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Old 10-09-2010, 07:00 AM   #1 (permalink)
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Join Date: Jul 2010
Location: Melbourne, Australia
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bugler - '91 Mazda 626
90 day: 35.89 mpg (US)
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Antenna, how to make a DIY internal or aerodynamic external antenna

Hi all,
I have taken out my antenna today, it has always annoyed me using power when it goes up and down and the aerodynamic drag so after several hours of working out how to get the damn thing out of the car its finally out. So now its out im trying to work out how to best get reception back.

I tried just a length of wire routed around my car cabin but the reception isn't great. I remember seeing a few RF people on the forum so i thought id ask what are the important things to consider when making a "DIY" antenna

So a few questions/statements to get the ideas flowing
- Will just a piece of wire work as good as a telescoping antenna?, i can still use the telescoping antenna and mount it inside the cabin.
- I have to assume internal antennas are going to pick up less signal compared to external since the car metal work is earthed. Would it be better to run a wire around the top of the roof where it isn't shielded.
- The length of the aerial is important, quarter, half or full wavelength is ideal. Anywhere inbetween and the signal is not ideal i assume this is for resonance but im a bit rusty on my RF theory.
- Does the Length of aerial need to be all in one direction, can say a 1 meter aerial be half meter long one way and half meter long at 90 degrees. (asking so i can wrap it around in the cabin) I could have a full wavelength of wire and have it routed around the cabin roof, a quarter wavelength on each side of the cabin roof.
- Should the antenna be ideally sticking upward instead of going along the roof line, if so is there much signal reduction because of bad orientation
- Should coax cable with shield connected at both ends be used all the way up to the point where the antenna (or wire) starts.

I haven't really tried to match the antenna length yet or orient the wire properly but im still picking up a few radio stations with just a random piece of wire shoved into the antenna plug. So i figure with a few pointers i might be able to get normal reception fairly easily.

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