PROBLEM: System is unable to capture WEFAX imagery.
DIAGNOSTIC STEPS:
STEP 1] Is the satellite transmitting? Occasionally, the WEFAX downlink service is interrupted for various reasons, but usually for no more than a day or two except in extreme cases. If possible, verify that target GOES/METEOSAT/GMS/GOMS WEFAX satellite is not off-line, either with other Direct Broadcast User, unit, station, or responsible agency.
STEP 2] Check cabling. The aux 12VDC power supply should be connected to the appropriate input on your receiver to insert DC power for the downconverter. On a PC-137 or PRO board, that would be the DSUB9 Pin connector below the two BNC connectors. If using a multi-channel system, this should be on the same adapter that you are connecting the WEFAX downconverter coax to.
If your AFMIT system has had the AFMIT POWERMOD modification added to it, as described on our website:
In that case, you should be able to connect power to either the PC-137 or PC-GMS boards, and the external red pilot light will be lit. If it is not, with power applied, the problem is probably a blown fuse. Replace the 1 Amp slo-blo fuse and retest. If replacing the fuse does not restore the red pilot light, verify that the 12VDC power supply is providing power.(14-17VDC with no load from an unregulated supply, 12-15 VDC from a regulated supply.)
STEP 3] Check the downconverter response to 12VDC power. Setup the computer for WEFAX reception, with squelch circuit OFF/disabled and speaker ON/enabled. Find the signal strength indicator, either on the Capture_Setup page (if using the DOS based AFMIT software) or on the main WtCap control dialog(if using the new Windows-94/NT based software.) This is a small horizontal bar graph. Even if the dish is not aimed at a WEFAX satellite, the indicated signal strength should respond dramatically to removal/insertion of the aux. 12VDC power as the noise floor is raised/lowered. Temporarily disconnect the aux. 12VDC power supply, which should be connected to the DSUB9 connector Pin1/Pin6 on your PC137 or PRO adapter. (You can easily remove the power simply by unplugging the aux 12VDC power supply from the local mains.)
Does the signal strength indicator drop dramatically when the 12VDC power is removed, and does it rise appreciably when the 12VDC power is re-inserted? If it does, then the following is probably true: your system is properly setup for WEFAX reception, the aux 12VDC power supply is providing power to the downconverter, the coax cable is connected correctly, the cable is not shorted/broken, the in-line fuse is not blown, the DC-insertion circuit has not failed/shorted to ground, the receiver signal strength circuit has not failed, and the downconverter has not failed, so the problem is probably dish alignment, and you can proceed to STEP 10.
STEP 4] If the signal strength indicator does not respond to this test, then at least one of the following is probably true: your system is not setup properly for WEFAX reception, the aux 12VDC power supply is not providing power to the downconverter, the coax cable is connected incorrectly, the cable is shorted/broken, the in-line fuse is blown, the DC-insertion circuit has failed/is shorted to ground, the downconverter has failed.
NOTE: The following steps require a multi-meter. If one is unavailable, assume the problem is a blown fuse and proceed to STEP 6-B]
STEP 5] Remove the aux 12VDC power from the DSUB9 connector on the receiver board. With the power supply plugged in, carefully measure the (+)Voltage on Pin1, referenced to (-) on Pin 6. You might measure a Voltage as high as 17VDC on an unregulated supply with no load.
If there is no Voltage, or the Voltage is under 11 VDC, replace the power supply and retest the system.
If the power supply Voltage is ok, proceed to STEP 6]
STEP 6] With the power connector still removed, remove the coax cable from the receiver UHF connector and measure the DC RESISTANCE between the DSUB9 PIN 1 connector on the receiver and the UHF BNC connector center pin on the receiver. The UHF connector is the connector farthest away from the DSUB9 pin connector.
If the resistance is near 0.0 Ohms, the internal in-line fuse is not blown, and you can proceed to STEP 7].
If the resistance is very high/infinite, then the internal in-line fuse is probably blown, and you should proceed to STEP 6-B]. If replacing the fuse does not fix the problem, or the fuse blows again after replacing it, then continue with STEP 7].
STEP 6-B] Replace the in-line 1 Amp slo-blo fuse on the PC-137, PC-GMS, or PRO board and retest. (This is the most common cause of failure.) If unable to obtain a slo-blo fuse, the equivalent fast-blo fuse can be substituted. These can be obtained from RADIO SHACK or any electronics or automotive supply store. On a few older systems, the in-line fuse is a small, green soldered-in PICO type fuse. If your PC-137 or PC-GMS does not have a removable cartridge fuse on, it is recommended that you return the board for fuse replacement.
If unable to proceed because of lack of a multi-meter, then you will need to return the receiver, cables, and downconverter for factory diagnostics/repair. Please call to obtain an RMA# before sending anything, or it may not be accepted for repair.
If you have access to a multi-meter, and have completed the previous steps, proceed as follows.
STEP 7] With the power connector and coax cable still removed, measure the DC RESISTANCE between the UHF BNC connector center pin and UHF BNC connector outer shell. It should be very high/infinite.
If the resistance is very high/infinite, then the internal capacitor on the DC insertion circuit has not failed/shorted to ground, and you can proceed to STEP 8].
If the resistance is very low/near 0.0 Ohms, then the internal capacitor on the DC insertion circuit has probably failed by shorting to ground, and the system will continue to blow fuses every time a fuse is replaced and power is applied. The receiver must be returned for repair, as field replacement of the capacitor requires de-soldering and re-soldering the capacitor on the multi-layer board, and could result in catastrophic board failure (fire) if not properly performed. While the board is returned for repair, continue checking the remainder of the system via STEP 8].
STEP 8] With the coax connector removed from the receiver, but still connected to the downconverter, measure the DC RESISTANCE between the coax cable BNC center pin and shell. It should read between 9K and 11K Ohms( 9,000 and 11,000 Ohms.)
If the DC RESISTANCE is between 9K and 11K Ohms, then the coax cable is not DC shorted(there still could be a capacitively coupled HF short, however) or broken, and is connected to the downconverter. Proceed with STEP 9]
If the DC RESISTANCE is near 0 Ohms, then there is a DC short, either in the coax cable or the downconverter. Remove the coax cable from the downconverter, and repeat the measurement. If the now open at both ends coax cable assembly still reads 0-1 Ohms between the center pin and shell(it should be infinite), there is a short in the coax cable assembly. The short is probably at one of the connectors on either end of the cable. Which end can be detected by carefully noting the small resistance measured at each end between the BNC center pin and shell. The end with the short will read near 0.0 Ohms, while the opposite end will read some nominal small resistance (like 1.1 Ohms in a typical 100 ft RG/58 coax.) If an intermediate small resistance is measured at both ends, the the coax cable itself might be crushed/damaged at some midpoint. The approximate location can be estimated by ratioing the resistances measured at each end with the total resistance(RA/(RA + RB)), and noting that the short will be closest to the end with the lowest resistance. Repair/replace the cable as necessary.
STEP 9] With the coax cable removed from the downconverter, measure the DC RESISTANCE between the downconverter output connector center pin and shell. It should be between 9K and 10K Ohms. If it is, then there is not DC short in the downconverter output. If the resistance is very low/0.0 Ohms, then the downconverter has failed and requires replacement.
If you have performed all steps through 9 without finding any failures, reconnect all cables and repeat STEP 3]. If the system still does not respond, repeat STEP 3] with the coax cable disconnected from the downconverter; with the coax cable removed at the downconverter, measure the DC VOLTAGE present on the end of the coax cable that would normally be connected to the downconverter, and verify that the DC Voltage is present with (+) on the coax center pin referenced to (-) on the shell. If this is the case, and the system signal strength is not responding to 12VDC insertion with the coax cable properly in place, then it is likely that the downconverter has failed and must be replaced.
If the system is now responding to changes in 12VDC insertion, retest. If still unable to capture WEFAX imagery, the problem is probably dish alignment(but still could be either a downconverter or receiver failure. If the receiver is functioning properly with APT, then the receiver is probably not the failure.) Proceed with STEP 10] to check dish alignment before calling to return downconverter for evaluation/replacement.
STEP 10] Check the WEFAX dish alignment. The dish might not have been securely locked and have been blown by the wind, or the satellite might have moved. (Or, the satellite might be off-line and not transmitting…)
With the system properly cabled, powered, and setup for WEFAX reception, disable the speaker SQUELCH and enable the speaker output. Either monitor the receiver audio output at the computer, or route the audio to the dish site; it is often possible to temporarily use the APT coax cable for this purpose, using adapters and 'alligator' clips to route the 8-Ohm speaker output to a set of headphones at the dish site.
Loosen the dish azimuth and elevation adjustments and freely swing the dish in the direction of the WEFAX satellite. Sweep the sky, listening for either signal or quiet carrier. If you find either, lock elevation, and swing the azimuth through extremes about this center point to make sure you are not aligned on a side lobe(local maximum). Center the azimuth at position of least static noise and lock. Then, loosen the elevation adjustment, and repeat the centering process. Then, lock the elevation. Repeat again with azimuth and elevation until the dish is aligned at position of quietest signal/least noise.
If there is still residual noise/static, feed polarization my be near one of two 'null' points in the linear field. These null points are located 180 degrees from each other. Loosen the feed polarization adjusting ring, and rotate the feed clockwise or counter-clockwise by 60 to 90 degrees, and relock. Repeat the azimuth/elevation adjustment, if necessary.
If the signal still has residual noise/static, then there may be an RF short in the cable or one of the connectors, causing a weak signal. Or, the downconverter oscillator crystal may have drifted by a small amount.(Diagnosis of this type of failure requires the use of a spectrum analyzer or the DOS based SPECTRUM utility provided with the AFMIT system.)
If the downconverter has drifted by more than a few kiloHertz, then the receiver will not have tuned to the WEFAX signal at all, but if the drift is small, it can be corrected by specifying the corresponding shift up/down in the downconverted 137.500 MHz in the WEFAX configuration. This should be regarded as a temporary fix, however, as it is possible that the downconverter may continue to shift if the oscillator is failing with age. The downconverter will probably ultimately need to be replaced if it experiencing significant drift.
FINALLY:
If none of the above diagnostics return the system to operating condition, the system components will need to be returned for evaluation. Contact us to obtain an RMA# before returning anything.