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Old 07-06-2007, 13:55   #16
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Dave:

No you won't. I "retired" from Gov't 18 years ago and still haven't found the time to do the things I want to!

Funny, I'm just back from a 3-day shakedown cruise to see what broke over the winter, and I'm also thinking about refrigeration: my long-suffering (26-year old) Adler Barbour Cold Machine is laboring too much. Been looking at new ones :-)

Bill
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Old 07-06-2007, 14:04   #17
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Mine is only 18 years but has been in constant use since we move aboard during the season.It is a Nova Cool unit and the replacement unit will have the same footprint but a more efficient compressor and incorporate the 134 refrigerant.
It should be a one day job.
I have just been putting a block of ice in the frig since april but the days are getting hotter and do you know how much a few pounds of hard water cost?
Dave
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Old 08-06-2007, 04:41   #18
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Originally Posted by btrayfors
... As you probably know, I HATE dynaplates. Because they're unnecessary. Because they're a ripoff. Because if they work at all it's only in the first few months, after which you better find a way to keep 'em clean. Near impossible. Save your mone
... Sorry. I just can't abide dynaplates. Bill
What Bill said, and more that he knows but didn’t say.
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Old 08-06-2007, 06:41   #19
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Ok then, i'm here for the long haul..what would be your preferred method of installing the Ground system .
Dave
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Old 08-06-2007, 13:24   #20
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Dave:

Been a bit busy...sorry to be late replying.

Well, I'm not sure I know you that well :-)

And, I don't know your boat. Ground systems are very much an individual thing. Know why almost all "authorities" on HF installations recommend the ground-plate and "100-square feet of copper" solutions? Because they're adaptable to most boats. Not because they're particularly efficient or effective. But, they can be done on virtually any boat.

Basically, what you're trying to do is either: (1) couple the ground side of the antenna tuner to the seawater, either capacitatively or directly; OR (2) construct a pseudo ground which serves as the other half of the "dipole" antenna. I prefer the latter approach, using lifeline, radials, pushpit/pulpit, toerails, s/s rub rails, etc. Some authorities advocate the coupling-to-seawater approach via groundplates, through-hulls, lead keels, aluminum tanks, "100sqft of copper", etc.

On your boat, you gotta do what works best. It's not a bad idea to couple the tuner ground lug to a closeby bronze thruhull, if you have one. This provides a DC ground, if nothing else, useful for bleeding off static electricity which can build on the antenna. Then, think about "the other half of the dipole". To test things out, lay some wire on your side decks. Use any kind of insulated wire you have handy, of any size and type. Try just one....a 1/4 wave radial....first. You'll be amazed at how easy it tunes up. Take it from there, experimenting with additional radials of varying lengths. When you're satisfied that his really works...as it surely will...then think about how you're gonna mount these radials permanently under the deck somewhere.

Don't be afraid to experiment. This ain't rocket science. It's 50% radio science and 50% luck on your own vessel.

Bill
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Old 08-06-2007, 13:57   #21
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Well l guess thats where l was going in my first post, l have only Marlon thruhulls and the dynaplate was connected to the mast which is in contact with the shrouds and stays so my thinking was this would be a good source of ground plane..but as you said..lightning strikes once and poof!
l do have lots of tankage below decks 150 gal water,40 gal holding,45 gal fuel all of metal but none with connection to seawater,a small "plate" thru the hull should suffice l would guess. ALTERNATIVELY YOUR "WIRE" runs would have to be fished through the cabin liner and brought to a common buss.then fed to the ground on the radio.
I am in the habit of totally disconnecting electronics in lightning conditions and not just switching them off.
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Old 08-06-2007, 14:07   #22
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... I am in the habit of totally disconnecting electronics in lightning conditions and not just switching them off.
dave
An excellent policy!
Separate the antenna & power leads, from the equipment by as much distance as possible (> 3 Ft / 1m would be nice).
Also remember, there is lightning anytime there is thunder.
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Old 08-06-2007, 14:11   #23
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Dave:

You don't want the grounds going to the radio. You want them going to the ground lug on the TUNER.

Also, you don't need a DIRECT connection to the seawater. Your tanks, etc. will capacitatively connect to the seawater just fine. If that's the way you want to do it.

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Old 08-06-2007, 14:18   #24
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just for clarification Bill, what gets connected to the ground lug on the radio??
And bonding all tankage without a seawater ground should be sufficient?(led to the Ground lug on the tuner).
In as much as my wife usually elbows me in the ribs every time we are caught in a lightning storm that suffices to alert me to disconnect the radios.
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Old 08-06-2007, 14:19   #25
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oops, it's time to disconnect the radios l just got the elbow, looks like a good blow up here in Toronto this afternoon.
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Old 08-06-2007, 14:25   #26
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Dave, current wisdom is to not connect anything to the ground lug on the radio. The DC is grounded though the power cable, and the RF is grounded to the tuner through the coax. By connecting the counterpoise to the ground lug you are opening yourself up to ground loops.
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Old 08-06-2007, 14:35   #27
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Dave:

Nothing gets connected to the ground lug on the radio. It's superfluous. Connecting a ground wire to it can cause "ground loops" which are not desirable. Forget the instruction manuals.

You don't need a direct connection to seawater. Capacitative coupling will take place whenever a conductor is in proximity to the water. Inside the hull is fine. If you're gonna use the tanks, be sure to use wide copper strips between the tuner and the tanks.

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Old 08-06-2007, 15:00   #28
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Quote:
Originally Posted by btrayfors
... Nothing gets connected to the ground lug on the radio. It's superfluous. Connecting a ground wire to it can cause "ground loops" which are not desirable. Forget the instruction manuals...
Quote:
Originally Posted by DeepFrz
Dave, current wisdom is to not connect anything to the ground lug on the radio. The DC is grounded though the power cable, and the RF is grounded to the tuner through the coax. By connecting the counterpoise to the ground lug you are opening yourself up to ground loops.
Fully agreeing /w btrayfors & DeepFrz, I wonder if anyone has engaged the manufacturers on the subject?
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Old 08-06-2007, 15:11   #29
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Gord,

There's a problem here. Manufacturers and professional radio "installers" are concerned about product and service LIABILITY. Hey, if something's not grounded and someone, somehow, thinks they got hurt as a result.....

This garbage about "100 sq ft" of counterpoise is a good example. There's no science to back this up. It's been repeated from one "authority" to the next. Ditto for connecting to ground plates or thru hulls.

The SCIENCE of RF transmission points in an entirely different direction.

Factoid:

RF is absorbed in only a few inches of seawater. Why in the world would anyone want to pump RF energy into a ground plate located 4-6' underwater? To heat the surrounding sea?

Factoid 2:

The most efficient HF antenna you can mount on a sailboat is a vertical dipole. It will outperform just about any other PRACTICAL antenna, putting most of its energy out within a few degrees of the horizon...exactly where you want it for long-distance communications. And, this antenna doesn't require ANY separate RF ground! It's self-contained. No connection to seawater. No "100 square feet" of copper. No connection to water tanks or ground plates or seacocks. Not even a tuner needed, when trimmed properly.

A few manufacturers have, rather reluctantly it seems, allowed some of this reality-based "science" to creep into their discussions of antennas and RF grounds. But, most of them....and most authors...are still deeply rooted in the "tried and true", "very safe" recommendation that an RF ground connection to the seawater is best.

Bill
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Old 08-06-2007, 15:40   #30
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“Vertical Dipoles and Ground Planes” ~ by L. B. Cebik, W4RNL
Vertical Dipoles and Ground Planes

See also,Bill’s excellent article:
“Tuning a Marine Dipole Antenna”
http://cruisenews.net/cgi-bin/mmham/webbbs_config.pl/noframes/read/487


and:
Making a dipole antenna for your SSB radio ~ by James Baldwin
Atom Voyages | Making a Dipole Antenna

Not doubting your (& others) stated opinions, I wonder what possible "liabilties" the manufacturers might be hoping to mitigat?
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