INSTALLATION ON SHEARWATER
By Tom Assenmacher
We recently completed a Single Sideband Radio installation on our 1975 MK-II yawl SHEARWATER. We’ve been monitoring and communicating with cruisers on the CRUISEHEIMER’s Net on 8152 kHz Marine SSB (we’re not a Ham Operators yet) as far north as the North Channel in Canada, and as far south as Venezuela – most reception is as clear as VHF especially the longer range contacts due to the skip zones. We purchased an ICOM 710 and an ICOM AT-130 Tuner from Ebay (for about ½ the cost of a new unit) and have had no problems with the radio equipment. We had hoped to find an ICOM 710 RT model (the 710 with a remote control head) on Ebay but couldn’t find one listed at the time. The RT model allows installation of the bulk of the radio transceiver separate from the control head, leaving much more room at the nav station. Currently we are running the ICOM equipment directly through fused leads from the house batteries. We have mounted the transceiver at the Nav station and the tuner on the lazarette bulkhead just to the port of the mizzen mast knee.
We seem to be having good transmission and reception with the “home made” antenna that we installed.
Two great and invaluable sources of information regarding the “care and feeding” of ICOM SSB radio equipment are:
- The Cruising Club of
Both these websites have a lot of SSB downloadable documents and information. There are also numerous other sources for SSB/HAM information.
Since the A-37 yawl uses a “Y” shaped backstay, and since we use the split portion of the backstay as a tensioner, the backstay itself did not lend itself readily as an insulated (and structural) backstay. After considering various antenna options, we decided on using a “triadic” type of antenna running from the mainmast truck to the mizzen truck, using a piece of ¼” 1x19 SS wire that we had on hand with an “egg” type insulator on each end of the antenna. Since the antenna tuner is located in close proximity to the mizzen mast, we led the antenna lead (Ancor GTO-15 shielded cable) internally up through the mizzen mast and culminating in a short lead to the insulated antenna. Since this “triadic” antenna is not structural, it does not require special insulators – simply off-the-shelf inexpensive components (i.e., several nicropress fittings, SS thimbles, “egg” insulators etc.). The insulators were purchased on-line from Universal Radio (http://www.universal-radio.com/) for less than $3.00 each (estimated cost of the antenna including antenna lead wire was less than $50)! The installation of the antenna was relatively simple, since we had the mainmast out of the boat when we began the SSB installation. We were able to drill the antenna attaching points on the mainmast and mizzen mast trucks while the masts were out of the boat. However, it wouldn’t be too much of a problem to do this work from a bos’n chair.
Once the antenna design was firm, we made one trip up the mainmast and one up the mizzen mast to finalize the antenna installation.
For the ground plane, we ran heavy 3” copper foil from the ICOM transceiver along the port side of the boat (behind the quarter berth teak plywood outboard panel) to the antenna tuner. We also ran the copper foil from the tuner through the “tunnel” (the area underneath the cockpit sole), through the engine compartment and into the area above the bilge sump. While we had the boat out of the water early this summer (the boat had just been returned from a major exterior refurbishing by “Alex” of Whitby Boat), we installed 2 grounding plates, one on either side of the hull (outside) about 18” below the waterline adjacent to the bilge sump area to which the copper foil from the antenna tuner was attached. The grounding plates were constructed out of ¼” x 4” x 2’ copper bar purchased from Online Metals (http://www.onlinemetals.com/). In our opinion, the copper bar is nearly as effective as a grounding plate as the commercially available “dynaplate”, and at a much lower price. These plates were bedded and through bolted using silicone bronze fasteners. We have not bonded the ground plane system to any of the water tanks or thru-hulls, as there are several electrolysis issues to consider, and the performance thus far seems to indicate that further extension of the ground plane may be unnecessary. We added ferrite chokes to all transceiver and tuner cables to suppress RF interference. The ferrites are available through Farallon Electronics (http://www.farallon.us/).
We are currently working on the HAM operator requirements, namely Morse code and the exam questions. We also have the equipment for working email aboard through the use of the SCS PACTOR modem, and also have begun working the receipt of NAVTEX, WEATHER FAX, etc. etc. – but that’s another story!
We think this is a good installation since it appears to work well!! One can spend many hours conversing with long distance cruisers and dreaming of far distance ports!!