" Not in my wife's VW. AM is useless on that car.
Factory defect?, dealer wouldn't fix it."

Volswagen: Sorriest looking p.o.c. ever to imitate an automobile.
Fortunately, Hitler's plan to nauseate the world, failed.

Bob Swinney

"garigue" wrote in message
...
Hello all .... The first thing I would tell the fellow is to definitely
stay away from Radio Shack. Also, I don't want to hurt anyone's feelings
but do the same for the CC Radio. I find the CC radio overpriced and
susceptible to noise sources that some of my other radios ignore. The CC
has some annoying features such as that damm beep on band change and that
click on the preselect buttons for tuning. Definitely the way to go would
be with a good antenna. I would do a search under broadcast band DXing.
There are a myriad of sites and ideas.

The radio I recommend would be an OLD car radio. I have been very
disappointed in the AM performance of car radios of late. I understand
that
this is purposeful as the radio is less susceptible to interference from
the
on board computers in the car. So instead of better shielding-design;
they
degenerate the AM sensitivity. A decent 12 V power supply can be cheaply
built or bought. I would stay away from the small switching supplies as
some generate a lot of hash. You know what your needs are in the valley
so
try some different combinations but trying to "buy" your way into good
reception would probably be counterproductive and disappointing.

God Bless and good luck pulling them in ......Tom Popovic Belle Vernon
Pa.

Car radios have better low signal performance than the average domestic
radio--so use a car radio in your house and get a good external aerial.

On Fri, 25 Feb 2005 09:08:59 -0600, "Robert Swinney"
wrote:


Errr, lessee. "Standard" pole spacing used on some RR's was 30 poles per
mile. 5/30 mile = 880 feet. That's a some fancy plinking alright!

Musta been a non-standard spur line. It sure wasn't 880 feet.

Hi Jerry,

Sorry it took so long to get back ...I don't seem to have a lot of time to
read posts lately. What I'd like to do (if possible/practical) is set up
antenna(s) for am & fm to serve at least 2 recovers, both have external
antenna connections and have access to the same external wall on the house.
By standard antenna I mean the ones that came with the unit, also I'd like
to try the stringing wire method before I spend $$$ on some powered gadget.
What info do you need to better advise me?

Thanks ...and thanks to all that responded

Andrew V
"Jerry Martes" wrote in message
news:lnaTd.15693$uc.4300@trnddc09...

Andrew

I might be able to assist you. I have a little experience with similar
problems in the San Diego Calif. desert. I dont know what your "standard
antenna" is. If your radio has no connections for attaching an external
antenna, there is little you can do to improve the AM reception.

If you want to get involved in amplified AM antennas, I might be of some
help.

Jerry



"Andrew V" wrote in message
...
I've seen people reference a news group for radios and am wondering which
one (found many radio related newsgroups). My questions relate to
improving AM/FM reception in a valley area. I can get the stations on the
car radio but almost nothing in the house(wood frame). I have the
standard antennas hooked up and want to do some research before I find
myself at the mercy of the radio shack sales guy.

Thanks

Andrew V

Thanks to all who replied, as usual this group possesses a wealth of
knowledge far past basic metalworking. The CC crane link could prove useful
but I'd like to try stringing wires before I spend $$$. I do need to boost
AM & FM usage wise FM is a higher priority, I'm the only one that takes in
AM talk radio.

Thanks

Andrew V


"Andrew V" wrote in message
...
I've seen people reference a news group for radios and am wondering which
one (found many radio related newsgroups). My questions relate to
improving AM/FM reception in a valley area. I can get the stations on the
car radio but almost nothing in the house(wood frame). I have the standard
antennas hooked up and want to do some research before I find myself at
the mercy of the radio shack sales guy.

Thanks

Andrew V

On 24 Feb 2005 11:00:27 -0800, jim rozen
wrote:

In article , Don Foreman says...


That's how old loop antennas (the kind built on large crosses or
turnstyles) worked. IIRC they're sensitive off the edge of the
loop (it's been a while since I've had mine out and running).

Right. Think of the H field vectors as horizontal circles centered on
the (vertical) transmitting antenna. Voltage induced in the loop
will be roughly proportional to the cross-sectional area that is
perpendicular to those circles.

Andrew

All of my experience with commercial Amplified Antennas indicated that
they are usually not able to satisfactorily improve the system performance.
The concept of including an amplifier between the receiver and the antenna
is quite a good idea where transmission line loss is "unavoidable". There
is value in designing the receiver's input circuit so it can be adjusted to
accomodate whatever antenna impedance gets connected to it. But, that is
seldom done these days.

For your consideration - Since a car can get decent AM recption in your
neighborhood, there is adequet AM signal strength. I'd suggest that if you
have two antenna terminals in the back of a reasonably good household AM
receiver, you'll be able to construct a fairly simple antenna that works
well for all stations.

Can you locate the receiver close to where a long wire can be made
vertical and as long as practical? Then, can a wire be connected to a
ground (water pipe).

Dont be confused by thinking that the car antenna is just a short
telescoping element. The telescoping (short) mast is actually a probe that
couples to the car itself. The car is the antenna. The coax feed line in
the car is only a necesary component for minimizing induced noise. Dont
include any in the house radio antenna for AM.

For FM in remote locations, and in valleys, I have had some gtreat results
with simple home made Yagis. There are alot of web sites on Yagi antennas.
I am available for comments on any aspect of FM Yagi design. It seems so
easy to design and build FM Yagis, I'd encourage you to build a Yagi for
your FM needs. I would expect that you could design and build a Yagi that
performs better than the ones I've built. But, all those I've built have
have worked "good enough".

Jerry

"Andrew V" wrote in message
...
Hi Jerry,

Sorry it took so long to get back ...I don't seem to have a lot of time to
read posts lately. What I'd like to do (if possible/practical) is set up
antenna(s) for am & fm to serve at least 2 recovers, both have external
antenna connections and have access to the same external wall on the
house. By standard antenna I mean the ones that came with the unit, also
I'd like to try the stringing wire method before I spend $$$ on some
powered gadget. What info do you need to better advise me?

Thanks ...and thanks to all that responded

Andrew V
"Jerry Martes" wrote in message
news:lnaTd.15693$uc.4300@trnddc09...

Andrew

I might be able to assist you. I have a little experience with similar
problems in the San Diego Calif. desert. I dont know what your
"standard antenna" is. If your radio has no connections for attaching
an external antenna, there is little you can do to improve the AM
reception.

If you want to get involved in amplified AM antennas, I might be of some
help.

Jerry



"Andrew V" wrote in message
...
I've seen people reference a news group for radios and am wondering
which one (found many radio related newsgroups). My questions relate to
improving AM/FM reception in a valley area. I can get the stations on
the car radio but almost nothing in the house(wood frame). I have the
standard antennas hooked up and want to do some research before I find
myself at the mercy of the radio shack sales guy.

Thanks

Andrew V

On Fri, 25 Feb 2005 09:08:59 -0600, "Robert Swinney"
wrote:

Don sez:
I've heard that too. I've also heard that those green glass
insulators were fun to plink with a .22, plinking from fewer than 5
poles distant didn't count.

Errr, lessee. "Standard" pole spacing used on some RR's was 30 poles per
mile. 5/30 mile = 880 feet. That's a some fancy plinking alright!

'specially with .22 shorts. I used to save the lead while squirrel
hunting with .22 shorts by running down range and catching the slugs
in an old horsehide glove.
Gerry :-)}
London, Canada

On Fri, 25 Feb 2005 18:05:30 -0500, "Andrew V"
wrote:


"Andrew V" wrote in message
...
I've seen people reference a news group for radios and am wondering which
one (found many radio related newsgroups). My questions relate to
improving AM/FM reception in a valley area. I can get the stations on the
car radio but almost nothing in the house(wood frame). I have the standard
antennas hooked up and want to do some research before I find myself at
the mercy of the radio shack sales guy.

Thanks

Andrew V



For FM reception, try a dipole antenna made from 300 ohm twin lead.
Gerry :-)}
London, Canada

In article %WOTd.62179$wc.45982@trnddc07, Jerry Martes says...

Dont be confused by thinking that the car antenna is just a short
telescoping element. The telescoping (short) mast is actually a probe that
couples to the car itself. The car is the antenna. The coax feed line in
the car is only a necesary component for minimizing induced noise.

This is a new one on me - I thought they were verticals using the
car body as a ground plane.

How does this work?

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

"jim rozen" wrote in message
...
In article %WOTd.62179$wc.45982@trnddc07, Jerry Martes says...

Dont be confused by thinking that the car antenna is just a short
telescoping element. The telescoping (short) mast is actually a probe
that
couples to the car itself. The car is the antenna. The coax feed line in
the car is only a necesary component for minimizing induced noise.

This is a new one on me - I thought they were verticals using the
car body as a ground plane.

How does this work?

Jim

Jim

I dont know that viewing the telescoping element as the antenna and the
car body as the ground plane is wrong. But, at these wavelengths, it is
pretty difficult to identify what the antenna really is. Also, have you
noticed the car AM antennas that are imbeded in the windshield? Few cars
strive to keep the "aerials" vertical, but they all cars seem to work OK.
You can be pretty sure the AM signals are vertically polarized., so any
currents induced in a conductor will have resulted from their getting in the
way of a passing AM radio wave. Since there is more car than "car aerials"
it gets difficult to analyze just what is going on in a car radio antenna
for AM stations.

Jerry

Jim, you are correct. The antenna is the vertical element and the
vehicle is the ground plane. That is why the coax is grounded at both
ends and one small open area causes noise. Some of the new antennas are
hidden in the glass with the defroster, or just in the glass around the
edge. Then there are diversity antennas that have 4 antennas embedded in
the bumper covers or other plastic trim. Those are connected to a box
that senses the different signal levels and uses the strongest. Anyone
who thinks otherwise doesn't know how a radio signal functions.

--
Steve Williams

"jim rozen" wrote in message
...
In article %WOTd.62179$wc.45982@trnddc07, Jerry Martes says...

Dont be confused by thinking that the car antenna is just a short
telescoping element. The telescoping (short) mast is actually a
probe that
couples to the car itself. The car is the antenna. The coax feed
line in
the car is only a necesary component for minimizing induced noise.

This is a new one on me - I thought they were verticals using the
car body as a ground plane.

How does this work?

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================



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Gee Steve, thanks for setting me straight! I must be one of those that
thinks otherwise.

Bob Swinney
"Steve W." wrote in message
...
Jim, you are correct. The antenna is the vertical element and the
vehicle is the ground plane. That is why the coax is grounded at both
ends and one small open area causes noise. Some of the new antennas are
hidden in the glass with the defroster, or just in the glass around the
edge. Then there are diversity antennas that have 4 antennas embedded in
the bumper covers or other plastic trim. Those are connected to a box
that senses the different signal levels and uses the strongest. Anyone
who thinks otherwise doesn't know how a radio signal functions.

--
Steve Williams

"jim rozen" wrote in message
...
In article %WOTd.62179$wc.45982@trnddc07, Jerry Martes says...

Dont be confused by thinking that the car antenna is just a short
telescoping element. The telescoping (short) mast is actually a
probe that
couples to the car itself. The car is the antenna. The coax feed
line in
the car is only a necesary component for minimizing induced noise.

This is a new one on me - I thought they were verticals using the
car body as a ground plane.

How does this work?

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================



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Newsgroups
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=----

"Steve W." wrote in message
...
Jim, you are correct. The antenna is the vertical element and the
vehicle is the ground plane. That is why the coax is grounded at both
ends and one small open area causes noise. Some of the new antennas are
hidden in the glass with the defroster, or just in the glass around the
edge. Then there are diversity antennas that have 4 antennas embedded in
the bumper covers or other plastic trim. Those are connected to a box
that senses the different signal levels and uses the strongest. Anyone
who thinks otherwise doesn't know how a radio signal functions.

--
Steve Williams

Steve

I'm surprized that you state that anyome who doesnt accept that the car is
a ground plane doesnt know how radio signals function.. I assume that you
agree that the impinging radio signal is vertically polarized. I asume you
also are considering cars that are only about 1 or 2 electrical degrees
high. Can a conductor that small (short) be considered a "Ground Plane"??

I didnt realize that cars had been equipped with an AM antenna systems
that select one or more of several probes in the trim and/or bumpers. That
seems to be unnecessary complexity, but it must provide some improvement.
Where can I find more information on the car that has the 4 embeded
antennas?

Jerry

On Fri, 25 Feb 2005 19:00:04 -0500, Gerald Miller
wrote:

On Fri, 25 Feb 2005 09:08:59 -0600, "Robert Swinney"
wrote:

Don sez:
I've heard that too. I've also heard that those green glass
insulators were fun to plink with a .22, plinking from fewer than 5
poles distant didn't count.

Errr, lessee. "Standard" pole spacing used on some RR's was 30 poles per
mile. 5/30 mile = 880 feet. That's a some fancy plinking alright!

'specially with .22 shorts. I used to save the lead while squirrel
hunting with .22 shorts by running down range and catching the slugs
in an old horsehide glove.

Scoff thee on; .22 LR from a Mossberg bolt-action rifle is good
training. There is definitely a lot of drop in a .22 LR at range.
That's true of any round at range, just a matter of what range.
Wind and optical refraction from temperature gradients (same effect
as mirages on a hot highway) also contribute to the challenge.

One might go plinking with a 30.06 or 7.62 mm in Montana, but probably
not in Southern Michigan even in the '50's.

Practice makes a rifleman, not caliber or powder charge. A kid could
buy a lot of .22 LR ammo with paper route earnings back then.

"Jerry Martes" wrote in message
newsmTTd.47166$uc.41105@trnddc03...

"Steve W." wrote in message
...
Jim, you are correct. The antenna is the vertical element and the
vehicle is the ground plane. That is why the coax is grounded at
both
ends and one small open area causes noise. Some of the new antennas
are
hidden in the glass with the defroster, or just in the glass around
the
edge. Then there are diversity antennas that have 4 antennas
embedded in
the bumper covers or other plastic trim. Those are connected to a
box
that senses the different signal levels and uses the strongest.
Anyone
who thinks otherwise doesn't know how a radio signal functions.

--
Steve Williams

Steve

I'm surprized that you state that anyome who doesnt accept that the
car is
a ground plane doesnt know how radio signals function.. I assume
that you
agree that the impinging radio signal is vertically polarized. I
asume you
also are considering cars that are only about 1 or 2 electrical
degrees
high. Can a conductor that small (short) be considered a "Ground
Plane"??

I didnt realize that cars had been equipped with an AM antenna
systems
that select one or more of several probes in the trim and/or bumpers.
That
seems to be unnecessary complexity, but it must provide some
improvement.
Where can I find more information on the car that has the 4 embeded
antennas?

Jerry



Jerry,
The chassis of the vehicle is the ground plane of the antenna on every
vehicle I have ever seen. The vehicle height is not how the ground plane
is measured, it is measured by the amount of continuous connected
conductive surface area located around the antenna whip. That is also
why radio stations fade at different amounts based on which direction
the vehicle is headed. The different amount of ground plane relative to
the location of the whip on the vehicle changes the received signal
strength.

AM/FM broadcast signals are both vertically polarized. Have been for a
long time.

Lots of diversity equipped vehicles out there. Most of them are high end
luxury cars but there are a few pedestrian models as well. The town car
is one, Mercedes has a couple as well as BMW and Audi.

If you really want to see a strange antenna system take a look at the
ones used by XM and Sirius. Short vertical antenna to receive a circular
polarized signal that alters its angle of reflection as you move.



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In article , Don Foreman says...

On Fri, 25 Feb 2005 19:00:04 -0500, Gerald Miller
wrote:

On Fri, 25 Feb 2005 09:08:59 -0600, "Robert Swinney"
wrote:

Don sez:
I've heard that too. I've also heard that those green glass
insulators were fun to plink with a .22, plinking from fewer than 5
poles distant didn't count.

Errr, lessee. "Standard" pole spacing used on some RR's was 30 poles per
mile. 5/30 mile = 880 feet. That's a some fancy plinking alright!

'specially with .22 shorts. I used to save the lead while squirrel
hunting with .22 shorts by running down range and catching the slugs
in an old horsehide glove.

Scoff thee on; .22 LR from a Mossberg bolt-action rifle is good
training. There is definitely a lot of drop in a .22 LR at range.
That's true of any round at range, just a matter of what range.
Wind and optical refraction from temperature gradients (same effect
as mirages on a hot highway) also contribute to the challenge.

One might go plinking with a 30.06 or 7.62 mm in Montana, but probably
not in Southern Michigan even in the '50's.

Practice makes a rifleman, not caliber or powder charge. A kid could
buy a lot of .22 LR ammo with paper route earnings back then.

Hmm. 880 feet, that's about 300 yards.

22LR, with iron sights? One of those insulators probably
gives a four inch cross section, roughly.

This is outside my ability, at 46 years old. Maybe we
could get somebody else's opinion here....

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

"Steve W." wrote in message
...

"Jerry Martes" wrote in message
newsmTTd.47166$uc.41105@trnddc03...

"Steve W." wrote in message
...
Jim, you are correct. The antenna is the vertical element and the
vehicle is the ground plane. That is why the coax is grounded at
both
ends and one small open area causes noise. Some of the new antennas
are
hidden in the glass with the defroster, or just in the glass around
the
edge. Then there are diversity antennas that have 4 antennas
embedded in
the bumper covers or other plastic trim. Those are connected to a
box
that senses the different signal levels and uses the strongest.
Anyone
who thinks otherwise doesn't know how a radio signal functions.

--
Steve Williams

Steve

I'm surprized that you state that anyome who doesnt accept that the
car is
a ground plane doesnt know how radio signals function.. I assume
that you
agree that the impinging radio signal is vertically polarized. I
asume you
also are considering cars that are only about 1 or 2 electrical
degrees
high. Can a conductor that small (short) be considered a "Ground
Plane"??

I didnt realize that cars had been equipped with an AM antenna
systems
that select one or more of several probes in the trim and/or bumpers.
That
seems to be unnecessary complexity, but it must provide some
improvement.
Where can I find more information on the car that has the 4 embeded
antennas?

Jerry



Jerry,
The chassis of the vehicle is the ground plane of the antenna on every
vehicle I have ever seen. The vehicle height is not how the ground plane
is measured, it is measured by the amount of continuous connected
conductive surface area located around the antenna whip. That is also
why radio stations fade at different amounts based on which direction
the vehicle is headed. The different amount of ground plane relative to
the location of the whip on the vehicle changes the received signal
strength.

AM/FM broadcast signals are both vertically polarized. Have been for a
long time.

Lots of diversity equipped vehicles out there. Most of them are high end
luxury cars but there are a few pedestrian models as well. The town car
is one, Mercedes has a couple as well as BMW and Audi.

If you really want to see a strange antenna system take a look at the
ones used by XM and Sirius. Short vertical antenna to receive a circular
polarized signal that alters its angle of reflection as you move.



----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet
News==----
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Newsgroups
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=----

Steve

I used to think about antennas most of the working day. I still couldnt
refer to a car chassis as a "ground plane" for AM radio. It is just too
small. A car is in the vicinity of 1/100th of a wavelength. long, and half
that wide. That seems way too short to be worthy of being referred to as a
"ground plane", isnt it?.

There is alot of car information that has escaped my understanding. I
used to reserve the term "chassis" to describe the frame the cars body
bolted to. But, since that construction method isnt used much any more, I
guess you refer to the metal part of a car when you write "chassis".

You are apparently learning things I dont know about.
I thought we were considering AM radio for car antennas.
When did FM stations go to vertical polarization? I was thinking they
were circularly polarized.
On that "diversity equipped vehicle", do you suppose that diversity is
for satellite receiving antennas? I have problems with trying to imagine
how the radiation pattern at AM could be made directional, no matter where
it got "connected to" by the transmitter (or receiver). The car is just
too small in terms of wavelength to get directional.

You can feel free to use technical terms to tell me how the AM radio
signals are received by a car. There are alot of really well informed guys
on this news group. Even I thought I understood enough about car radio AM
antennas till you showed me that I dont to understand correctly.

Jerry

In article DmTTd.47166$uc.41105@trnddc03, Jerry Martes says...

I'm surprized that you state that anyome who doesnt accept that the car is
a ground plane doesnt know how radio signals function.. I assume that you
agree that the impinging radio signal is vertically polarized. I asume you
also are considering cars that are only about 1 or 2 electrical degrees
high. Can a conductor that small (short) be considered a "Ground Plane"??

I always figured that the polarization is pretty scrambled
by the time the car sees it. Other cars, phone and power wires
nearby, that sort of thing.

I remember making a 15 meter vertical antenna that was loaded
along its length and had a bunch of droopy ground radials. They
were supposed to be 1/4 L but they were shorter. The vertical
was helically wound on a stick with a short whip at the top.
That worked out pretty well.

I figure that the car radio manufacturers must load the input
circuit to get it near resonanace. There's no way that anything
car-sized is even going to come *close* to being a resonant
dipole at 1 mHz.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

On 26 Feb 2005 07:08:44 -0800, jim rozen
wrote:


Hmm. 880 feet, that's about 300 yards.

22LR, with iron sights? One of those insulators probably
gives a four inch cross section, roughly.

This is outside my ability, at 46 years old. Maybe we
could get somebody else's opinion here....

It was nowhere near 880 feet. Those are Swinney's poles!

On Sat, 26 Feb 2005 08:08:43 -0500, "Steve W."
wrote:


"Jerry Martes" wrote in message
newsmTTd.47166$uc.41105@trnddc03...

"Steve W." wrote in message
...
Jim, you are correct. The antenna is the vertical element and the
vehicle is the ground plane. That is why the coax is grounded at
both
ends and one small open area causes noise. Some of the new antennas
are
hidden in the glass with the defroster, or just in the glass around
the
edge. Then there are diversity antennas that have 4 antennas
embedded in
the bumper covers or other plastic trim. Those are connected to a
box
that senses the different signal levels and uses the strongest.
Anyone
who thinks otherwise doesn't know how a radio signal functions.

--
Steve Williams

Steve

The chassis of the vehicle is the ground plane of the antenna on every
vehicle I have ever seen. The vehicle height is not how the ground plane
is measured, it is measured by the amount of continuous connected
conductive surface area located around the antenna whip. That is also
why radio stations fade at different amounts based on which direction
the vehicle is headed. The different amount of ground plane relative to
the location of the whip on the vehicle changes the received signal
strength.

Semantics! The vertical whip is an E-field probe, the body of the
car is a capacitive counterpoise for it to work against. An antenna
is a two-terminal network.

Steve, if the car body were a ground plane, then a radio connected
with its antenna terminal to the body and grounded to good earth
ground would receive no signal. What do you think would really
happen?

"jim rozen" wrote in message
...
In article DmTTd.47166$uc.41105@trnddc03, Jerry Martes says...

I'm surprized that you state that anyome who doesnt accept that the car
is
a ground plane doesnt know how radio signals function.. I assume that
you
agree that the impinging radio signal is vertically polarized. I asume
you
also are considering cars that are only about 1 or 2 electrical degrees
high. Can a conductor that small (short) be considered a "Ground
Plane"??

I always figured that the polarization is pretty scrambled
by the time the car sees it. Other cars, phone and power wires
nearby, that sort of thing.

I remember making a 15 meter vertical antenna that was loaded
along its length and had a bunch of droopy ground radials. They
were supposed to be 1/4 L but they were shorter. The vertical
was helically wound on a stick with a short whip at the top.
That worked out pretty well.

I figure that the car radio manufacturers must load the input
circuit to get it near resonanace. There's no way that anything
car-sized is even going to come *close* to being a resonant
dipole at 1 mHz.

Jim

Jim

I'd bet that the guys who design AM antennas for cars dont think in terms
of making them resonant. They are just too small (short.). There is one
interesting design consideration that sometimes gets abused. It is the coax
lead that connects the "antenna' to the receiver. That feed line is seen by
the receiver as a capacitance that shunts the input terminals. And, since
the "antenna' looks like a highly capacitive load, the feed line capacitance
is shunting alot of signal from the receiver input. Some radio designers
used to provided a way to tune the combination of all the reactances for
each individual installations. I dont think thats done much any more.

I dont actually have any data on the polarization of AM (broadcast band)
radio waves. I do doubt that the horizontal component of any AM radio wave
can exist so close to the ground as where a car is.

Jerry

In article Om2Ud.13430$QQ3.9866@trnddc02, Jerry Martes says...

I dont actually have any data on the polarization of AM (broadcast band)
radio waves. I do doubt that the horizontal component of any AM radio wave
can exist so close to the ground as where a car is.

Oh, the idea that E(horizontal) must be zero at the boundary conditions, at
the earth's surface. That's got to be true to some large degree.

Jim


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In article , Don Foreman says...

Steve, if the car body were a ground plane, then a radio connected
with its antenna terminal to the body and grounded to good earth
ground would receive no signal.

I was the one who first brought the term 'ground plane'
into the discussion. Of course a better term is counterpoise.

As you say, it's a two terminal antenna with the whip being
one terminal, and a steel plate of some indeterminate size,
more or less perpendicular to the whip, as the other terminal.

Counterpoise, reflector, etc. are better terms.

The impedance between the vehicle chasssis and the ground
is obviously pretty large.

Jim


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In article , Don Foreman says...

On 26 Feb 2005 07:08:44 -0800, jim rozen
wrote:


Hmm. 880 feet, that's about 300 yards.

22LR, with iron sights? One of those insulators probably
gives a four inch cross section, roughly.

This is outside my ability, at 46 years old. Maybe we
could get somebody else's opinion here....

It was nowhere near 880 feet. Those are Swinney's poles!

Come to think of it, the antenna in question was an 80
meter dipole. It would have required two streches of
wire (three poles) and I think the formula is 246/f(mhz)
to give something like 82 feet. So the poles were a
*lot* closer together!

Five sounds better in that light.

Jim


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Nay! Damnspot! Those were railroad (actually Western Union) spaced poles,
30 to the mile.

Bob Swinney


"Don Foreman" wrote in message
...
On 26 Feb 2005 07:08:44 -0800, jim rozen
wrote:


Hmm. 880 feet, that's about 300 yards.

22LR, with iron sights? One of those insulators probably
gives a four inch cross section, roughly.

This is outside my ability, at 46 years old. Maybe we
could get somebody else's opinion here....

It was nowhere near 880 feet. Those are Swinney's poles!

On Sat, 26 Feb 2005 12:28:56 -0600, "Robert Swinney"
wrote:

Nay! Damnspot! Those were railroad (actually Western Union) spaced poles,
30 to the mile.

Don't doubt you, Bob. This was not your mainline railroad, who knows
whose poles they were. There were grade crossings where this RR
crossed a couple of roads, but definitely no gates and I don't even
recall there being lights. We called it the "tryweekly" RR. An
engine and a caboose would crawl down to Hillsdale one week, try to
get back the next. I never did see a real train on it.

"jim rozen" wrote in message
...
In article Om2Ud.13430$QQ3.9866@trnddc02, Jerry Martes says...

I dont actually have any data on the polarization of AM (broadcast
band)
radio waves. I do doubt that the horizontal component of any AM radio
wave
can exist so close to the ground as where a car is.

Oh, the idea that E(horizontal) must be zero at the boundary conditions,
at
the earth's surface. That's got to be true to some large degree.

Whoa. Check out the ARRL Antenna Handbook (if they still publish it; many
libraries have it). Or an old high school physics book.

AM waves, because of their frequency and not because of their modulation,
propagate mostly by ground wave, which follows the earth's surface, during
the daytime. Power = distance, because it's a nearly a straight
distance-squared (not distance-cubed) relationship. There is no skip. Unlike
VHF and above, the waves follow the curvature of the earth, "clinging" close
to the ground.

At night, the ground wave shrinks to very short distances, and, given the
right conditions, classical ionospheric skip takes over. This is
low-ionosphere skip; it requires multiple hops to go long distances. But the
high-power, clear-channel stations can make multiple skips.

I didn't read the earlier posts to this thread so I apologize if I'm
repeating something that's been said.

--
Ed Huntress

"Jerry Martes" wrote in message
news:Om2Ud.13430$QQ3.9866@trnddc02...

"jim rozen" wrote in message
...
In article DmTTd.47166$uc.41105@trnddc03, Jerry Martes says...

I'm surprized that you state that anyome who doesnt accept that the car
is
a ground plane doesnt know how radio signals function.. I assume that
you
agree that the impinging radio signal is vertically polarized. I asume
you
also are considering cars that are only about 1 or 2 electrical degrees
high. Can a conductor that small (short) be considered a "Ground
Plane"??

I always figured that the polarization is pretty scrambled
by the time the car sees it. Other cars, phone and power wires
nearby, that sort of thing.

I remember making a 15 meter vertical antenna that was loaded
along its length and had a bunch of droopy ground radials. They
were supposed to be 1/4 L but they were shorter. The vertical
was helically wound on a stick with a short whip at the top.
That worked out pretty well.

I figure that the car radio manufacturers must load the input
circuit to get it near resonanace. There's no way that anything
car-sized is even going to come *close* to being a resonant
dipole at 1 mHz.

Jim

Jim

I'd bet that the guys who design AM antennas for cars dont think in terms
of making them resonant. They are just too small (short.). There is
one interesting design consideration that sometimes gets abused. It is
the coax lead that connects the "antenna' to the receiver. That feed line
is seen by the receiver as a capacitance that shunts the input terminals.
And, since the "antenna' looks like a highly capacitive load, the feed
line capacitance is shunting alot of signal from the receiver input. Some
radio designers used to provided a way to tune the combination of all the
reactances for each individual installations. I dont think thats done
much any more.

I dont actually have any data on the polarization of AM (broadcast band)
radio waves. I do doubt that the horizontal component of any AM radio
wave can exist so close to the ground as where a car is.

Jerry

From Terman:

"Practical Receiving Antennas -- The main considerations involved in
receiving antennas are the amount of energy that can be be delivered to the
receiver, the directivity, the cost and the freedom from extraneous
disturbances.

A receiving antenna should abstract sufficient energy from passing waves so
that even the energy abstracted from the weak radio waves representing
static and other noises will under normal conditions be at least comparable
with the thermal-agitation energy existing in the input of the receiver.
The signal-to-noise ratio cannot then be improved by further increase in
received energy, and no further improvement is possible in the antenna
system as far as energy pick-up is concerned. The amount of energy that can
be abstracted by an antenna depends upon its physical size, the frequency,
and the loss resistance. The abstracted energy tends to decrease with
increased frequency, particulary when the antenna dimensions do not exceed a
quarter of a wave length. As a result, the problem of obtaining adequate
energy pick-up is most imprortant at high and ultra-high frequencies.

When it is desired to avoid marked directional effects at broadcast and
lower requenmcies, it is customary to employ a single wire running to a
height of 15 to 50 feet. With such an antenna the horizontal portions are
relatively unimportant because waves of broadcast and lower frequencies are
vertically polarized when near the earth.

Automobile Antennas -- A great variety of antenna arrangements are used in
automobile receivers. Perhaps the most effective is a vertical whip,
connected to the receiver by means of a transmission line. Other
arrangements that are employed include plates mounted below the running
board and insulated from the body of the car, and a plate connected in the
top. This latter arrangenment is suitable only for cars in which the top is
not all metal."

Terman's comments reflect the general premise of most of the foregoing
thread. That is: Broadcast antennas are best when they are composed of a
wire vertically mounted. Horizontal sections of the wire do not appreciably
add to the amount of energy abstracted because broadcast signals are
vertically polarized. Terman's comments re. placement of antennas in
different locations within the automobile do, in some measure, substantiate
other posters' claims concerning diversity. I can't say for certain that
diversity antennas aren't used for broadcast reception, although I doubt it.
In recent practical experience, "diversity" is only seen in UHF practice,
particularly in frequencies above 1000 mHz. An antenna system can employ
both space diversity and frequency diversity. Both have long been in use at
microwave frequencies. Sectorization and tilt as commonly employed in
cellular practice are not included in the definition of diversity. As I see
it, presently evolving "smart" antennas utilize the diversity concept
whereby individual elements of the same antenna are diversely managed.
Smart antenna design is a cut-throat business. A company I worked for had a
PHD vice president heading up a large department engaged in smart antenna
design. He squandered vast amounts of company funds, never got an antenna
design past the FCC as far as I know, and was eventually fired.

Bob Swinney

Robert Swinney wrote:

Terman's comments reflect the general premise of most of the foregoing
thread. That is: Broadcast antennas are best when they are composed of a
wire vertically mounted.


The question (or statement) as I understood it from the OP, was that if
you didn't consider the body of the car a "ground plane" (presumably at
MF frequencies) you don't know how radio signals function. I guess I
have to be among the unknowing, which is a shame since I've been
spec'ing and measuring antennas for ground vehicle and aircraft
applications for too many years.


I can't say for certain that
diversity antennas aren't used for broadcast reception, although I doubt it.

Space diversity FM broadcast antenna systems are fairly common in autos
to reduce the effects of multipath. These are generally pretty simple
systems with two antennas, with the receiver being switched to whichever
antenna has the strongest signal. The first factory supplied system that
I heard of was the Saab, about 8 or 10 years ago.

Do you miss the fun at the antenna factory?

Kevin Gallimore

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"axolotl" wrote in message
...
Robert Swinney wrote:

Terman's comments reflect the general premise of most of the foregoing
thread. That is: Broadcast antennas are best when they are composed of
a wire vertically mounted.


The question (or statement) as I understood it from the OP, was that if
you didn't consider the body of the car a "ground plane" (presumably at MF
frequencies) you don't know how radio signals function. I guess I have to
be among the unknowing, which is a shame since I've been spec'ing and
measuring antennas for ground vehicle and aircraft applications for too
many years.


I can't say for certain that
diversity antennas aren't used for broadcast reception, although I doubt
it.

Space diversity FM broadcast antenna systems are fairly common in autos to
reduce the effects of multipath. These are generally pretty simple systems
with two antennas, with the receiver being switched to whichever antenna
has the strongest signal. The first factory supplied system that I heard
of was the Saab, about 8 or 10 years ago.

Do you miss the fun at the antenna factory?

Kevin Gallimore

Kevin

You probably got a mixture of messages while reading these posts. But, I
would put myself amoungst thoes who wouldnt find value in using the term
"ground plane" when working with a conductor thats shorter than a few
electrical degrees at the frequency of interest.
I would not (hopefully ever) write that "someone doesnt understand how
radio waves work".
I expect to benefit from any experience others might have for getting the
maximum peerformance from short AM and FM antennas.

My news group provider shows thr OP to be Andrew V, who wants to provide
his home with adequet RF into his radios on both AM and FM. I jumped in
with some advice that doesnt seem to be acceptable to all readers. It is
my assumption that all the information submitted so far by me is absolutely
correct. But, I have no quarrel with anyone who wants to theorize that a
1/100th wave long conductor is a "ground plane". That terminology just
doesnt fit with my knowledge.

What would you consider the minimum length of a conductor that fits the
definition of "ground plane"?

Jerry

"Jerry Martes" wrote in message
news:wY5Ud.56428$uc.36861@trnddc04...

What would you consider the minimum length of a conductor that fits the
definition of "ground plane"?

Jerry, unless the terminology has changed in recent years, the term ground
plane refers to an artificial, highly conducting ground, not to the
radiator. Typical ground planes are crossed or radially displaced
conductors, wire meshes, or metal sheets that lie in a horizontal plane and
are grounded as effectively as conditions permit. If the grounding is very
effective, the ground plane doesn't radiate at all. That's the condition
that's usually desired.

As for the radiator, it can be any length. But the usual purpose is to have
effective radiation perpendicular to the radiator (vertical radiator;
horizontal radiation, with a single lobe pointing just slightly upwards,
shaped like a donut cut off just below its greatest periphery). At
frequencies up to the edge of UHF, that usually dictates a quarter-wave
radiator.

Is this what you're talking about, or am I on the wrong page here?

--
Ed Huntress

I believe the idea was that the size of a car top was not nearly large
enough to serve as a good ground plane, esp. for AM broadcast freqs.

Sorry, as for my comment re. broadcast space diversity, I meant AM. I'm not
surprised that space diversity is used for FM broadcast, although, I doubt
very much if the improvement in reception is commensurate with the increased
cost.

No, I don't miss the fun. I didn't work at an antenna factory, per se. My
primary responsibility was getting amplifier products type accepted by the
FCC. The antenna guys would borrow my FCC regs - and then come back and ask
me how to proceed.

Bob Swinney
"axolotl" wrote in message
...
Robert Swinney wrote:

Terman's comments reflect the general premise of most of the foregoing
thread. That is: Broadcast antennas are best when they are composed of
a wire vertically mounted.


The question (or statement) as I understood it from the OP, was that if
you didn't consider the body of the car a "ground plane" (presumably at MF
frequencies) you don't know how radio signals function. I guess I have to
be among the unknowing, which is a shame since I've been spec'ing and
measuring antennas for ground vehicle and aircraft applications for too
many years.


I can't say for certain that
diversity antennas aren't used for broadcast reception, although I doubt
it.

Space diversity FM broadcast antenna systems are fairly common in autos to
reduce the effects of multipath. These are generally pretty simple systems
with two antennas, with the receiver being switched to whichever antenna
has the strongest signal. The first factory supplied system that I heard
of was the Saab, about 8 or 10 years ago.

Do you miss the fun at the antenna factory?

Kevin Gallimore

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Jerry Martes wrote:


You probably got a mixture of messages while reading these posts.

Yes, I should should identify the OP by other than "OP". As far as I can
tell from the thread path the original statement was by a "Steve W." I
am agreeing with you, although I am doing a lousy job of it.

But, I have no quarrel with anyone who wants to theorize that a
1/100th wave long conductor is a "ground plane". That terminology just
doesnt fit with my knowledge.

Or mine.

What would you consider the minimum length of a conductor that fits the
definition of "ground plane"?

To me, a "ground plane" is a mythical beast. I usually don't run into
structures performing as a perfect counterpoise.

And I may have screwed up further by asking Bob if he missed the antenna
factory; Bob has worked for Andrew, and his adaptive antenna story is
one I've seen duplicated in other places. I'm guessing from your other
posts that you may have worked for a manufacturer too. If you've
designed anything painted green, I have probably had them bolted on to
something.

My apologies if I somehow gave the impression that you didn't know the
subject at hand.

Kevin Gallimore







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Ed,
You're on it like a cheap suit! A ground plane must have an area at least
1/4 lambda ^2 to be effective. The top of a car doesn't have sufficient
area to work as ground plane at broadcast freqs. Essentially, ground plane
radials provide an artificial ground that is elevated to the effective
height of the antenna wherever it is above earth. It is generally
understood when we speak of "ground plane" re. communications antennas we
are referring to 50 ohm antennas.

Bob Swinney
"Ed Huntress" wrote in message
...
"Jerry Martes" wrote in message
news:wY5Ud.56428$uc.36861@trnddc04...

What would you consider the minimum length of a conductor that fits the
definition of "ground plane"?

Jerry, unless the terminology has changed in recent years, the term ground
plane refers to an artificial, highly conducting ground, not to the
radiator. Typical ground planes are crossed or radially displaced
conductors, wire meshes, or metal sheets that lie in a horizontal plane
and
are grounded as effectively as conditions permit. If the grounding is very
effective, the ground plane doesn't radiate at all. That's the condition
that's usually desired.

As for the radiator, it can be any length. But the usual purpose is to
have
effective radiation perpendicular to the radiator (vertical radiator;
horizontal radiation, with a single lobe pointing just slightly upwards,
shaped like a donut cut off just below its greatest periphery). At
frequencies up to the edge of UHF, that usually dictates a quarter-wave
radiator.

Is this what you're talking about, or am I on the wrong page here?

--
Ed Huntress

"Robert Swinney" wrote in message
...
Ed,
You're on it like a cheap suit! A ground plane must have an area at least
1/4 lambda ^2 to be effective. The top of a car doesn't have sufficient
area to work as ground plane at broadcast freqs.

Yeah, it would take one hell of a car. And an effective radiator would be
tall enough to wipe out the power lines wherever you drove, while the ground
plane would wipe out the utility poles on both sides of the road. g

Essentially, ground plane
radials provide an artificial ground that is elevated to the effective
height of the antenna wherever it is above earth. It is generally
understood when we speak of "ground plane" re. communications antennas we
are referring to 50 ohm antennas.

Thanks, Bob. It's good to hear that antenna theory didn't invert itself
since I studied for my 1st Class Phone license.

I'm not following this thread very closely but it sounds to me that some
people are mixing up transmitting-antenna theory with receiving-antenna
theory. A car antenna is just a conductor stuck up there to suck up as much
electromagnetic radiation as possible. Some of them are loaded at the base,
but I always assumed that was for FM. 'Don't know for sure.

--
Ed Huntress

"Ed Huntress" wrote in message
...
"Robert Swinney" wrote in message
...
Ed,
You're on it like a cheap suit! A ground plane must have an area at
least
1/4 lambda ^2 to be effective. The top of a car doesn't have sufficient
area to work as ground plane at broadcast freqs.

Yeah, it would take one hell of a car. And an effective radiator would be
tall enough to wipe out the power lines wherever you drove, while the
ground
plane would wipe out the utility poles on both sides of the road. g

Essentially, ground plane
radials provide an artificial ground that is elevated to the effective
height of the antenna wherever it is above earth. It is generally
understood when we speak of "ground plane" re. communications antennas we
are referring to 50 ohm antennas.

Thanks, Bob. It's good to hear that antenna theory didn't invert itself
since I studied for my 1st Class Phone license.

I'm not following this thread very closely but it sounds to me that some
people are mixing up transmitting-antenna theory with receiving-antenna
theory. A car antenna is just a conductor stuck up there to suck up as
much
electromagnetic radiation as possible. Some of them are loaded at the
base,
but I always assumed that was for FM. 'Don't know for sure.

--
Ed Huntress

Ed

How does transmitting-antenna theory differ from receiving-antenna theory?

Jerry

In article , Robert Swinney says...

Ed,
You're on it like a cheap suit! A ground plane must have an area at least
1/4 lambda ^2 to be effective.

Umm. It won't be a resonant antenna. But the car's body
will improve the signal seen at the input to the radio.

It doesn't *have* to be a resonant system for the antenna
to work.

Jim


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On Sat, 26 Feb 2005 17:33:20 -0500, "Ed Huntress"

wrote:

If I understand it correctly, (which I doubt ), since the car doesn't
act as the ground plane, the ground must. If this so, how come a car
radio that worked very well at recieving faint stations, hardly picks
up anything when I tried to use on the bench with a regular car
antenna? The antenna was connected properly, with the cable plugged
into the radio and the antenna mounting screw connected to the ground
screw on the radio.
Thanks,
Eric

"Robert Swinney" wrote in message
...
Ed,
You're on it like a cheap suit! A ground plane must have an area at least
1/4 lambda ^2 to be effective. The top of a car doesn't have sufficient
area to work as ground plane at broadcast freqs.

Yeah, it would take one hell of a car. And an effective radiator would be
tall enough to wipe out the power lines wherever you drove, while the ground
plane would wipe out the utility poles on both sides of the road. g

Essentially, ground plane
radials provide an artificial ground that is elevated to the effective
height of the antenna wherever it is above earth. It is generally
understood when we speak of "ground plane" re. communications antennas we
are referring to 50 ohm antennas.

Thanks, Bob. It's good to hear that antenna theory didn't invert itself
since I studied for my 1st Class Phone license.

I'm not following this thread very closely but it sounds to me that some
people are mixing up transmitting-antenna theory with receiving-antenna
theory. A car antenna is just a conductor stuck up there to suck up as much
electromagnetic radiation as possible. Some of them are loaded at the base,
but I always assumed that was for FM. 'Don't know for sure.

"Eric R Snow" wrote in message
...
On Sat, 26 Feb 2005 17:33:20 -0500, "Ed Huntress"

wrote:

If I understand it correctly, (which I doubt ), since the car doesn't
act as the ground plane, the ground must. If this so, how come a car
radio that worked very well at recieving faint stations, hardly picks
up anything when I tried to use on the bench with a regular car
antenna? The antenna was connected properly, with the cable plugged
into the radio and the antenna mounting screw connected to the ground
screw on the radio.
Thanks,
Eric


Eric

I'd submit that your experience with transferring the car's "antenna" to
the bench (without the car) gives credence to my theory that the car is the
antenna, and what we call a car antenna is a probe that senses the currents
induced in the car by the radio wave as it passes (at AM frequencies).

Jerry

In article wY5Ud.56428$uc.36861@trnddc04, Jerry Martes says...


You probably got a mixture of messages while reading these posts. But, I
would put myself amoungst thoes who wouldnt find value in using the term
"ground plane" when working with a conductor thats shorter than a few
electrical degrees at the frequency of interest.

It's a semanitic issue, I know. For the sake of argument, one
could say that the body of a car is the 'other part of a non-resonant
dipole antenna.'

Because it's a mostly flat part and mostly planar in shape, the
temptation to call it a ground plane is obvious.

If it were a 2 meter whip antanna stuck on the roof of the car,
it would be a very good description. For 1 MHz radiation the description
does leave a bit to be desired as you say.

Circuit board designers call the continuous conductor on their
board a "ground plane" even though that could be a few inches
square.

Obviously it would look silly stuck at the end of even a 2-meter
quarter wave vertical.

For me the term "ground plane" does not have to have any
particular wavelength of interest to be applied. I like the
term 'ground plane' even for a car body, for 1 MHz am because
it's descriptive of the *shape* of the conductor more than
anything else. That, and the input coil of the receiver is
stuck across that coax feedline, and the shield of the coax
is bonded in most cases to the chassis of the radio, and to
the car body at the other end.

The idea being that there is some rf voltage developed between
the bottom of the vertical and the body of the car, by virtue
of it (the vertical) being immersed in the local rf field.

This voltage is larger than the voltage that would be there, if the
car body were absent; that is if the coax shield simply stopped and
the whip were tagged on the end, out in the middle of nowhere.

Granted not a lot bigger, about a factor of two or three
probably. Remember that while the car is sitting on top
of rubber tires, there's a large capacitence between the car
body, and the actual ground. Consider that if there is
only 0.1 mfd between the car body and ground, that is one
ohm at a MHz.

Jim


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