Category: radio mods

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Adding an INA219 power monitor to a chinese USDX+ transceiver

The (tr)uSDX has hardware to measure the power amplifier voltage/current/input power. Since the output power is also measured, it can calculate and show efficiency. This is very useful for tuning the class-E output stage, and is also useful in the field to see battery voltage and other parameters.

I have an uSDX+ transceiver from China. Let’s add the power monitor to it too. This description should apply to other radios based on the uSDX.

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TR-9000 CW semi-BK mod

To transmit CW on the Kenwood TR-9000, TR-9130, TR-9300, TR-9500 (and maybe other) transceivers one has to hold the PTT on the microphone (or on the optional BO-9 base) and only then transmit using the KEY. For some reason the Kenwood thought this would be an excellent idea.

This is a simple external semi-BK circuit implementation, so that you can just press the key to transmit. No modifications inside the radio are necessary.

The circuit is connected to the STBY (2.5mm jack) and KEY (3.5mm jack). Connect the key to the CW KEY terminals. To increase the time make the capacitor bigger, currently it is 3000uF (3x 1000uF in parallel). The diodes are any silicon diode like 1N4148, 1N914, 1N4001 etc.

Keep in mind that the capacitor is charged to 8V, so that the key has temporarlily 360mA flowing thorugh it. No problem for a straight key, but it might be an issue with some electronic keyers.

See the circuit in action here:

VY 73 de SQ5BPF