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Very little information about the situation of the transceiver is provided, it might be a complex one. The Kenwood TS-940SAT features a built-in automatic antenna tuner covers the amateur bands 160 through 10 meters. It is advisable for you to reinstall the transceiver and follow the right set up step to see if it works out eventually.
The FT-840 uses a die-cast RF power amp
with thermally switched fan to ensure full power output (up to 100
watts). The digitally synthesized local signals ensure clean, low-noise
transmitter output on all HF amateur band. There might be no AC line interference. it has strong Rf output. any AC line intersect does not affect its radio performance. Check and adjust RF power so to maintain proper output. some times more RF power generated at the output may cause interference. adjust Rf power..Even some unfiltered Noise getting the other end of the end may calso cause interference. Check for any Ripple voltages present at the output. Contact authorised service station for further Rectification. thank you shanth
You've replaced the pre driver, the drivers and finals. Set bias and still low output. The pre driver is the same transistor used as the tx exciter transistor on other pcb chassis on bottom of radio. Follow the gray coaxial wire from the pre driver on the RF circuit board back to the tx/rx i.f. Circuit board. The gray coax cable plugs right next to the tx exciter transistor on this pcb. Again it's on a different pcb all together and on the bottom of the radio and also. Replace it! And check for open bias or emitter to ground chip resistor next to it. You will get your drive back. Very few rigs have I seen the actual Finals blown in the mosfet or the bipolar version. Just the driver stage with a week pre driver and the SMT "pre" pre driver on the same RF pcb. And the tx exciter on the other pcb.
You have to ADD a PL Tone board. There should be a front panel switch that says TS that is the on/off power to the connector. There is a connector inside for +12VDC, switched ground and Encoder input. Look online for the schematic, or contact CommSpecialists for the sheet that lists the colors of the wires on the connector and where you connect them when you add a CTCSS Tone board.73's
73s I have heard of similar problems and some were heating related. the best is to check if your rig is heating up causing it to switch off and lose memory when switched back on. I have a buddy who had an unusual experience where he actually dropped frequencies so low that he could pick up ordinary radio frequency and also go into bands like 27mhz and 25mhz. But once switched off, the rig worked normal again. If you are experiencing heat problems then i suggest you put in a fan and remove all dust from inside the rig. You could probably also be having problems with power supply either internal or external. If all else fails, refer to a good repair shop this type of radios are very sensitive.
Fuses and Breakers Attach the red or positive wire to a 5 amp circuit breaker. If the unit is connected directly to the boat’s battery, include a 2 amp in-line fuse. (In-line fuses are available at most marine supply stores.) The power cable includes a smaller "shield" wire. Connect this to a good ground.
Extending the Power Cable If you need to extend the power wiring by more than 10 feet, use a larger wire size. This will allow the wires to deliver the correct voltage in spite of the longer wire distance. For runs of 20 to 35 feet, use #14 AWG cable. If you extend the power wiring, be sure all electrical connections are solid and durable. Soldering is the best way to make these connections. Insulate all connections using heat-shrink tubing or electrical tape. You may also use crimp connectors or a terminal strip, but be sure to use good-quality marine-grade parts.
Yes, radio is the least secure connection of all. Every means of transmission is subject to interception. In radio transmission, it should be assumed that all transmissions are intercepted. Messages using modern cryptographic systems may prevent an enemy from understanding a message. However, they can still learn a lot. Headings, receipts, acknowledgments, relays, routing instructions, and services are also used by an enemy. Communications experts can often learn much about an opponent from these studies. Direction finders are another aid the enemy can use to determine where messages originate.