G6LVB Shack Configuration 26 May 2000
The above allows use of a single piece of coax from the shack to the roof. Using duplexers, triplexers coax switches and preamps, a combined full duplex satellite operation works.
In practice, I rarely use the halo or the eggbeater. For mode B/J, only the X5000 is used. For mode A the 10m Dipole is use for RX and the X5000 for TX. (nb in the diagram above it is incorrectly called an SX2000, which as we all know is an SWR meter!)
The Remote Console has a simple transistor arrangement which switches smoothed (but unregulated) 24VDC at 2 amps up the coax. This is combined with the RF signal using a coupling capacitor and a high current large inductance. In order to signal the Remote Controller, the RS232 300bps signal from the computer switches the DC off and on (normally it's on).
At the Remote Controller, a PIC 16F876 microcontroller decodes the async signal and switches the preamps and coax relays on and off. The RF signal is split off using a capacitor and the DC and 300bps signal is extracted using a similar inductor to that in the Remote Console. The DC is kept constant using a rectifier diode and smoothing capacitor followed by a 12V regulator and a 5V regulator. The control signal is extracted using a resistor and zener voltage clamp, which is fed into one of the PIC16C876 inputs.
The PIC16F876 controls three 8 bit shift register/latches (UCN5821). These outputs are used to feed some medium power PNP Transistors to switch 12V to the preamps and coax relays. Only 4 of the 24 available outputs are used.
The PIC16F876 could easily be changed to the 16F84, however in the future I want to be able to control a rotator and be able to read back the position. The 16F876 has A/D converters on chip to allow this.
The PIC microcontroller is currently programmed in C to reflect the 8 bit RS232 signal on the first eight outputs. As only the bottom 4 bits are used, using a terminal emulator, the outputs are set by keying (for example) ASCII 0-9,J,K,L,M,N,O in order to set the 16 combinations of 4 bits.
Mail Howard, G6LVB