AM antenna construction
safetyguy
How do I construct an antenna to receive AM signals more clearly and from
greater distances?
safe...@linknet.net
George Gonzalez
A length of wire, run outside, as long and as high as possible.
The ideal AM antenna would be around 200 feet long and up at least 100
feet. Most of us are limited to shorter distances and closer to the
ground. This is not a huge problem as most AM radios have plenty of
extra gain. Having the wire closer to the ground lowers its
signal pickup, and raises its preferred angle of pickup, so it will do
a bit more poorly on long-skip signals.
You should also strive to keep the antenna away from power lines and
other sources of electrical noise. A lightning arrester may make life
easier on your radios and insurance company.
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George R. Gonzalez g...@boombox.micro.umn.edu
Sr. Sys. Programmer University of Minnesota
Leo Stone
safetyguy wrote:
>
> How do I construct an antenna to receive AM signals more clearly and from
> greater distances?
> safe...@linknet.net
The ARRL Antenna Book will tell you all you need to know; probably more than
you need to know; and definately more than you ever dreamed of existed. :)
LS
MSAWDEY
The classic setup is a straight copper wire, running horizontally for 50 -
100 feet, as high up as possible, supported on insulators at both ends,
with one end brought down as the lead-in to the receiver. This works well
for older units with a single antenna terminal (unbalanced input). The
lead-in should be connected to a "lightening arrestor," which has its
other terminal connected to a ground stake.
For later radios that have a built-in antenna of some sort (either loop or
ferrite), you can get a remarkable improvement with a passive-coupled
antenna: a number of turns of copper wire wound around a large cardboard
box, or around the frame of a window, for that matter, with a salvaged
tuning capacitor across the two ends of the loop. Place the radio a couple
feet from the antenna, with the radio's antenna parallel to the passive
unit, then adjust the tuning capacitor across the antenna for the best
signal.
Floyd Sense
To expand on what's already been covered: If your radio has no RF
stage, then a long high wire may be needed. If the radio does have a
good RF stage, then a long high wire may be just what you DON'T need.
Expecially if looking for particular stations from a certain direction.
The additional signal strength from the longer antenna may do nothing
but make matters worse. If your radio already suffers from poor
selectivity, you won't benefit from hearing more strong signals on
adjacent frequencies. One type of antenna that works quite well and is
very easy to build (although, the wife acceptance factor is low), is a
shielded loop that can be used from within your house. This antenna
provides you with deep nulls that you can steer towards the unwanted
station by rotating the antenna until the signal strength drops. I've
seen cases where you can listen to two different AM stations on the very
same frequency just by rotating the loop to null out the unwanted
station. And- the shielded loop design greatly attenuates some static
sources you will encounter. Plans for such an antenna used to be in the
ARRL handbook and various ham related antenna books.
M.Endicott
In article <01bc0494$badabea0$b98c...@ns.linknet.net>, safe...@linknet.net
says...
>
>How do I construct an antenna to receive AM signals more clearly and from
>greater distances?
>safe...@linknet.net
>
to get IU basketball games through all the Chicago noise. See p.5-13 of Hints
and Kinks for the radio amateur 12th edition. I do still have a q-basic
program to do the math and calculate #turns, etc that I can email, but you
will need microsoft q-basic to run it.
Matt