OT improving radio reception

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

Reply to
Don Foreman

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

Reply to
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

Reply to
Andrew V

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.

Reply to
Don Foreman

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

Reply to
Jerry Martes

'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

Reply to
Gerald Miller

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

Reply to
Gerald Miller

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

Reply to
jim rozen

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

Reply to
Jerry Martes

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.

Reply to
Steve W.

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

Reply to
Robert Swinney

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

Reply to
Jerry Martes

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.

Reply to
Don Foreman

embedded in

degrees

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.

Reply to
Steve W.

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

Reply to
jim rozen

Reply to
Jerry Martes

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

Reply to
jim rozen

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

Reply to
Don Foreman

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?

Reply to
Don Foreman

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