Do cars with plastic bodies, like the Saturn, give bad radio reception?

[micky]

Do cars with plastic bodies, like the Saturn, give bad radio reception?

[Dick Wood]

[RosemontCrest]

"The metal surface enables the signal generated when *transmitting* to reflect off the surface and travel into the atmosphere."

"It is worth noting that a poor ground plane or radiating surface may not affect radio *reception*. You may still *receive* transmissions from other radios with or without a ground plane. Basically, you can

*receive* transmissions on a clothes hanger!"

[Clare Snyder]

What would prompt that question? What properties of Plastic, or the behavior of radio waves???? If you are thinking of "ground planes" for the antenna, provisions for that are easily designed into plastic vehicles, just like on airplanes

- but ground planes are most important for transmitting. Yes, a ground plane WILL improve reception, but automotive radio antenna are seldom anywhere CLOSE to "optimized" so the lack of a ground plane would make an almost inperceptible difference to reception.

[gfretwell]

I had a Corvette and the only accommodation they made for the radio was shielding the HV ignition parts. There is still plenty of metal there to establish a ground plane.

[invalid unparseable]

Looking up frequencies there might be a difference in AM and FM transmission in Corvette space frame but I guess question is mote as antenna is outside.

Many different plastics are used in all plastic auto-body cars. Corvette used fiber glass but I recall in Fiero use of four different plastics depending on the part mostly polyurethane and sheet molding compound. Chrysler minivan had PET fenders and I recall in very expensive sports cars, carbon composites.

Metal stamping dies cost a fortune and often even though the plastic is more expensive than sheet steel in a small build where not a lot of cars are made like sports cars it is cheaper to use plastic.

[Sam Block]

Not necessarily. Long wires work fine.

but automotive radio antenna are seldom

[gfretwell]

In a corvette with a fiberglass hood, there is no "outside". If you don't have the shielding package you will hear the ignition interference in your radio. In fact people next to me could hear it. I didn't have a radio in mine and it did not have the shielding. (8 track only)

[Ralph Mowery]

It is not so much the shielding,but the RF supression like resistor plugs and wiring.

A friend replaced all the wiring on his 1956 Chevy with regular wire and plugs around 1970. You could tell he was near you because about 4 blocks away the tv set would start acting up and at 2 blocks it was almost unusable, and totally wiped out the TV if he was in the driveway.

[invalid unparseable]

I had not considered the engine interfering with the radio but there is no plastic body part between it and the engine. I do recall in the house having a dimmer switch that interfered with the TV and a replacement switch solved the problem.

[micky]

Actually, it's that car radios have always given me better reception than house radios have. Is it the antenna, the ground plane? What?

[micky]

LOL. What did he say when this was brought to his attention?

[gfretwell]

They all shipped with R44 plugs but if you ordered a radio there were metal covers over the distributor and plug wires.

[gfretwell]

Better radio to start with and the 30" whip is better than that little ferrite wound antenna in a radio. Also you are outside.

[micky]

Actually, it's that car radios have always given me better reception than house radios have. Is it the antenna, the ground plane? What?

[Clare Snyder]

Generally auto radios are TRF instead of super-regernerative - and regardless they are built with higher sensitivity than many home radios.

[Clare Snyder]

It's actually illegal to "interfere" with radio transmissions and to "broadcast" without a licence.

[Ralph Mowery]

I doubt that hardly any radio for the broadcast band has been either TRF or super-regernerative has been used by the general public from around

1955 on. Probably almost never used in cars unless they may have been before 1940 or 50. I do have one of the regenerative sets built around the 1960. But they were not bought by the masses of people.

However they are usually built with better sensitivity than the average home radio and the whip is better than the built in antenna of most home radios.

[Michael Trew]

Typically better reception in the car, yes, but that all depends on the antenna set up. You can have a very good antenna at home, but one with a fault in a car. I've owned both. I'd like to build an AM loop in my attic to get better AM reception at some point.

I am very into AM radio, especially long-distance AM stations at night. I've owned cars where they seem to put no thought into the AM radio band, and it shows (sounds). Dad had a Chevy Trailblazer (2006?) where you could always hear the transmission or something interfering with the AM reception.

[micky]

Wow.

The '72 Buick and then the '84 Chrysler and 88 Chrysler would get perfectly here in Baltimore WRC, 980AM, in Washington, DC, a station no indoor radio, even the fancy receiver, would get at all. (I've only lost interest in that station because it changed format.)

And for decades, one car radio after another, (maybe the Buick,) Chryler and Toyota, would get WAMU, 88.5FM, (American University in DC), perfectly, when only one inside radio would get it. Even now a much different Toyota radio gets WAMU usually perfectly, when the one inside radio no longer does as well. (For a while I was reporting to the WAMU engineer when reception was good or bad, and he got it good, but months later, it got weak again sometimes. (And like I say, that's the one radio that gets it at all.)

At one point a friend gave me a nice wood "box" designed to hold a car radio, an antenna, and a DC adapter, just for the sake of using a car radio indoors, but at the same time he told me that it didnt' work for him (which is why he was giving it to me). So it seems like the difference is the metal body on cars, all but a few cars.

The urls people have posted here (before electronics.repair was added) make clear that the ground plane in the car makes a difference, and that cars without one need a special antenna cable, but a) they're mostly pushed for CB radios, b) it's not at all clear that the special antenna is as good c) when shopping for an antenna, any with ground plane provision probably make note of it, but those without do not, afaik, warn people what is missing.