HF Signals

Wiring up the BITX40

Before starting...

Below is the connection diagram.

This diagram is all you need to know to hook you your BITX40. You may want to follow the steps below to hook it up.

Step 1: The Antenna Connector

Step 2: DC Power Connections

The DC power from the socket goes to the board through the on/off switch on the volume control. From the ON/OFF switch, route the power

  • A parallel connection also goes to the transmitter power amplifier. This is kept as a separate connection on the board so that you can feed the power amp with a higher voltage.

    Step 3: Wireup the Raduino

    Take the LCD display apart from the Raduino and mount it on the front-panel. Now, plug-in the Raduino behind it. Carefully note that all the 16 pins of the display are properly slipped into the Raduino connector.

    Connect the tuning pot

    Connect to the DDS connector of the BITX

    The brown wire of the Raduino's 5 pin connector does NOT connect to the brown wire of the BITX's DDS conenctor!

    Step 4: Volume Control

    Step 5: Speaker

    Step 6: Wiring up the microphone and Push to Talk

    Don't solder the ground (black) wire of the speaker to the ground. It should only connect to the speaker or the earphone jack.
    You may optionaly route the audio through the supplied stereo earphone jack to the speaker such that if you plug in the earphones/headset the speaker will disconnect. This is left as an exercise to you.

    Step 8: Operate!

    Always use the BITX40 with a properly tuned antenna or a dummy load.

    Are you still reading? Go and work some DX!

    Alignment of the BITX40

    The BITX40 comes pre-aligned out of the box. However, it may go out of alignment for some reason and here are the steps to align it. Keep the circuit handy while you do it. If you can't understand what it means to 'insert the ammeter into the power line' ask someone for help.

    1. Attach a dummy load to the antenna
    2. Insert a ammeter (you may use your VOM meter in high amps range) into the PA power supply's positive line
    3. Keep the PA BIAS preset (RV1) to fully clockwise position. Now when you press the PTT button, the ammeter should read about zero.
    4. Increase PA BIAS without speaking into the mic until the PA current shows 100 ma
    5. Give a loud and long HAAAALLLOOWW into the mic and the current should jump to slightly over 1 amp
    6. Adjust the RV136 to increase the PA drive if the current doesn't jump all the way to 1A
    7. Keep monitoring your signal on a nearby receiver.
    <>Note: You may use the RV136 to reduce the output power to drive an external linear or go QRPp.

    Calibrating the Raduino

    Due to variations in the frequency of the crystals used, the frequencies generated by the Raduino may be off by a few hundred hertz. You can easily calibrate like this :

    Be sure to keep the RED wire from shorting to the ground again unless you want to recalibrate the Raduino.