What happened to Car Radio Antennas?...

[Rob]

Brian Gregory <void-invalid-dead-dontuse@email.invalid> wrote:

On 29/07/2021 12:35, Rob wrote:
Energy is expensive here and a typical radio station cannot pay the 100kW-1MW
power consumption of an AM transmitter.

AM transmitters with over 50kW output are not used in the US at all.
(There were a handful of experimental ones at one stage in the past)

Yes in Europe higher powers were not uncommon, a few were as high as 1MW.

As I explained in another followup, it seems related to the situation that
in Europe radio stations traditionally were a state thing, and you
would have to cover an entire country with the same signal, so high
output power is a reasonable move. In the USA, it looks like it always
was a commercial thing and more focused on local operation, servicing
a single town and surrounding area.

Still, with 50kW transmitter output AM a typical station would rather
place 5 FM transmitters of 5kW and have the same coverage area but
with much better quality. For a 5kW AM transmitter a single FM site
would probably do it.
(FM transmitters usually have antennas with ~ 10dB of gain so they
effectively transmit 10 times more than their rated output power, which
cannot reasonably done with MW (AM) transmitters due to physical limitations)

 

[Phil Allison]

Michael Trew wrote:
===============

** All these alternatives to the time honored telescopic whip are compromised.

1. They are *directional* - complete null in two possible orientations.

2. Framed in a steel structure so partially Faraday shielded.

Guess having no ugly antenna sells cars to those who value cosmetics above results.
No wonder the are many \"after market\" alternatives available.


Personally, I\'d rather have a full whip antenna. I owned a \'99 Chevy
(Geo) Metro that had a retractable one.

https://www.youtube.com/watch?v=KuZDVXhdYG8


..... Phil

 

[Phil Allison]

Michael Trew wrote:
===============

** All these alternatives to the time honored telescopic whip are compromised.

1. They are *directional* - complete null in two possible orientations.

2. Framed in a steel structure so partially Faraday shielded.

Guess having no ugly antenna sells cars to those who value cosmetics above results.
No wonder the are many \"after market\" alternatives available.


Personally, I\'d rather have a full whip antenna. I owned a \'99 Chevy
(Geo) Metro that had a retractable one.

https://www.youtube.com/watch?v=KuZDVXhdYG8


..... Phil

 

[Rob]

Phil Allison <pallison49@gmail.com> wrote:

Hi,

you may have noticed that few modern cars have any visible AM/FM antennas these days.
Many have a \"shark fin\" antenna on the roof for GPS and possibly 4G cell phones - frequencies used are similar.
Others have a short whip antenna somewhere, not much good for AM.

The answer ( found by Googling) is they often use the rear window \"defroster\" grid for AM and FM reception.
It can be made to work like a frame antenna for AM and a L shaped wire for FM. A booster amp is added near the window for impedance matching.

Some makers ( BMW ?) have two printed antennas on rear side windows that are boosted and fed into a selector unit that sends the stronger one to the receiver. This is called \"antenna diversity\" as is commonly used with radio mics.

If anyone knows more, make my day.

Over here, the FM radio network was originally built with horizontal
polarisation. Maybe not much thought was spent on it, and it was done
just the same way as TV was done. Or maybe they had some valid reason
for it that did not work out as expected.

Anyway, that of course did not work well with typical car antennas of
the time. So at first, vertical polarisation was \"added\" to the
antennas (making it circular, I guess, depending on the phasing it could
also be slant polarisation). And later, when the antennas were
completely replaced because the contract to transmit FM signals went
from the incumbant telecom company to a commercial company, they
switched over to purely vertical polarisation.

Ironically, now the cars tend to have antennas that are more horizontally
polarized. But hey, they do not want us to use FM anyway.

 

[Rob]

Phil Allison <pallison49@gmail.com> wrote:

Hi,

you may have noticed that few modern cars have any visible AM/FM antennas these days.
Many have a \"shark fin\" antenna on the roof for GPS and possibly 4G cell phones - frequencies used are similar.
Others have a short whip antenna somewhere, not much good for AM.

The answer ( found by Googling) is they often use the rear window \"defroster\" grid for AM and FM reception.
It can be made to work like a frame antenna for AM and a L shaped wire for FM. A booster amp is added near the window for impedance matching.

Some makers ( BMW ?) have two printed antennas on rear side windows that are boosted and fed into a selector unit that sends the stronger one to the receiver. This is called \"antenna diversity\" as is commonly used with radio mics.

If anyone knows more, make my day.

Over here, the FM radio network was originally built with horizontal
polarisation. Maybe not much thought was spent on it, and it was done
just the same way as TV was done. Or maybe they had some valid reason
for it that did not work out as expected.

Anyway, that of course did not work well with typical car antennas of
the time. So at first, vertical polarisation was \"added\" to the
antennas (making it circular, I guess, depending on the phasing it could
also be slant polarisation). And later, when the antennas were
completely replaced because the contract to transmit FM signals went
from the incumbant telecom company to a commercial company, they
switched over to purely vertical polarisation.

Ironically, now the cars tend to have antennas that are more horizontally
polarized. But hey, they do not want us to use FM anyway.

 

[Rob]

Phil Allison <pallison49@gmail.com> wrote:

Hi,

you may have noticed that few modern cars have any visible AM/FM antennas these days.
Many have a \"shark fin\" antenna on the roof for GPS and possibly 4G cell phones - frequencies used are similar.
Others have a short whip antenna somewhere, not much good for AM.

The answer ( found by Googling) is they often use the rear window \"defroster\" grid for AM and FM reception.
It can be made to work like a frame antenna for AM and a L shaped wire for FM. A booster amp is added near the window for impedance matching.

Some makers ( BMW ?) have two printed antennas on rear side windows that are boosted and fed into a selector unit that sends the stronger one to the receiver. This is called \"antenna diversity\" as is commonly used with radio mics.

If anyone knows more, make my day.

Over here, the FM radio network was originally built with horizontal
polarisation. Maybe not much thought was spent on it, and it was done
just the same way as TV was done. Or maybe they had some valid reason
for it that did not work out as expected.

Anyway, that of course did not work well with typical car antennas of
the time. So at first, vertical polarisation was \"added\" to the
antennas (making it circular, I guess, depending on the phasing it could
also be slant polarisation). And later, when the antennas were
completely replaced because the contract to transmit FM signals went
from the incumbant telecom company to a commercial company, they
switched over to purely vertical polarisation.

Ironically, now the cars tend to have antennas that are more horizontally
polarized. But hey, they do not want us to use FM anyway.

 

[Phil Allison]

Rob wrote:
=======

If anyone knows more, make my day.

... Phil


Over here, the FM radio network was originally built with horizontal
polarisation. Maybe not much thought was spent on it, and it was done
just the same way as TV was done. Or maybe they had some valid reason
for it that did not work out as expected.

** Not sure just where you are - but the same occurred in Aussie land in the mid 1970s.

Anyway, that of course did not work well with typical car antennas of
the time. So at first, vertical polarisation was \"added\" to the
antennas (making it circular, I guess, depending on the phasing it could
also be slant polarisation). And later, when the antennas were
completely replaced because the contract to transmit FM signals went
from the incumbant telecom company to a commercial company, they
switched over to purely vertical polarisation.

** Initially all FM Tx was horizontal here.

It was expected that TV antennas would be the norm and FM car radios hardly existed.
In any case, the main broadcasters were classic music oriented so not so car listener concerned.

Then it changed, commercial broadcasters started up and went for circular antennas.

Ironically, now the cars tend to have antennas that are more horizontally
polarized. But hey, they do not want us to use FM anyway.

** Your average \"invisible\" car antenna tends to be horizontal.

Heinrich Hertz would not be amused ....



....... Phil

 

[Phil Allison]

Rob wrote:
=======

If anyone knows more, make my day.

... Phil


Over here, the FM radio network was originally built with horizontal
polarisation. Maybe not much thought was spent on it, and it was done
just the same way as TV was done. Or maybe they had some valid reason
for it that did not work out as expected.

** Not sure just where you are - but the same occurred in Aussie land in the mid 1970s.

Anyway, that of course did not work well with typical car antennas of
the time. So at first, vertical polarisation was \"added\" to the
antennas (making it circular, I guess, depending on the phasing it could
also be slant polarisation). And later, when the antennas were
completely replaced because the contract to transmit FM signals went
from the incumbant telecom company to a commercial company, they
switched over to purely vertical polarisation.

** Initially all FM Tx was horizontal here.

It was expected that TV antennas would be the norm and FM car radios hardly existed.
In any case, the main broadcasters were classic music oriented so not so car listener concerned.

Then it changed, commercial broadcasters started up and went for circular antennas.

Ironically, now the cars tend to have antennas that are more horizontally
polarized. But hey, they do not want us to use FM anyway.

** Your average \"invisible\" car antenna tends to be horizontal.

Heinrich Hertz would not be amused ....



....... Phil

 

[Michael Trew]

On 7/27/2021 12:24 AM, Phil Allison wrote:

Michael Trew wrote:
===============

** All these alternatives to the time honored telescopic whip are compromised.

1. They are *directional* - complete null in two possible orientations.

2. Framed in a steel structure so partially Faraday shielded.

Guess having no ugly antenna sells cars to those who value cosmetics above results.
No wonder the are many \"after market\" alternatives available.


Personally, I\'d rather have a full whip antenna. I owned a \'99 Chevy
(Geo) Metro that had a retractable one.


https://www.youtube.com/watch?v=KuZDVXhdYG8


.... Phil

Haha, not a power one. I can\'t remember the last time I\'ve seen a car
with a power retractable antenna.

 

[David Lesher]

Brian Gregory <void-invalid-dead-dontuse@email.invalid> writes:


>But most cars nowadays only have FM and DAB+ anyway.

For some reason, Tesla\'s do not have an AM band.
I can\'t imagine why that is...

--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that\'s close..........................
Unless the host (that isn\'t close).........................pob 1433
is busy, hung or dead....................................20915-1433

 

[Michael Trew]

On 7/27/2021 12:24 AM, Phil Allison wrote:

Michael Trew wrote:
===============

** All these alternatives to the time honored telescopic whip are compromised.

1. They are *directional* - complete null in two possible orientations.

2. Framed in a steel structure so partially Faraday shielded.

Guess having no ugly antenna sells cars to those who value cosmetics above results.
No wonder the are many \"after market\" alternatives available.


Personally, I\'d rather have a full whip antenna. I owned a \'99 Chevy
(Geo) Metro that had a retractable one.


https://www.youtube.com/watch?v=KuZDVXhdYG8


.... Phil

Haha, not a power one. I can\'t remember the last time I\'ve seen a car
with a power retractable antenna.

 

[Michael Trew]

On 7/27/2021 12:24 AM, Phil Allison wrote:

Michael Trew wrote:
===============

** All these alternatives to the time honored telescopic whip are compromised.

1. They are *directional* - complete null in two possible orientations.

2. Framed in a steel structure so partially Faraday shielded.

Guess having no ugly antenna sells cars to those who value cosmetics above results.
No wonder the are many \"after market\" alternatives available.


Personally, I\'d rather have a full whip antenna. I owned a \'99 Chevy
(Geo) Metro that had a retractable one.


https://www.youtube.com/watch?v=KuZDVXhdYG8


.... Phil

Haha, not a power one. I can\'t remember the last time I\'ve seen a car
with a power retractable antenna.

 

[David Lesher]

Brian Gregory <void-invalid-dead-dontuse@email.invalid> writes:


>AM transmitters with over 50kW output are not used in the US at all.

cough, cough....

WLW. It ran 500KW+ in the past, but regulators cut them back to
the ordinary 50KW level in ~1940.

The transmitter tubes had 3-phase filiments, if that gives you
some idea of their size.

There were multiple stories of farmers getting bit by their hot
barbed wire fences, metal roofs that played WLW, etc.



--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that\'s close..........................
Unless the host (that isn\'t close).........................pob 1433
is busy, hung or dead....................................20915-1433

 

[David Lesher]

Brian Gregory <void-invalid-dead-dontuse@email.invalid> writes:


>AM transmitters with over 50kW output are not used in the US at all.

cough, cough....

WLW. It ran 500KW+ in the past, but regulators cut them back to
the ordinary 50KW level in ~1940.

The transmitter tubes had 3-phase filiments, if that gives you
some idea of their size.

There were multiple stories of farmers getting bit by their hot
barbed wire fences, metal roofs that played WLW, etc.



--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that\'s close..........................
Unless the host (that isn\'t close).........................pob 1433
is busy, hung or dead....................................20915-1433

 

[Allodoxaphobia]

On Mon, 26 Jul 2021 23:54:40 -0400, Michael Trew wrote:

Guess having no ugly antenna sells cars to those who value cosmetics
above results. No wonder the are many \"after market\" alternatives
available.

Similarly for Schmart Fones.
Selling either \'glitz\' or \'cheap\' wins hands down.
Audio fidelity comes in _far_ distant.

 

[Allodoxaphobia]

On Mon, 26 Jul 2021 23:54:40 -0400, Michael Trew wrote:

Guess having no ugly antenna sells cars to those who value cosmetics
above results. No wonder the are many \"after market\" alternatives
available.

Similarly for Schmart Fones.
Selling either \'glitz\' or \'cheap\' wins hands down.
Audio fidelity comes in _far_ distant.

 

[Rob]

David Lesher <wb8foz@panix.com> wrote:

Brian Gregory <void-invalid-dead-dontuse@email.invalid> writes:


But most cars nowadays only have FM and DAB+ anyway.

For some reason, Tesla\'s do not have an AM band.
I can\'t imagine why that is...

You can\'t? Well I can!
- not useful in large parts of the world
- interference from motor control

 

[Rob]

David Lesher <wb8foz@panix.com> wrote:

Brian Gregory <void-invalid-dead-dontuse@email.invalid> writes:


But most cars nowadays only have FM and DAB+ anyway.

For some reason, Tesla\'s do not have an AM band.
I can\'t imagine why that is...

You can\'t? Well I can!
- not useful in large parts of the world
- interference from motor control

 

[Brian Gregory]

On 26/07/2021 06:44, Phil Allison wrote:

you may have noticed that few modern cars have any visible AM/FM antennas these days.
Many have a \"shark fin\" antenna on the roof for GPS and possibly 4G cell phones - frequencies used are similar.
Others have a short whip antenna somewhere, not much good for AM.

I don\'t think a loop aerial on a car window would work at all well
surrounded by the much bigger thinker more conductive loop consisting of
the metal body of the vehicle in which the window is fitted.

I think it\'d be better to just use it all as a short wire antenna much
like the short whips even for MW and LW.

But most cars nowadays only have FM and DAB+ anyway.

--
Brian Gregory (in England).

 

[Brian Gregory]

On 26/07/2021 06:44, Phil Allison wrote:

you may have noticed that few modern cars have any visible AM/FM antennas these days.
Many have a \"shark fin\" antenna on the roof for GPS and possibly 4G cell phones - frequencies used are similar.
Others have a short whip antenna somewhere, not much good for AM.

I don\'t think a loop aerial on a car window would work at all well
surrounded by the much bigger thinker more conductive loop consisting of
the metal body of the vehicle in which the window is fitted.

I think it\'d be better to just use it all as a short wire antenna much
like the short whips even for MW and LW.

But most cars nowadays only have FM and DAB+ anyway.

--
Brian Gregory (in England).