Beverage Controller

Remote and controller boxes laid 
out for wiring.

With these Beverage antennas, I needed a way to switch between them quickly and easily. 

Taking a cue from the K9AY Controller, I didn't want to just hook up a rotary switch. I wanted a push-button controller. Plus, a lot of the time I'm remotely operating my station on FT8 from the house, I wanted that capability as well. 

Design

I planned for at least three Beverages, maybe more. Plus I had the K9AY loops. That's at least four antennas, having a fifth would give me a spare.

The buttons and indicators needed to be convenient to operate, up front in the station without being intrusive. 

The receiving antenna feed lines also needed to terminate at the Single Point Ground (SPG). Best option was a remote relay box to do the switching, and a small controller box containing the buttons and indicators.

Test positioning the Controller

Adding a serial port to the controller allowed the antenna selection to be interrogated and selected. I already the PIC16F18426 chips on hand. This 14-pin device has a built-in EUSART. A MAX232 would handle the RS-232 level conversion.

Construction

I found a small Bud box in my junk box for the remote. I ordered a die-cast aluminum box for the controller. It was small, but it fit very nicely up under the shelf supporting the P3. Convenient and unobtrusive.

Remote mounted on SPG

The remote has six RF connectors - four F-connectors for the Beverages, one BNC for the K9AY, and another BNC to connect to the K3. SPDT relays are used. When selected, the relay connects the antenna port to the K3 port. When unselected, an appropriate resistor connects across the antenna port. ( I used 82-ohm resistors for the F-connectors, 51-ohm for the BNC -- closest I had to 75 and 50 ohms, respectively )

I used 12 V relays. Unlike the KK1L 2x6 Antenna Switch, I didn't want to activate each relay with a separate line for +12 V. Instead, I sent +12 V to the remote box on a common conductor and then returned a signal for each relay to be grounded by the open drain pins on the PIC. 

This lead to a design problem. The PIC doesn't support true open drain outputs. Each pin is clamped to Vdd, which in this case is +5 V. That left about 6 or so volts across each relay, pulling them all in. 

To solve this, I added 2N3904 NPN transistors to the relay box as open collector drivers for each relay. A 3 K resistor connects the base of each transistor back to the PIC. Instead of a logic 0 activating the relay, a logic 1 does the same job.

The controller box is really tight. I borrowed five switches from the K1EL Keyer. The LEDs and switches barely fit. The controller itself is simple. Five RA port pins connect to the pushbuttons. Five RC port pins drive the LED indicators and NPN relay driver. One RA pin and one RC pin communicate with the serial port. 

Changing the sense of the relay switching required re-wiring of the LEDs. Before, they were tied to +12 with the cathode of each LED brought to ground by the PIC. Except that didn't work due to the design problem. Instead the cathodes went through a common 330 ohm resistor to ground, and the anodes were connected across the activation lines for each relay.

Debugging

I debugged this design in parts, starting with the controller box, then the relay box separately. Once I connected them together, I found the design problem that required much re-wiring. 

The button selection worked great. The serial port has been more of a problem. While the PIC receives commands correctly, it doesn't appear to transmit anything at all. It is a puzzlement.