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Antenna booster for AM reception

Discussion in 'Electronic Design' started by lytecap, Feb 27, 2008.

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  1. lytecap

    lytecap Guest

    My dad has a radio that has terrible AM reception and I saw that there
    are something called Antenna Booster that you have to build/solder etc
    -
    If this is true, a couple of questions please:
    1) Does it really work? Does it boost the reception?
    2) Are there ones that are already built?
    3) If I have to build it, is it advanced or simple?

    Thanks in advance,
     
  2. Robert Baer

    Robert Baer Guest

    Back in the good old dayz of tubes, some of the radios had a built-in
    antenna booster to be used when needed.
    There are a few ways to do this; make a "large" loop of many turns of
    wire (usually a flat loop geometrically wound like a spiral and large
    unused center).
    One side goes to ground of radio signal input.
    Usually a low-Z tap from the loop connects to the radio antenna,
    sometimes witha small trimmer cap (5pF-25pF).
    Some variations use a tuning cap across the loop.
    Orient the loop for best reception.
    Other variants use a long outdoor antenna coupled to the loop with
    the tuning cap.
     
  3. mpm

    mpm Guest

    What city & state are you in?
    What is the AM Station call sign you are trying to receive?
     
  4. Mike

    Mike Guest

    1 - Yes they can work very well
    2 - Yes, See http://www.ramseyelectronics.com/cgi-bin/commerce.exe?preadd=action&key=SM100
    It is pretty expensive, but is available built and tested. I'm sure there are others.
    I built my own similar to this one and it works very well.
    3 - Advanced/Simple depends on your perspective, but if you can solder & read you can probably buid a kit.

    Mike


    "In view of such harmony in the cosmos which I,
    with my limited human mind, am able to recognize,
    there are yet people who say there is no God.
    But what really makes me angry is that they quote
    me for the support of such views."
    Albert Einstein (theoretical Physicist)
     
  5. lytecap

    lytecap Guest

    I was looking at some that are ready built, but I guess they just
    boost the level of sound, not the signal. So I will have to re-
    request what I am looking for - I live in Canada and my dad listens to
    CFRB 1010 (out of Toronto, Ontario Canada) on AM all the time. He
    stopped listening to it because it was so staticky. He uses a normal
    Cdn Tire radio, so I thought I would boost the signal for a birthday
    present....
     
  6. Tom Bruhns

    Tom Bruhns Guest

    What is your budget for this?

    A really good thing to do before leaping to conclusions is to spend a
    little time understanding WHY the problem exists. (This advice
    extends beyond static on AM radios...) Is the static caused by some
    local noise-generating device(s)? Is it caused by thunderstorms? Can
    you characterize the noise better: is it impulsive, or just random
    "white" noise? Is it synchronized with the power lines, or not? Is
    the signal basically strong, but the noise overpowering it, or is the
    signal very weak and it's not taking much noise to overpower it?
    Finding an optimal solution depends, I think, on a good understanding
    the nature of the problem. From your posting, I don't have the
    feeling you're at that point yet.

    Also, what do you have to work with? Does the radio in question have
    an external antenna input, or does it rely totally on the built-in
    antenna? Is it feasible to replace the radio itself? What are your
    constraints involving installing an external antenna? (Can it go
    outside up in trees, or will it be limited to being next to the radio
    itself--in which case there may be no significant advantage to an
    external antenna...?) Have you tried the radio in different locations
    and different orientations? (The built in antenna is undoubtedly
    directional, with a couple deep nulls; bad news if the station you
    want is in a null!) I notice that CFRB apparently has streaming audio
    on the internet (it doesn't seem to be making it through our firewall
    at the moment...); is that a possible way to deliver the signal to
    your dad? Can you think of other possible solutions to the basic
    problem of letting your dad listen to the audio he wants?

    Cheers,
    Tom
     
  7. lytecap

    lytecap Guest

    I would like to spend around $20-$40. He likes that radio where it
    is, tucked away in a corner. He is set in his ways and won't use the
    internet or move the radio...the noise is an overpowering static and
    in and out (you know when someone walks by). You can hear the voices,
    but the static and white noise is so annoying it wouldn't be worth
    it. I don't know what is causing the static - other AM stations are
    fine and the FM is good (just tested it). He uses a speaker wire
    antennae that came with it attached to the unit.
    If buying a better radio would help, I would gladly do that. I didnt
    realise the scope and complexity of getting a radio station, so I
    thought a booster would just do the trick.
     
  8. Rich Grise

    Rich Grise Guest

    Here's something you can try. Get a spool of hook-up wire in some
    inconspicuous color. Strip the insulation off one end, and use the
    screw in the nearest electric outlet to ground that end. Wrap 5 or 10
    turns of wire around the radio itself, as if you're making an
    electromagnet. Orient this winding so that it makes a transformer primary
    with the loopstick in the radio as the secondary. Run the other end of the
    wire up the wall, across the ceiling, and down, but line this "big loop"
    up edgewise to the station. Leave the other end dangle.

    Antenna booster, two bucks and some labor. :)

    Good Luck!
    Rich



     
  9. Nobody mentioned a ferrite rod?
    Get a cheap transistor with ferrite rod, turn for max signal min noise.
     
  10. lytecap

    lytecap Guest

    I like the idea, but as a birthday present, it is not exactly going to
    go over well with my dad - he will probably think I am trying to
    electrocute him!
    What is a ferrite rod? How do they work?
     
  11. It is a rod made of compressed iron powder material, with a coil wound around it
    that is part of a circuit that is tuned the transmitter.
    These antennas grab the _magnetic_, not the electric field (as a normal
    wire antenna does).
    They are highly directional, and the good thing is: Almost all modern
    radios have one.
    It is absolutely possible that just turning your dad's radio 90 degrees
    will fix the problem if it has such a ferrite rod.
    But hardly a present, but should be tried.
    If it does not help grab some normal transistor radio and go there,
    and see what direction you need to turn it for best reception,
    then buy a nice transistor for him :)
    Any modern radio back to the sixties uses a ferrite rod for AM medium wave
    and long wave reception.

    transmitter

    direction of max sensitivity
    |
    |
    \ /

    L
    ========================////////====== ferrite rod <---- direction of minimal sensitivity
    | |
    --||--
    C

    / \
    |
    |
    direction of max sensitivity

    http://www.radio-electronics.com/info/antennas/ferrite_rod_antenna/ferrite_rod_antenna.php
     
  12. mpm

    mpm Guest

    To the OP:

    CFRB AM (1010 kHz) is a 50kW Daytime / 50kW Nightime station.
    The towers are at Lat: 43-30-15 Lon: 79-37-52.

    Here is the daytime pattern:
    http://www.fcc.gov/ftp/Bureaus/MB/Databases/AM_DA_patterns/306332-5349.pdf

    Here is the night time pattern:
    http://www.fcc.gov/ftp/Bureaus/MB/Databases/AM_DA_patterns/306332-5350.pdf

    So back to my original question to you, where are you in relation to
    these patterns?
    Is reception better day or night, or the same?
    What city or town is the receiver located in (so distance calculations
    can be performed)?
    Can you reasonably expect static-free operation at this distance?

    50kW is a fairly healthy signal by the way.
    -mpm
     
  13. Tom Bruhns

    Tom Bruhns Guest

    ....
    OK, one more idea for you, along the lines of identifying the static
    source. First, change the orientation of the radio, basically where
    it is right now. Do things improve? Next, take the radio to a
    different place in the house, and turn it over at least a 180 degree
    range, and try tilting it too, to see if the static goes away or gets
    much lower. Then if possible, take it to another house nearby--or if
    it runs on batteries, just down the street a ways. In other words,
    see if the static is really local, or if you are just dealing with a
    tiny signal. This is along the lines of what mpm is getting at, too.
    If you have only a tiny signal to work with, getting good reception
    likely won't be easy, because there's so much atmospheric noise in
    that frequency range anyway. If you're dealing with low signal
    strength, my recommendation is to get a good AM radio with an external
    antenna connection that will disable or bypass the internal antenna
    (that I'm assuming the radio in question has) and put up a decent
    antenna outside. "Decent" might be a long piece of wire, or a modest
    size loop properly constructed and installed.

    The fact that you say the static varies as someone walks by suggest to
    me that it's being generated very close to the receiver, and you MAY
    be able to find the source and kill it. The fact that other stations
    come in fine suggest to me that the static source MAY be something
    like a microprocessor embedded in some electronic gadget nearby,
    generating hash over a narrow band of frequencies. Once again,
    understanding WHY the static is there may be 99% of the solution.

    Cheers,
    Tom
     
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