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  • Antenna

    From BEN RITCHEY@1:393/68 to ALL on Sun Jul 3 11:48:33 2005
    I have a weather radio that get's poor reception so I'd like to extend and/or complement the telescopic indoor antenna with an external antenna. I have a 17 foot piece of insulated #12 copper wire I'd like to use. 1st question; does it need to be bare wire? The entire length? By the time I feed outside, that's about 2 feet horizontal. Another 4.5 feet vertical to the eaves where I can turn and go horizontal for another "x" feet, up to 20 feet. Full wavelength for a frequency of 162.5 MHz is exactly 6 feet (remainder less than an inch), so how long should I make "x" above? I cannot extend the vertical portion longer than 4.5 feet ...

    --
    Be well :^)

    : Ben aka cMech http://bellsouthpwp.net/c/m/cmech617/
    :
    + WildCat! Board 24/7 +1-337-232-4155 V92 56k 8,N,1
    --- GoldEd+/DOS v1.1.5cM
    * Origin: FIDONet - The Positronium Repository (1:393/68)
  • From Andrew Ball@1:261/38 to Ben Ritchey on Mon Jul 4 22:46:34 2005
    Hello Ben,

    BR> I have a weather radio that get's poor reception so
    > I'd like to extend and/or complement the telescopic
    > indoor antenna with an external antenna.

    Your copper wire may help. If not, you could look for a weather radio that has
    an external antenna jack. I use an inexpensive hand-held scanner and get good results with the supplied rubber duck. It has a BNC connector though, so I could position an external antenna somewhere convenient and run coaxial cable into the house. If you're just too far from any of the VHF FM NOAA stations, perhaps long-wave is an option. I inherited a small transistor radio that has LW coverage (unusual in the U.S. I think) and find that I can also receive weather radio that way.

    BR> Full wavelength for a frequency of 162.5 MHz is
    > exactly 6 feet (remainder less than an inch)...

    300 / 162.5 = 1.8461538m (roughly 6ft). Without knowing how your radio's internal antenna is wired (what loading coil is used etc.) it's non-trivial to use these numbers in a meaningful way. There's velocity factor to be taken into consideration too. At least it's a receiver, so antenna measurements are perhaps less critical.

    - Andy, KB9YLW

    --- BBBS/LiI v4.01 Flag-5
    * Origin: Prism bbs (1:261/38)
  • From Thom LaCosta@1:261/1352 to BEN RITCHEY on Tue Jul 5 07:43:33 2005
    BEN RITCHEY wrote in a message to ALL:

    I have a weather radio that get's poor reception so I'd like to
    extend and/or complement the telescopic indoor antenna with an
    external antenna. I have a 17 foot piece of insulated #12 copper
    wire I'd like to use. 1st question; does it need to be bare wire?

    Shouldn't make any difference whether or not the wire is naked(other than
    if some wire prude catches you).

    The entire length? By the time I feed outside, that's about 2 feet horizontal. Another 4.5 feet vertical to the eaves where I can turn
    and go horizontal for another "x" feet, up to 20 feet. Full
    wavelength for a frequency of 162.5 MHz is exactly 6 feet
    (remainder less than an inch), so how long should I make "x" above?
    I cannot extend the vertical portion longer than 4.5 feet ...

    The internal circuits of the radio may be such that it doesn't expect a full wave length antenna....and by using that, you could have a rather large impedence mis-match.

    Some folks have used a "long wire" and coupled it loosely to the receiver using
    a coil that resonates at the frequency of interest....you could try
    wrapping a few turns of the insulated antenna wire around the rod antenna.

    Another factor to consider is the polarization of the transmitted signal. Most
    of VHF stuff is vertical....your sky catcher has a decent amount of
    vertical capture.

    If it were me...I'd play not only with the loose coupling, but also the orientation of the wire....and at the same time look around for a vhf pre-amp....

    Good luck!

    cya,
    thom
    http://www.tlchost.net/echolist/
    --- GEcho 1.20/Pro
    * Origin: Home of The Other Robot (1:261/1352)
  • From BEN RITCHEY@1:393/68 to ANDREW BALL on Tue Jul 5 11:48:37 2005
    * An ongoing debate between Andrew Ball and Ben Ritchey rages on ...

    I have a weather radio that get's poor reception so

    | AB> just too far from any of the VHF FM NOAA stations, perhaps long-wave
    | AB> receiver, so antenna measurements are perhaps less critical.

    Ok, thanks.

    --
    Be well :^)

    : Ben aka cMech http://bellsouthpwp.net/c/m/cmech617/
    :
    + WildCat! Board 24/7 +1-337-232-4155 any BAUD 8,N,1
    --- GoldEd+/DOS v1.1.5cM
    * Origin: FIDONet - The Positronium Repository (1:393/68)
  • From BEN RITCHEY@1:393/68 to THOM LACOSTA on Tue Jul 5 11:48:37 2005
    * An ongoing debate between Thom Lacosta and Ben Ritchey rages on ...

    I have a weather radio that get's poor reception so I'd like to
    | TL> Some folks have used a "long wire" and coupled it loosely to the
    | TL> receiver using a coil that resonates at the frequency of
    | TL> interest....you could try wrapping a few turns of the insulated
    | TL> antenna wire around the rod antenna.

    Don't I need some sort of tank circuit to resonate the coil? Assuming a Freq of 162.4 MHz how many turns of #12 wire around a 1/4" rod would I need to resonate properly, if feasible to do so that way?

    | TL> Another factor to consider is the polarization of the transmitted
    | TL> signal. Most of VHF stuff is vertical....your sky catcher has a
    | TL> decent amount of vertical capture.

    I wondered about that. Assuming a long-wire antenna (2-4l), would excess horizontal tend to attenuate the vertical portion of the reception?

    | TL> If it were me...I'd play not only with the loose coupling, but also
    | TL> the orientation of the wire....and at the same time look around for a
    | TL> vhf pre-amp....

    Sounds like a plan, thanks.

    --
    Be well :^)

    : Ben aka cMech http://bellsouthpwp.net/c/m/cmech617/
    :
    + WildCat! Board 24/7 +1-337-232-4155 any BAUD 8,N,1
    --- GoldEd+/DOS v1.1.5cM
    * Origin: FIDONet - The Positronium Repository (1:393/68)