Radio antenna

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Old 16 Mar 2006, 06:28 pm   #1 (permalink)
doolittle & sitmore
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Default Radio antenna

I just purchased a 2000 toyota camry and can't see a radio antenna
anywhere although the radio plays just fine. Where is the antenna?

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Old 16 Mar 2006, 06:30 pm   #2 (permalink)
Nobody Important
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Default Re: Radio antenna

doolittle & sitmore wrote:
> I just purchased a 2000 toyota camry and can't see a radio antenna
> anywhere although the radio plays just fine. Where is the antenna?
>


There's an FM dipole in the rear window, and an AM antenna in the body
of the radio.
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Old 17 Mar 2006, 03:26 pm   #3 (permalink)
jerryrigged@optonline.net
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Default Re: Radio antenna

No antenna, its built into the glass.

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Old 18 Mar 2006, 03:49 pm   #4 (permalink)
Travis Jordan
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Default Re: Radio antenna

Nobody Important wrote:
> There's an FM dipole in the rear window, and an AM antenna in the body
> of the radio.


I believe the window glass antenna is operable both on AM and FM.


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Old 18 Mar 2006, 05:04 pm   #5 (permalink)
Nobody Important
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Default Re: Radio antenna

Travis Jordan wrote:
> I believe the window glass antenna is operable both on AM and FM.


Sure, all antennas will work for all modulation schemes. Having fixed a
frequency, though, the electrical length of the antenna needs to be
matched approximately. 1/4 wavelength is a commonly used length. The
optimal electrical length for a commercial FM band antenna is 100 times
shorter than that for the commercial AM band.

If you open up your radio, I think you'll find what's known as a ferrite
bar antenna inside, whose electrical length corresponds to 1/4 the
wavelength of the commercial AM band.
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Old 19 Mar 2006, 05:55 am   #6 (permalink)
Travis Jordan
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Default Re: Radio antenna

Nobody Important wrote:
> Travis Jordan wrote:
> > I believe the window glass antenna is operable both on AM and FM.

>
> Sure, all antennas will work for all modulation schemes. Having
> fixed a frequency, though, the electrical length of the antenna needs
> to be matched approximately. 1/4 wavelength is a commonly used
> length. The optimal electrical length for a commercial FM band
> antenna is 100 times shorter than that for the commercial AM band.


Of course. I should have said, "I believe the window glass antenna is
used for both AM broadcast band and FM broadcast band reception".

> If you open up your radio, I think you'll find what's known as a
> ferrite bar antenna inside, whose electrical length corresponds to
> 1/4 the wavelength of the commercial AM band.


No, you won't. Any internal antenna would be shielded by the metal of
the dash, hood, etc. No modern car radio uses internal antennas - they
are always external.


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Old 19 Mar 2006, 06:27 am   #7 (permalink)
Ove Delin
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Default Re: Radio antenna

Travis Jordan wrote:
> Nobody Important wrote:
>> Travis Jordan wrote:
>>> I believe the window glass antenna is operable both on AM and FM.

>> Sure, all antennas will work for all modulation schemes. Having
>> fixed a frequency, though, the electrical length of the antenna needs
>> to be matched approximately. 1/4 wavelength is a commonly used
>> length. The optimal electrical length for a commercial FM band
>> antenna is 100 times shorter than that for the commercial AM band.

>
> Of course. I should have said, "I believe the window glass antenna is
> used for both AM broadcast band and FM broadcast band reception".
>
>> If you open up your radio, I think you'll find what's known as a
>> ferrite bar antenna inside, whose electrical length corresponds to
>> 1/4 the wavelength of the commercial AM band.

>
> No, you won't. Any internal antenna would be shielded by the metal of
> the dash, hood, etc. No modern car radio uses internal antennas - they
> are always external.
>
>

The too short length, for AM, of the antenna is compensated for in the
radio by connecting it to a resonance circuit in the input amplifier of
the radio. This converts the antenna into a so called active antenna,
which can be nearly equally efficient as a passive full length antenna.
The only drawback of the active antenna is that it only covers a very
small frequency band, but when you tune the radio it will tune the
antenna as well and since radio channels are very narrow (as compared
for instance to television channels) this impose no problem.
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Old 19 Mar 2006, 09:52 am   #8 (permalink)
Nobody Important
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Default Re: Radio antenna

Ove Delin wrote:
> The too short length, for AM, of the antenna is compensated for in the
> radio by connecting it to a resonance circuit in the input amplifier of
> the radio.


Cool. I didn't know that, despite a lotta schooling including graduate
studies in radio frequency integrated circuits. I will have to look
into it.
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Old 23 Mar 2006, 07:24 am   #9 (permalink)
skewe
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Default Re: Radio antenna

most new cars have it that way...

http://www.golfer-review.com/m_toyota/camry.htm

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