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Discussion in 'General CB Services Discussion' started by muppet62, Jun 29, 2008.

  1. muppet62

    muppet62 Member

    Jun 29, 2008
    Likes Received:

    We must be ready to the new solar cycle and repair or setup our old 10 meter hr radio (one of the best ever made).

    here is a real good power modification for the hr-2510, hr-2600 and Lincoln.
    Or use this as a upgrade if your MRF477 or MRF497 fail. I have done many of this mod/upgrades with exellent results.

    1 small washer
    1 47uF to 100uF 25V capacitor
    1 68 ohms resitor 1/2w
    6 silver mica caps (values shows in pictures)(they are really needed)
    1 SD1446 Pill (more cheap than mrf455)
    1 small piece of wire
    2 small screws (used to attach the pill to the radio cooler)
    heat sink compound (silicon not metal)
    Screwdriver, a drill and cutters

    After installing all the stuff and power on the radio adjust am power to no more than 15 W dead carrier.

    Download instructions here

    Any questions just let me know.

    Thanks and Enjoy!!!!
  2. Justme

    Justme Active Member

    Jan 28, 2008
    Likes Received:
    First, this is just an ordinary improvement wich can be found on the net, the only difference is you indeed replace the C's in the PA stage for larger power handling ones.

    Secondly, i use thee MRF455 and get 65 watts easy, grounding the emitters is crucial, removing the - lead from where it is soldered to the PCB to the point where the emitterleads are of the new transistor will up the gain.

    Secondly, you still let the DC go through the first ringcore wich degrades the handling capabillety of said ringcore, disconnect the + through the ringcore, and bring the + directly from the + input wire through an decent rf choke and decoupling to the collector.

    Pulling 70 watts SSB and 20 watts carrier in AM and 75 modulated here.
    Then use screening to pervent the hf radiating into the rest of the radio.

    Did this 15 years back, the radio's i rebuild still work fine as my Lincoln does now for 10 meter use.

    More power is fine, but hhow about reception?

    Replace the first stage transistor with an decent transistor, i use thee european BFY 90, you will find an replacement over there, the BFY 90 is an low noise fist stage pre amp transistor with an cutoff frequency of 1300 mHz.

    Then put in an xtal filter of 10.695 mHz in the MF replace the first C of 3 pF where you see 3 cans wich serve as rude bandpassfilter.

    This will prevent bleedthrough, sharpen the bandwidth of your MF, and improve reception.

    It still doesn't come close to my FT100, but for in my van it's good enough.


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