Auto Antenna

:I have a new Lexus 400h and live a distance away from the FM stations I like :to listen to. Reception is very poor very dependent on direction of vehicle. :I blame the window antenna. Would I be better off with a whip antenna? : :Paul :

Not necessarily. Will depend on transmitted FM power, distance from Tx, and intervening terrain between Tx and Rx antenna.

How far is "quite a distance"?

By design FM transmitters are not designed to go very far. Antenna will not help.

ONLY AM, SHORTWAVE, SSB, and MICROWAVE. The 2 Meter can go far because of the repeater station, but that's a different story.

Yak...

Probably, but you may also have a defective radio. If an FM radio loses one or two transistors, often the only symptom is a loss of sensitivity. Compare to another car radio in the same location tuned to the same stations.

How far away are your stations? FM signals travel in straight line-of-sight paths -- there is no ground wave as with AM, nor ionospheric reflection. 50 miles is about the limit.

It's not the way the transmitters are designed, it is the behavior of the earth and its atmosphere at those frequencies. The transmitters are actually very powerful.

For broadcasting, limited, predictable range is a good thing because it allows another station to be on the same frequency 100 or 150 miles away without interfering with it.

Microwaves are even worse -- they travel only in a straight line -- which is why microwave towers are tall and have antennas aimed directly at each other. But in that situation the transmitters don't have to be very powerful.

Although I'm not suggesting you cut holes in your new Lexus, when windshield antennas first came out in the 70's, I made a good bit of money replacing them with whips. They may have improved since, but back then, there was always a significant improvement in reception.

Comments in the thread about checking the existing antenna is well-advised, however.

jak

Yes. But a fixed roof mounted one is the ideal - uses the roof as a ground plane.

--
*Why is the third hand on the watch called a second hand?

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

Jak, I did have Lexus check out the system and they claim it is "working as designed". Since a whip is omnidirectional and the windshield antenna is directional at least car direction would not cause reception problems. From your experience it would seem that the gain of the whip is as good or better than the windshield type. Would you agree with that?

Paul

Whips are omni but are rarely placed on an unobstructed surface. Verticals have more noise than a horzontal. Vertical placed in the center of the roof would be best, about

29 inches long.

greg

Total BS.

Please disregard this guy.

If your logic is true then why FM cannot defeat other modulation? Assuming they all have equal RF wattages?

FYI - You preaching to the guy who built Powerful RF transmitters, minimum

5Kw.

You're not expressing yourself very clearly. "FM" is both a modulation technique and (in much of the world) a broadcast frequency band. Propagation is largely a matter of frequency. It is true that FM does not perform as well with weak signals as AM, which in turn is not as good as SSB.

Note that you could experiment with a vertical antenna without drilling into the car. Get a magnet-mount ham radio antenna and change the whip so it is

30 inches long. Of course, you will still have to gain access to the antenna connector on the radio -- which is probably not hard; most newer car radios pull out forward if you use the appropriate special tools to unlock them.

Idiot. It's obvious that you have never worked in broadcast. C-band TV transponders are about 10 watts at 4 GHz, and the 20 MHz wide FM signal travels over 11,000 miles from the bird to the receiving antenna.

A local UHF station's tower is in Orange City, Florida. We received a reception report from the Dallas / Ft. Worth area from a man who watched our station for over six hours one evening.

I know that this isn't normal reception, and was at a time of high sunspot activity, but the point is that you can't make blank, meaningless statements like: "By design FM transmitters are not designed to go very far."

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

What the hell is "FM cannot defeat other modulation" supposed to mean? Do you have ANY idea about capture effect, quieting, receiver desensing, or other real world problems that affect clear reception on a car radio? A local TV station on Channel six can desese the low end of the FM band. Other high level noise sources can wipe out most, or all of the FM band.

You think 5 KW is powerful? You say absolutely NOTHING about the application, the tower height, antenna type, feedline loss, or a hundred other details. Try building a 5 MW EIRP UHF TV station with a 1749 foot AAT antenna. Or even a 1.3 MW EIRP UHF TV station on a 300 ft tower.

BTW, that 1749 foot AAT TV tower also had five of the Orlando FM stations at the site, fed to a curtain antenna at 1200 feet AAT. The combiner had three more ports for either standby transmitters, or to add more stations.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

All of you missed the point. Just buy an American car. One of the best things we can do to help our economy & our country. And if you are going to tell me that many American cars are built in another country, you don't understand the bigger picture of the economics.