Radio Shack Voice Simplex Repeater with CW ID ... Introduction The purpose of this document is to document work I did on creating a PIC base CW ID device for use with the Radio Shack Voice Simplex Repeater. The objective was to use as much of the electronics already present in the Simplex Repeater. This work was done originally for Mike Bogard, KD0FW, for use on a high altitude balloon he flew in the 2002 GPSL. Many balloonists have flown the Radio Shack Simplex Repeater on their balloon packages to provide an avenue for other amateurs to become involved with some of the activity surrounding this exciting aspect of out hobby. Mike wanted to as well but preferred to have the package ID itself properly and not rely on an ID message from ground. In order to accomplish this I initially undertook the task of writing the CW ID software from scratch. Before actually getting committed to this process I discovered the article on the CW IDER by Bob Anding in the Jan 1998 QST. With some modification with software would be just ideal for my application. My version and the original article are included in this document for completeness only. My thanks go to Bob for his interesting algorithms for generating CW. The next step was to analyze the Radio Shack Voice Simplex Repeater’s circuit and determine how I needed to interface to it. I wanted to use as much of its internal circuitry as possible to both reduce the number of parts I needed to add and reduce my construction time. If your interested in the source code I wrote for this project you can get it using the link in this sentence. A full size composite schematic is also available. Power Supply The first aspect of the Radio Shack Voice Simplex Repeater I looked into was the power supply circuitry. I wanted to be able to run off internal cells or the external power port and use the internal regulators. Figure 1 show the schematic of the power supply section. Figure 1 Some interesting aspects of this circuit are the disconnect scheme for the internal batteries, the use of diodes for isolation and the fact that an internal 5 volt regulator would allow me to power the PIC from this circuit. Since it appeared that when running under internal batteries the logic runs off a voltage significantly less than 5 volts I decided to only run the system off the external input port. Audio & Keying Interface This portion of the Radio Shack Voice Simplex Repeater was a little more complicated and more difficult to trace because of the surface mount components. Figure 2 is the schematic for the portion I traced. Figure 2 Since the Radio Shack Voice Simplex Repeater has a beep at the end of the transmission there was a circuit to reduce the 5 Volt peak to peak beep tone to a level suitable for the connected transceiver. I capitalized on this by using a single 10K resistor to inject my CD ID tones, also 5 Volt peak to peak, into the audio stream. Keying the Radio Shack Voice Simplex Repeater when I wanted to ID required me to cause the KEYING FET to conduct. Keying this transistor keys the transceiver via its microphone connection by causing a current draw form the microphone port. This is common in most handy-talkies. In order not to alter the original keying function, I had to add a 1K series resistor so both my CW ID PIC and the Simplex Repeater circuitry could key the transmitter. As an added advantage I was now able to let the PIC in on the timing cycle of the Simplex Repeater. All I needed to do was to program the PIC to read the same line that it uses to cause transmission.  By monitoring this line I could tell when the Simplex Repeater was done transmitting. If it was time for a CW ID I would wait until the next transmit cycle and ID when it was completed. This would make reception impossible during the ID of course. I could also transmit the ID at the beginning of the cycle since the audio ID level could be adjusted and was mixed with the stored audio. PIC uProcessor By using the properties and circuitry of the Simplex Repeater I was able to get by with a minimal amount of components. Figure 3 is the PIC CW IDER. Figure 3 I left the software code in place for the Countdown LED but did not actually use it in the balloon version. An 8.00 MHz ceramic resonator clocks the PIC. The 1N4148 diode in the /MCLR circuit allows for an in circuit programming port to be implemented. Only four lines actually connect the PIC control to the Radio Shack Voice Simplex Repeater. Two of these are power and ground. The other two are PTT/Monitor and CW Morse output. Interfacing could not have been easier. I used the ICP because I did not use a socket and I wanted to change call letters and ID string from time to time. Unused pins were programmed as inputs and grounded.