To swing or not to swing

[JoeDirt]

ron, yes, what you are saying does make sense.

the reason for the confusion is the terminology itself.
that is what i was trying to explain in my last post.

the ONLY reason to use the "swing mod" for the 29LTD type chassis (and most every other AM only transformer modulated CB radio) is to lower the deadkey to use a linear amp while maintaining a high swing to better modulate the amp.
(im certainly not offering an opinion on whether its a good or bad thing to do, just clarifying)

what these guys are talking about is called a "swing mod" sometimes, but is more appropriately called an NPC mod. (Negative Peak Compression)


this is a great discussion!
i hope everyone stays as cool as they have been so far, as this has been very informative so far, and i hope that continues.

the first person i know of that applied the "NPC mod" to CB radios was Billy Dean Ward who has been doing it for many many years.
maybe i can get him to come in here and offer a new viewpoint, as he certainly has a great amount of experience with this type of mod.

keep up the great posts!
LC

I agree with you, this is a good discussion!

I was trying to think of Billy Dean Wards name earlier, I have read a lot of his posts! He did a writeup on a 148 with the NPC... pretty much the same thing im doing with a Galaxy. I had a writeup on a different forum... but it got dumped because of a bad server.

Im waiting for my video to upload right now....

 

[JoeDirt]

Here you go Shockwave!


Too Files - Free File Hosting - No limit - Video

 

[Mr Clean]

I run about 550 watts DK. 1500 pep on a Diawa true pep meter. On avg its doing about 375 DK and swinging 525 or so. I was under the impression that 100 percent mod would have you neg and pos peaks reading the same and your avg meter not moving under mod. Am I wrong in my thinking. Also are you guys talking about a pep or avg meter when talking about 1 to 4 carrier to peak. I would think your talking a peak reading meter.

 

[BOOTY MONSTER]

so what is the difference between a swing mod or NPC and the super wack pack from radioactive ?

 

[Mr Clean]

This is a good simple piece on mod.


Measuring modulation

 

[BOOTY MONSTER]

A.M. TUTORIAL

 

[ron103067]

Ok well to give you an update my radio dk 4 watts and swings to 16 watts. It goes into my texas star dx250hdv which keys at 150 and swings to 250 and today I talked to a base about 30 miles away and was doing a good job which is what I wanted all along. Now I am happy with my setup, and wont get a swing kit in any of my radios. That is just my opinion if they work for you then that is good.

 

[cbdoctor]

Loosecannon, I do see where the NPC mod claims it does give negative peak compression and that is a step in the right direction. Keep in mind with Joe's 250% positive peaks and only 95% negative peaks, that's a good deal of compression for a simple diode to achieve. Even more remarkable is the fact when you look at the scope picture, the negative peaks show no trace of when that diode is conducting on them.

If the scope pictures really represent the values he claims then the NPC diode mod on the Galaxy is the perfect negative peak limiter. Something I highly doubt. It takes a little more then a diode to produce that carrier and modulated waveform. Otherwise the carrier was turned up to get rid of the RF cutoff. Perhaps you could post a video of the scope from carrier to full modulation several times.

I was asked to join in on this thread. I am sure that some on this forum have heard what I have to say but it totally BLOWS MY MIND how many talk about the NPC-RC without having ever experienced it.

The above is absolutely the fact.The NPC-RC is the perfect NEGATIVE PEAK LIMITER but in the form of compression. Yes it can be done with just one tiny diode. Quit doubting it and simply do the NPC-RC on an 88 or any of the 3600xxxx boards.

I do AT LEAST 5 to 10 NPC-RC modifications per week and have been doing so for about 11 years. I have NEVER had a problem with the mod and it does NOT sound crappy to anyone that has heard my radios. It sounds fantastic and has NO NEGATIVE effects whatsoever.

Anyone that says that the Positive Peaks cannot be modulated to up to 400 % without having the negative peaks reach zero and flat-top has simply never seen the NPC-RC modification done correctly.

I was WA6DSE (Amateur Extra) for over 40 years. (Now expired) I was first class liscensed from 1966 until they discontinued that ticket. I worked with the NPC-RC modification for CB's in 1981. I used the idea in an amplifier that I manufactured from 1971--Golden Eagle--The class AB biased units with band filters.

Every time someone starts talking about swing kits on any of these forums this entire lists of posts gets re-posted as though they are new and all of the hams join in and tell the lowly cb'ers the same crap again without even taking time to find out the facts.

 

[BOOTY MONSTER]

http://www.11meteroutlaws.com/viewtopic.php?f=39&t=532

 

[sp5it]

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[BOOTY MONSTER]

sorry about that . it is a decent forum and it does have some interesting threads and some (IMO) good folks there . its not a very busy forum , but if you join to view the thread id suggest browsing some of the other threads there too . im not a believer in the MMM stuff there , but theres some good stuff there

 

[C2]

I was asked to join in on this thread. I am sure that some on this forum have heard what I have to say but it totally BLOWS MY MIND how many talk about the NPC-RC without having ever experienced it.

The above is absolutely the fact.The NPC-RC is the perfect NEGATIVE PEAK LIMITER but in the form of compression. Yes it can be done with just one tiny diode. Quit doubting it and simply do the NPC-RC on an 88 or any of the 3600xxxx boards.

I do AT LEAST 5 to 10 NPC-RC modifications per week and have been doing so for about 11 years. I have NEVER had a problem with the mod and it does NOT sound crappy to anyone that has heard my radios. It sounds fantastic and has NO NEGATIVE effects whatsoever.

Anyone that says that the Positive Peaks cannot be modulated to up to 400 % without having the negative peaks reach zero and flat-top has simply never seen the NPC-RC modification done correctly.

I was WA6DSE (Amateur Extra) for over 40 years. (Now expired) I was first class liscensed from 1966 until they discontinued that ticket. I worked with the NPC-RC modification for CB's in 1981. I used the idea in an amplifier that I manufactured from 1971--Golden Eagle--The class AB biased units with band filters.

Every time someone starts talking about swing kits on any of these forums this entire lists of posts gets re-posted as though they are new and all of the hams join in and tell the lowly cb'ers the same crap again without even taking time to find out the facts.

Still waiting for you to put your money where you mouth is...the spectral purity plots.

:rasperries:

 

[Shockwave]

I'll admit I haven't tried the NPC CB mod but I am experienced with negative peak limiting. I should probably look at the schematic but here is what I do know. If the diode is installed in any stage that is followed by capacitive coupling, much of the offset between the negative and positive peaks will be gone because of the loss of the DC base line reference point. If the posted scope pictures are accurate, the NPC mod works well in this series of radios.

The problem I have are these ridiculous posts of a 1 watt carrier with 30 watts PEP sounding good, regardless of negative peak limiting. At best it will sound like a class C amp running on SSB and chances are it will sound more like DSB with that low carrier. Way too much for the standard AM detector to demodulate cleanly. My point is there are limits to what will sound good and 1 watt carrier with 30 watts PEP will not sound good. I doubt the CB Doctor will argue this.

 

[JoeDirt]

I'll admit I haven't tried the NPC CB mod but I am experienced with negative peak limiting. I should probably look at the schematic but here is what I do know. If the diode is installed in any stage that is followed by capacitive coupling, much of the offset between the negative and positive peaks will be gone because of the loss of the DC base line reference point. If the posted scope pictures are accurate, the NPC mod works well in this series of radios.

The problem I have are these ridiculous posts of a 1 watt carrier with 30 watts PEP sounding good, regardless of negative peak limiting. At best it will sound like a class C amp running on SSB and chances are it will sound more like DSB with that low carrier. Way too much for the standard AM detector to demodulate cleanly. My point is there are limits to what will sound good and 1 watt carrier with 30 watts PEP will not sound good. I doubt the CB Doctor will argue this.

The gate of my radio i posted was dead keying 1 watt and swinging 40+, did it sound fine to you? I still dont think your understanding, the NPC lets the carrier raise up and down with your modulation, Your never going over %100 modulation so stock regular CB radio can demodulate it just fine!

Hey CB Doctor how can you show your true modulation percentage on a scope with the NPC?

 

[BOOTY MONSTER]

but 1 watt swinging to 60 or 80 watts will sound great !!
right ? right ?? right ?????????