Juma TRX-2 Transmitter Signal Levels

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Juma TRX-2 Transmitter Signal Levels

Postby 5B4AIY » 01 Mar 2017 09:36

Whilst assisting an amateur who is experiencing some problems getting his kit to work, I made some measurements on my transceiver to show the sort of waveforms and signal levels you are likely to encounter.

For these measurements, the transceiver was set to 1.8MHz, as even a fairly modest oscilloscope should be able to deal with this, a x10 probe was used to minimise any loading, the transceiver was set to the TUNE mode. As I am using my firmware, the 3dB attenuator is in circuit in this mode, so the signal levels in the pre-amp, driver, and PA stages represent the signal levels for a power output of about 4W, whereas the signal levels in the RF filter board represent the signal levels at the maximum output. Note that the A4 modification of the PA Board, incorporating resistor R5 and capacitor C2 in the emitter circuit of TR1 has not been made - yet! The DC voltage across C19 on the main board in this state is about 1V. This voltage governs the carrier level.

I am in the process of writing a technical manual for this transceiver, and I hope this information may be of some use to other constructors.

73, Adrian, 5B4AIY
RF Signal Levels
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