This is primarily for PhilB if he's around, but also for other SStran users.
This is primarily for PhilB if he's around, but also for other SStran users.
I'd like to try a SStran, but I've read over and over how it's designed primarily to be mounted at ground level, use a loading coil and ground radials.
However, as some of you know, I'm attempting to set up a station on my boat. Of course there is no possibilty of mounting it on the water. The only way to ground the TX is to run a wire either to the boat's ground, which involves a ground bus, the engine, through hulls, DC powered lights and motors, etc, and is also connected to shore power ground ... or simply over the side, which, from the mount point, is going to be at least 6 or 7 feet to the water
If the SStran requires a straight rf ground, is there any practical way to solve this issue? Is a MFJ-931 artificial ground necessary?
TIA ...
try and drop a piece of copper wire in the water and attach the other end to the sstran ground.
the sea water i would think becomes your RF ground and ground plane. because sea water has the highest conductivity on the planet.
I would agree, I don't see why the water would not act as a ground plane. I'm not an engineer, but I don't think you would want to tie your antenna/radio ground to your boats ground system at all, spark plug noise would probably get injected that way. I imagine you will need to do some research to find some type of "ground anchor" that conducts well but doesn't corrode. I'd actually have multiple "ground anchors" that dip into the water. That way you can do maintenance on them (aka clean the corrosion off them) one at a time without taking the system offline. Since on land it's good to use an 8' or longer grounding rod, I'd go at least that deep with your anchors. Of course you need to experiment though, who knows what will really work until you try it.
Thanks guys ... I know it would work, but the problem is "ground lead" length. The TX is not at the water, it's on a short mast on the cabin roof. The wire to the water is going to be too long to be included in the antenna, transmission line (not a problem), ground lead combination ... or do other rules apply in this case?
Grounds on sailboat masts are usually (on bigger boats) part of the electrical system design. The main mast is usually grounded for lightning and static discharge safety. Wind blowing through all that rigging can build up one heck of a charge. You might check the base of the mast for a ground lead. If not, it is legal to run a ground lead from the mast to the water, or metal making direct contact with the water, for safety. If you have a metal mast or a metal runner the mainsail hooks to, use it as the ground conductor. Hook the transmitter ground to the grounded metal. The safety ground is not necessarily included in the ground lead length in Section 15.219. The argument has already been made, it is not. The wire from the transmitter to the metal safety ground should be as short as possible (maybe 3-4 inches).
Not a sailboat. It's an old classic cruiser, 30' Owens Sea-Skiff. The antenna mount is a 3' pipe and standard roof tripod on the cabin roof.
I'm thinking I want a separate, more direct RF/safety ground at this point. Will this work OK with the design params of an SStran TX?
Hi Ken,
As others have said, salt water has the highest ground conductivity. There have been many reports of extraordinary range over salt water.
I wouldn't be too concerned over the length of your ground lead. The only way to comply strictly to the rule would be to mount your transmitter a few inches above water level. Not a good idea! A practical mounting height, given your conditions, is definitely above the cabin where salt spray will be minimal (when travelling).
I would recommend something other than just throwing a wire over the side. The ground should be physically stable. A wire over the side would work but as it drifts around, it will likely affect the tuning. I see nothing wrong with grounding the transmitter to the boat's common electrical ground as long as there is ample contact with the water. I assume there is a ground plate or something on the bottom that is submerged.
You may likely experience an audio ground loop hum problem. You may need a ground loop isolator that is commonly required in car audio systems. Radio Shack, Wal-mart, and any car audio dealer has them. If you're audio source is battery powered, you won't need one, but if AC powered, it likely will be required. The possibility of a ground loop will increase if you ground the antenna separately from the boat's electrical ground.
Phil B
Thanks for the repy ...
Negative battery terminal and negative side of all the DC powered gear, including radios, and also AC shore power ground are all connected to the engine, DC power panel ground bus, and copper strap to the transom through-hull plate below the water line.
There is already audio gear aboard, no hum so far. The sound will come from the computer, which has no hum I can hear.