Back when I could still remember everything, I think I had a radio “filter” on my first 55 that filtered out static from large engines and electric power lines. It seems to me it was located in or near the distributor. On my way home from practically anywhere, I have to drive for a while below electric transmission lines. Or sitting at a stop light next to a semi, I get so much noise I can’t hear the radio at all. Who knows, I might miss the ad that tells me how to invest my money in gold or bitcoin. Is this “filter” a real thing or did I make it all up?

 

You didn’t make it up. Both EMI & RFI are real.

 

BTW, AM signal is always more susceptible to EMI/RFI. If your radio signal suffers from noise in the FM signal first check to ensure you have a very solid FM radio cable & antenna.

 

To have FM radio would be nice but my 55 has the original AM only radio. So still hoping for a cure.

 

Driving a different route or removing/relocating the offending electrical lines is not an option?

 

A condenser on the generator to limit the RF noise generated by the tiny sparks you see with the brushes and commutator (hash). Another on the coil to reduce the RF ignition noise with points (rapid clicking). Another on the voltage regulator to reduce the RF noise on the voltage adjustment contact (harsh hum). Suppression spark plug wires assuming your plug gaps are reasonable and not wide like .060" (intermittent RPM clicking). Then signal strength and maximize signal to noise ratio: At night in a radio quiet location such as out in the country away from power line and LED noise: Extend antenna to max length, tune a weaker station up in the graveyard around 1400kc and peak the antenna trimmer for maximum signal amplitude with a non conductive straight blade tuning tool. You can make one with a small dowel filed to a chisel end, or use a nylon diddle stick if you have access to one. If you plan on always running with the antenna retracted, then tune the antenna that way. Once in a while a tired mechanical vibrator can introduce some annoying noise. All of this might be found in your year specific service manual, at least it is in 1952.

Welcome to the old days world of AM radio reception. Todays telemetry and raised noise floor due to dirty electronics is the new normal in communications, at least until some new technology supersedes where we are now. A FM converter hidden in glove compartment will bring you full quieting FM reception with your 55 radio. You might then pipe your favorite music or programming through with one of those BT to FM transmitters powered from cigar lighter found everywhere.

 

As suggested by coldwar an electrical condenser (two or several) could/might resolve your issue. Personally, the very first place I would look to address the issue is in your AM antenna. Make certain the cable is solid and any connections on that cable are squeaky tight & clean. You can introduce a literal TON of varying signals if the antenna is not sufficiently isolated and grounded properly. Look at each antenna connector to ensure it's tight and solid.

When a semi-trailer truck (or the power lines) get within a select distance from your radio, your radio begins to operate as a Geiger counter (so-to-speak) - picking up all the signals you are not filtering (trapping). Those unwanted signals move into your radio and become amplified. You want to eliminate those unwanted signals. An antenna is a trap, consider it a filter. Think of it as a dish satellite (so-to-speak). Traps/Antennas/Filters operate in one of two manners (generally): (1) They trap/filter unwanted interference and allow only a select signal or signals to be received; or, (2) They trap/filter ONLY the selected signal with no regard for other signals. If you turn off your AM radio the noise is gone. The signals themselves remain, they don't become noise until you turn on the radio. As you move farther away from the offending signals, the noise is diminished - you are no longer trapping/filtering that noise. Let's say you have a very faulty AM radio antenna - what then becomes the largest trap/filter for the AM radio in your car? Yes, the entire metal car itself. It will trap ALL of the noise and push it right into the AM radio's reception. So, at its simplest, the very first avenue I would approach is to ensure your AM radio antenna cable is isolated and has solid connectors; then, move onto additional methods to trap/filter unwanted signals because even after adding condensers, filters, capacitors (condensers), traps, etc. - if the radio antenna is not isolated the best it can be, you allow signal leakage to occur.

 

It could also be a bad filter capacitor within the radio itself.

 

Most certainly. Depending on the radio, it's likely to suspect there exists more than one capacitor, as well. Older equipment often requires what is referred to in the industry as a "re-cap" - replacing (most often) all the capacitors.

 

Great information. Thank you. FYI the antenna is new. That should eliminate some of the problems.

 

Thank you this info. Will I sound stupid if I go to O’Reillys and ask for a condenser as you suggest or should I go to a radio shop?

 

The type of interference you are receiving is normal for an am radio. There are in line antenna filters you can purchase that may reduce some of it.

 

I am NOT suggesting the antenna is not installed correctly, but I would take the small time it takes to be certain the antenna is installed correctly - it's your car, so do as you like. Regardless if it's new - it needs to be installed correctly.

There are two basic antennas (1) Mono-pole & (2) Di-Pole. A Mono-pole antenna requires a solid ground to Earth in order to eliminate voltage (the ground operates as a sink to discharge voltage). Ensure the ground is tied to a proper ground point on the chassis. Do not assume some bracket which appears on the backside near the radio or what appears to be a bracket mounted to the dash is a solid ground. Ensure the ground is tied to the chassis (do not use the negative [-] battery terminal) - the ground must be tied to the chassis with a solid ground - clean paint free and rust free. The most important is this type antenna must be grounded. A Di-Pole antenna should never be grounded. Validate whoever did the install did it properly.

 

The noise you get from power lines and semi trucks is RF overload. Basically they are producing broad spectrum noise that drowns out the radio station signal. Like trying to hear a conversation on a cell phone at a rock concert, there is too much noise! There is no filter available that will fix that. As mentioned above though, you can reduce the noise floor of your vehicle's local environment by cleaning and securing all factory grounds including the base of your newly installed antenna. You can also give the connector in the radio a couple back-and-forth twists to make sure you have a solid ground connection there. Oxidized connections on the shielding of the antenna coax connector can reduce the noise filtering abilities. Make sure your new antenna is good quality as well. Cheap antennas may have sketchy coax shielding.

 

Good ideas.

 

Let us know what you figure out. It may have been said already but make sure all of your grounds are solid. Adding a clean ground from the engine block to the frame can really help sometimes.