OT improving radio reception

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

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On Thu, 24 Feb 2005 01:48:01 GMT, "Jerry Martes"

I suspect Jerry may be someone yall want to listen to.
Gunner
Rule #35 "That which does not kill you, has made a huge tactical error"
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wrote:

Roger that!
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wrote:

Thanks for the vote of confidence. But, I actually dont know how much improvement the CCCrane add on antenna provides. That might be a 'fix' for the Andrew V's poor reception. I understand their advertisement for their $100.00 Twin ferrite antenna indicates that it will double the reception. I would think doubling the output would be about 3 db. I didnt realize a 3 db gain antenna would be something that would be worth $100.00. I'd like to hear from someone who has tried the CCCrane AM antenna.
Jerry
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The CC Crane is a ferrite antenna and RF amplifier. It requires a 9-volt battery and claims 32 dB of gain. The primary value of (low noise) gain is to overcome noise and lack of gain in a mediocre receiver -- so the worse the receiver the more it helps.
Being ferrite, it is probably an H-field antenna which would exhibit some directionality. That's good: helps prefer a given signal over external atmospheric and galactic noise.
Once an antenna captures enough signal + external noise to provide signal significantly greater than the receiver's (or amplifier's) internal noise, more antenna doesn't help until it is large enough to have significant directional gain. At broadcast band, that's hundreds of feet.
Making a low-noise broadcast band RF amp is simple, but probably more than $100 worth of screwing around unless one enjoys building elex.
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wrote:

Roger on Don's Roger.
Bob Swinney
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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

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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

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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
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Jerry Martes says...

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
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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" <jim snipped-for-privacy@newsguy.com> wrote in message
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Gee Steve, thanks for setting me straight! I must be one of those that thinks otherwise.
Bob Swinney
Jerry Martes says...

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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
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both
are
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Plane"??
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That
improvement.
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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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
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wrote:

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?
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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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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
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Jerry Martes says...

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
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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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