How To Combine With Auxiliary Equipment - Furuno LC-90 Owner's Manual

Coing back to our example, if the Mastor and the two optimum secondaries
happened to be exhibiting SNR's of 99, then we might select the "11"
station to observe in order to evaluate subtle changes in SNR. readings
due to interference from other sources on the boat.
Make sure you are in Function #1. Move down to the third line, usinu the
down arrow
▼
cursor. Hit ICLRl , and then hit the key, followed
by HÉNT| to change the "A" to "d," disabling the Automatic Selection
process. Move the cursor with the
▼
down arrow down to the fourth
line, hit [CLR|
[TI |T] I
ENT|. Now go back to function
#6,
by hitting the
GO key and then the 00 key. Observe the SNR of the weakest station,
and write the numbers for all three stations down in the back of this
manual. Now you can proceed to step 4 below.
4. Now, turn on the other electronics on the boat (radar, echosounder, etc.)
one at a time and observe the SNR readings over a period of several
minutes. Make sure you operate the other equipment in all possible
modes. For example, make sure that the radar is used in both standby
and then transmit modes, with the scanner turning and turned off, etc.
Write down the resulting SNR's for each piece of gear, and then shut it
off and do the next piece of equipment. If the SNR reading drops from,
say, 90 to 85, then you are probably OK, but if it drops from 90 to 60 or
lower, you have a definite interference problem that a qualified electronics
technician is going to have to fix before you can obtain proper Loran-C
performance. Your written record of SNR values will be helpful to him.
If yod are quite fortunate you will find that no other piece of electronics on
board your boat interferes badly with your new Loran-C. Assuming that
your luck is with you and that this is indeed the case, let's go on to test a
device that in at least 90 percent of Loran-C installations does cause an
interference problem: the alternator.
There are several technical reasons why alternators seem to be aniagonistic
toward Loran-C receivers, but going into the why's and wherefore's isn't as
iniportant as figuring out how to cure the little beast of this nasty habit.
Start your engine and increase engine speed un til your charging ammeter
goes upscale. You will probably now notice that the SNR indication of your
Loran-C begins to plummet.
Not all alternators respond to interference-removal techniques in the same
manner. Some alternators, it is sad to say, cannot be suppressed at all, and
these must be replaced or rebuilt if you wish to have useable Loran-C
operation. Don't blame the Loran-C receiver! It is a sensitive instrument,
and it is simply responding to the noise broadcast by the alternator.
The first step to take when alternator noise is discovered is to try a large
electrolytic capacitor mounted right at the output terminals of the alternator.
The capacitor must be rated for the nominal output voltage of the alternator,
plus a 50% safety factor. For example, if the alternator is a nominal 32
V.D.C. unit, you should use a capacitor rated for no less than 32 + 32/2, or
48 Volts. A 50 V.D.C. unit should suffice.
of the capacitor is connected with a short lead (less than 4 inches long) to
the Output terminal of the alternator, using a large crimp lug to go under
the terminal, in parallel with the heavy lead going to the battery bank.
The negative terminal of the capacitor should go to a mounting bolt used to
secure the alternator to its mounting frame. This lead also must be kept
shorter than 4 inches or so in order for the capacitor to do its job.
Do Not connect the capacitor to the Field terminal of the alternator, at the
risk of destroying the alternator itself.
Hopefully, the electrolytic capacitor will do the job for you, and if that is the
case you can proceed to mount it securely to the alternator, perhaps by
using "tie-wraps". Make sure the capacitor isn't able to move around under
vibration, since the leads could be broken off.
If you have any doubts about what you are doing, it is time to call in a
qualified electronics technician, especially if the simple capacitor treatment
doesn't do the trick.
Color TV1 s: One other particularly nasty interference source is the typical
home-grade color television, although sometimes a regular black and white TV
will wreak havoc on Loran-C reception. Unfortunately, the only solution to
this sort of interference is to turn the offending TV off, or else purchase a
commercial grade TV receiver which is better shielded than the home-quality
units.
HOW TO COMBINE WITH AUXILIARY EQUIPMENT
The LC-90 provides a data output connector on the back panel. This is used
for connection to peripheral equipment, such as a position plotter, a printer,
or an autopilot.
Position data is sent outside the LC-90 in one of several different data
formats:
a. Furuno CIF (Computer InterFace) for Furuno peripherals.
b. NMEA 0183 Complex Format, for plotters.
c. NMEA 0180 Simple Format, for Autopilots.
An optional connector cable kit (LC-1091 — Furuno Code No. 000-041-156) is
needed to access the output data.
The interconnection diagram is shown on the next page.
This capacitor should be a "computer-grade" unit, that has internal vents in
case it should overheat and possibly explode, and the capacity of the
electrolytic capacitor should be about 10,000 microfarads or so. Be careful to
observe the polarity of the capacitor. Reverse polarity will destroy the
capacitor, and could damage the charging system as well. The positive lead
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