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Author Topic:   Antenna Static Shock
gbcbu posted 06-01-2007 09:06 AM ET (US)   Profile for gbcbu   Send Email to gbcbu  
On my 170 Montauk I have a Shakespeare antenna with ratchet mounting. I place it down after using the boat so that my mooring cover fits correctly. The last two times I went to the boat to get ready to go out I touched the antenna to raise it for its correct position and received what can be described as a static electric shock. Not intense but enough to get my attention and more so than when you slide across a carpet on a winter day. Is this "normal" and if not what do I need to do?


jimh posted 06-01-2007 09:20 AM ET (US)     Profile for jimh  Send Email to jimh     
Does the cover rub on the antenna?
gbcbu posted 06-01-2007 03:49 PM ET (US)     Profile for gbcbu  Send Email to gbcbu     
Yes it would rub against it as I'm taking it off as I work my way from back to that the foot on the rug effect?
roloaddict posted 06-02-2007 12:29 AM ET (US)     Profile for roloaddict  Send Email to roloaddict     
Not too unusual. In 20+ years of marine electronic experience I have develop a strong dislike for the fiberglass antennas for two reasons. Number one is that they can fail in ways that are not visible to the eye ( trained or untrained). The number 2 reason is the static charge they can build in any wind and especially when cold/dry. One of my nightmares involves me checking the structural integrity of the antenna during an inspection and discharging the charge. The ship is a tanker loading/discharging some highly flammable cargo.Boom.

Since you can duplicate the problem, you could try an experiment that I have wanted to try. Try rubbing the antenna down with a anti-static dryer sheet an see if it cures the problem. I would be interested in the results.



gbcbu posted 06-02-2007 06:25 AM ET (US)     Profile for gbcbu  Send Email to gbcbu     
Roloaddict Thanks for responding. My antennea is all metal...I'll try the anti-static dryer sheet anyway if you'll think it will work. I'll rub the antenna with the sheet and see if it happens the next time which may be 3-4 days after using the anti-static sheet.

I think Jimh's question answers mine in that it may very well be the rubbing of the sunbrella fabric along the 2'-3' of antenna that builds up the charge. My initial reaction is that this poses no risk on my 170 Montauk as I can't see any fuel fumes from my 12 and 6 gal tanks being effected. Is it safe to assume that the "charge" will not damage the electrical system also?

I'll be going out in a couple of hours...fair weather for most of the day w/ t-showers predicted for late this afternoon...Thanks again

jimh posted 06-02-2007 08:21 AM ET (US)     Profile for jimh  Send Email to jimh     
What is the model number of the Shakespeare all-metal antenna?
gbcbu posted 06-03-2007 08:18 AM ET (US)     Profile for gbcbu  Send Email to gbcbu     
The factory installed Shakespeare antenna is a 5240-R or a 5241-R. According to the literature they are low profile , end-fed 1/2 wave, stainless steel...of 36" length. They are designed for use consoles...or any vessel where a standard fiberglass antenna may be too obtrusive or too difficult to install. It also mentions that it does not require an external or internal ground system. Thanks
jimh posted 06-03-2007 11:06 AM ET (US)     Profile for jimh  Send Email to jimh     
If you happen to have an ohm meter, perhaps you could make a measurement:

--turn off radio
--disconnect antenna transmission line from radio
--measure DC resistance of the antenna transmission line from center pin to collar at the connector

Usually these end-fed half-wave antennas have a shunt feed system and are at ground potential.

Do you get the shock from touching the metal whip portion of the antenna?

gbcbu posted 06-04-2007 06:34 AM ET (US)     Profile for gbcbu  Send Email to gbcbu     
Yes Jim I get the shock from touching the whip protion of the antenna. I don't have a meter but I'll ask around at the dock and will try to follow your instructions. It did not happen Saturday. This may take a week or so. Appreciate it.
jimh posted 06-04-2007 08:58 AM ET (US)     Profile for jimh  Send Email to jimh     
I am just curious to see if the antenna is grounded via its internal matching system to the shield of the transmission line. This would mean the antenna is also probably grounded to the negative battery terminal, and that in turn would mean the antenna is bonded to the sea via the bonding system or the anodes on the outboard motor.

I guess I am assuming you get this shock while the boat is sitting in the water, and not on the trailer.

gbcbu posted 06-04-2007 11:40 AM ET (US)     Profile for gbcbu  Send Email to gbcbu     
Yes while at the dock not on the trailer. Thanks
Bulldog posted 06-04-2007 04:24 PM ET (US)     Profile for Bulldog  Send Email to Bulldog     
Another question, are you on the dock or in the boat? If on the dock , what is it constructed of?.......Jack
gbcbu posted 06-06-2007 03:31 PM ET (US)     Profile for gbcbu  Send Email to gbcbu     
On the boat while it is at the dock. The dock is wood but I don't think it comes into play. As the weather is getting consitently warmer the problem hasn't re-occured. Also I've gone to the CC cover instead of the mooring cover so there is alot less contact with the canvas. I spoke to the teck where I bought the boat and he says it's normal. Thanks for your interest.
bluewaterpirate posted 06-06-2007 03:39 PM ET (US)     Profile for bluewaterpirate  Send Email to bluewaterpirate     
Not to hijack this, but I've seen static electricity build up on fishing rods while fishing offshore, especially the ones in the rocket launchers. When there are [electrical charges in the atmosphere] in the area you can actually get sapped by a static shock when taking the rods down even the ones in the gunnel holders.


jimh posted 06-06-2007 09:44 PM ET (US)     Profile for jimh  Send Email to jimh     
Many years ago, when I was intensely interested in amateur radio, we were dog-sitting for a friend who had a very elaborate antenna array, a "LAZY-H" which was strung between two 140-foot tall towers which were about 250-feet apart. This large wire array was completely insulated from ground, and was conducted by a very elaborate balanced 600-ohm open wire transmission line to the radio shack in the basement of the fellow's home, about 300-feet from the towers. The array was on top of a hill. That summer evening a big front of thunderstorms was approaching from the west. I began to hear these strange noises from the basement, and I went down to investigate. The noises were from electrical arcs which were jumping off the transmission line to ground. There were some grounding straps with clip-on leads nearby, but I was afraid to try to attach them to the antenna transmission line. That big array was alive with electrical energy from the approaching storm. It was arcing over an air gap in a tuning capacitor for an antenna tuning unit attached to the 600-ohm line. (The capacitor probably had an air gap good for 6,000-volts or more.)I figured it was better to let it arc than to kill myself trying to ground it.

Eventually it started to rain. When that rain hit the static charge in the air was gone, and the arching stopped. That was my best first-hand experience with a static charge conducted out of the air.

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