SwissUnit automatic antenna switch for a second receiver

Add an SDR receiver to your transceiver


SwissUnit is an automatic antenna relay for one transceiver and one receiver on the same antenna.

The use of an SDR with a traditional HF receive is a nice enhancement of any amateur radio station. With suitable software the transceiver can be controlled by the SDR interface. This brings new life to any older radios by adding an up-to-date waterfall feature. But often you face the question, where to get the antenna signal from. Not every transceiver offers an antenna monitor output. What to do?

Swiss Unit FrontThis is exactly the issue the Swiss made “SwissUnit” addresses. Swiss Unit is the combination of an antenna splitter with an antenna relay and the required controller electronics.

When receiving the antenna signal is split up to both – the transceiver and the SDR receiver. You can use the received signal on both systems, on the radio and on the computer. When switching to transmit mode the relay cuts off the SDR branch of the splitter and the antenna is directly connected to the transceiver. This protects the receiver input of the SDR. As a result you get a very comfortable system with up-to-date SDR reception and waterfall, and your trusted transmitter from the existing radio.

At the same time as switching the HF signal, the SwissUnit also switches an audio signal. This is used to cut off the audio signal coming from the SDR via the computer soundcard to the speaker system, to prevent audio feedback when transmitting. The supplied switching electronics box takes the PTT signal and supply voltage from the transceiver and switches the relays when going to transmit. The signaling is very simple, a cable can be homemade within a few minutes. Practically any transceiver can be used.

The HF relay and splitter is a qualit product with excellent specifications, which can switch up to 100W power. The splitter is specified up to 400 MHz, but can be used up to the 70cm band without too much losses. The antenna connectors are N sockets, the radio side uses BNC sockets. The control cable from the transceiver uses a 4 pin rund Foster type connector, as it is found on microphones as well.

A control cable radio to use with the FT-991/A is offered as well, other transceiver cables are planned. But it is very easy to make a cable on your own, the required connector is supplied

SwissUnit is a product by HB9IQK and marketed by Wimo