"G.R. Patterson III" wrote in message
...
[...] Significant position errors can result when the
master and either of the slave stations are in line with your aircraft
(you're
between them or they are both off to one side).

Interesting. My position errors always occur in the same geographical
location (just east of the Olympic Mountains)...I wonder if that location
happens to be in line with a master and a slave.

Yep. Mine wants to change chains about the North Carolina/South Carolina
border.
Reception sucks sometimes in Knoxville, and that's on a border as well.
IIRC, you're
in Washington State? If so, you're at the boundary of the U.S and Canadian
West Coast
chains. To make matters worse, the slave in your area (located in the
middle of the
State) is shared by both chains.

You recall correctly. Based out of Paine Field, just north of Seattle. The
"zone of confusion" lies about 15-25 miles roughly southwest of Paine. I
have noticed that the receiver is marginally better when using the US West
Coast chain, but for whatever reason it always wants to use the Canadian
West Coast chain in the Puget Sound region. That's certainly a programming
issue: no way to override the chain in use. I can switch it manually, but
the LORAN unit immediately starts bugging me to switch back.

Back to the previous question of position errors... I found the locations
of the various LORAN chains, with the master and slaves. It doesn't appear
that the general area where I get the errors is in line with the master (in
Williams Lake, BC) and the slave (in George, WA). In fact, I'd have to be
over on the other side of the Cascades for that to happen.

However, I *am* flying near the Olympic Mountains, which might cause signal
reflections. I have seen some bizarre effects flying NDB approaches near
shorelines, where the ADF shows me right on course, but visually I can see
I'm well to the side (over a mile off in some cases). I wonder if similar
variations affect LORAN. The calculations must assume straight-line signal
propagation, so I suppose anything that caused the signal to not follow a
straight line would cause errors.

Though, now that I think about it, a reflection would make it appear I was
farther from the station, and the errors I'm getting are putting me closer
to it.

Ahh well...the mystery continues. Anyway, just wanted to mention that not
all units are afflicted with the same delay in position calculations your
unit appears to be.

Pete