Swing Kit Vs. NPC (ept3600)

[LeapFrog]

Would you like to explain the difference? On a galaxy what mod is a swing kit and what mod is an NPC?

It depends on the pc board in question, on a DX66V (ept360014) a swing kit is 1N4001 diode added in series with R238, sometimes hackshops just remove the resistor and install a diode in place of R238, then they cut the AMC resistor.
This allows the radio to swing to near max p.e.p. from any dead key, it looks rough on the scope.


NPC involves a wire to "volt the finals", a diode (1N914 or 1N4148) + resistor (100-350ohm) tied in series, then installed in parallel @ C189 [added between collector of TR51 and emmiter of TR49].
(I used a 500ohm variable resistor/ trimmer potentiometer in place of a fixed value resistor, to get a final tune, then replaced the trimmer pot with a resistor nearing what the pot "ohm'ed out" to)

If set correctly, the negative peaks will compress allowing over 100% positive modulation (asymmetry ) while appearing clean on the 'scope. The radio will not "swing" nearly as much with an NPC mod, say 2-4 watts avg(depends on the final modulation %), it is 'linear', 1-2 watts, 2-4 watts, 3-6 watts; the forward power or "swing" is dependant on the dead key and modulation limit / final tune.

While a "swing kit radio" will swing forward to 10 *bird watts or more, regardless of the dead key. It's "super-mod" box car audio, not clean asymmetry. (good for box builders to show big #'s) It's a surefire way to splatter (swing kit) turning the mic gain way down still doesn't fix the negative peaks.


There's a difference gentlemen.
73

 

[Robb]

Are these your thoughts; or are you quoting someone?

 

[JoeDirt]

It depends on the pc board in question, on a DX66V (ept360014) a swing kit is 1N4001 diode added in series with R238, sometimes hackshops just remove the resistor and install a diode in place of R238, then they cut the AMC resistor.
This allows the radio to swing to near max p.e.p. from any dead key, it looks rough on the scope.


NPC involves a wire to "volt the finals", a diode (1N914 or 1N4148) + resistor (100-350ohm) tied in series, then installed in parallel @ C189 [added between collector of TR51 and emmiter of TR49].
(I used a 500ohm variable resistor/ trimmer potentiometer in place of a fixed value resistor, to get a final tune, then replaced the trimmer pot with a resistor nearing what the pot "ohm'ed out" to)

If set correctly, the negative peaks will compress allowing over 100% positive modulation (asymmetry ) while appearing clean on the 'scope. The radio will not "swing" nearly as much with an NPC mod, say 2-4 watts avg(depends on the final modulation %), it is 'linear', 1-2 watts, 2-4 watts, 3-6 watts; the forward power or "swing" is dependant on the dead key and modulation limit / final tune.

While a "swing kit radio" will swing forward to 10 *bird watts or more, regardless of the dead key. It's "super-mod" box car audio, not clean asymmetry. (good for box builders to show big #'s) It's a surefire way to splatter (swing kit) turning the mic gain way down still doesn't fix the negative peaks.


There's a difference gentlemen.
73

So you can volt the final with either mod so that doesn't matter. 1N914 or 1N4148 diode dont make any difference being fast switching, your only dealing with audio frequency's nothing higher.

So do this for me, volt the final (since you do it anyways on the NPC) Then install the 1N4001 (or your fast switching diodes dont matter) in series with R238.
Now put your 500 ohm pot across C189, I betcha see the same results as your NPC claim.

 

[JoeDirt]

Are these your thoughts; or are you quoting someone?

Its in response to my comments Robb Galaxy DX 66v swing mod

 

[LeapFrog]

JoeDirt, I would have to try that sometime my friend, I'm just saying somethings that I have found personally from messing around with the Internet mods, I am no authority in the matter!

http://www.deepsouthradiosDOTcom/forum/showthread.php?t=5972 [Link intentionally broken, replace DOT with "."]

I found this thread on another forum, the man gives voltage measurements.
like I said in the other thread it's all about how everything is set up in the end and yes as long as you have a signal diode it should not matter what kind, part of me cringes when I see a rectifier diode installed. ( even though it doesn't make a huge difference )

 

[JoeDirt]

The only thing I have noticed different between the two mods is installing the diode at the resistor R238 has slightly flatter frequency response. (A non issue really)
The diode installed in the two different locations has the same effect, all it does is raise the carrier at an audio rate to keep it from pinching off. You really never have more than a ℅100 modulation in the position direction. Since the scope only sees voltage you have to use a pretty decent spectrum analyzer so see the carrier rise and fall with modulation.

 

[LeapFrog]

So you are telling me that all I have observed is a positive carrier shift and not true asymmetry?

If I had an REA station monitor, I think I could easily tell by myself!
If the avg output increases due to high modulation percent, would the increased avg output not "confuse" the interpretation of the spectrum analyzer results?

 

[JoeDirt]

So you are telling me that all I have observed is a positive carrier shift and not true asymmetry?

If I had an REA station monitor, I think I could easily tell by myself!
If the avg output increases due to high modulation percent, would the increased avg output not "confuse" the interpretation of the spectrum analyzer results?

Correct, I don't know anything about the REA monitor......

 

[LeapFrog]

Interesting, time for me to buy some more test equipment so I can prove/disprove this for myself.

 

[711]

For me, in my experience , the R238 swing kit will see a little more pep but the c189 will do better in the RMS department. You may not see it in the output of the radio going into a wattmeter but the proof is in how the amplifier stages amplify that RMS. Not saying it's the text book answer, just things I've noticed . I take out a lot of R238 mods, C189 sonically sounds better to my ears. All in the user and what they like. The R238 swings a lot on a wattmeter though. Meter watchers like to see that.

Ok this part is an addendum to my post after reading the other post from leapfrog. Any swing kit can be made to sound good. Even with the limiter out. When the radio is adjusted beyond its "linearity" range is where you'll run into your problems. You'll run into a few different types of splatter when over done. Over done in regards to over modulation and also bandwidth mods. JD can attest to this. I cheat, I don't own a spectrum analyzer , I use an SDR dongle. Have you seen the waveform from a radio putting out 10-20khz wide audio bandwidth? There are ridges and valleys for days up and down the band, even outside the 11 meter band. You can adjust for every anomaly out there but like Robb said the proof is in the pudding and what you hear over the air, in his case a monitor radio. That's what I do as well, however a modded receive CB.

 

[Robb]

My experience is that if these chassis have these mods done to them, it always - w/o exception - makes SSB absolutely/practically useless. And I have work on many of these radios in particular. I feel quite strongly that can say that - and should - if any reader should think they can have both and are considering these mods. You cannot have you cake and eat it too - so to speak.

 

[711]

My experience is that if these chassis have these mods done to them, it always - w/o exception - makes SSB absolutely/practically useless. And I have work on many of these radios in particular. I feel quite strongly that can say that - and should - if any reader should think they can have both and are considering these mods. You cannot have you cake and eat it too - so to speak.

I'm sorry Robb but I'll have to disagree with you on this one. Anything done in the the NPC/swing kit area is strictly for AM only purposes. Once the SSB switch is flipped, it puts straight 12 volts to the collector and takes all those AM mods out of the picture. All modulation is now low level modulated by the BM. Also the NPC and swing mods in the wrong hands can be made to look and sound like crap. Carefully adjusted, you can sound pretty good. Anything used improperly can be made into crap. 9 times out of 10 that's what happens. These mods get a bad rap because they're normally used improperly.

 

[LeapFrog]

I'm sorry Robb but I'll have to disagree with you on this one. Anything done in the the NPC/swing kit area is strictly for AM only purposes. Once the SSB switch is flipped, it puts straight 12 volts to the collector and takes all those AM mods out of the picture. All modulation is now low level modulated by the BM.

I think Robb is saying the same thing in a way, there are a lot of variables here especially how somebody can cut the limiter right out of the radio and somebody else can get better performance with the limiter still in, but I can say that I have never had good luck with any of these modifications on a single Side Band radio operating in any mode besides a.m.

From my experience it's a lot harder to set it up correctly then just adding a diode, I set out to make a radio asymmetrical and I followed an old guide on the internet, proving the results would be great!
There's gotta be a software plug-in for SDR# to show modulation percentages?!

 

[Robb]

I'm sorry Robb but I'll have to disagree with you on this one. Anything done in the the NPC/swing kit area is strictly for AM only purposes. Once the SSB switch is flipped, it puts straight 12 volts to the collector and takes all those AM mods out of the picture. All modulation is now low level modulated by the BM. Also the NPC and swing mods in the wrong hands can be made to look and sound like crap. Carefully adjusted, you can sound pretty good. Anything used improperly can be made into crap. 9 times out of 10 that's what happens. These mods get a bad rap because they're normally used improperly.

Yeah; that's what I hear. Adjusted a lot of radios and used to think the the NPC/RC could be adjusted satisfactory. However, it just never worked out that way despite the time I put in it to make it work. Even with the AM Limiter still in, it still wouldn't come around. BTW - the NPC mod that most users say that the limiter must come out and is no longer necessary. That's all fine and dandy if you only use the radio for AM use. But if SSB use is desired, they always come up with bad reports. Limiter in is better than limiter out; but still a bit gravelly in SSB mode.
Why is that?
Perhaps because removing R238 disables the ALC control?

Had a local repairman that swore by those modules that dealt with R238. So we did an experiment and left one in one radio, and the other radio I replaced the original resistor and just peaked the TX coils. The difference was obvious and undeniable. Not to mention that I found him 3 1/2 more peak watts on AM - to boot. He never talked to me again. Oh well . . .

Since most die hard AMers will tolerate poor SSB performance for blaring AM, guess they think it is a fair trade off. But that is just a guess.

 

[711]

I think Robb is saying the same thing in a way, there are a lot of variables here especially how somebody can cut the limiter right out of the radio and somebody else can get better performance with the limiter still in, but I can say that I have never had good luck with any of these modifications on a single Side Band radio operating in any mode besides a.m.

From my experience it's a lot harder to set it up correctly then just adding a diode, I set out to make a radio asymmetrical and I followed an old guide on the internet, proving the results would be great!
There's gotta be a software plug-in for SDR# to show modulation percentages?!

If you follow the schematic in most of the common CB SSB radios, the AM is high level modulation via the darlington pair in the AM regulator area. Carrier adjustments changes the bias voltage to the collectors of the final and driver, that normally varies from 2-6.5 volts. The audio comes from the audio preamp, whether it be the 4558 or the 7222ap. After that the audio splits it path , one to the AM regulator and the other to the Balanced modulator. You could take the darlington pair off the board and SSB would be completly unaffected . Look for yourself. In fact try it the next time you have a bad darlington pair, switch it to SSB and see if you're affected. Give a can of paint to an artist , he'll paint a master piece, give that same can of paint to Joe Shmoe and you'll get a different result.