In article .com,
"Terry K" wrote:

I have a
Furuno LC-80 Loran c in the basement, it came uninstalled with a boat,
but I never needed to use it nor had it connected for any reason. It
has only 3 pins in the connector, and a big base loading coil.
A relay in there might enable use of the 8 foot glass whip at other
freqs.

Terry K

Inside that "big base loading coil" is an active Preamp and impedance
coupling system that is designed to match an 8' CB Whip antenna
(Shakespear 10-4) at Loran C operating frequency of 100Khz. The "Three
Wires" are +DC Power, Ground and RF signal.

"Lynn Coffelt" wrote in message
...

"Terry K" wrote in message
oups.com...
Unless the radiating element was decoupled from matching for 100khz and
connected to matching capable of transmit at some other freq? Thence
the need for a tx line in the antenna cable.

I don't claim to know every option available on these things. I have a
Furuno LC-80 Loran c in the basement, it came uninstalled with a boat,
but I never needed to use it nor had it connected for any reason. It
has only 3 pins in the connector, and a big base loading coil.
A relay in there might enable use of the 8 foot glass whip at other
freqs.

Terry K

Well, tx and rx lines are necessary because the antenna module must
get
programming data from the display unit. In other words, it must receive
(rx)
data from the display, asking for the unit to tune to the proper GRI and
slaves for the area in which it is being used. THEN, the LORAN received
(and
decoded?) data must be transmitted (tx) to the displaying unit. The tx and
rx lines give this serial port connection the steering and coordination
necessary to get the job done.
Old Chief Lynn

I started to warn of bad information in my response to the "antenna
coupler question", but after "Googling" for a few minutes I see on the
Lowrance site, in the company history, there is this sentence:
"In 1988, the Company introduced the first fully waterproof SONAR/Loran-C
combination units featuring all Loran-C circuitry and software contained
solely in the antenna coupler module."
So, as I recall (pretty thin stuff to work with), this coupler was
really a departure from all the other manufacturer's use of the coupler as
merely a tuned, very selective, 100khz amplifier, for use with an 8' whip.
(ok, a couple used a shorter, stainless steel whip)
I have actually seen one of these LMS-300/LC-1 combination work.....
not like a Furuno, of course, but still did function.
I stick to the quasi serial cable story.
Old Chief Lynn