[alberg30] loran

[Gordon E. White]

Lee,
    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 Radio Amateurs' Handbook) 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.

    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.

    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.

                            - Gordon White
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