This page is all about electronics....both
fishing related and other. You will find more about electronics at these other
electronics related pages:
Electronics Links
Fish Finders
Installing a Fish Finder
VHF Marine radio channels
System Design
LORAN
LORAN was the first method of electronic navigation for
me. It revolutionized fishing for me in many ways. Prior to LORAN, we used a
chart, ruler and compass to navigate. Finding our way out and home again was
time consuming, distracting and sometimes dangerous.
When most peole mention LORAN, they refer to LORAN C
which is a refinement of earlier LORAN systems. LORAN C is widely misunderstood
and does have it's peculiarities. The basic concept uses a radio receiver to
determine a vessel's position by determining the time delays or TD's of an array
(typically 2) of LORAN stations. Here in the Chesapeake LORAN operates on the
9960 Chain of LORAN stations. Most receivers can obtain TD's for W, X, Y and Z
stations. X and Y stations are used for virtually all naviagtion in our region,
Typical values are 26700- 27400 for X the station and 41400-42100 for the Y
station. Normally X is the first TD and Y is the second. The pair of numbers
displayed on a LORAN equates to a certain geographic position. The exact value
can be affected by several factors but the repeatability of a fix obtained by
LORAN is excellent. Charts are often overlaid with lines of position for W,
X, Y and Z stations. The predicted lines are very accurate over open water but
cannot be predicted over land.
A few years back there was a big scare related to
possible shutdown of the LORAN C system. As a result, most mariners including
myself scrambled to buy GPS receivers. Later the government decided to extend
the life of LORAN C. Popularity of LORAN equipment never regained it's momentum
and I seldom hear of new equipment being purchased. LORAN has several
characteristics that make less attractive than the new GPS equipment. LORAN
needs a bulky antenna, making portable units impractical. Other disadvantages
are the need for specialized charts, area specific coverage and LORAN's tendency
to shut down during electrical storms.
Most old timers like myself have a crumpled old book
filled with pairs of LORAN TD's for every manner of fishing spot, wreck, buoy
and the like. Likewise many of us have TD's written in pencil all over the dash
of our boats. In general we have no idea what destination each pair goes to.
Many anglers still use the TD pair system in leiu of the Latitude/Longitude
format favored among GPS users. Many GPS units will read position in LORAN TD's
for those of us that are geographically impaired. The exact conversion of TD's
to geographic position or GP's is difficult and dependant upon several factors
including the position involved and the specific model of LORAN. Near perfect
results for a batch of numbers within a limited area can be done using a
computer program from Andren Software called "LORANGPS". Basically a fix needs
to be taken for a test spot within the conversion file area with both the LORAN
and a GPS. Additional secondary factors or ASF's can then be adjusted in the
chosen program until the LORAN and GPS positons match. Once a value for ASF's is
attained, it can be applied to all positons within the local area. The result is
a group of old LORAN data which can now be used with a GPS. The use of LORAN
coordinates is also explained in detail by this Garmin
LORAN
TD Position Handbook.
GPS Units
GPS receivers are one of the most popular electronic
devices today. Equipment ranges from simple hand held units for around $125 to
programs driven by modules which attach to a PC. I have chosen a very simple
hand held GPS unit, the Garmin 12XL and 76
models for my needs. Other popular hand held models are available from Garmin as
well as companies like Magellan, and Lowrance. I consider my GPS to be essential
to fishing and use it extensively. The unit has many advantages and has
revolutionized the way I fish. It is portable, durable, independent of vessel
power, simple to use and extremely powerful. On Daybreak, I plug my unit into
the boat electrical system for power. Otherwise, I power the unit with 4 AA
batteries. I prefer nickel-metal hydride rechargeable batteries although
disposable batteries will work.
The features I use the most are the waypoint list,
plotter, routes and upload/download function. The waypoint list gives me the
ability to keep track of the numerous waypoints that I use while fishing. The
plotter is used to see my position in relation to other waypoints. This comes in
handy while trying to navigate around obstacles, return to the position of a
hook-up or drift over a wreck. The route function gives me navigational
information as I negotiate the many channels of the Chesapeake Bay and coastal
inlets.
The most revolutionary feature of the present day GPS
units are the charting capabilities. Upload/download capabilities are usfeul as
well.
I use the upload/downloadfeature to edit recent waypoints,
upload files from other sources and create backup files.
Coupled with the appropriate software, a mariner can
manage waypoint lists, view waypoints overlaid onto digital charts and much
more. Software for this feature is abundant but may be limited to specific GPS
models. I try to keep things as simple as possible and like a few popular
programs including
Waypoint+ , LORANGPS and
Chartview Planner . Some GPS units can also receive software updates right
from the internet using the upload feature!
Some disadvantages of portable GPS units are their lack
of an external antenna, need for batteries and the small screen.
A great review of GPS units from
my friend Mack
Fish Finders
Fish Finder Information
Cell Phones
Cellular phones are becoming standard
equipment on most fishing boats. They are, however, best used for calling your
spouse on the way in or lining up tomorrow's crew. The are proven unreliable
offshore and should not be relied on as a primary means of emergency
communication.
Cellular phone users who use a phone far
offshore may need to get a high gain antenna. A cheaper but less effective
option is to mount an automotive type antenna on the windshield or on the roof
of the boat. Fixed mount antennas can be interfaced to many popular portable
cell phones via an adaptor cable.
VHF Marine Radios
VHF marine radios are essential equipment on a boat.
The usable range of a VHF radio system is dependant on several factors including
the weather, the boat , the antenna and the health of the radio. The most
important part of the system is the antenna. Marine antennas should be mounted
as high as practical. Another important quality of an antenna is it's gain.
Gain is rated in decibels or dB. Most experts recommend
a quality antenna with 6 a gain of dB for powerboats under 50 ft. The antenna
system can be tested by measuring the VSWR of the antenna. The VSWR should
be as low as possible, typically 1.5 to 1 or lower on a healthy antenna.
Other radio problems can stem from the radio or the
vessel electrical system. One of the most frequent radio system failures on a
powerboat is when a poor connection, normally from corrosion, exists between the radio and
battery. The radio will normally come on but may transmit erratically or not at
all. If other accessories like lorans, gps, etc. are on the same circuit, keying
the radio transmitter will likely reset or shut down these units. This is a most
annoying and dangerous problem which is more often than not intermittent. If the
trouble can be duplicated, it can be located easily by checking voltage along
various parts of the radio power circuit while having a helper key the radio.
Battery voltage should be around 12.5 volts and should not drop more than
about .1 volts across any connector, fuse, etc. when the transmitter is keyed.
Some small drop is normal but trouble is likely if the radio is not getting at
least 12 volts all the time.
Receivers, including radios, LORAN units and GPS units
can all suffer from interference on a boat. Much of this can come from other
sources in the boats electrical system. One common example is "clicking" or
"pinging" heard in the radio when a fish finder is on. This and other crazy
symptoms can be minimized by running the proper sized electrical power wiring
for each device all the way to the battery switch. In some cases electrical
filters will need to be installed to combat interference. If you have a problem
like this, call a friend in the electronics business (me) for specifics or see
your local marine electronics shop.
The two new acroynms that boaters may want to learn about
are Digital Selective Calling (DSC) and the Global Maritime Distress and Safety
System (GMDSS). DSC is secure digital format which allows users to communicate
with other DSC equipped radios. In a nutshell GMDSS is a system that allows a
radio to send an automated distress call which can include vessel position
information..... IF....... the radio is connected to a working GPS unit.
If you have a DSC capable radio you will want to obtain an MMSI number. MMSI
numbers are explained and are available from the first link below. The MMSI
number for Daybreak is 338026299.
Several FAQs and webpages explain this in
detail. Here are a few links for more information:
http://www.boatus.com/mmsi/default.htm
http://www.navcen.uscg.gov/marcomms/gmdss/gmdssfaq.htm
http://www.uscg.mil/rescue21/faq/
http://www.ybw.com/ybw/vhf/faq.html
http://www.travelbygps.com/training.php
http://www.bluewatersc.org/radio_procedure.htm
http://portal.etsi.org/erm/kta/maritime/maritime.asp
VHF Marine radio channels
EPIRBS
This URL provides EPIRB information:
http://www.sarsat.noaa.gov/
Fittings and Adaptors
There are several types of connectors
found on marine electronics. UHF fittings are the most common, normally on
VHF radios. Another common type is BNC which will often be used on LORAN or GPS
antennas. Other types are mini-UHF, N, SMA and TNC.
The connectors pictured are from
left to right:
TNC, BNC, UHF, MINI-UHF, N, SMA
