Slight whine in radio

$40 bucks years ago? If they still have it it won't be $40 bucks.

Ted

 

Would you like some cheese to go with your whine, sir??



HAHAHA I couldnt resist...

 

My vote is for the positive wire coming off the fuse block causing the whine. I don't have any reason for this other than personal experience. If you run both leads to the batteries, preferably the one farthest from the battery cables to the truck, I bet you'll get rid of your whine. I've had good luck using co-ax for my power cord, FWIW.

 

Josh stumbled upon a good point: every connection along the chain of DC power from the battery has the potential to develop some resistance (a little corrosion, some random cab mung, etc.). Under a large load (like transmitting), the voltage drop across that point of resistance will increase. Also, the small resistance also serves to isolate the load from the filtering effect that the battery usually provides. That's why a lead of the proper size going straight to the battery can be "quieter" than one going to a fuse block.

If the noises diminish without the antenna hooked into the radio, then the noise needs to be suppressed at its source. That's typically done with bypass capacitors across the DC leads at the wiper motors, fuel pump, alternator, etc. The capacitors shunt the RF trash noise that would otherwise use their DC wiring as miniature antennas, and "boost" the RF level they produce. The part of the noise that is sent through the nearby environment gets picked by the antenna on the radio like any other radio signal.

Adding the DC filter (choke) shown in the linked project keeps the noise that was conducted into the rest of the DC system from being picked up through the power leads of the radio.

I've had great luck with the filter choke shown in the plans. I've got larger wire wound on the shackle, so I can run a radio I have that draws about 28 amps on transmit (commercial UHF, tuned to ham band). As has been noted, put it as close to the input of the radio as is practical, to limit the amount of unfiltered lead that powers the radio (and therefore less length to serve as an unintended antenna).

-- Handlebar --

 

Yep, run both wires to the battery. Fuse them (both) at the battery terminals in case they get rubbed through the insulation. I always fuse my negative in case it rubs through on something positive.

 

Yes, what DeerSlayer asked, and Josh said. Sorry if I wrote my typical "book form" answer above.
Or, if you can make sure the leads running from the battery and ground to the so-marked terminals under your dash are spotless and tight at all connections, you may use that.
I prefer to do it as Josh does, though. That way I know there are only four connections to worry about on the red and four on the black: Radio connector, "battery side" of the fuse, "radio side" of the fuse, and the battery connection.

Some radios come with a fused black lead already, in case somehow the vehicle loses its own ground path back to the battery. When that happens, all the current draw of the vehicle may try to use your radio's hookup as the vehicle's ground, and would vaporize your radio's ground lead.

And use as large a ground wire as your red wire is, because the DC path is the total length from the battery, out one lead, through the radio, and back to the battery. It would be about the same length for the ground if you used the chassis, cuz it still has to get back to the battery, but copper wire is a better conductor than steel.

 

I love it went around the world and hid the problem but its still there. When a 2ft piece of 1/2 inch braded ground wire from the Alt to the frame will fix this problem for all your electrical circuits that are being fed dirty Voltage right off your Altenator. You need to fix problems at the source not the final end.