Most manufacturers provide excellent
installation instructions and technical support with their HF
equipment. See links at end. Follows some general basic tips that might be useful when planning your SSB
installation.
Please don’t hesitate in posing
specific queries.
HF Installation Basics:
1. Install transceiver as close to your operation site and to the power supply system (batteries) as possible.
2. The
antenna must be installed in an open space and as far as possible from your operating point. As an example, on a sailboat, use the backstay as the
antenna, since it is the farthest point away from the rest of the vessel.
3. The antenna coupler must be installed at the base of the antenna.
4. Always create your own ground with radial wire or copper straps. They are the only ones that will guarantee a solid and proper ground system.
5. All
cables - power supply, control or coaxial - must always be as short as possible and/or necessary. Any excess cable should be shortened to the proper length - never coiled.
RF Grounding Basics:
Overall, there are probably as many different ways to create a good RF ground as there are people giving advice about them. What works in one boat may or may not work well in another. Be prepared to adjust your RF grounding as you test it and remember that it will degrade over time, so you also need to be ready to maintain it.
1. Get as much metal into your RF ground as you can. On some boats the
engine,
keel, thru-hulls, and even copper plates are connected together into the RF ground.
When anchored (or docked), you can improve your RF Ground by temporarily connecting an
overboard ground plate. Connect a wire from your Tuner Ground Lug to a Fround Plate which is led
overboard and immersed in the
water.
2. Keep ground straps as short as possible. Connecting to your RF ground can be tricky. Often people will use a Volt-Ohmmeter to check their ground straps and declare them good because there is little or no resistance. However, the ground strap is not for DC
current. An RF ground is carrying RF energy and a DC resistance to ground will not show if there is an impedance to ground at RF frequencies. Be aware that RF conductivity is not the same as DC conductivity.
3. Don’t confuse your
safety ground (equipment chassis, reefer, etc) with your RF ground. The RF ground is required for the ANTENNA and is an RF circuit. Your
safety ground on the DC circuits is NOT intended to handle RF. While many boats connect these together successfully, it can cause
interference. RF energy carried through the DC ground may get into instrumentation or other
equipment. It is normally best to have the RF and DC grounds be separate.
4. Dynaplates and other external devices meant to connect your RF ground to seawater can be very effective, but they will only be so if you maintain them properly. If you connect your RF ground to Dynaplates, thru-hulls, and other fittings, then you must inspect them regularly and CLEAN them regularly. Dynaplates should not be left more than 3 months without
inspection and
cleaning.
5. Inspect your connections regularly. A
salt water environment is hard on any sort of
electrical connections. Your RF ground and your antenna need to be inspected regularly because the tuner will hide slow changes in your antenna or ground system until it can no longer compensate for them. You may operate for a long time as your fittings corrode and then find that you can’t operate at all. It will seem sudden, but the problem grows gradually.
6. A useful test of the quality of your ground is to lay out several long wires on
deck connected to the RF ground connection on your tuner. You might also throw a wire over the side to connect to seawater as well. When you remove these temporary wires, reconnect to your boat’s grounding system. The signal should get better. If it gets worse, your RF grounding system needs
work.
7. Bonding a lot of metal in your boat together with short, direct copper straps can create a very suitable grounding system. The
engine,
fuel and
water tanks, the
keel, and any other piece of metal of significant size can be bonded together effectively. Copper foil or wire is usually best here.
8. Some boat owners install a large area of copper foil on the inside surface or their
fiberglass hull and use this as an RF ground. It capacitively couples to the seawater and makes a generally excellent grounding system.
9. A leaded keel also makes an excellent RF ground. Depending on the construction of the
hull, you may or may not be able to make a good connection to the
keel bolts.
Icom:
http://www.icomamerica.com/
Manuals:
http://www.icomamerica.com/downloads/manuals.asp
Specifically:
718 BaseTransceiver Manual:
http://icomamerica.com/support/manuals/ic-718.pdf
AH-4 Tuner Manual:
http://icomamerica.com/support/manuals/ah-4.pdf
And some further reading:
Marine antenna and grounding considerations:
http://icomamerica.com/support/docum..._grounding.pdf
Marine SSB
Single Sideband Simplified - by Gordon West:
http://icomamerica.com/downloads/default.asp
HTH,
Gord
Linear Mode
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