INSTALLING THE DOPPLER/RS-232 INTERFACE BY ROBERT SWAIN This project is not for beginners. The builder must adhere to procedures that commonly apply to delicate electronics, static grounding and chip lead temperature tolerance when soldering. You must be familiar with pinouts of integrated circuits. Of course any modification to a unit under warranty will void that warranty! This is a consumer installed modification and the consumer must accept resposibility for the result. 1) OVERVIEW The following are instructions for connecting the Doppler/RS-232 interface to a doppler unit. Since there are many different types of doppler DF units currently in use, be sure to use the instruc- tions that apply to your unit. (This is especially true for the Roanoke variations) Although the following instructions are written for the interface unit to be added as an external unit, it is also just as easily installed inside your doppler unit if space permits. If you decide to install the interface in the doppler, you will need to install a DB-9 or DB-25 connector in the back panel of your doppler for the RS-232 cable to connect to your computer. All doppler DF units are interfaced the same way: 1. Mount an external connector (female recommended) onto your DF unit. 2. Install wires from the connector to various points on the DF circuit. 3. Wire a mating connector to the interface card. 4. Set the jumpers on the interface card. 5. Connect and power-up the system. 2)GENERAL INSTRUCTION THAT APPLY TO ALL DOPPLER DF UNITS Install a connector of your choice with at least 7 pins onto the DF box. D B-9 or DB-15 connectors work well. One of the first considerations for the Doppler/RS-232 interface is DC power. The circuit runs on +5 VDC and draws about 100 ma. Your choices are (1) Add a tap from +5 volts inside your doppler unit to run the interface, (2) Use +12 VDC and reduce it to +5 VDC via a 7805 or similar. If you have a heavy duty regulator in your doppler unit, you may choose to simply add a wire from +5V to your connector. If you have only +12 VDC available, you can add a regulator inside the doppler unit or on the interface board without much difficulty. When taking taps off IC pins be sure to have the power off and use a grounded soldering iron. If you have your ICs in sockets, a better way to make these connections is to insert wire wrap sockets into the soldered sockets. Then install the IC in the wire wrap socket. Solder the tap on to the wire wrap socket legs. Add a tap from ground to your connector for the external circuit ground. Add tap from the audio input, before the first capacitor, to your connector. 3) INSTALLATION INSTRUCTIONS FOR SPECIFIC DF UNITS. 3.1 DOPPLER SYSTEMS, INC. Locate the 74154 IC. It is a large 24 pin IC that drives the 16 LEDs used for direction indication. Pins 20, 21, 22, 23 are the pins needed for the interface. Pin 23 is the least significant digit (LSD) also called bit A. Pin 22 is bit B, 21 is bit C and 20 is bit D, the most significant digit (MSD). Add taps from these pins to interface pads A, B, C, and D via your connector. These are the data bit lines. Locate the IC numbered 4520 (U10) not (U18). Add a tap from pin 13 to R on the interface board via your connector. This pin has the 18.75 hz clock signal. This is the character rate line. NOTE: No latch line is required. This DF unit provides latched data to the interface automatically. Set jumper (J1) on the doppler interface to the DIS position. 3.2 ROANOKE AND VARIANTS NOTE: There are several versions of the original Roanoke Doppler unit. Below are the instructions for the most popular variations. 3.2.1 The 8 LED Original Model Roanoke Doppler Unit (N4FQ shown in "Transmitter Hunting: Radio Direction Finding Simplified" by K0OV and WB6UZZ) NOTE: This is the original circuit shown in the book without any of the book mods added. NOTE: This unit will be referred to later in the instructions as "Roanoke version 1". Locate the IC numbered 7445. It is the IC that drives the 8 LEDs used for direction indication. Pins 13,14,15 are the pins needed for the interface. Pin 15 is the least significant digit (LSD) or also called bit A. Pin 14 is bit B, 13 is bit C or the most significant digit (MSD). Add taps from these pins to interface pads B, C, and D via your connector. These are the data bit lines. Run a wire from pad A on the interface to ground. Locate the IC numbered 4024 (U9). Add a tap from pin 3 to R on the interface board via your connector. This should read near 62 hz in operation. This is the character rate line. NOTE: No latch line is required. This unit provides latched data to the interface automatically. Set jumper (J1) on the doppler interface to the DIS position. 3.2.2 The 16 LED Modification of the Original 8 LED Roanoke Dop- pler Unit. (N4FQ shown in "Transmitter Hunting: Radio Direction Finding Simplified" by K0OV and WB6UZZ) NOTE: This is the original Roanoke unit in the book with the book 16 LED modification added. NOTE: This unit will be referred to later in the instructions as "Roanoke version 2". Locate the IC numbered 4514. It is a large 24 pin IC that decodes data for the 16 LEDs used for direction indication. Pins 1,2,3,21,22 are the pins needed for the interface. Pin 1 is the LATCH pin. Pin 2 is the least significant digit (LSD) or also called bit A. Pin 3 is bit B, 21 is bit C and 22 is bit D or the most significant digit (MSD). Add taps from these five pins to the interface via your connector. These are the data bit lines. Locate the IC numbered 4024 (U9). Add a tap from pin 3 to R on the interface board via your connector. This should read near 62 hz in operation. This is the character rate line. NOTE: This model requires the external latch chip included on the interface. For this unit, set the LATCH jumper (J1) to the EN position. 3.2.3 The 16 LED, Single Board Roanoke Doppler DF. (N4FQ/KK6VF) Also known as the Douglas RF Devices Doppler Board. NOTE: This is the most current modification of the Roanoke dop- pler. This unit has the book modifications for LOW signal detect as well as an improved 16 LED display. NOTE: This unit will be referred to later in the instructions as "Roanoke version 3". Locate the IC numbered 74154. It is a narrow 24 pin IC located in the center of the 16 LEDs used for direction indication. Pins 23,22,21,20 are the pins needed for the interface. Pin 23 is the least significant digit (LSD) or also called bit A. Pin 22 is bit B, 21 is bit C and 20 is bit D or the most significant digit (MSD). Add taps from these four pins to the interface via your connector. These are the data bit lines. Locate the IC numbered 4024 (U9). Add a tap from pin 3 to R on the interface board via your connector. This should read 62 hz in operation. This is the character rate line. NOTE: No latch line is required. This unit provides latched data to the interface automatically. Set jumper (J1) on the doppler interface to the DIS position. 3.2.4 DOP-SCAN RDF (WB2AOZ) A 16 LED modification of the original 8 LED Roanoke doppler unit with 8 antennas instead of the original 4. NOTE: This unit will be referred to later in the instructions as "Roanoke version 4". Locate the IC numbered 4514. It is a large 24 pin IC that decodes data for the 16 LEDs used for direction indication. Pins 1,2,3,21,22 are the pins needed for the interface. Pin 1 is the LATCH pin. Pin 2 is the least significant digit (LSD) or also called bit A. Pin 3 is bit B, 21 is bit C and 22 is bit D or the most significant digit (MSD). Add taps from these five pins to the interface via your connector. These are the data bit lines. Locate the IC numbered 4024 (U5). Add a tap from pin 3 to R on the interface board via your connector. This should read near 590 hz in operation. This is the character rate line. NOTE: This model requires the external latch chip included on the interface. For this unit, set the LATCH jumper (J1) to the EN position. 3.3 DICK SMITH RADIO DIRECTION FINDER Locate the IC numbered 40174. Pins 5,7,10,12 are the pins needed for the interface. Pin 5 is the least significant digit (LSD) or also called bit A. Pin 7 is bit B, 10 is bit C and 12 is bit D or the most significant digit (MSD). Add taps from these four pins to the interface via your connector. These are the data bit lines. Locate the IC numbered 4024 (IC10) not (IC3). Add a tap from pin 3 to R on the interface board via your connector. This should read near 312 hz in operation. This is the character rate line. NOTE: No latch line is required. This unit provides latched data to the interface automatically. Set jumper (J1) on the doppler interface to the DIS position. 3.4 QST / DOPPLESCANT (WA4BVY) Locate the IC numbered 4515. It is a large 24 pin IC that drives the 16 LEDs used for direction indication. Pins 1,2,3,21,22 are the pins needed for the interface. Pin 1 is the LATCH pin. Pin 2 is the least significant digit (LSD) or also called bit A. Pin 3 is bit B, 21 is bit C and 22 is bit D or the most significant digit (MSD). Add taps from these five pins to the interface via your connector. These are the data bit lines. Locate the IC numbered 4024 (U1). Add a tap from pin 3 to R on the interface board via your connector. This should read near 75 hz in operation. This is the character rate line. NOTE: This model requires the external latch chip included on the interface. For this unit, set the LATCH jumper (J1) to the EN position. 3.5 Other units Due to the vast number of variations possible, here are some general rules that must be followed to connect a unit to the Doppler/RS-232 interface. *If your unit allows more than one LED/lamp to be illuminated at a time, you must add circuitry to interpolate the two LEDs to a single direction (one lamp at a time lit). Example - South and East lamps lit would light a single SOUTHEAST lamp. AND gates? *The voltages must not exceed 5 VDC. *The output must be ACTIVE HI LOGIC. (5 volts = logic 1, 0 volts = logic 0) *Only one LED on at a time. Once these requirements are met, you can continue with the inter- face connections. For dopplers without 8-line-to-3-line encoders: Tap from the output of your circuit to an 8 line to 3 line encod- er (74148). This will output your LED direction in binary for the interface however the output of the 74148 must be inverted first (7404). The top LED should be the lowest number on the encoder chip (0). The first LED clockwise is the number 1 etc up to the maximum of 8 LEDS. Do not exceed the voltage limits of the encod- er IC. Connect the output from the encoder/inverter to pads A through D via your connector. These are the data bit lines. NOTE: If your unit uses the 4514 or 4515 chip to drive the LED display, an external latch is required and included on the interface board. Set the LATCH jumper (J1) to EN and include the latch line from the 4514/5 to the interface board. 4) GETTING THE DATA TO THE INTERFACE Your connector on the doppler unit should now contain, 5 VDC, GND, 3 or 4 data lines, a character rate line, and a LATCH line. (if your unit requires a separate latch) On the interface card you will find the pads for connections required. LATCH and DATA-A may go unused if your unit does not require these connections. Tie DATA-A to ground if not used. Install a cable of your choice from the doppler unit connector and the interface board. Add wires from your TX(3) and GND(7) near U4 on the interface board to a connector to mate with the serial port on your computer. If you use a DB-25, connect TX(3) to pin 3 and GND(7) to pin 7 on the connector. If you use a DB-9, connect TX(3) to pin 2 and GND(7) to pin 5. 5) SETTING THE JUMPERS ON THE DOPPLER/RS-232 INTERFACE The interface designed for 2400 BAUD, No parity, 8 bits, 1 stop bit. If your unit does not require a separate LATCH line, be sure to DISable jumper (J1) or the interface will not operate properly. Set jumper (J2) to the CW (clockwise) position. This is a jumper for doppler units that rotate CCW (counter-clockwise). The dopplers listed above all rotate CW. Set jumper (J3) according to the chart below. This is the characters per second jumper. Set for 8 characters per second. TYPE J1 J2 J3 input rate ---------------------------------------------------- Doppler Systems dis CW B 18.75 hz Roanoke ver 1 dis CW D 62 hz Roanoke ver 2 en CW D 62 hz Roanoke ver 3 dis CW D 62 hz Roanoke ver 4 en CW G 590 hz Dick Smith dis CW F 312 hz QST/Dopplescant en CW D 75 hz 6) OPERATION AND ADJUSTMENT If you installed a connector between the doppler and the interface board, operate your doppler unit and radio without the interface connected to make sure everything works as before. Connect the interface unit after all jumpers have been set. When power is applied to the doppler unit, the interface LED 1 should also indicate power on. Set the radio volume to normal doppler level (mid range if using an HT). Open the squelch to noise. You should hear noise on your doppler monitor speaker (if equipped) and adjust the VOX sensitivity so that the VOX LED just lights. When you close the squelch, the LED should go out indicating no audio signal present. A more accurate way to set the VOX is to listen to a local repeater or strong signal that has very little traffic. During the quiet period (no modulation, just doppler whine) adjust the VOX such that the LED just lights. It should go out as soon as the signal stops. NOTE: The data stream is not going to the computer any time the LED is not lit. Connect the output from the interface to a computer communications port. Using Procomm or a similar communications program, configure the program for 2400 baud, N,8,1 and set the comm port for the port you are using. With the doppler, radio and interface switched on and the squelch open, you should see the capital letters A-O and sometimes the @ symbol is displayed. If you are using the APRS program, configure it for a DF unit to be connected. NOTE: You must have the registered copy of APRS or later and have a DF validation code for the doppler interface to be recognized. See README.DF in APRS documentation files for further assistance. 7) WHAT IF IT DOESN'T WORK? (TROUBLESHOOTING) Check all connections. Are all units switched on? Is power going to everything? LED 1 indicates power to the interface board. Is it lit? Is the LED installed with correct polarity? Does the radio work by itself? Does the doppler unit work by itself? Does the doppler unit and the radio work together without the interface connected? It the doppler antenna connected to the radio? Is audio going from the radio to the doppler? If your doppler has a monitor speaker, does it have the proper sound? (doppler whine) Is audio going from the doppler to the interface? Are jumpers J1, J2 and J3 set properly? Is the VOX sensitivity set properly? LED 2 indicates an audio signal present. Is it lit when the squelch is open to noise or an audio signal? Is the LED installed with correct polarity? Is the radio volume set to normal listening level? Is the BAUD rate and comm port set correctly in the communications program (2400,N,8,1)? APRS is set to 2400,N,8,1. Are the letters going across the screen in your communications program (Procomm) upper case? Make sure J2 is set to CW. Is your REGISTERED copy of APRS version 3.0 or later activated with your DF validation code and in the DF mode? ----------------------------------------------------------------------- Update 7/12/95 DATA MUTE This circuit mutes the data going to the computer serial port while the local APRS radio is transmitting. This is necessary for enhancing the DF system accuracy and allow APRS to decay the transmit period. Without this circuit, each time the local radio transmits APRS data, the DF radio hears the signal from the nearby transmitter. This causes the DF unit to output false information to the computer. Also, APRS is now modified to decay the transmit period from the DF if there is no data. Without this modification, when the local APRS transmitter causes interference with the DF unit, the interface will output data to APRS and never allow the transmit period to decay. Connection To The Interface Board 1. Tap off from your TNC's "PTT" line and connect it to the cathode of diode "D1". NOTE: The value of C3 and R6 set the "hang time" of the circuit after the PTT line returns to "not transmitting" state. This delay is necessary for the transmitter to stop, and the Doppler receiver to squelch. Increasing the value of either R6 or C3 will increase the hang time. If the circuit is built using the values provided in the schematic, the hang time should be sufficient for most radios. Bench Test Set the interface card for operation by it's instructions. (ie. Squelch open-LED 2 lights, squelch closed-LED 2 out) Proper operation of this circuit will cause the data LED (LED 2) on the interface card to go out when the TNC is transmitting. Open the squelch on the Doppler unit radio with the volume set normal DF setting. When the TNC PTT line goes low, the flow of data to the RS-232 port stops and LED 2 goes out. When the TNC releases the ground signal from the PTT line, there will be a delay (less than 1 second) before LED 2 lights. Real Time Test With all components of the DF station reconnected, and the TNC/radio combination ready, start APRS. Open the squelch on the DF radio and LED 2 will illuminate. When the TNC keys the transmitter, LED 2 will go out and delay slightly beyond the transmit duration. With everything operational, and no signal on the DF radio, APRS (version 6 or later) will start to decay the transmit interval. When a signal is being DF'ed and the TNC transmits, interference may be heard on the DF speaker. No data will flow to the serial port during transmit. This prevents the interference from skewing the data to APRS. It is important to note that NO DATA, skewed or otherwise, is going to APRS during TNC transmit. OPTIONAL BAUD RATES Changes were made in APRS that require additional baud rate options between the interface and the computer. This allows several serial port units to share a single port provided they are all using the same baud rate. APRS originally required 2400 baud from the Doppler interface but recent changes have caused this requirement. Four pins on the AY-5-8116T (U3) set the outgoing baud rate. These pins are 13,14,15,16. If you are familiar with binary counting, you will quickly see there are 16 baud rates to choose from. (50 thru 19,200 baud). As orginally designed, 2400 baud is "hardwired" to these pins. Here's how to change it: Presently for 2400 baud pins 13-16 are tied as follows: 13 hi, 14 lo, 15 hi, 16 lo, for 2400 baud. To change to 4800 baud, cut traces and rewire as follows: 13 hi, 14 hi, 15 lo, 16 lo, for 4800 baud. To change to 1200 baud, cut traces and rewire as follows: 13 lo, 14 hi, 15 hi, 16 hi, for 1200 baud. To change to 9600 baud, cut traces and rewire as follows: 13 hi, 14 hi, 15 hi, 16 lo, for 9600 baud. -30-