Dave WI6R shows off his Hammond 1402DV (V for Vented since the heat sinks are inside).
It’s tight with the Volume Control mounted in between the display and the extrusion. So the PCB is mounted as close as you can get to the right side extrusion, then mark for the display and pot, with the encoder centered between the display and right side.
Dave used his own connectors for Mic, Headphones and Paddle and a Power Pole power connection on the rear panel. On the far left is the stock BNC antenna connector.
There was room to later mount a USB cable as show. Dave thinks he should have centred the Power Pole connector with the USB rear panel connection, but that’s what happens when you add things in later …
Dennis Yancey asked the group “Has anyone used a dynamic mic on the uBITx?” Dave WI6R responded with a guide for modifying the uBITx to use a Dynamic Mic:
Referring to the uBITX Schematic
. The Gain of the Mic PreAmp is controlled by R63 in the Emitter of Q6 to C62/R64. It basically decouples the audio bypass of R64 by C62 to limit gain for the high output Electret Mics.
Substituting a Dynamic Mic
Replacing R63 with a Zero Ohm resistor and putting a 10K potentiometer at the Mic input should allow a Dynamic Mic to work now with a Mic Gain Control. Also, R60 that supplies Mic BIAS to the Electret-Condenser Mic needs to be removed. If there is not enough gain after this mod, you might have to reduce the value of R64 to maybe 470 Ohms or so.
If you cannot look at your transmitted signal on a scope at least listen to your audio on another receiver to verify you are not causing distortion.
More Gain for an Electret Mic
To simply get more gain with an Electret Mic you might try dropping another 47 Ohm resistor on top of the existing R63. You can solder another chip resistor on top by soldering one end at a time.
[EDITOR: you can also bridge the surface mount resistor with a standard through hole resistor. Shorten the leads and bend over about 1/8″ or 3mm for soldering to the ends of the surface mount component]