and then again maybe not, depends on the radio.
Since you are new just use one of the forum's recommended techs...... don't worry about waveforms and splatter. 99% of Cbers want to just sound impressive and could care less about bleeding over a few channels. If a radio doesn't have enough audio to scatter a few channels, it is anemic.
I have heard my mobile on the base and it is the best sounding one in the whole area.....it also bleeds a bunch of channels.
If the radio is WAY overmodulated to the point of sounding horrible, there are issues......Channel 6 is a perfect example. Crackley audio that scatters all 40 is a badge of honor on that channel.
I have heard beautiful sounding radios bleed over bad and then there are the scratchy, tight sounding setups that will do the same but nail all electronic devices within a stone's throw.
Most of the forum users here are perfectionists so just have fun with a nicely tuned radio.
STAY AWAY FROM RADIOACTIVE RADIOS!!!!!!!! His tuneups are just radio rapes.
Ok! Thank you PSYCHO. YEA I HAVE NEVER DEALT WITH radiohactive as some have called them. These radios are fun to learn about, so I do appreciate the info n heads up
Yes I have definately heard some of the scatterboxes on that channel. N sometimes I wonder if any of these guys have ever heard themselves. I know that mine isn't the so called BIG RADIO but I do like for it to sound as good as possible without it being distorted
On channel 6 it's all about signal strength and audio quality means nothing. Instead of using the 1-4 carrier power/peak swing power ratio the 6 guys use the same formula only upside down. Key 10,000 watts and backswing to 2500 watts. :laugh:
The 'Negative Peak Compression/Reduced Carrier' mod is used in commercial broadcast radio and is set up correctly so it will operate correctly. Few CB operators operate or set it up correctly - IMO. Removing the AM Limiter is never really necessary to do; as others think that doing that is essential and the same thing as the NPC/RC mod. It is not.
Sure, removing the AM Limiter will give more modulation/greater than 100%. But the net result is just distortion and nothing more. It is useless in itself to just remove it. Changing the ratio will keep the distortion away only/if the complete NPC/RC mod is done properly. Put that limiter back in your radio and stop passing out this clipped limiter myth. There is plenty of info available to show that clipping out the limiter is obsolete. Don't even bother to do the NPC/RC mod unless you are going the distance and install the whole enchilada, set it up/adjust it, and run EVERYTHING correctly.
The whole idea behind this NPC/RC mod is to increase the % of the positive peak envelope. The 'compression' occurs at the negative part of that cycle. The negative part of the cycle is kept from distorting the waveform by the addition of a capacitor and diode. This will keep the negative stroke of the cycle from shutting off the AM carrier between cycles. The NPC/RC mod targets the negative stroke for compression; not the positive stroke.
Keeping the AM Limiter intact and using a resistor in series to that transistors' collector will pretty much nullify the built-in positive stroke limiting - or 'compression' - of that circuit while keeping the ALC/SSB circuit functional. Removing the AM Limiter from the circuit will cause the ALC/SSB circuit to default to full open. This will pretty much destroy the waveform in SSB mode; rendering SSB useless. So; keeping the AM Limiter in is essential for keeping the radio capable of use in all transmit modes.
If done correctly and set up correctly, it will still have compression. Because there is another compression circuit added ('capacitor and diode' or even a 'resistor and diode'; depends on the model of radio and where it is placed in the cicuit) and relieves the AM Limiter of that duty. The 'reduced carrier' is a consequence of compression. The final output device now operates differently; but the way it is utilizing power is perhaps - arguably - more efficient. So long as it is set up properly (not an easy chore), it will run cooler and transmit better due to the higher % of positive peaks with no negative peak shutoff/distortion.
Removing just the AM Limiter will cause positive peak clipping ('square waving') as well as the negative peak shutting off the AM carrier; the consequence of that is even more distortion.
At least, that is what I understand about it - at this point . . .
Sure, removing the AM Limiter will give more modulation/greater than 100%. But the net result is just distortion and nothing more. It is useless in itself to just remove it. Changing the ratio will keep the distortion away only/if the complete NPC/RC mod is done properly. Put that limiter back in your radio and stop passing out this clipped limiter myth. There is plenty of info available to show that clipping out the limiter is obsolete. Don't even bother to do the NPC/RC mod unless you are going the distance and install the whole enchilada, set it up/adjust it, and run EVERYTHING correctly.
The whole idea behind this NPC/RC mod is to increase the % of the positive peak envelope. The 'compression' occurs at the negative part of that cycle. The negative part of the cycle is kept from distorting the waveform by the addition of a capacitor and diode. This will keep the negative stroke of the cycle from shutting off the AM carrier between cycles. The NPC/RC mod targets the negative stroke for compression; not the positive stroke.
Keeping the AM Limiter intact and using a resistor in series to that transistors' collector will pretty much nullify the built-in positive stroke limiting - or 'compression' - of that circuit while keeping the ALC/SSB circuit functional. Removing the AM Limiter from the circuit will cause the ALC/SSB circuit to default to full open. This will pretty much destroy the waveform in SSB mode; rendering SSB useless. So; keeping the AM Limiter in is essential for keeping the radio capable of use in all transmit modes.
If done correctly and set up correctly, it will still have compression. Because there is another compression circuit added ('capacitor and diode' or even a 'resistor and diode'; depends on the model of radio and where it is placed in the cicuit) and relieves the AM Limiter of that duty. The 'reduced carrier' is a consequence of compression. The final output device now operates differently; but the way it is utilizing power is perhaps - arguably - more efficient. So long as it is set up properly (not an easy chore), it will run cooler and transmit better due to the higher % of positive peaks with no negative peak shutoff/distortion.
Removing just the AM Limiter will cause positive peak clipping ('square waving') as well as the negative peak shutting off the AM carrier; the consequence of that is even more distortion.
At least, that is what I understand about it - at this point . . .
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OK!!! very well explained... I had never tried it. Have only seen post over it & the 1 to 4 ratio theory
Forget using your meter to monitor your audio. Use a scope.
Some will learn this most won't . Only meter I watch is reflect . My scope is my best friend other than my power that is.
Agreed. The ONLY meter I will look at when checking modulation is this one. At nearly $1000 new it certainly is no Dosy and the quality and accuracy is no Dosy either. It does AM (and SSB) and FM from 1.5 Megahertz to 2.0 Gigahertz, 0-100% mod + and - as well as FM deviation from 10 KHz to 100 KHz full scale both + and - deviation as well. It also provides sampled audio out for monitoring.For general use I still use a scope.
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