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Discussion in 'Electronic Repair' started by Paul Del Priore, Feb 4, 2008.

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  1. 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
     
  2. Ross Herbert

    Ross Herbert Guest

    :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"?
     
  3. Jakthehammer

    Jakthehammer Guest

    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...
     
  4. mc

    mc Guest

    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.
     
  5. mc

    mc Guest

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

    jakdedert Guest

    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
     
  7. Yes. But a fixed roof mounted one is the ideal - uses the roof as a ground
    plane.
     
  8. 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
     
  9. GregS

    GregS Guest


    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
     
  10. Don Bowey

    Don Bowey Guest

    Total BS.

    Please disregard this guy.
     
  11. Jakthehammer

    Jakthehammer Guest


    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.
     
  12. mc

    mc Guest

    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.
     
  13. mc

    mc Guest

    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.
     

  14. 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
     

  15. 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
     
  16. Bob

    Bob Guest

    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.
     
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