Simple Sequencer For TRX-2 /SPE Linear Amplifier

[5B4AIY]

When using the Juma TRX-2 to key a linear amplifier such as the SPE Expert series, because the TX/RX switching in the linear takes longer than the TRX-2 switching, it is possible to provoke a High SWR alarm from the transceiver. Version 7 of the firmware attempts to provide a software solution to this by delaying the emission of RF from the transceiver until after a suitable delay, and whilst this is OK for SSB speech and CW modes, it is not entirely satisfactory for DATA modes. See the previous post regarding version 7 for details.

As the TX/RX switching in the TRX-2 is a hardware function, in order to effect a complete solution to the spurious RF 'glitch' a sequencer is required. Attached to this post is a PDF document describing a simple 2-transistor sequencer I made that can be used with the SPE linear, and probably many others. Note that this would only be required if you intend to operate DATA modes such as JT-65, FT-8, RTTY etc, for speech and CW the software delay works fine. If you do use this sequencer, then turn the TX Delay OFF, as it would not be needed for speech, but it would still be required for CW as the internal TX/RX switching is tied to a Morse key contact closure, not the PTT line, and in the CW case you would still need the keying line from the AUX connector on the TRX-2.

73, Adrian, 5B4AIY