Yet another SSB antenna installation...

[toddster8]

About a year ago, I "upgraded" to a significantly larger boat, moved aboard, and brought my SSB system with me. In this age of satellite and cellular communications, the HF radio is probably now more of an optional hobby item, so it hasn't been a big priority. But I'm not ready to throw it away. Since then, it has been knocking around in cardboard boxes, taking up space and getting in the way. But now, I am doing some other installs, have access panels open and am trying to figure out how to run the SSB cables.

To cut to the chase, I have two options for installing the AT-140 antenna tuner. Both seem to have problems and advantages. The backstay runs through a gap in the middle of the solar panel array, which is cantilevered forward of an aluminum arch. The arch is populated with various other electronic toys.



Option one: conventionally below deck, with a lot of GTO-15 snaking around the backstay adjuster, solar panels, radar, etc. (Or a long run up one leg of the arch, but that's close to other wiring.) This requires only one deck penetration (well, two if I also put up the DSC antenna) but I don't really like the idea of antenna wire on the hydraulic backstay adjuster, which has to, well, adjust. That's also what you inevitably grab on to when climbing up the swim ladder. And this route seems to have great potential for mutual interferences.

Option two: mount the AT-140 up on the aluminum arch, beneath the solar panels. This would require at least one extra deck penetration but would put the antenna stud only 6-8 inches from the backstay and put almost all the radiating wire above the arch.

But... how would I run the ground from the tuner, way up there? My thought is to run a short strap (probably aluminum for galvanic reasons) from the tuner stud directly to the nearest tube of the tower. The tower (and the panel frames) is connected to the ship's bonding system through its legs, below deck. I could probably improve this by running copper strap (on hand) from the (stainless) mounting bolts of one leg to the strut mounting bolts. (There is quite a lot of "structure" in between.) Getting it to a keel bolt would be even more of a project but might be possible. So that's a pretty long connection from the tuner to ground, but is there some reason why this wouldn't work / is a dumb idea?
Better to find out now, before all that work!

Either way, I'm going to have to send away for some longer cables - but the tuner placement would determine which ones need to be longer. I've got one of those GAM split-lead things "for now," but if this works, would get an insulated backstay next time the rigging is worked on.

[Wotname]

The short answer is the tuner should be halfway between the antenna and the ground. The antenna starts at the tuner and the ground starts at the tuner.

IF your ground includes the arch, then option 2 sounds better than option 1.

Ideally though, the lower insulator on the backstay would then be just above the arch.

Every boat SSB antenna / ground installation is a comprise, you have to make the best comprise and accept that it can never be theoretically perfect. The AT-140 will tune a wet noodle and often a wet noodle will radiate enough RF to establish coms most days. Other factors such as freq used, time of day, ionospheric conditions etc have huge impacts on the workability of HF coms.

Given the detail you posted and depending on the location of the lower insulator in the backstay, option 2 sounds the best to me.

[Wotname]

After re-reading the OP, it seems you do not have an insulated backstay - if so then wherever you connect to the backstay, the entire backstay is active.

In this instance, I'd mount the tuner below the deck and connect to the closest point of the backstay and the ground to the nearest underwater metal (seacock / keel / dynaplate etc).

You may or may not have to disconnect the bonding on arch legs; suck and see!

[wholybee]

Most definitely, below deck. You want it as close to ground as possible, and you want to use copper strip at least 2" and preferably 4" wide to connect the tuner to ground. How would you run that strip up to the tuner? That must be more difficult than running the GTO-15 up to that level. You would also be running the control cable that extra distance, and sometimes there are issues with the control cable "receiving" the transmitted signal and causing issues. So you should minimize that risk.

The ideal place is for the tuner to mount below decks, under the backstay, or as close to that location as possible. The deck penetration should be as close to the chainplate as you can make it, and the GTO-15 following the backstay to above the insulator. If the chainplate isn't bonded, then the GTO-15 can be attached directly to the backstay. If the chainplate is bonded, you still can run it directly attached to the backstay, but standoffs are preferred. Adding some slack to go around an adjuster is no issue.

The antenna starts right at the connection to the tuner, so the GTO-15 is part of the antenna also.

[toddster8]

Thanks guys, but you're a bit off the mark. To reiterate:

I'm initially using one of those GAM split-lead antennas. The backstay will not be energized at this point. I certainly will never energize the hydraulic backstay adjuster.

The proposed method of connecting the (elevated) ground is to run a short strap, no more than twelve inches, directly to the aluminum arch, which is connected to the boat's bonding system. Then "improve" that connection with a copper strap below deck from an arch leg to the strut, which is in contact with sea-water. The arch would effectively BE the upper part of the grounding "strap." Although the connection through the deck would be via the four bolts connecting the foot to the backing plate. (Same situation as the strut itself, or a keel bolt.) I could potentially tie in more than one foot.

This is a little different from the various diagrams proffered on-line that show assorted conducting surfaces (towers, lifelines, toe rails, tanks, keel, etc.) and radials all connected back to the ground stud with separate leads in a star pattern. (In reality, the stud isn't big enough for many connections like that. I think it's only a short #8.)

Other sources contradict this and say that only one ground should be chosen. I.e. strap directly to through-hull shoe or similar.

Then there are the manuals that say to also connect the transmitter to the ground and others that say not to. (I didn't, on the last boat.)

Another consideration is that the boat spends part of the year in freshwater, during which coupling to sea water will not be available. So hopefully tying in all the bonded stuff might be advantageous.

[Wotname]

OK, it using the GAM unit as the antenna and the arch etc as ground, the same rules apply. Fit the tuner halfway between the antenna and ground which in your case means option 2.