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Howdy,
We’ve talked before about this, and I realize the experimental nature of my endeavors, but I’d like some clarification on a few issues.
Howdy,
We’ve talked before about this, and I realize the experimental nature of my endeavors, but I’d like some clarification on a few issues.
1) My boat is not large, about 28 ft., weighing in at about 6 tons. It’s wood, last of the Owens wood lapstrake and plywood hulls.
2) The cabin roof is where I want to mount the antenna system. It’s about 6 vertical ft. from the waterline.
3) The boat has two separate power systems: (a) Batteries, 2 banks — 12 vdc on board, negative ground bonded to the through-hull at the transom which is under the water line (zinc block). There is a power panel inside the cabin mounted in the starboard bulkhead by the cabin entry ladder. (b) Shore Power — 110 vac, normal neutral ground, two 20 amp breaker boxes in the head area of the cabin.
The only place they come together is the Marine Charging System, which isolates them.
4) I want to propagate signal up into town as far as I can get. There are some cliffs, buildings, and parking lots above my portion of the marina.
5) I’d like to power the system from the battery side, the same as the LORAN and VHF, but the PS’ for the computer supplying the audio and also the TX are 110 vac adapters. The computer one outputs 24.5 vdc/2.65 a. The TX one outputs 15 vdc/.8 a. Both are regulated.
The questions go like this:
A) What would happen if I use a 12 vdc to 110 vac inverter to plug the current PS’ into? I have no idea how those things handle grounding.
B) My best idea is a compromise: A rooftop style tripod with a 3′ steel pipe mast. The pipe clamped by the tripod, but also mounted to a flange on the cabin roof and to a flange on the bottom of the loading coil. The TX feed line a shielded cable inside the pipe, not visible outside. The TX mounted to the underside, i.e., the cabin ceiling out of the weather … also very close to the 12 vdc Power Panel (for ground). I don’t see how this could radiate anything significant … certainly no more than audio cables on some units. How legal would it be (hey, TH transmitters can use TX line cables)?
The antenna in this case, instead of the old Shakespeare whip, would be a sort of cross between the SSTRAN-style antenna and the Manteca Magnum … tunable. Except for polishing and preserving the copper, this is ready to go. I would guy the top portion with 4000 lb. poly lines.
Overall, it should be a very stable, clean, and good-looking installation, but a lot of work. I can loosen one of the tripod legs and the pipe from the flange to lay it down by the other two leg hinges in case of a really heavy storm.
C) …But will it work?
Total posts : 45366If you are on salt water…. I would keep everything separated from the marine system and just drop a 10′ copper wire over the side for your ground system. Make sure your power supply has transformer isolation with no components wiring around the transformer. Ditto for the audio/internet. Use a audio transformer to isolate your transmitter on the audio side. If you are on salt water I bet you get good range. Even wood boats suffer with electrolysis and you have to be careful. It’s been awhile but if I remember correctly make sure all 12V systems are isolated with transformers also. You don’t want any current on the shore power ground lead. Dave
Total posts : 45366And the coolest of all is the Ground Conductivity Map number for salt water. While the land numbers range from 2 – 30, the salt water number is… 5000!
I think the best answer to “C” would be to set up a simple trial with a ten foot wire antenna and a piece of bare copper wire overboard for a ground. For power, just use a battery – perhaps not the one in the boat (Lapstrake Owens = JEALOUS! I live up by the border so I might need to swing by and tune in.), but the SSTRAN site says:
“User-supplied Power information:
DC output voltage should be rated between 20 – 24 VDC. Adapter should be rated for at least 200 mA output current. ”So four 6-volt lantern batteries would give you about 50 hours of testing power.
If the test platform indicated you’re on to something, then start substituting test items with permanent work – antenna, ground, power, etc.
Total posts : 45366I really hope this setup works for you.
Man, what a great opportunity for long range low power broadcasting.
5000 compared to my measly 2 ground conductivity.You just might become a legend in part 15 history, maybe even get d.x. reports if all works according to plan.
*****
5 Stars
Total posts : 45366Well, the marine system is of course used for all the other radio gear onboard, e.g., VHF transceiver, LORAN, CB, DepthSounder, etc. I don’t understand why the AM TX (a Spitfire) should be any different. I’ll check again, but I believe all of their grounds are the negative side, wired to the Power Panel.
I’ve owned this boat for 15 years. Electrolysis is indeed a little problem, but not so bad for copper. The boat uses copper fasteners. So, I’m not worried about electrolysis … the boat’s ground bonding to the Zinc block takes care of that. But I still have to inspect the copper braid and how much Zinc is left from time to time.
What does this mean: “Make sure your power supply has transformer isolation with no components wiring around the transformer.”?
Are you telling me to connect to shore power only? The thing is, I want to stay up and running if shore power goes down.
This TX came with a regulated 110 vAC/240 vAC to 15 vDC power supply. The manual says I can use 12 vDC 200 ma or more. The boat system shows just over 14 v.
The charger isolates the two systems … AFAIK all marine charger installations do that.
If I use an inverter for 110 vAC power instead of shore power, I would use it for the TX, the computer, and the wireless internet modem/antenna. Do inverters isolate the 12 vDC input from the 110 vAC output? Of course it will have to be plugged into the onboard 12 vDC, else there would be no way to keep a separate battery charged. I can’t afford a solar charging system, and if a separate charger was connected to shore power, I’d be right back where I started.
Total posts : 45366Hello again Ken. I suggested a separate system not knowing the extent of your experience with marine power systems. I was just suggesting that you not connect your transmitter, DC wise, to the rest of the electrical system since I also was recommending a 10′ wire be tossed over the side for your RF ground possibly forming one side of a galvanic circuit that if bonded to the other grounds in your system would form a battery with other metals immersed in the water on your boat or other boats (if you didn’t have a galvanic isolator in the ac ground lead) in the marina. Isolation is the first line of defense. Zincs are a fall back position. Dave
Total posts : 45366I always wanted to try a marine part 15 setup because of the reasons rock7 gave. It will be interesting to hear how it works. I wasn’t into part 15 when I lived on my boat but wish I had been. I sure would have experimented with it.
Total posts : 45366Ken,
I don’t know much about marine wiring and galvanic action but from what Dave presented perhaps you should put a capacitor in series with the RF ground wire. This would pass the RF and block any DC current resulting from galvanic action between the ground in the water and the boat metal. Something on the order of .047 or .1 mfd should work.
Neil
Total posts : 45366Thanks, that makes sense.
As hot as this marina is, the only way to help prevent electrolysis in my TX circuit would be to do that. West Marine article suggests a 1/10″ gap in RF grounding tape (mounted on a nonelectrolitic mounting block, like phenolic) with 4 @ 0.15 uF monolithic capacitors soldered across it.
Since the VHF radio that came with the boat died, I wonder now if it was ever blocked that way. It doesn’t need a ground plane, but it could still pick up electrolysis.
I guess the purpose of having 4 caps rather than 1 is to keep it working if one of them bites the dust.
Well, it’s going to take longer to get up and running … Y’all have me questioning the robustness and correctness of the whole onboard electrical system now, so I’m going to go through it all.
Total posts : 45366Ken I was not trying to wire down the electrolysis panic button. Generally it takes a while to do it’s damage. I am not aware of these problems causing any “on Board” damage to equipment. It’s only at the metal-saltwater junction that there’s problems (wood,nails,thru-hulls,prop,rudder,etc,). If you power your tx with a wall wart and again isolate your audio systems you should be fine. I Think a valid test would be to hook everything up and then do an ohmeter check from the transmitter rf ground to your ships ground. It should show a high resistance if everythings OK. The salt water will conduct some so it won’t be infinite.
Total posts : 45366Hi Dave,
It’s OK. Most metal parts like you mentioned should not be wired to anything, but many of those parts have unlike metals and will defiinitely need Zincs. OTOH, the parts that are grounded to the engine and the through-hull, which is also the DC return, should generally be OK with one big Zinc on the transom and one in the little holder on the engine.
But I’m finding that it’s desirable to have radio RF ground with a capacitor break. The water is pretty darned hot in this marina, probably due to people failing to isolate shore power and neutrals go to ground on the boat. It’s a constant problem in marinas. West Marine’s article suggests doing that.
I think I have it covered, the ground bus looks good, but I need to check the transom run. I do want the water to form a counterpoise.
How about height? How much would I benefit by height? I could go back to the Shakespeare whip and raise it all, but it would mean making a very weatherproof dry case for the TX. Total height could be 16 ft of mast (2 glass sections), loading coil and 102″ whip. How much would that benefit me?
Total posts : 45366The higher it is the less it will be obstructed by buildings, trees, cars, ect. At Flea powers height can play a big role.
Total posts : 45366Pictures speak louder than words. So I’ll try to take some shots that show my situation.
Thanks to everyone for all the help. I haven’t read about anyone trying a Part 25 marine setup here or anywhere else, and my limited overall experience is leaving me with quetsions.
I understand obstructions, but I’ve also been hearing the other side of the issue because AM radio travels on the surface in daylight hours. I’m about 120 yards from the shore, the elevation there is approx. 60+ ft. to the main town. So, I’m not sure elevating the antenna base beyond the 10 ft. or so above sea level if mounted to 3 ft. mast, or up to a maximum of 26 ft above sea level if mounted to a 16 ft. mast, would make any difference.
If it does and I still want to use my copper antenna, I’d probably mount everything on the glass masts, including the TX and an inline coil, and cover the whole thing with a capped PVC pipe right up to the antenna, which would be mounted on adapters at the top. IOW, everything except the antenna would be inside a big 16 ft. high drain pipe. Best protection I can think of.
That would truly be a pain to mount on the cabin roof, especially if I want it to knock it down in a really bad storm. OTOH, especially if I stuck some ring braces between the center mast and the inside of the pipe, it would be very strong.
Now what do y’all think?
Total posts : 45366Oops! I meant Part 15 (not Part 25) Sorreee …
Total posts : 45366Used to cruise my Hans Christian 43 cutter up thru there and north every year. I always ate at the mexican place each year. mmm
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