Transverter Common-IF Box

May 1st, 2010 by k8gu Leave a reply »

I weighed the pros and cons of tapping the low-level TX and RX lines inside of my FT-840 (the TS-930 brings these to the rear panel) versus installing an attenuator in the TX line.  I opted for the attenuator instead of doing surgery on the radio.

The circuit is not particularly remarkable:  the transceiver RF jack goes to a relay T/R switch.  The TX side of the relay goes through a hefty 20-dB attenuator to a BNC jack.  The attenuator is rated at 5 watts continuous duty and considerably more at lower duty cycles, perfect for this application.  The RX side goes straight through to a second BNC jack.  The TX circuit is normally closed (and RX normally open).  This minimizes the chance of accidentally dumping 5 watts into the RX side of the transverter.