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Test equipment question

Discussion in 'CB and Export Equipment and Accessories' started by kaos513, Oct 17, 2018.

  1. kaos513

    kaos513 Well-Known Member

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    Im aligning a 25 ltd for the first time calls for dummyload, watt meter and modulation meter i know about that but where does the signal generator and osciliscope all go into at once.


     
    Shadetree Mechanic likes this.

  2. Martian

    Martian Active Member

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    If its generating audio - mic jack
    RF - antenna.
    Just don't transmit into your signal gen unless it can handle it.

    Scope? What are you measuring?
    I have not looked at the alignment procedure so I am going to guess RF?
    You need an RF sampler like a Bird 4275, etc.
     
  3. kaos513

    kaos513 Well-Known Member

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    k thanks will look more into it
     
  4. Martian

    Martian Active Member

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    If you can list specific pieces of equipment you have we can tell you what else may needed to keep that equipment safe.
    For example, if you use a communications test set that can handle 50 watts then you can connect that to the radio directly.
    But if you use a Rigol SA, then you need an RF sampler+dc block OR attenuator+dc block because the input on the Rigol cant handle several watts on it's input.
    (A DC block is just good practice when using an SA )
     
  5. kaos513

    kaos513 Well-Known Member

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    100mhz scope hp signal generator 1000 watt meter/modulation as well ac/dc bench meter
     
  6. Martian

    Martian Active Member

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    Whats the model on the HP?
     
  7. Robb

    Robb Yup

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    First off, you don't hook up the sig/gen to the radio when you are working on the tx side of testing. So why are you trying to hook all of that up at the same time? Do the tx first with the radio > rf sampler > o-scope (modulation/carrier test)/freq counter (pll align) > power meter > dummy load setup.

    Once tx is all finished; then go on to doing rx.
    Radio so-239 > sig/gen; radio audio out > sinad meter.
     
    #7 Robb, Oct 17, 2018
    Last edited: Oct 18, 2018
  8. kaos513

    kaos513 Well-Known Member

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    ok is see tx alignment is seperate and the rx alignment is seperate?
     
    #8 kaos513, Oct 17, 2018
    Last edited: Oct 17, 2018
    Robb likes this.
  9. kaos513

    kaos513 Well-Known Member

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    I will post what testing equipment i i have.
     
  10. Handy Andy

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

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    Do PLL testing first - Dummy load on antenna and place Scope and / or DVM to Test points - Mic has Mic just no audio - set to Channel 19 (Mid band) first in RX - TX side? Your scope is in side on a TP 3 or TP 4.

    TP 1 is Ground (Negative)
    TP 2 - Varactor Voltage (use DVM - Verify Channel 1 and Channel 40 also - Bare wire of R59 Adj. L15 as needed)
    TP 3 - RX and VCO - Scope this - Tune to Ch 19 adj for Max - then tweak for Ch 1 and 40 for best waveform)

    In TX mode

    TP 4 - Channel 19 for best waveform - L17, L18 and L19 - Equalize for Channel 1 and Channel 40

    That's pretty much what you'll need the Scope for PLL and TX - RX? - NB uses it at L19 C15 for best shape waveform...

    Rest is by Wattmeter and if you have one SINAD for RX "volume" - 8 ohm Dummy load needed if SINAD used or DVM on S/RF meter leads - or just watch the show on the old analog S/RF meter diplay - just be sure RF gain is set to MAX for later on in the tuneup.

    TX - Channel 19 - ADJ L17, L18, L19 and L14 for last step in chain, for best reading on Wattmeter (terminated with a Dummy Load)
    Do the same for Channel 1 and Channel 40 to balance readings - may be necessary to Adj L10.

    SET VR3 to show 3 to 4 (TX part of S/RF meter)

    Set VR 2 to Mid-point (2nd IF Gain)
    Set RF gain to MAX
    Set Squelch to OFF
    Set ANL/NB to OFF

    RX - Channel 19 - Short Pin 1 to Pin 4 of Mic Jack if needed - place Sig Gen at antenna, set Channel on display and for 100uV 30% mod and tune L1, L2, L3, L4, L5, L6 and L7 - use AF VTVM or SINAD meter - or use S/RF meter look for maximum deflection

    NB ON - Adj L19 for best waveform (Scope to C15 - closest leg towards L5) use S-Meter display or tap DVM onto S/RF meter leads...

    If using AF VTVM or SINAD meter - on EXT SP Jack - 8 ohm termination - adjust VOLUME knob as needed.

    Equalize RX - Channel 1 and Channel 40 - Adj L1 and L2 between channels for best equalized S-Meter reading balance. Reset Channel to 19.

    Set VR2 to show S-9 on S/RF meter.

    Set Sig Gen to 1000uV and Squelch to MAX - Adjust VR 4 until SQUELCH just opens

    Disconnect Sig Gen at antenna - replace with Wattmeter and Dummy load - attach Microphone to Mic jack - Dynamike ON FULL - TX Mode - Adj L10 for 4~5Watt Deflection on meter - Channel 19, Channel 1 and Channel 40 - all should be equal - VR5 sets for 85 - 95% Modulation

    The Above comes from my own notes...per their Tune-up manual..

    HOWEVER, I know that folks would rather make it easy on themselves...

    Get PLL stable and in Lock first L15 and L16 do that...

    Get RX stable as above - VR2 (IF Gain) for best results not just "S-9" - NB and ANL are affected by this control too. L1 and L2 to balance out RX "noise" with L7

    VR4 for Squelch as necessary

    VR5 (if you go by the book) for Limiter action - affects L10...

    If VR 5 is active (working) just adj L10 for max deflection on wattmeter when audio is applied - preferably using the stock mike with FM interstation "hiss" available with "Mute off" feature on many FM stereo receivers. (White noise)

    VR3 for RF Power meter
    VR1 for Signal meter (VR2 affects this control as well)

    L16 may need to be tweaked/used for best performance balance between RX and TX.
     
  11. Robalo

    Robalo Active Member

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    copy and paste to practice on that radio when i have time.
     
  12. kaos513

    kaos513 Well-Known Member

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    Thanks
     
  13. Crossbow

    Crossbow Active Member

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    While I love the Sinad software meter you can get for to run on your computer you can also build a homemade RX test meter using an VU meter.
    Parts you will need:
    1- VU meter
    1- 8 ohm 8RΩJ 20 watt Axial Ceramic Cement Power Resistor.
    1- 1/8 inch Mono plug
    Some small wire to hook it all up.
    Here is what mine looks like:
    UV2.JPG

    UV1.JPG
    I also added an S Meter to watch both while setting the RX cans to keep things in line. Very easy to build and use with your signal generator. Yeah its was all put into a cottage cheese bowl. I was lazy and cheap! LOL.
     
  14. kaos513

    kaos513 Well-Known Member

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    I have sinnad meter as well
     
  15. Handy Andy

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

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    You did remove, consume or just plain enjoy it's contents before you did this - right?
     

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