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Lee,
<BR> A "coupler" is a device to match the impedance of
the antenna to the receiver; used in various radio applications. Essentially
a transformer at radio-frequency allowing energy to be transferred from
one circuit to another. You have an inductance/capacitance circuit resonant
at the incoming frequency, with circuitry matched to the outgoing side.
(P. 45 of my <I>Radio Amateurs' Handbook) </I>I believe (may all hams out
there correct me) that in the case of loran, it is impossible to put up
an antenna that matches even a quarter wavelength so there is a device
consisting of specially-wound coils and capacitors creating a network that
does its best to match the rather short antenna to the coaxial cable and
thence to the receiver - kinda fools the incoming signal into thinking
the antenna is a quarter-wave and matches it to the 72 ohm coax.
<P> So, yes, it is more than something to physically
attach the antenna to the cable. It is "potted" in plastic at the base
of the antenna - the whip does screw into the top of the base containing
the coupling network and the coax attaches to the base.
<P> Still, it is not very complicated - no computer chips.
A ham could whip one up for a couple of dollars, but getting the proper
threads to screw in the whip and to fasten the coax and attach to the mount
probably costs more than the little coils and capacitors. Usually the coupler
has the coax potted in place, so you are paying for $30 worth of
cable, too.
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- Gordon White</HTML>