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Swing Kit Vs. NPC (ept3600)

Discussion in 'CB Radio Modifications' started by LeapFrog, Jan 14, 2017.

  1. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    Give a soldering Iron to a knuckle head and you get a golden screwdriver radio on eBay.
    The best modulator circuit I have ever seen is the one built into the S45HP.
    Set it for 2 watts dead key and swing for the fences with 70 to 80 watts peak.
    Always got good reports for sound quality, signal strength and it looked good on the scope and with the spectrum analyzers. The person on the other station would always notice the S/RF meter bouncing with the modulation.


     
    Robb and LeapFrog like this.

  2. LeapFrog

    LeapFrog Wielding Hanlon's Razor

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    While that is very novel, I don't see why such an amount of swing is good for anything besides driving a box hard, or getting huge peak to carrier ratios (LOUD?) ?

    Watching the needle swing around can be fun, but give me a 4:1 ratio and I'll be happy, unless It's true asymmetry that's obtainable!
     
    #17 LeapFrog, Jan 15, 2017
    Last edited: Jan 15, 2017
  3. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    You can hear the difference. With all of the talk about audio quality on this site it would seem apparent the benefits of a properly modulated signal. It does punch through the noise and jabber on the frequency.

    And yes it is a true asymmetrical modulation.
     
  4. LeapFrog

    LeapFrog Wielding Hanlon's Razor

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    Very good, I guess what I'm trying to say with this thread is that people can often attempt to make the radio perform in such a manner and fall short of a clean signal.

    I have seen many Cobras set up with a super modulation kit look very poor on the oscilloscope, some of the export radios I have seen have a quality signal, that is apparently asymmetrical, & they produce good loud audio.
    BUT! Most of them I come across are setup like "swing kits" and look poor on the scope. In my opinion the modification is done incorrectly if the carrier gets piched, or the pos. peaks flat-top/distort at all, REGARDLESS of how the radio sounds on air!


    That same Galaxy radio set up incorrectly, would perform like an incorrectly set up Cobra.. (distortion/flat topping/negs crash/pinched carrier)

    That is why I say there is a difference between a swing kit and an NPC.

    Tallman's radio is likely very clean (while producing moderate "swing"), I would go as far as to say that I have a Galaxy DX66V that can be made to operate in a very similar fashion.
    [ I believe I've recreated the results found by using one of the Magnum modules in an export, just by goofing around & I'm no 'real' scientist after all.]

    It all comes down to who's operating the radio, what the radio is capable of, & the the tune/configuration.

    Some people can produce a clean asymmetrical waveform, while others can only produce shark teeth with this mod and we're talking about the same radio,
    perhaps even the "2 seperate modifications" actually occur in the same circuit.
    (one with poor results in my opinion, and the other producing an apparently clean & asymmetrical waveform)

    Hell, the same value components can produce nasty results if the radio is not setup correctly! :mad:
    But with enough patience, you eventually figure out how to dummy proof the radio (in component value selection and trimmer pot adjustment) so that it does not "over modulate" (the negs ;)) no matter where the microphone gain is. (y)

    That is the only kind of "loud as hell" radio I would ever dream of running, the typical swing kit results that I see on the average transformer modulated Cobra mobile radio looks like absolute garbage and would never be worth running no matter how the radio sounded on air.

    Time for me to get a spectrum analyzer because this story only goes deeper!
    Not only in regards to the export radios with modifications, but the Uniden NPC mod may have a serious fault as well.

    Captain Kilowatt, Unit_399, ExitThirteen, Loosecannon, & other prominent members have recently discussed in an older thread, that there may be problems associated with "harmonic distortion" ? (I forget the term) not normally noticed with the spectrum analyzer unless specifically tested for, when using the NPC mod.
    This kind of blew my mind a little bit, because I was really excited about the idea of clean asymmetrical modulation from a modified c.b. radio!
    The only thing that I can demonstrate at this point, is clean modulation on the oscilloscope; I lack further test equipment.
    (It's probably not as easy, as simply adding a diode :eek:)

    I'll have to find the link for this thread, if you find the thread before me please link it here.


    I associate the term "swing kit" with "splatter box", while a proper npc modified radio does not have to be so "RF McNasty"; I don't care for ghost watts.
    ...Mean is Clean, do the best that you can! 73
     
    #19 LeapFrog, Jan 15, 2017
    Last edited: Jan 16, 2017
  5. jon666

    jon666 Sr. Member

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    im not a swinger
     
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  6. LeapFrog

    LeapFrog Wielding Hanlon's Razor

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    Somebody once told me to try swingin', they said it be could fun to meet new partners even if only for a night! {Sinner Alert}
     
  7. 391redneckradio

    391redneckradio New Member

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    I have a question I always wanted answered. If a radio sounds "golden" on the receive end and shows great watts on a meter but looks like total garbage on scope, do you fix it or leave it alone?
     
  8. binrat

    binrat WDX Club Coordinator
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    Fix.
     
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  9. LeapFrog

    LeapFrog Wielding Hanlon's Razor

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    The fun part is when they get it back and the "watts ain't right"...
    *YOU $%#@! MY RADIO WAS SWINGING 30 WATTS PLUS, YOU BROKE IT*

    Just kidding, but the scenario has played through my mind.
    I call it cognitive dissonance... it is what it is.
     
    #24 LeapFrog, Mar 21, 2019
    Last edited: Mar 22, 2019
  10. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    You know ...

    Take a closer look, the rest of you can double check the work but I think we've found out how they work this circuit to provide the asymmetrical envelope...

    You don't do too much to the AM Regulator...

    You use the "AM Power" control as a bias level in the Mic Amp loop.

    How?

    Well, the S45HP uses the feedback path that goes to the AM Regulator from the OUTPUT of the Main Regulator the 2SB754...

    Those Orange And Yellow wires - note their tap points...
    S45HPAMRegulator.jpg
    Not the Mic Amp section where this is part of the feedback path...
    S45MicAmpCompare.jpg

    To be fair, this is from another board similar to the Galaxy but from their A24 Maverick radio
    Note they have a Pre-set level of 270K in this between Pins 1 and 2 making it a FIXED feedback loop...
    S45MicAmp.jpg

    And when you adjust the "Bias" of AM Power - at the same time - this bias is a small voltage back at the Mic amp section - but uses this as added or summed into the Audio Bias that goes to the Final and Driver - the effect is to adjust the ENVELOPE power by using your AM power setting (RF Power) and the Audio amplified, then sent to the AM Regulator from the Pin 1 and Pin 2 of the 4558 chip...

    To make it work, the wires send power to Pin 1 and Pin 2 of the Mic amps Differential loop inputs - replacing the fixed 270K resistor (R195) with a more flexible design that uses the AM regulator's own audio injection points as well as AM carrier adjustment section. Note that RF Power the external control is involved, this simplifies the issue of symmetrical amplification thru all audio level power as well as carrier levels (except for FM - that's is handled separately). The loop is kept intact - only the OUTPUT of the AM regulator is quenched silent - this doesn't affect the loop the parts in the regulator section that set FM quieting are external to the loop.

    Just wanted to pass along KUDOS! to Tallman for posting the radio...at least the one he liked...
     

    Attached Files:

    Tallman likes this.
  11. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    It simply is the only radio I own with the NPC built in. I was amazed at how well it worked when I put it up on the bench. My son wants it, and every time I use this radio I get offers from people that want to buy it.
     
    Shadetree Mechanic likes this.
  12. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    You have something - a lot of other people want in their radio.

    Wish you the best - and for your son too, to have something that reminds him of you.
     
    Tallman likes this.
  13. Mustang 131

    Mustang 131 Well-Known Member

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    The cleanest signal in the world still sound like shit 99% of the time after 150% positive.
    If you need more swang just use SSB.
     
  14. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    Nope! Not true. You have not heard a radio modulated like that. Commercial A.M. stations do NPC all the time
     
    sp5it likes this.
  15. 9C1Driver

    9C1Driver Sr. Member

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    Two of the best sounding radio's I had back in the day was a Magnum Delta Force and a Mirrage 2950 EX. They both had a non volted final version of the NPC mod done by a local tech that used a scope. Great radio's.
     

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