Inside car antenna for working on radios

[electra225]

I have always had a metal roof to install a car radio antenna on. My shop will not have a metal roof, so I need ideas of how I can use a car antenna inside the building. Does the antenna have to be grounded, and, if so, to what? Can I use the traditional antenna like you would put on a car?

[19&41]

A Traditional antenna can work. The ground shield on the lead in cable can be grounded, to help inhibit the RFI present in the building. If you don't have metal in your roof sheathing, you could put it up in the attic. Also you could try a Terk tower amplified inside antenna and see what kind of reception you get. That's the antenna I use with my consoles.

[electra225]

What if I drill a hole in a shelf then mount a traditional car antenna like you would buy at AutoZone there. Then I could ground the shield to a screw on an outlet cover, if that would provide a sufficient ground. I want to avoid upstairs antennae because I don't want a hole in the ceiling. It may come to that, but as a last resort.

[19&41]

That would be something you would have to try, just to see what you get. If the RFI gets bad, you might want to unplug power supplies and lamps and bring them back up one at a time to see which is causing the problem.

[electra225]

County building codes "allegedly" specify LED lighting. I find that hard to believe. I need to verify before getting too excited. There are pot lights in the ceiling of the shop for lighting. I specified pot lights in the build so I could change bulbs if I got a lot of RFI in radios or generators. I have a collection of incandescent bulbs I can use in that case. I have taken extra pains to make sure there are no extraneous noise generators in the building. There may be LED's in the pot lights for inspection, but I will remove them and transplant with incandescent if I have too much noise. Will the bolts that hold outlet covers on provide enough grounding for the cable shield on the antenna? What if I went to the "real" ground right on the outlet? We have bonded electrical systems out here, which means the ground wire is connected to earth ground, not just to the common buss.

[19&41]

Get a good AM radio with an internal antenna, turn it on, then your lights. Tune across the range of the tuner and see what you catch. Hopefully it will be nothing.

[TC Chris]

On the antenna question, I have little real knowledge, so be warned. But I have read that the auto antenna, the formerly telescoping, now usually fixed whips, worked because they had a "ground plane"--that big expanse of sheet metal right underneath. I've always imagined that it's a bit like an unbalanced dipole.

For an omni antenna with a shielded lead-in, Metz makes a coil-base whip. Most tuners and receivers have an unbalanced 75 ohm antenna input for the coax and when they don't you can often find one behind the balun they have for the 300 ohm twinlead input. For best performance, disconnect the balun.

I have found that the Metz whips are great in strong signal environments without multipath challenges. Weak signals or multipath or both? They sound awful. Your good tuner will perform worse than an FM portable.

Chris Campbell

[electra225]

I have a spare antenna for the Buick I can experiment with and not have to buy an antenna that might not work. Where can I get said Metz antenna? I'm not familiar with those.

[William]

Metz antennas are used in marine applications, but I'm sure they would work in a home. Chris will know more about that than I do.


Bill

[electra225]

I found what appears to be a test antenna for working on car radios. I'll take a picture of it. If it works, that will be a dandy discovery. I won't have to mess with lead in wire. This thing plugs directly into the car radio. Never saw one like it, have no idea where I got it, never had seen it before in my life that I remember.

[TC Chris]

I have a spare antenna for the Buick I can experiment with and not have to buy an antenna that might not work. Where can I get said Metz antenna? I'm not familiar with those.

Here's the FM version. They do all sorts of antennas.
https://www.metzantennas.com/product/am-fm-magnum/

The price seems to have gone up.

Chris Campbell

[TC Chris]

I have a couple of these. Purists will sneer. But in my old office, this was the only antenna that worked. At my Mom's house, same result. She had an old stucco house with expanded-metal lath for the stucco, and it seems to have formed a Faraday cage (same problem at the old office, actually). The antenna hangs upside-down in a window, the position that works for the local public radio station while we work on clearing the house out.

https://www.ebay.com/itm/144226394910?

Can't beat the price.

Chris Campbell

[hermitcrab]

what were the inside the glass antennas comprised of?... they just looked like two wires strung across the glass... did they have a balum or something to match the input to the radio ?

[19&41]

I know the actual elements were metal filaments suspended in the elastomeric sheet that went between the windshield sheets. They had a attachment tab that was wired to the radio coax.

[TC Chris]

And they were notorious for lousy reception. Dipoles are directional, among other problems.

Chris Campbell