Minimal Antennas and Grounds
         by Daniel A. Grunberg   --   Kensington, Maryland U.S.A


Modern shortwave receivers, particularly modern portables, tend to
be very sensitive.  Modern shortwave receivers most often are
intolerant of overly strong signals, even strong signals well away
from the frequency being tuned.  For example, a local, strong MW
station might overload your receiver's front-end.  The result could
be images all over the SW bands, or it could be an apparent
lowering of the receiver's gain.  Therefore, IMHO the best (and
least costly) antenna is the least antenna that can receive what
you want to receive.  I'd try the following in turn, and stop when
I was satisfied with the reception I was getting.

1.  The receiver's built-in antenna.

2.  Up to twenty feet of wire (insulated or not) strung up as
    high as is convenient, inside the house.  Radio Shack has a
    reel-up wire for this purpose (278-1374), which easily can be
    taken down and stored when not in use.  Ask about Radio Shack's
    return policy, in case it doesn't work for you.

3.  Grounding the receiver and using antenna 1 or antenna 2
    (above).  The following grounding methods may increase the
    received signal-to-noise level, BUT THEY WILL NOT NECESSARILY
    PROTECT YOU, YOUR HOUSE, YOUR PROPERTY, OR YOUR RECEIVER FROM
    LIGHTNING.  REMEMBER, EVEN DISCHARGES OF STATIC ELECTRICITY
    AT LEVELS COMMONLY FOUND IN THE HOME HAVE BEEN KNOWN TO DAMAGE
    SOME RECEIVERS.

    Almost any sort of external ground _may_ help.  Improvised,
    less-than-ideal, external ground connections have been known
    markedly to increase signal-to-noise ratios.

    Sometimes just touching your receiver may make signals more
    readable.  That's because your touch is increasing the
    capacitive coupling between the receiver's circuit ground and
    the earth.  If there is no easy way to make a connection to the
    receiver's ground, a grounded sheet of metal that's has roughly
    same dimensions (or larger) as one of the larger sides of your
    receiver (a cookie sheet will serve for this) can be used
    instead of your hand.  Just use a clip lead to connect the
    sheet of metal to a cold water line or one of the other
    external grounds that I describe below.  Then lay or stand the
    receiver (whichever works better for you) on the sheet of
    metal.  It's a marginal connection to ground, but it MAY work
    for you.

    If your receiver has an external antenna connector, an external
    ground connection usually may be made via the sleeve of the
    connector's mating plug (see illustration below).  Inserting
    the plug into the receiver's antenna connector will disconnect
    the receiver's antenna from the receiver's front-end.  A clip
    lead, from the appropriate lug on the plug to the base of the
    whip antenna, can be used to reestablish a connection to the
    receiver's _whip_ antenna.


                 ||__________
                 ||__________||0 <--- to rcvr front-end
                 ||     ^
                      to rcvr
                       gnd

    You can try to eliminate the clip lead from the plug
    to the whip antenna by cutting the antenna plug.  What remains
    of the long part near the wire terminals (which were not drawn
    on the left part of the figure below) should be long enough to
    makes a non-intermittent ground connection when it is inserted
    into the radio's antenna jack, but should NOT be long enough to
    operate the antenna jack's switch and disconnect the antenna.
    The following figure shows what I mean.  The figure is not to
    scale, so no dimensions should be inferred from it.  [Actually,
    since I haven't tried cutting a plug, I don't know what the
    dimensions should be.]

                 ||______                    ____
                 ||______                    ____||0
                 ||   ^                        ^
                     insert                 throw
                     this part              this part
                     in receiver's          away
                     antenna jack

    The best way to ground your receiver is to connect its ground
    to a ground rod (Radio Shack has them, but I don't know the
    catalog number) driven into damp soil, as near to the receiver
    as possible.  The next best external ground connection is to a
    ground clamp mounted on a metal *cold* water line.  Ground
    clamps and ground rods often can be found in the electrical
    supply section of your local hardware store.  Usable cold water
    line connections also may be made by clipping a battery clip
    (Radio Shack 270-344, perhaps) to a cold water line, or by
    clipping one end of an ordinary clip lead to the handle of an
    UNPAINTED cold water cut-off-valve handle.  If you clip onto
    a plumbing ground, be sure to polish its surface lightly with
    fine emery cloth or steel wool, until the surface shines.

    Less satisfactory external ground connections may be made
    (in the USA anyway) to a #10-24x1.5" screw or a #10-32x1.5"
    screw that you have pushed into the small round ground-pin
    on a 120 VAC outlet.  DON'T USE THE WALL OUTLET GROUND UNLESS
    YOU KNOW *exactly* WHAT YOU ARE DOING AND YOU HAVE VERIFIED
    THAT THE OUTLET HAS BEEN WIRED CORRECTLY.

    The diagram below is meant to represent a 120-VAC, 60-Hz,
    grounded outlet like those used in all but the oldest house
    wiring in the USA and elsewhere.  The outlet has two parallel
    openings.  Although the parallel openings are of roughly the
    same size, it can be seen that one of the parallel openings,
    the one shown on your left in the diagram, is slightly longer
    than the other one.  The outlet has a third opening, the lowest
    one on the diagram, that is shaped differently and is smaller
    than the other two.


                         AC Power Socket
                         ________________
                        /                \
                       |                  |
                       |   ||             |
    Larger parallel    |   ||        ||   | Smaller parallel
       opening         |   ||        ||   |    opening
      (AC-return)      |   ||        ||   |   (117-VAC)
                       |                  |
                       |        ()        | Smallest opening
                       |                  |   (ground)
                        \________________/


    If the outlet was wired properly, the connector behind the
    smaller parallel opening is wired to the 117-VAC bus, the
    connector behind the larger parallel opening is wired to the
    AC-return bus, and the connector behind the smallest opening is
    wired to the house ground.

    Before you make a ground connection to the smallest opening,
    the outlet should be tested.  A simple way to test the outlet,
    is to plug an AC-outlet Analyzer, Radio Shack 22-101 (or
    equivalent) into the outlet.  READ AND FOLLOW ALL OF THE
    INSTRUCTIONS AND SAFETY MATERIAL THAT COME WITH THE OUTLET
    ANALYZER.  If the outlet does not pass the test, do not make
    the ground connection.

4.  A convenient length of wire (insulated or un-insulated),
    weighted with a washer or two, and dropped out of a convenient
    window.  (A length of fine magnet wire (Radio Shack 278-1345)
    used this way might be a reasonable "invisible" antenna for
    apartment dwellers.)  Try this with and without a ground.
    OUTDOOR ANTENNAS SHOULD BE DISCONNECTED AND GROUNDED WHEN NOT
    IN USE.  NEVER USE AN OUTDOOR ANTENNA WHEN THERE IS A
    LIKELIHOOD OF LIGHTENING IN THE AREA.  NEVER RUN AN OUTDOOR
    ANTENNA WHERE THERE IS A POSSIBILITY THAT IT MAY SWAY INTO A
    POWER LINE OR FALL ONTO A POWER LINE.

5.  If you want to try an indoor amplified antenna, consider Radio
    Shack's #20-280, placed near a window.  Ask about Radio Shack's
    return policy.  Radio Shack's antenna is inexpensive (compared
    to others), and if it doesn't work for you, you will know about
    taking it back.

6.  An end fed horizontal outdoor length of wire, used with a
    ground (see 3 above).  Radio Shack sells a reasonably priced
    kit (278-758) with wire, insulators, and a window feedthrough.
    The wire can be any convenient length, or you can research the
    project ("Build Your Own Shortwave Antennas" by Yoder, is
    available from Grove Enterprises and others).  OUTDOOR ANTENNAS
    SHOULD BE DISCONNECTED AND GROUNDED WHEN NOT IN USE.  NEVER
    USE AN OUTDOOR ANTENNA WHEN THERE IS A LIKELIHOOD OF LIGHTENING
    IN THE AREA.  NEVER RUN AN OUTDOOR ANTENNA OVER A POWER LINE.
    NEVER RUN AN OUTDOOR ANTENNA WHERE THERE IS A POSSIBILITY THAT
    IT MAY SWAY INTO A POWER LINE OR FALL ONTO A POWER LINE.

7.  If your receiver seems to perform worse with the outdoor
    antenna than without it, you may want to consider using either
    the LOCAL position of the receiver's LOCAL/DX sensitivity
    switch, an external attenuator, a filter, or a preselector
    between your antenna lead and the antenna plug.


Please be assured that I do not work for Radio Shack, MT, or Grove
Enterprises.  My only interest in Radio Shack or Grove is as a
customer.  My only interest in MT is as a subscriber.  







This article was last updated on 12 August 1997.

If you have any questions, feel free to Email me ce369@freenet.carleton.ca . I'll do my best to confuse you completely (:-). (Comments or corrections also are welcome.)



This is the [an error occurred while processing this directive] hit on this document since 27 August 1997.



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