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doesn't make sense to me

Discussion in 'General CB Services Discussion' started by 1iwilly, May 26, 2021.

  1. 1iwilly

    1iwilly Well-Known Member

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    handy andy what is the correct value for R 131 to get more out it that circuit i've seen people claiming to change it to 1.2 or 1.5 but never work me ??? other also say to go up on value ???


     

  2. Handy Andy

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

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    Well you really don't change R131, you change the LEVEL of signal it works with...

    R131 and (See Graphic below inclusive R130) set a "gain" of the Mic limiter...so keep the 10K and the 1.5K where they are...
    • You may have a Diode to control the DIRECTION of power escaping the Base of TR26 while others are Pre-Set to ON Class A...R130 or VR12 (per model)
    You change the OUTPUT of TR26 instead.

    Locate R127 a 1M (Brown Black Blue) - change it's value to a lower, much lower value - like 1K or even 680 - 560 ohms...

    The other side of TR26 looks at the AM Regulator - R166 and R165 - a simple divider - increase R166 to as high as 10K and REDUCE R165 to 1K - gives you a bigger window of drive for AMC...this affects the circuit you messed with earlier - R195 taps R166 and R165 - once you have R166 raised, and R165 lowered - you can leave the mess you were working with.
    Giving away my secretes (AGAIN!)
    upload_2021-5-28_19-15-19.png
    Why keep R131? Well, you can remove it, but if you run an amp - you might want to keep the ability to limit the input swing so you don't blow up the amp - especially if you are segue-ing to using MOSFET's in the near future.

    TR26 is on all the time, you tip the balance, scales or the waterfall effect - by changing the power available to flow across the Collector and Emitter - leave the Base alone, you can make the R131 and R130 (per graphic) equal - but that's not going to change much...The Diode forces AMC to work more towards Negative - the valve effect the Diode has, pertains to this.

    Think of TR26 as a Common Base amplifier, then you can figure out the rest a lot easier by just fiddling, fixing the power flow thru TR26 by changing R127, R166 and R165 - leave the ALC alone to fend for itself...
     
    #32 Handy Andy, May 29, 2021
    Last edited: May 29, 2021
    Shadetree Mechanic likes this.
  3. Shockwave

    Shockwave Sr. Member

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    The radio shack choke provided maximum performance.
     
  4. SIX-SHOOTER

    SIX-SHOOTER Sr. Member

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    A whistle is Useless for testing since Nobody I have ever spoken with whistles to communicate.Even if the power was 10 times as much on a whistle it's useless for actual communications.A Voice Peak is a Far Better choice for ny modulated signal since it's what is used for communicating.I hear people whistle to tune an amplifier & they get upset when the amp will not put out the same output when they talk.It's quiet Funny to me. :rolleyes::LOL::p

    SIX-SHOOTER
     
  5. SIX-SHOOTER

    SIX-SHOOTER Sr. Member

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    Many BIRD meters do have a PEP Reading Kit in them either from the factory or an aftermarket model so it's possible he has one of those but he did not say either way unless I missed it somewhere?

    SIX-SHOOTER
     
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  6. AudioShockwav

    AudioShockwav Extraterrestrial Admin
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    Watching the vids he posted it's AVG, no peak kit.

    73
    Jeff
     
  7. 1iwilly

    1iwilly Well-Known Member

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    audio shockwave yes bird is only for average for pep i use this meter
     

    Attached Files:

    SIX-SHOOTER likes this.
  8. 1iwilly

    1iwilly Well-Known Member

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    handy andy i change the r127 to 1k no go 560ohms no go either
     
    #38 1iwilly, May 29, 2021
    Last edited: May 29, 2021
  9. ExitThirteen

    ExitThirteen Grumpy and Cranky

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    Man, I need to pop in here and read the threads more often... Just been so busy.

    Looks like someone tried to do my NPC/RC mod, with less than favorable results.

    A few points to bring up...

    This HAS to be done with an o'scope, a signal generator, and a spectrum analyzer. Not a power meter.

    The AMC is not disabled, nor is it modified in my mod.

    The AMC was not properly adjusted in this case.

    It is not necessary to replace the C1419 with a TIP41C, but TIP41C's are cheap, and can run cooler.

    R228 doesn't have to be changed, it can be left alone, but I've found that changing it to 1.5K yields a small improvement.

    Changing or removing R131 is modifying the AMC circuit, and is a waste of time.

    I'll get back to this when I have time.


    ~Cheers~
     
  10. AudioShockwav

    AudioShockwav Extraterrestrial Admin
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    ( bang head on wall)

    I Did not connect exit 13 with
    Exit Thirteen
    Oops
    My bad

    73
    Jeff
     
  11. SIX-SHOOTER

    SIX-SHOOTER Sr. Member

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    Put a PEP Kit in the BIRD.

    SIX-SHOOTER
     
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  12. 1iwilly

    1iwilly Well-Known Member

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    SIX-SHOOTER i have a separate pep meter and besides that not the problem
    if you watch the video at that low power level when listening to the audio on another radio you can hear the audio falling off but never at a higher level



     
    #42 1iwilly, May 29, 2021
    Last edited: May 29, 2021
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  13. 1iwilly

    1iwilly Well-Known Member

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    hello exitthirteen if you read thru my remarks there is only one bug that it's only in the 1/2 to 1-watt range level yes the mod was done as you wrote it took it to a shop to be adjusted on a scope BUT keyword here it said set radio around 2 watts no problem
    until when i run my 2 pills and the drive falls in the 1/2 watt or 1 watt and while talking local barefooted when i been told my audio is fading bring the dead key up and problem solve


     
  14. freecell

    freecell Active Member

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    bird operation manual, 2016.

    "like similar diode devices, the Bird 43 indicates the carrier component of
    amplitude modulation, with very little response to side band components
    added by modulation."

    https://birdrf.com/~/media/Bird/Files/PDF/Manuals/920-43.ashx
     
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  15. AudioShockwav

    AudioShockwav Extraterrestrial Admin
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    So it works ok without the amp?
    What is the input SWR on the Amp?
    What I am asking, if you put a SWR meter behind the radio and in front of the amp, turn amp on , key up, adjust set point, read SWR going into the amp.
    Is it high?

    73
    Jeff
     

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