1270b.2

   CLEANING UP THE MFJ-1270B

   Sufficient reduction in the energy emitted by the 1270B can be had with
some relatively simple modifications to the 1270B. These modifications
should reduce the broadband noise level to a insignificant level for most
sites. Harmonics that cause problems to specific frequency can usually be
moved far enough off frequency by 'rubbering' the crystal with the trimmer
in the TNC.

  1. Scrape the paint from the inside of the cover and the outside of the
     chassis near the four screws that hold the cover on.

  2. Remove the circuit board from the chassis and scrape the paint from
     the top of the four posts that hold the circuit board.

  3. Add a low inductance strap from the mounting hole near the power
     switch to the ground trace at the edge of the circuit card. (The
     bottom side of the card works the best.)

  4. On the bottom side of the card add a 'small' 0.001 uf capacitor from
     each of the four active pins on the DIN connector to the ground foil
     immediately adjacent.

  5. Add a ground strap from the foil on the bottom side of the card under
     the DIN connector.  The ground end of this strap can be left dangling
     until the card is reinstalled and then looped to the outside of the
     chassis and grounded with a small self tapping screw on the lip just
     below the DIN connector.

  If you are at a shared site, you owe it to the other services to be a
  good neighbor.

 AL, K0VM