EME215 RX Active Switch

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EME215 RX Active Switch Description:

The RX Active Switch has been designed for HF Radio Transceivers that only have a single antenna socket and no optional RX only antenna input. This allows a separate Loop or Active whip receive antenna to be connected in RX mode, and a main Transmit antenna to be connected in TX mode. The design incorporates a Bias Tee ( DC power injector ), so that active whip and loop antennas can be directly powered via the coaxial cable. A Relay and RF detector circuitry is used to disconnect the RX Active antenna to protect it when DC power is disconnected, or when in transmit mode. The active switch has better than 50dB isolation up to 50MHz, so can easily handle up to 500Watts of RF power.

Kit Constructors Alert:

1/ The board overlay diagram in Kit notes Rev1.0 shows D7 around the wrong way. The anode connection should be to ground.

Construction Notes:

The images below show both sides of the board. The construction is quite easy if you start with the SMD components on the bottom side of the board first, and then fit the conventional leaded components after. The only difficult part is the winding of transformer TFMR1 as the windings have to be correctly connected for the correct phasing polarity. An incorrectly phased transformer cancels the signals and produces no gain. Click the pictures below for a more detailed view.

EME215 Module Top View
Top view of the EME215 RX Active Switch Module
EME215 Module Bottom View
Bottom View of the EME215 RX Active Switch Module
EME215-DC Power connections
Picture shows the connections from the DC socket to the toggle switch.
EME215-DC Power connections
Picture shows the connections from the DC socket to the toggle switch.
EME215-Relay-Mounting
How the Relay is directly soldered to the pads on the board

EME215 RX Active Switch Tests:

S21 TX Loss 0.1 to 100MHz
EME215 0.1 to 100MHz S21 Loss from the Radio to Antenna connectors when powered off or in TX mode.
S11 TX Return Loss 0.1 to 100MHz
EME215 0.1 to 100MHz S11 Return Loss from the Radio to Antenna connectors when powered off or in TX mode.
S21 RX Loss 0.1 to 100MHz
EME215 0.1 to 100MHz S21 Loss from the Radio to RX Active connectors when powered off or in TX mode.

Changes and Modifications:

1/ The board overlay diagram in Kit notes Rev1.0 shows D7 around the wrong way. The anode connection should be to ground.

2/ A report of the LED not fully turning off when going to TX mode was traced to the FDN338P MosFET being leaky.