B
BOOTY MONSTER
Guest
like the title says ... whats the difference between a NPC mod and the top gun modulator ? all i can tell is they both give radios excessive swing , but im not a tech by any means .
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probably not a lot of difference,possibly a bit of filtering added to the top gun to reduce harmonic content,
i don't know because i haven't opened one,they ain't that popular here due to lack of AM usage,hence the reason i said probably,if i'd had known i would have said for definite.their may be no difference at all,the waveform on an oscilloscope on top guns website looks very similar too the npc/rc waveform.
NPC stands for Negative Peak Compression.
the idea is that the negative peaks of your audio are what make you sound bad when they exceed 100% (well, in a manner of speaking. cant be less than zero so they get clipped off) the NPC is supposed to keep those negative peaks at about 98% and allow the positive peaks to exceed 100% which is supposed to make you sound louder without distorting.
(please dont flame me on the "exceed 100%" thing. this is how its explained by Billy Dean Ward who has been doing this mod forever and a day)
an NPC mod does not lower your carrier.
that is a separate step that you can choose to do to set the deadkey where you want it, and the radio will swing up from there.
the Top Gun modulator, as i understand it, is basically a swing mod that lowers your deadkey and lets the radio swing up to its fullest PEP wattage.
as far as i know it does not tailor the audio in any way. (well, i think they sound like crap but thats another story)
my guess is that its sort of like the cap/resistor added to the 29LTD chassis.
you have DC voltage going to the driver and final, with your modulation which is AC riding along with it.
the resistor lowers the DC voltage thereby lowering the carrier.
the electrolytic cap will not pass DC but will pass AC so your modulation does not get attenuated.
i did the NPC mod to my Galaxy 929 which involves removing a disc cap, and soldering in a diode in series with a 100ohm resistor in its place.
the disc cap is then replaced on the bottom side of the PC board.
my 929 previously had a diode placed in series with R264 which is known as the galaxy "swing mod".
i did notice a bit of an improvement in the sound of the audio.
some people probably hate the sound, but i think my radio sounds good.
it deadkeys at 5 watts and swings up to about 25.
LC
the idea is that the negative peaks of your audio are what make you sound bad when they exceed 100% (well, in a manner of speaking. cant be less than zero so they get clipped off) the NPC is supposed to keep those negative peaks at about 98% and allow the positive peaks to exceed 100% which is supposed to make you sound louder without distorting.
(please dont flame me on the "exceed 100%" thing. this is how its explained by Billy Dean Ward who has been doing this mod forever and a day)
an NPC mod does not lower your carrier.
that is a separate step that you can choose to do to set the deadkey where you want it, and the radio will swing up from there.
the Top Gun modulator, as i understand it, is basically a swing mod that lowers your deadkey and lets the radio swing up to its fullest PEP wattage.
as far as i know it does not tailor the audio in any way. (well, i think they sound like crap but thats another story)
my guess is that its sort of like the cap/resistor added to the 29LTD chassis.
you have DC voltage going to the driver and final, with your modulation which is AC riding along with it.
the resistor lowers the DC voltage thereby lowering the carrier.
the electrolytic cap will not pass DC but will pass AC so your modulation does not get attenuated.
i did the NPC mod to my Galaxy 929 which involves removing a disc cap, and soldering in a diode in series with a 100ohm resistor in its place.
the disc cap is then replaced on the bottom side of the PC board.
my 929 previously had a diode placed in series with R264 which is known as the galaxy "swing mod".
i did notice a bit of an improvement in the sound of the audio.
some people probably hate the sound, but i think my radio sounds good.
it deadkeys at 5 watts and swings up to about 25.
LC
What is the difference to what the NPC mod does - and carrier-suppressed dual side band AM?
No; I'm not being cheeky.
Just trying to learn a bit.
No; I'm not being cheeky.
Just trying to learn a bit.
the NPC mod does not lower or remove the carrier.
it is a way to alter the waveform that your voice produces.
its often confused because it gets combined with an RC (reduced carrier) mod.
known as the NPC-RC mod.
this is just a guess, but in a 29LTD if you removed JP36 and replaced it with an electrolytic capacitor without using the resistor, you might be in DSB mode.
the idea is that there would be no DC feed to the driver and final to supply the carrier, but the cap would pass the AC voltage of your modulation.
i might have to try that someday just for kicks.
i bet it sounds like shite though. LOL
LC
it is a way to alter the waveform that your voice produces.
its often confused because it gets combined with an RC (reduced carrier) mod.
known as the NPC-RC mod.
this is just a guess, but in a 29LTD if you removed JP36 and replaced it with an electrolytic capacitor without using the resistor, you might be in DSB mode.
the idea is that there would be no DC feed to the driver and final to supply the carrier, but the cap would pass the AC voltage of your modulation.
i might have to try that someday just for kicks.
i bet it sounds like shite though. LOL
LC
the difference between npc mod and suppressed carrier AM is you need to reinsert a carrier on the receiving end to demodulate suppressed carrier AM,you can use either lsb or usb to receive it,the benefit is if there was an interfering signal on usb you could tune it out on lsb and vice versa.you could also receive it in AM mode if you used a BFO with it too but you would lose the ability to choose which sideband to demodulate.
npc mod is just basic AM with the forward swing increased beyond 100% modulation and the negative swing limited to stop it shutting off for the periods it would go beyond 100% as you can't go more than 100% negative swing.
I know this is an old thread but the 100% in question is NOT a given amount of anything. You can have 100-200-300-400% of modulation to carrier ratio that is what your meters and scopes are measuring. Its not like there's some modulation units to be measured and you only get 100 units to work with. If I whisper at 3db and then yell at 28db how much increase did I have (oh you cant have more than 100%) I guess more increased stopped at 6db and the other 22db are all harmonics at 54mhz.
So, if I'm reading this right, if you want the NPC mod. you'd be just as well off using a good compression-amp mic like a turner +3. As that mic takes a lot of speech and compresses it into a 100% modulation waveform.
Negative Peak Compression ('NPC/RC') is a mod that keeps the negative peak on an AM modulated signal from going 100% negative and additionally allows for the positive peak to be increased by a percentage of the original AM waveform.
When the positive peak percentage has been increased; the consequence to the final/driver is that they will now be overdriven. Because it has more gain than it did before; it becomes necessary to Reduce the Carrier (or 'dead key wattage').
Not anything like audio compression found in a Turner mic circuit.
The NPC mod is done in the audio circuit and AM Regulator before it is sent to the output mixer circuit.
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Okay, I see. with a compression-Amp mic it's all done before it even enters the radio. Does the positive peak still go above the 100% modulation line with this mod?
Absolutely. But only one of these NPC mods is worthwhile - IMO. There are NPC mods, and then there are NPC mods. Check out ExitThirteen (forum member/tech) version of the NPC mod. While I haven't tried it yet, it is probably the only one I would try. Makes SSB usable and can get quite a bit of modulation well above 100% on AM. Most of the other NPC mods can't make that claim.
http://www.worldwidedx.com/threads/over-130-modulation.163831/
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It's been a while but here goes, stop with all the tricks of trying to make your radio sound like a big radio and just buy a bigger radio or amp. Do you know why big commercial stations come in so strong because 50K watts make it possible. And yes they compression as audio filters but they also half a million in studio equipment. If you want to sound like Motormouth Maul or Prime Minister your going to a couple of $10K some studio equipment, at least 5k watts, and a voice that's made for radio, not to mention a tower witha set of beams. So in short don't waste time or money on radio mods, but rather invest in a better Mic, bigger amp, taller tower, or better antenna.