Yes, one of the reasons for my suggestions is that one ought to try the easiest, most convient method for creating an
antenna first, time permitting, in order to perhaps be pleasantly surprised by good (or even great) results.
Use "ordinary"
marine grade ac
wiring like 14-2 or 14-3 to obtain the desired number of conductors. If, for example, you figure that you need 5 conductors use a 14-2 and a 14-3 OR/ use two 14-3
cables (more is better yet don't get carried away with too much "more" because it merely costs you more) and marry them together every 10 inches or so with tie wraps. You WANT these wires to be as intimate as possible in order to take advantage of mutual inductance gained by having the conductors very close without electrically touching. Think of a copper foil as being a series of side-by side conductors without being insulated from each other. In that case you get no mutual inductance benefit.
Strip the ends and terminate them in a ring terminal which will accept all of the wires. You may
wind up with a terminal that has a ring diameter much larger than the fastener upon which it goes. In that case, use
bronze or copper washers of appropriate size so as to make good
electrical contact with the fastener (which should have a "bottom" shoulder consisting of a boss or another washer anyway). IN the case of ICOM tuners they provide S/S washers. Replace the S/S washer with
bronze or copper. Keep in mind that
stainless steel is about 50 times less conductive than copper or bronze and, therefore, is not good for carrying
current. You will apply a protectorant over the end result to keep everything pristine.
It is easier to terminate the tuner "output" wire using a ring terminal placed on the lowest fastener inside your
boat that attaches your chainplate. If not, or when using S/S
rigging wire to "jumper" over toggles, etc., serve the wire placed parallel with the stay. Cover the serving with 3-M
electrical protectorant (comes in a can that even Home Depot sells). Do not tape over the connection or use anythig like that that cannot completely prevent
salt water from entering the connection via wicking through the gaps between the stay individual wire strands. Do not use ANY type of silicone sealer, it ultimately will fail because if its lack of ability to adhere to stainless.
If the rig happens to facilitate a reasonable SWR at the frequency that you desire you will generate an effective radiated output
power and communicate well. If not, then you may opt to investigate other means of making up your
antenna but first check all bands of frequencies that you desire to use. The easiest manner to check for this is to place an rf ammeter on the tuner output wire to see just how many rf amps are going into the wire. You probably will not do that and are left with attempting to communicate with some distant station as a check. If you are in a marina with many masts around then they will affect your ability to communicate even with an ideal antenna so keep that in mind as well as to be aware of bluffs, buildings, etc. which will also negatively affect you.
A HAM friend may have an SWR meter to offer as a check yet measuring the SWR (this measurement is valid only at the tuner end of the transceiver coax, not the transceiver end unless the coax length is exactly a half-wave multiple in electrical length AT the frequency of measurement...many HAMS and installers do not realize this fact). Anyway, the SWR reading only tells you that the tuner has achieved a match between its internal reactive components and the impedance seen at the end of the coax thereby allowing the transmitter to output power without automatically cutting back due to a mismatch. It can happen that you can put out 200 Watts of peak power from the transceiver and put out nothing into the antenna, the power gets absorbed by the internal "matching" components of the tuner.
During the tuning process the AT120 only "tells" the transmitter to use a few Watts. After a tune is achieved then the transmitter will ouput as much as you drive it as long as there is no poor SWR to cut down the power (that the transmitter has built in to save it from damage in case of a bad match).
Some installation may work well on 4, 7, 8, 12, 14 MHz and not at all on 16 and then fine on higher bands....you just don't know in advance with a particular
boat. This is an easy thing to try without cost, only effort. If you determine that your particular "antenna" is not sufficient THEN use a different approach, yet leave the tuner and its "ground" as is.
If your "antenna" happens to appear to have quarter-wave-like lengths at your frequency of operation then the voltage at and near the tuner is minimum, the
current is maximum, therefore, there is little to fear from if one were to touch the radiator. Even with a bad match if you were to touch the wire you could get a slight burn which turns the skin white. You will not be shocked and your brain and liver will not get fried. The worst problem with getting an rf burn is to feel the pain and jerk back causing collateral damage so that is not good.
More later if you have questions. Hope this helps.
Regards,
Rick
Linear Mode
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