A model build with PA mods, AGC and anti-pop mods

Mike N6CMY enjoyed his first build of the µBITx so much he built another one! This one avoided all of the mistakes of the first build.

Modifications

TX:

1. Choke in series with R86.
2. All emitter resistors in buffer, predriver and driver bypassed.
3. Feedback resistor in PA increased to 600 Ohms.
4. Output Xformer replace with 2:4 on BN43-202.
5. Adafruit audio compressor in mic line with chokes to eliminate RF feedback.
6. PA powered by buck boost at 13.8V the rest of the board by 12V battery.

RESULTS:

30W on 80 and 40, 20W on 20. RV1 adjusted to reduce output to 15W.

RX:

1. ND6T AGC installed (underneath main board) at K3 powered by 5V regulator.

2. Additional stage of audio gain installed between Q70 and U1 to make up for loss due to AGC.

RESULT:

Plenty of audio!! and good AGC action.
3. VE1BWV audio pop mod (similar to the one standard on the new ubitx) installed underneath the main board.

4. To further enhance the pop suppression PIN 1 at K3 is grounded.

RESULTS: Sounds fine to me.

TRIVIAL MODS:

A red/green LED TX/RX LED is installed on front and a TX/RX relay to key an external PA is installed on the back.

Reference

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