1. You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
    Dismiss Notice
Dismiss Notice
This forum does not allow a single user to have more than one username. If anyone wants to change their username contact an admin and it will be done. Multiple accounts belonging to the same member will be deleted without warning.

Uniden pc78ltd dead key adjustment?

Discussion in 'CB Radio Modifications' started by widowmaker1, Feb 9, 2017.

  1. 711

    711 Well-Known Member

    Joined:
    Mar 22, 2008
    Messages:
    302
    Likes Received:
    305
    543,
    Interested in your IF tap and what kind of performance you were getting. I been wanting to build me a circuit to interface my dongle. Didn't know if they needed a buffer and/or LNA. Following your progress on the 3 diode TF mod.

     

  2. 543_Dallas

    543_Dallas Sr. Member

    Joined:
    Jul 25, 2011
    Messages:
    2,854
    Likes Received:
    3,986
    The performance is great. Good sensitivity and plenty of bandwidth. I can be on ch40, see a transmission on 1. If I click on it I can listen, run multiple reveivers with the sdr and listen to several channels simultaneously. I can receive ssb just can't transmit it.

    All I've done is tap L7 with a low value cap. 5pf is all you need. I ran mini coax to the bnc I installed on the back.Tune the sdr to 10.695.

    I instainstalled a relay in the radio to break the connection to the IF and short the coax going to the sdr when I transmit. This makes the noise floor on the sdr drop, with proper squelch settings the rx drops out on transmit.

    No plans of doing the 3 diode circuit to this rig. It is modulated with external gear. More info is on the MD forum...unless thats a different 711 over there.
     
    tecnicoloco likes this.
  3. 711

    711 Well-Known Member

    Joined:
    Mar 22, 2008
    Messages:
    302
    Likes Received:
    305
    I am the same, however I rarely stop by, lots of non technical stuff going on over there , guess i need to start looking closer. I've got an 880 that I'm trying to figure out at the moment. That 78 looks closer to the 980 though
     
  4. Clint Murphy

    Clint Murphy New Member

    Joined:
    Jul 28, 2020
    Messages:
    5
    Likes Received:
    0
    Just out of curiosity, why are you using that choke in place of the original diode? Thanks and have a good day.
     
  5. 543_Dallas

    543_Dallas Sr. Member

    Joined:
    Jul 25, 2011
    Messages:
    2,854
    Likes Received:
    3,986
    If memory serves me correctly I had some fuzz on the modulation peaks that I thought was caused by rf getting into the modulator. I had some of those chokes and it solved the problem.

    I originally got into this with a mauldulator and cobra 29. After that I started using the choke on every one I installed. The wire in that picture is coming from an asymod board.
     
  6. Clint Murphy

    Clint Murphy New Member

    Joined:
    Jul 28, 2020
    Messages:
    5
    Likes Received:
    0
    Thanks buddy!! Any more tune up/mod info floating around on these radios? This thread is the only thing I've found online as well as a YT vid with a cap and resistor mod done on the 68 LTX radio.
     
  7. 543_Dallas

    543_Dallas Sr. Member

    Joined:
    Jul 25, 2011
    Messages:
    2,854
    Likes Received:
    3,986
    I'm not sure. I haven't played with many of the new rigs and rarely work on stuff for other people.
     
  8. Clint Murphy

    Clint Murphy New Member

    Joined:
    Jul 28, 2020
    Messages:
    5
    Likes Received:
    0
    I see guys getting 30-40 watts PEP from these radios, I cant get mine to do that. 15-16 PEP is all I see from mine. Are their meters happy or is my meter just sad?
     
  9. DTB Radio

    DTB Radio Well-Known Member

    Joined:
    Sep 14, 2005
    Messages:
    1,014
    Likes Received:
    62
    There is a fairly simple way to add variable power to this radio. Go to www.dtbradio.com. click on the menu button that says "DIY Circuits", then click the "Variable Power KJit" link. That circuit can be adapted to almost any radio, and would not be hard to implement in your Uniden.
     
  10. 543_Dallas

    543_Dallas Sr. Member

    Joined:
    Jul 25, 2011
    Messages:
    2,854
    Likes Received:
    3,986
    It might be possible. Mine was set up to do 6 to 8 pep. I was after audio quality not quantity.
     
  11. Clint Murphy

    Clint Murphy New Member

    Joined:
    Jul 28, 2020
    Messages:
    5
    Likes Received:
    0
    How'd that work out for you? These radios seem to have tons of audio to me.
     
  12. 543_Dallas

    543_Dallas Sr. Member

    Joined:
    Jul 25, 2011
    Messages:
    2,854
    Likes Received:
    3,986
    Good.
     

Share This Page

  • About Us

    The WorldwideDX Radio Forum was originally established in 2001. We pride ourselves on welcoming Radio Hobby enthusiasts of all types, while offering unbiased, informative, and friendly discussion among the members. We are working every day to make sure our community is the best Radio Hobbyist's site.
  • Like us on Facebook

  • Premium VIP Member

    The management works very hard to make sure the community is running the best software, best designs, and all the other bells and whistles. Care to buy us a beer? We'd really appreciate it!

    Donate to us!