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  • Passive PTT Line Splitter

This Passive PTT line splitter takes the single PTT keying output from the back of most radio transceivers and splits it into 3 separate outputs (2 isolated and 1 direct). Ideal for connecting to 'Ground on Transmit' devices such as an external RF amplifier while also bypassing an external X-Phase style noise reduction unit and maybe an SDR antenna splitter unit. The possibilities are endless with this simple but very useful unit.

One red RCA socket on the side is connected to 2 seperate black RCA sockets on the top via isolating diodes and smoothing capacitors which help keep external devices isolated from each other. The other red RCA socket on the top is a direct connection and can be used to activate an external device that already has a built in isolation diode. This unit is passive which means it does not need any external power to operate and is not a PTT relay or buffer device. 

I use mine in the shack connected to an IC-7610. One isolated output keys an Elecraft KPA500 amplifier, the second isolated output controls a custom relay unit that removes power from an active HF receive antenna and the direct output places an X-Phase RX noise cancelling unit into bypass mode.

Please note:

You will need to check the schematics of your outboard equipment to see if it already has an isolating diode in the key line. If it does then you will need to make sure the keying operation works when connected to the isolated outputs (ensure that all bypass relays actuate before passing any RF through) otherwise it will need to connect to the direct output. I have a cheap X-Phase unit that appears to key when connected to an isolated port (the PTT LED turns on) but does not pass enough current to close the internal relays so please pay close attention to what your system requires. LMK Technical Services will not be held responsible for any misconfiguration.

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Passive PTT Line Splitter

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Tags: PTT, Key Line, Splitter