FRONT PANEL CONTROL FUNCTIONS:
OFF - VOLUME: Applies power to circuit board and sets output level to speaker. Wall plug power adapter should be plugged in first.
SCANNING - AUTO - MANUAL: In auto, starts to scan the listed frequencies when squelch is ON (ie - receiver is silenced). Stops scanning when signal is detected or if squelch is off (ie - squelch control counterclockwise) and resumes scan when signal is lost or if red (or white) button is pushed and held in. In MANUAL, scanning proceeds one frequency at a time when button is pushed in. Scans continuously if button is held in, stops scanning when released. Not affected by squelch control or whether a signal is received. Note that the button only enables the counter. You must hold the red (or white) button in briefly to wait for the clock pulse before the counter advances. Scanning can also be stopped with a TTL low to pin 5 of the DIN connector.
LED FREQUENCY INDICATORS: Shows the frequency the synthesizer is currently locked on to, ONLY when MEMORY is in BANK 1.
MEMORY - BANK 1, BANK 2 : Sets the EPROM address the synthesizer chip will read. BANK 1 reads the frequencies shown next to each red LED. BANK 2 is only for 5 KHz offsets from 137.5 MHz. for compensating for drift or small frequency conversion errors of down-converters for the GOES satellites. Mentally substitute the following frequencies for the ones shown next to the LED's : 137.485, 137.490, 137.495, 137.500, 137.505, 137.510, 137.515 and 137.520 MHz. Can be re-programmed for other frequencies on special order.
SQUELCH: Sets the threshold where the audio level will be cut off. Quiets the receiver until a signal is received. Can be set to operate on a signal as weak as .1 microvolt. Operates on signal-to-noise ratio, therefore should not be advanced beyond the point where the noise suddenly stops when no signal is received or squelch may never open.
REAR PANEL FUNCTIONS:
FUSE HOLDER: Contains a 1/2 amp fuse which will blow if the circuit board develops a short circuit due to a component failure or if you apply too much voltage at the DC input jack.
DC INPUT JACK: Accepts a coaxial power plug with a 2.1 mm center pin. The center pin is the positive terminal. The applied voltage should be at least 13.5 VDC as it must pass through a 12 Volt regulator. If you use the wall plug adapter supplied with the receiver you should have no problem.
OUTPUT JACK: This is a standard 5 pin DIN connector to be used with the cable supplied with the receiver. One end of the cable plugs into the DIN connector on the receiver; the other end has stripped leads. The video output is the red lead, the copper braid is ground. You can solder a plug that mates with your FAX board or solder the leads directly. Pin 3 is for a 100 uA meter to read signal strength. You can also use a high impedance voltmeter in the 0-5 Volts DC range. There are 2 TTL ouputs avaialble but only one goes to the DIN connector. To output a TTL high instead of low on signal capture, switch the lead from DIN pin 4 to the adjacent free pad on the circuit board. Unsolder from the ground-plane side.
IMPORTANT: Only connect devices compatible with TTL loads. CMOS loads can be used if you add resistors in series. Do not try to switch equipment on directly with TTL. It should be used only as a control signal for activating remote controls for VCR's or for activating a transistor controlled relay. Applying more than 5 volts to the TTL outputs could backfire through the entire circuit board and destroy all the IC's if the voltage is high enough. Make sure you know what you're doing if you use the TTL outputs. An optocoupler is probably the safest interface if you're experimenting .
PREAMP ON: This switch applies 12 VDC through a 300 Ohm resistor (as a current limiter) and through an RF choke to the antenna jack center conductor. This supplies power to a VANGUARD preamp which would normally be placed up at the antenna. You can use it with other preamps equipped with a power bridge but you might have to change the 330 Ohm current limiting resistor on the circuit board. Leave the switch in the off position if you're not using a preamp. If you're using a preamp remember that turning the switch off will cause the preamp to act as an attenuator as it will not be bypassed.
ANTENNA CONNECTOR: This is now a standard BNC female receptacle which mates with a BNC male plug (not supplied). Some users (the military in particular) prefer type "N" connectors however the performance will be exactly the same at the frequencies used. If you are accustomed to using type "N" you can get a BNC to type N adapter at Radio Shack.
REMOVAL OF COVERS: To gain access to the components, remove the bottom cover by removing the single screw located on the cover at the rear panel then slide the cover off from the rear. Removing the top cover exposes the circuit board ground plane. Do not make any adjustments other than the one described below without the proper test equipment.
USER ADJUSTMENTS: The only user adjustment under the bottom cover is the audio/video output to your scan converter FAX board. The factory setting is approximately mid-range. Unless you have a separate gain control on your FAX board you will have to adjust the level as recommended by the instructions with your FAX board. On the WEPIX-2000-B there are 3 trimpots (some early versions had 2). The correct one to adjust is near the LM-386 and in line with the fuse holder. Do not adjust the trim pot located near the 6601C; it's used to set the phase-locked-loop free running frequency. Do not adjust any trimmer capacitors as most of them will not appear to change anything at the output but can adversely affect such things as bandwidth and image rejection which may not be noticed at first
NOTE: If you prefer the have the output to your FAX board controlled from the receiver front panel and the speaker volume preset with the trim-pot just swap the wires going to the DIN connector and the speaker. Both outputs use identical amplifiers. Unsolder the wires from the ground-plane side as the holes are plated through.