Hi,

Your post interested me because I need a coupler for a SITEX unit. I am
not an electronics expert but have successfully fabricated circuits from
schematics in the past. The long and short of is that I would like to
attempt to build my own coupler. Do you or anyone else here have access
to SITEX service manuals that may show the circuit used. I would think
that such low frequency stuff would not be too touchy to fabricate if
one had the schematic and parts list. I have a SITEX LORAN 797.

TIA

Bob

chuck wrote:

Morrow is one of the companies that use "active" antennas to
overcome the fatal signal losses resulting from enormously
high impedance (~ 1 Megohm, albeit mostly reactive) of
extremely short antennas fed into 50-ohm receiver inputs.

Your circuit board probably contains an FET follower to
convert the high impedance of the antenna to a low impedance
of 50 ohms. To do this with a coil would probably render the
system so lossy as to not work at all.

You should be able to vary the antenna length modest amounts
(I'm thinking +/- 20%)with no noticeable difference. Just
how far you can go will be a question you can answer easily
by trying different lengths of substitute antenna.

On the other hand, if it was working fine with no antenna at
all, (was the coax connected to the circuit board?) do you
really need to go to this trouble?

Good luck, and let us know how you make out!

Chuck

RB wrote:
Does the length of a LORAN metal whip matter much? I recall a time when I
found I didn't even have an antenna on my LORAN (years ago); just a coil of
coax under the console, and it worked fine. So, can I stick just about any
whip on the coupler and get good results? Or, is there some reasonant
length that is needed?

I'm putting a LORAN in my 18' cc, and want to use a short metal whip on the
coupler, if that'll work OK.