Why do we need an antenna?

[Deleted member 59498]

I only use radio, AM mostly, sports and news and stuff. Stub antennas lose a good amount of signal around here.

Sponsored

 

[blnewt]

I like the stock antenna, lets me know if that branch overhead is something I need to be concerned with
And what's this AM/FM thing you guys are talking about???

 

[carmigo]

So, stupid question. But I've removed the antenna from my JL due to car wash concerns and will be replacing it with a small flexi I bought once the proper adapter arrives.


But, the entire vehicle body is made of metal, why do we need an antenna instead of just hooking to that? I clearly don't understand how antennas work because it seems like a giant hunk of metal would be an excellent one, but if that were true then antennas would not exist.


Anyone able to science me on this?

Did a little research and most cars use the antenna for the radio. In newer cars, it can also be used for bluetooth, Wi-Fi, keyless unlocking, and emergency services like onstar.

 

[The Chubbernaut]

No they don't.

Yes, they do.

How does an antenna work?
The antenna at the transmitter generates the radio wave. A voltage at the desired frequency is applied to the antenna. The voltage across the antenna elements and the current through them create the electric and magnetic waves, respectively. At the receiver, the electromagnetic wave passing over the antenna induces a small voltage. Thus, the antenna becomes the signal source for the receiver input.

https://www.electronicdesign.com/te...333/electronic-design-welcome-to-antennas-101

 

[JLUHT]

Yes, they do.

How does an antenna work?
The antenna at the transmitter generates the radio wave. A voltage at the desired frequency is applied to the antenna. The voltage across the antenna elements and the current through them create the electric and magnetic waves, respectively. At the receiver, the electromagnetic wave passing over the antenna induces a small voltage. Thus, the antenna becomes the signal source for the receiver input.

https://www.electronicdesign.com/te...333/electronic-design-welcome-to-antennas-101

"..induces a small voltage" is key. that voltage isn't present in the absence of the RF

The antenna as a receiver I don't believe is energized or biased in any way to facilitate reception.

 

[rikity]

the car wash bent mine so I took it off. Radio works fine in the city, but I now live 30 miles from it now and the radio doesnt come in very well at all. Doesnt hurt my feelings though, I dont listen to the radio. I put a 256gb drive loaded with mp3's in and just listen to that, or stream something from my phone.

 

[The Chubbernaut]

"..induces a small voltage" is key. that voltage isn't present in the absence of the RF

The antenna as a receiver I don't believe is energized or biased in any way to facilitate reception.

"A voltage at the desired frequency is applied to the antenna." was the important part. My understanding of it is that the application of a very faint electrical charge was what allowed you to tune into different radio stations. Admittedly though, my own knowledge of the system is limited and I could be going off of false or assumed information. If that is the case, I stand corrected.

 

[jaymz]

Here’s a bit of science on the subject. It seems that the body is too big to receive a clean radio signal.

 

[JLUHT]

"A voltage at the desired frequency is applied to the antenna." was the important part. My understanding of it is that the application of a very faint electrical charge was what allowed you to tune into different radio stations. Admittedly though, my own knowledge of the system is limited and I could be going off of false or assumed information. If that is the case, I stand corrected.

The wavelength of the desired carrier to be received would be what would inform us the minimum length of the receiving antenna which is not biased with any voltage (correct me here) whereas the transmitting antenna is propagating radiation as result of the power applied.

"A voltage at the desired frequency is applied to the antenna." This is the transmitting antenna not the receiving antenna.

 

[AnnDee4444]

Another option:

 

[keeperman13]

Yes, they do.

How does an antenna work?
The antenna at the transmitter generates the radio wave. A voltage at the desired frequency is applied to the antenna. The voltage across the antenna elements and the current through them create the electric and magnetic waves, respectively. At the receiver, the electromagnetic wave passing over the antenna induces a small voltage. Thus, the antenna becomes the signal source for the receiver input.

https://www.electronicdesign.com/te...333/electronic-design-welcome-to-antennas-101

Everything before the "receiver" portion is referring to the transmitting station, not your Jeep but the station that is sending out the signal.

The portion, "At the receiver..." refers to your Jeep. I don't know of any antennas that are energized on the receiving side. The RF wave passing through the antenna induces the voltage, but the energy comes from the station.

One other thing to illustrate the point is the Crystal Radio which some folks have undoubtedly used. It has no power whatsoever and the energy to power the speaker is actually the power from the radio signal it receives. Pretty cool actually. Had one when I was a kid.

 

[21JLURDG]

Another option:

Right Hand Drive models are inconvenient in the correct-side driving world.

Antennas are sized to the wavelength of the frequency band in which they operate. They can be made smaller in fractional amounts (e.g. 1/2, 1/4 wave) by several different methods to emulate a bigger antenna (e.g. windings around antenna, bottom coils, etc.) but all of these are generally less efficient and therefore have less performance. That's why a "stubby" rubber duck antenna might work in the city but not receive signals in the suburbs.

And that's why many report poor performance of their GMRS, CB, etc. radios when they mount a small or stealth antenna for looks. If the terrain (i.e. trees) allow it, I use a 5 ft. CB antenna that always outperforms more expensive radios using a 2 ft. antenna. I also have 3 ft. and 2 ft. antennas that I use as required (i.e. trees, garage). They're all 5/8 wave, but the "tricks" used to emulate a 5/8 wave is less efficient the shorter the antenna.

 

[AnnDee4444]

Right Hand Drive models are inconvenient in the correct-side driving world.

Cool.



It's just a 2nd trail rated badge for my antenna delete... and right had drive doesn't change the antenna side anyway.

 

[Sidewalk]

I haven't washed my Jeep yet, so I haven't had that problem.

Still says "Wash Me" that someone wrote on it, and "Fvck you" as my response.

Personally, AM/FM is the only thing I've listened to in the vehicle for over 15 years.

I tuned into one of my local stations that I used to listen to as a teen, but stopped when I got shipped out 20+ years ago. I was surprised how great the programming was. I will be tuning in more often.

 

[navyflyer]

I removed mine and put a matching badge in its place.

Sponsored