Antenna, how to make a DIY internal or aerodynamic external antenna - Fuel Economy, Hypermiling, EcoModding News and Forum

saand · 10-09-2010, 08:00 AM

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.

Daox · 10-09-2010, 10:48 AM

I'm interested in this as well. I was just about to replace my broken antenna and looked at internal ones. If I could DIY all the better!

tjts1 · 10-09-2010, 11:24 AM

I hooked up the antenna wire to the rear window defogger. It has great reception. The defogger is disabled now (disconnected at both ends) but its not an issue because the tint on the inside of the windows seems to prevent that from happening. The defogger button and circuit and be reused for other purposes. I use it to go between a FE and power fuel table in MS.

cfg83 · 10-09-2010, 12:59 PM

tjts1 -

I always wanted to do that but never got around to it. I pulled the fuse of the rear defogger in preparation, but I didn't do the next step of figuring out where to hook into it. I was going to hook into one of the connectors where the fuse was, but I have to make sure I don't connect it to the "hot" connector, or I'll fry my radio.

CarloSW2

Zerohour · 10-09-2010, 04:43 PM

I shaved the antenna on my 86 Cavalier. Removed the front fender, arched the antenna over the wheel well. Patched the antenna hole, painted the fender, reinstalled. Somehow it didn't effect the reception of the local stations. But the Factory GM radio/antenna setup never picked up anything beyond the local broadcasts. Might be larger effect on a more modern radio that has better reception.

RobertSmalls · 10-09-2010, 05:43 PM

I was going to install a 95cm (=100MHz quarter-wave) antenna under a plastic or fiberglass body panel, but the stock antenna located inside the car is doing an adequate job. The stock antenna is about 40cm long, and is powered. Correction: it was powered.

Clev · 10-09-2010, 06:16 PM

I thought I remembered reading here about somebody who took a regular car antenna and stuck it behind the plastic trim piece on the A-pillar. If I actually cared about radio reception, I'd probably try that.

Rokeby · 10-09-2010, 08:57 PM

Here are two possible solutions that mount to the inside of the windshield,
~$20:

I know they aren't DIY, but hey, only $20, could save a lot of hassel!

Universal Am-Fm Hidden Windshield Antenna : eBay Motors

Interior Antenna AM/FM glass mount Road Rage: eBay Motors

Other possible solutions by Googling, "inside car am/fm antenna".

Good luck!

cfg83 · 10-09-2010, 09:47 PM

Clev -

Quote:

Originally Posted by Clev

I thought I remembered reading here about somebody who took a regular car antenna and stuck it behind the plastic trim piece on the A-pillar. If I actually cared about radio reception, I'd probably try that.

I did this one, which is what you are descrobing :

Free Stealth Antenna Mod w/ Pics - SaturnFans Forums

The reception is not as good as it was. I think I should have "sheathed" the antenna in heat-shrink tubing.

CarloSW2

tjts1 · 10-09-2010, 11:02 PM

Quote:

Originally Posted by cfg83

tjts1 -

I always wanted to do that but never got around to it. I pulled the fuse of the rear defogger in preparation, but I didn't do the next step of figuring out where to hook into it. I was going to hook into one of the connectors where the fuse was, but I have to make sure I don't connect it to the "hot" connector, or I'll fry my radio.

CarloSW2

I connected the antenna wire directly to the defogger on the window. It has 2 small plugs, one on each side of the window. Other cars might be different but usually there is a pretty simple plug glued to the glass.
good luck
Justin