WallyP

"Why 37.66"? "

Why not? If you don't like that number, you can pick almost any number that you like from the internet...




"FM waves, like any other wave, travels at the speed of light, and has a specific length to the signal waves (called wavelength). For some reason that is beyond my understanding, antennas built to multiples of 5/8th of the wavelength get the strongest signals - even stronger than full wavelength antennas; using a multiple of the 5/8th length increases the strength a bit with each multiple, up to the limit of resistance on the wire (in other words, an antenna 6 times the 5/8ths length might work, but anything beyond 12 times probably can't send the signal from the ends down the wire to the radio).

Formula:
300 / (frequency in Mhz) * (5/8) * (1/2) = length in meters of the ideal 5/8ths antenna using twinlead 300 Ohm wire.

To simplify the formula:
93.75 / Freq in Mhz = length in meters of the ideal 5/8th's antenna.

So, to get the length of the ideal 5/8ths antenna for the full FM radio spectrum (centered on 98Mhz):
93.75 / 98 = .95663265306 meters, or 95.66 centimeters
(which converts to 37.66 inches). "



"Archived from groups: rec.radio.amateur.antenna,rec.audio.car,rec.audio.tech
"Frank" wrote:
> What is the best type of "wire" for making a homemade
> car antenna to pick up FM radio. Is it copper? Aluminium?

Traditional is steel (i.e. coat-hanger wire :-)

In reality, it makes no difference except mechanically.

> What thickness or size.

It is a mechanical issue. What makes it self-supporting?
Electrically it is of no significance.

> Lenght?

Well, the middle of the FM broadcast band is ~98MHz
and 1/4 wavelength is ~28.5 inches.
http://www.csgnetwork.com/antennag [...] ncalc.html "


"The simplest thing you could do, and it might work fairly well if the FM stations are not too far away, is to use a straight piece of wire about 57" long as your antenna. This is the proper length for a "half-wave" FM antenna. "

Randy V

You'll have to do better than that, Wally.

Mrmerlin

Ken you forgot to take pictures of the doors and quarter panels where the speakers are whats your solution for those??

Wally i am still looking for this wire and was wondering exactly where to connect the wire to when I do get some??
My guess is that the car wire ends at the feed through at the base of the windshield under the front cowl where the wipers are , your thougts please.

abrexrode

Why not get XM or Sirius??? Magnetic low profile receiver and you never lose a station unless your in a tunnel.

Bill Ball

Stan:

Here's enough to make about 100 of those antennas.

http://www.radioshack.com/product/in...LAID=107598728

mirousse

I bought a coaxial antenna wire that I ran underneath the passenger seat carpet, up in the in the door frame under the plastic moulding and to the sunroof motor housing where I surgically soldered the inner wire to the existing antenna amp connection. I roughly tied the shield meshes of both cables and strenghten the newly formed cable with heat shrink. The antenna works perfectly.

By the way, if you want to refresh your antenna mast, buy a Toyota Yaris 2007 antenna mast, they're the same (30$ or so).

Michel.

Mrmerlin

I am trying to get an antenna thats not on the car.
IE it had a windshield antenna then the windshield was replaced with a non antenna unit.
So i dont want to drill any holes in the roof,Non sunroof car and i dont want to put a hole in the left rear fender to mount a Hirschman antenna even though the wires are inside the fender for an auto antenna.
Wally came up with a great idea and i will cruise down to radio shack and see what they have.
Thanks Bill for the idea

JHowell37

People who make stained glass windows have a special copper tape they use to wrap the edges of the glass so the solder will stick. If you have a guitar shop nearby, they may even sell some with a conductive adhesive.

byrdman454

Wally,
Does the 37.66" measurement you provided the length of the wire that is above the dash (open to air) or does this measurement also include the 6" or so extra required to route under the dash and hook up with the stock windshield antenna booster? I just need to know if I need to add some extra length to it in order to route and interface with the booster.

Thanks

WallyP

The very precise measurement was very tongue-in-cheek. It doesn't make that much difference. As you could see in my later post, you can find a reference for almost any precise length within several inches of that measurement.

Randy V

You've been Wally-ed, Mike!

tlsmith1999

I wonder what you could pick up if the wire was 39.66"?? Kind of like having an 11 on the amp.

jpitman2

Years ago I bought a 'stick-on' aerial which was a very fine wire stuck down the centre of a length of clear 1/2" sticky tape, with a short length of coax and std car aerial plug on one end. Terminate the plug with the radio connection under the dash somehwere, run it out onto the inside of the screen at one bottom corner, up the side and across the top, or basically wherever was least visible. Worked for me for many years, until the tape obvioulsy died dur to heat and UV exposure or something along those lines. Wouldnt be hard to make up something similar?
Many modern cars have their aerials laid on the rear window in amongst the demister copper runs....
jp 83 Euro S AT 52k
jp 83

leperboy

I have this setup on my Galaxie. I mounted this type of antenna with double-sided tape behind the rear-view mirror then ran the wiring under the headliner to the A-pillar and then into the dash. It works well and is easy to install.

Matt

jpitman2

I also had something wrong with radio in the 928 - only 1 am station worked. Eventually I replaced the whole aerial mast (wouldnt retract - broken inner cable). Along the way I followed the lead into the body, which ended in a small tin box badged Hirschmann(~ 2 cigarette box size), tucked under the quarter panel. The connections to this were badly corroded so I disconnected this whole unit. Then I did a continuity check on the coax going fwd to the dash, and there wasnt any. A gentle pull on the core wire showed it was just broken inside. Since I couldnt find a single aerial lead long enough in any of the local car places, I bought two extensions and joined them up, problem fixed.
jp 83 Euro S AT 52k