2 Antenna Questions

[Nuckman]

1) Why do NASCAR radios use short stubby antennas?

2) I bought a mobile scanner antenna (for the car) to put outside my basement in hopes of better reception with my portable indoors. I get nothing. Shouldn't I be getting much BETTER reception?

Thank you!

 

[ka3jjz]

1) Likely as not the stubby antennas are meant to restrict the distance from which they can be heard..

2) You didn't say anything here about how you are using the mobile antenna. Most antennas that use a mag mounting need some sort of metallic (ferrous, preferably) surface to couple to in order to create a ground plane against which the antenna works. And putting the antenna in a much lower area (a basement) with who knows how many obstacles around it would make it perform much poorer than on a car, slightly elevated and somewhat away from obstacles. Height matters! Try putting your mobile antenna on a ferrous surface in a higher environment - say a 2nd floor window - and I'm sure you'll notice an improvement.

You also didn't mention anything about the frequency range to which you were listening. A good rule of thumb is that the higher the frequency the more sensitive it becomes to obstacles that might block reception - and dry ground is a decent insulator at 800 mhz......

best regards...Mike

 

[W2PMX]

Range on most frequencies you'll be listening to depends, in part, on height above local ground (IOW, distance to the antenna's "horizon"). Outside your basement - on the ground - the antenna's horizon is a few dozen feet or so. *From 150MHz and up, most signals travel in straight lines, so if your antenna can't "see" the transmitting antenna, you'll get a very weak signal at best.)

The ground plane, if the antenna is on a decent ground (not all places "on the ground" are good grounds) you don't need a metallic ground plane. If you do need one, silver is best, copper next, etc. (The more electrically conductive the better.) Ferrous metal (basically iron) is a poor substitute for copper, but on a car it's usually the only choice you have.

As far as stubby antennas:

1) Shorter range.
2) More convenient if you're moving a lot. (You don't stab yourself in the ribs with the end of the antenna,)
3) People who are "radio-illiterate" think they "look better", or that they're supposed to use them, or some other reason that's a few light years removed from reality.

 

[Nuckman]

Ok... so my regualar sized antenna will work at NASCAR if I'm okay getting poked in the ribs. Cool. Thank you!

So... I understand the mobile antenna in the basement and line of sight, etc, but why would the portable work so well with the antenna it has, but plugging in the bigger antenna in the same spot gets nothing -- and it's bigger! I'll take it outside to experiment.

Thanks for the responses!

 

[W2NJS]

Your "long" UHF antenna should be about six inches. The stubby antenna is also six inches long underneath the covering, give or take a bit, but it's been coiled so that it's much shorter. As a result it won't work quite as well on both receive (and transmit) as the longer antenna, but at a track, hamfest, up and down your street, etc. it will work just as well as the long one. It's only when you get out to greater distances that the longer antenna has a real advantage, although it really pays to use the long antenna in all situations as much as you can because it's just more efficient than the stubby.

 

[KC0CSE]

460 meg uhf 6 inches......

 

[W2PMX]

why would the portable work so well with the antenna it has, but plugging in the bigger antenna in the same spot gets nothing -- and it's bigger!

With antennas bigger doesn't mean better. If the antenna isn't tuned to the frequency you're receiving it's worse. Many "scanner antennas" are just wires with dodads - pieces of plastic, coils, etc., that make them look "technical", but electronically they're just untuned wires. The antenna that comes with the scanner is usually tuned to the frequencies the scanner covers. Not very efficient, but better than a random length of wire. And if the mobile antenna is designed to work against a ground, sitting on a wood table or a basement floor almost guarantees that it won't work better than a wet piece of rope.