Got a question on LORAN sets. I don't want to get into the desireability of
GPS as the nav mode of choice today. I'm fiddling around with LORAN and
trying to get going with it.

1. What is/are LORAN operating frequencies?

2. Marine LORANS are found with external couplers (pre-amps) which go at
the base of the fiberglass/whip antenna. Can marine LORANs which are made
for use with external couplers give reasonably good performance without the
coupler? Or, is lack of the coupler a "killer"?

2. Are there marine LORAN receivers which don't require external couplers
(i.e., that hook direct to the antenna)?

3. If you have a marine LORAN which does in fact need an external coupler
to get enough signal through and you don't have the companion coupler unit,
are any commonly available pre-amp boards for the LORAN frequencies
available? If so, where find?

In article , "RB" wrote:
Got a question on LORAN sets. I don't want to get into the desireability of
GPS as the nav mode of choice today. I'm fiddling around with LORAN and
trying to get going with it.

1. What is/are LORAN operating frequencies?

2. Marine LORANS are found with external couplers (pre-amps) which go at
the base of the fiberglass/whip antenna. Can marine LORANs which are made
for use with external couplers give reasonably good performance without the
coupler? Or, is lack of the coupler a "killer"?

2. Are there marine LORAN receivers which don't require external couplers
(i.e., that hook direct to the antenna)?

3. If you have a marine LORAN which does in fact need an external coupler
to get enough signal through and you don't have the companion coupler unit,
are any commonly available pre-amp boards for the LORAN frequencies
available? If so, where find?



Man, I had to do a little searching. We used to track Loran to check long term timming
stability of atomic clocks. 100 kHz seems the right frequency. A loran signal
is probably best received using a loop antenna, but for receiving multiple direction
signals a whip is needed I'm sure.
All you need is a 100kHz amplifier, probably low passed and preferably
bandpassed matched to the antenna, and to the receiver input.

greg

"RB" wrote in
:

Got a question on LORAN sets. I don't want to get into the
desireability of GPS as the nav mode of choice today. I'm fiddling
around with LORAN and trying to get going with it.

1. What is/are LORAN operating frequencies?
100 Khz, all stations are on the same frequency, exactly. They use a
cesium beam frequency standard to make sure it's perfect.


2. Marine LORANS are found with external couplers (pre-amps) which go
at the base of the fiberglass/whip antenna. Can marine LORANs which
are made for use with external couplers give reasonably good
performance without the coupler? Or, is lack of the coupler a
"killer"?

Killer. The very-low frequency LORAN antenna is electrically 2340' long
(1/4 wavelength on 100 Khz). To achieve this in an 8' long whip it is
VERY heavily loaded with a large inductance and that coupler. No, you
can only get it working with the cou0ler or a 2,340' long whip, your
choice.


2. Are there marine LORAN receivers which don't require external
couplers (i.e., that hook direct to the antenna)?

The couplers on the marine antennas are built into the whip. They're
still there.


3. If you have a marine LORAN which does in fact need an external
coupler to get enough signal through and you don't have the companion
coupler unit, are any commonly available pre-amp boards for the LORAN
frequencies available? If so, where find?


It's not a preamp problem. There's tons of signal from teh MEGAWATT
LORAN-C pulse transmitters and their massive capacitor hat loaded 850'
tall antenna towers. The problem is that 2340' 1/4 wave whip it takes to
hook 'em up.

You need the antenna system it came with.....

"Larry" wrote in message . Killer. The very-low frequency
LORAN antenna is electrically 2340' long
(1/4 wavelength on 100 Khz). To achieve this in an 8' long whip it is
VERY heavily loaded with a large inductance and that coupler. No, you
can only get it working with the cou0ler or a 2,340' long whip, your
choice.


2. Are there marine LORAN receivers which don't require external
couplers (i.e., that hook direct to the antenna)?

The couplers on the marine antennas are built into the whip. They're
still there.


3. If you have a marine LORAN which does in fact need an external
coupler to get enough signal through and you don't have the companion
coupler unit, are any commonly available pre-amp boards for the LORAN
frequencies available? If so, where find?


It's not a preamp problem. There's tons of signal from teh MEGAWATT
LORAN-C pulse transmitters and their massive capacitor hat loaded 850'
tall antenna towers. The problem is that 2340' 1/4 wave whip it takes to
hook 'em up.

You need the antenna system it came with.....

While there is certainly no question that the matching coupler and 8' whip
are pretty much standard, just for fun we experimented with some of the old
TI lorans, and found that the SSB antennas on many power and sail boats
worked fairly well, with one major "gotcha". Loran C, at 100 khz is very
easily messed up by electrical noises from almost anything on a boat. Having
the 8' whip antenna up and away (several feet at least) from the noise
makers and the boat's wiring, made major differences in noise pick-up. Water
damaged TI loran couplers were pretty common, and you could pull the guts
out and throw them away, and jumper the whip connector to the signal feed
wire inside the coupler. Performance not perfect by a long shot, but if you
shut down the main engine and everything else, you could get a fix. (the
hard way)
Old Chief Lynn

OK. Thanks, Larry. That means all those nice LORAN receivers for sale on
Eprey without couplers basically aren't useable. Which is probably why the
go so cheap......

I have a few loran couplers laying around, some trimble, northstar, TI,
possibly a SI-Tex. I could give you one for the price of shipping if you
want. Don't know what model Loran your looking at, some couplers
interchangeable, some not.

Eric

"RB" wrote in message
...
3. If you have a marine LORAN which does in fact need an external coupler
to get enough signal through and you don't have the companion coupler
unit, are any commonly available pre-amp boards for the LORAN frequencies
available? If so, where find?

What is in these "couplers" is it just a huge inductor to cancel out
the capacitive reactance?

I discovered this phenomenon the hard way when I replaced the shielded
cable on my car antenna with just some simple coax. Absolutely no AM
signal at the end. Then I figured out why the real cable is a coax
with a very tiny center conductor inside a hollow tube to minimize the
capacitance. If you used something similar to connect any antenna to
your loran it would probably work better.

Have fun.

These are "active" antenna's. Power is provided via the coax and there is
a PCB in there with a pre-amplifier circuit. Some units have notch filters
and/or bandpass filters in them.

Eric

wrote in message
oups.com...
What is in these "couplers" is it just a huge inductor to cancel out
the capacitive reactance?

I discovered this phenomenon the hard way when I replaced the shielded
cable on my car antenna with just some simple coax. Absolutely no AM
signal at the end. Then I figured out why the real cable is a coax
with a very tiny center conductor inside a hollow tube to minimize the
capacitance. If you used something similar to connect any antenna to
your loran it would probably work better.

Have fun.

"Eric Fairbank" wrote in
:

These are "active" antenna's. Power is provided via the coax and
there is
a PCB in there with a pre-amplifier circuit. Some units have notch
filters and/or bandpass filters in them.

Eric



Don't confuse them. They think you can plug just any old thing into any
old thing just because it has the same BNC connector and it will be on the
cheap.

If we go telling them different, technicians' families will starve and have
a bad Christmas...

Not long ago I found a formerly-good GPS front end plugged into a formerly-
good LORAN receiver, myself...

They're pretty close, right?....(c;

On Fri, 23 Dec 2005 09:15:42 -0500, "Eric Fairbank"
wrote:

These are "active" antenna's. Power is provided via the coax and there is
a PCB in there with a pre-amplifier circuit. Some units have notch filters
and/or bandpass filters in them.

=====================================

Absolutely right. If anyone really wants to hack around with this
stuff I have a couple of Northstar LORAN-C units sitting around
without antennas or couplers. They were first class units in their
day and have SO-239 coax connectors on the back.