MKARS80 Update # 9

I have mentioned earlier that I had added a relay to the speaker circuit to remove the audio feedback that occurs when using a speaker/microphone.

This is a similar modification that I did to my BITX 20 V3.

To fit the relay into the case I have moved C2 from the board and, using a small cable tie, I have inverted it next to the new relay. Since I have also fitted a DC power cable and grommet and a DC power switch the back panel is quite congested. The relay is held in place by a thick wire running from one contact down to the ground where the internal speaker would be soldered. There is a second wire, blue in colour, that loops around the body of the DC switch to also hold the relay in place.

As a precaution against short circuits I have added PVC tape to the back panel, across the relay and on the underside of the aluminium case.

In addition to relocating C2 I have also cut a small track on the top side of the board near the original PTT relay. This allowed me easy access to the PTT line from the microphone as well as a place to control the original PTT relay with the new relay.

By switching the speaker out of circuit at the same time as applying PTT, using a double pole relay, I have removed the audio feedback.


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