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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

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