High Band Motorola Micor Mods for 220 Mhz

  1. Exciter TLD8262B9

    1. Remove the following capacitors and replace them with the new values shown:

      1. C430 - 68 pf
      2. C447 - 10 pf
      3. C433 - 150 pf
      4. C448 - 15 pf
      5. C434 - 120 pf
      6. C451 - 4.7 pf
      7. C437 - 20 pf
      8. C452 - 7.5 pf
      9. C439 - 22 pf
      10. C455 - 3.9 pf
      11. C440 - 51 pf
      12. C456 - 4.7 pf
      13. C443 - 15 pf
      14. C458 - 1.5 pf
      15. C444 - 12 pf
      16. C460 - 75 pf

      Replace all capacitors with the same type of part.

    2. The crystal formula is the same as the original high-band radio. The International Crystal catalog number is 161184Y. Be sure and specify "out of range". Midland 13-509 transmit crystals will work for test purposes.

    3. Tune up the exciter in accordance with the procedure in the Micor manual. The exciter should deliver a nominal 400 mw. If the exciter is used with the SAV15 power module, available from RF parts, an 8db pad should be placed between the exciter and the power module. The SAV15 requires about 80mw drive for 25 watts output.

    4. Exciter pin out is as follows:

      1. P902-13 = +9.6v keyed
      2. P902-7 = +13.8v
      3. P902-1 + 19 = Ground

      Ground P902-6 to enable the channel element in position number one.

  2. Receiver

      TLD8271 - 132 to 142 Mhz
      TLD8272 - 142 to 150 Mhz
      TLD8273 - 150.8 to 162 Mhz
      TLD8274 - 162 to 174 Mhz

      1. Remove the following capacitors and replace them with the new values shown:

        1. C108 - 27 pf
        2. C109 - 39 pf
        3. C113 - 2.2 pf
        4. C116 - 2.2 pf

        Replace all capacitors with parts of the same type.

      2. Replace R107 with a 12K. (R107 may already be 12K.)

      3. Remove the helical resonators and modify as shown below. Remove one less turn from L101. For 132 to 150.8 Mhz receivers, remove one extra turn from all the resonators. Replace the L102, L103 and L104 with screws that are 1/2" longer.

      4. The new crystal formula is:

        F = f - 11.7 / 12

        The multiplication factor is now 12X instead of 9X.

        Once the fundamental is calculated, plug it back into the original high band formula and give International Crystal the equivalent high band formula. The Inter- national Crystal catalog nuber is 161186.

      5. Tune up the receiver in accordance with the Micor manual.

      6. Receiver pin out is as follows:

        1. P904-1 and 16 = Ground
        2. P904-9 = +13.8v
        3. P904-6 and 13 = +9.6v
        4. P904-15 = discriminator output

        Install a jumper between P904-7 and P904-14 to enable metering of L108 and L109 adjustments.

        Ground P904-2 to enable the channel element in position number 1.