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MBHladilek
#1 Posted : Sunday, January 11, 2009 11:44:53 PM(UTC)
MBHladilek

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I'm adding a new (actually an old) hobby to my collection as I will be testing for my Technician and then General Class Radio Operator's Licenses before the boating season opens. I'm looking at how I can build a mini shack aboard the 'free spirit'. I haven't been able to find any good information on HF antenna design for aluminum boats. Besides HF I'll also have 2 meter (and maybe 70cm) aboard but that's the easy band.
I'd like to operate from 160 through 40 meters, SSB, RTTY & CW. Any suggestions?
73
Michael
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dougrose
#2 Posted : Monday, January 12, 2009 1:13:54 AM(UTC)
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I bought a 23' whip from Boaters' World for the SSB, and drive it with an antenna coupler that matches the load. I simply run a wire out to the whip, and use the boat hull (cabin top, really) for the negative (counterpoise).

I do this by mounting a vhf bulkhead connector in a hole just above the window on the horizontal surface under the roof. On the inside, I plug in a coax cable from the coupler. On the outside, I use a connector but run the center conductor to the antenna, shield removed. Seems to work. This setup should be fine for 160 thru 40 meters, or maybe even 20, since it is a base-loaded whip of less than 1/4 wavelength.

A whip like this starts acting strangely once the frequency is high enough to fit a wavelength into the whip, so you might want to get separate antennas for the 2 meter and 70 cm bands. The other problem is that a whip gives you vertical polarization, and my understanding is that most of the short-wavelength stuff is horizontally polarized.

I got two matching 2-piece whips (as Christmas presents) from Boater's World mostly because they were too long for UPS and BW had their own truck bring them to the store for free. Shipping costs will eat you alive on these long 2-piece units. The other whip is a marine vhf and it is terrific.






1975 32' Flybridge Sedan, twin Perkins 6-354 diesels, 1:1.53 velvetdrives, 16 X 19 props. Merritt Island, Florida
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MBHladilek
#3 Posted : Monday, January 12, 2009 1:48:32 AM(UTC)
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dougrose,
Thanks for the feedback. Do you ground couple your rig to the hull? Do you think using half the 23' whip might cover 2M and 70cm?
Do you use an independent antenna tuner? Is there a difference in salt vs fresh water when the hull acts as the counterpoise? Have you ever heard of someone using a beam? Sorry for the boat load of questions but these are some of the things going through my head as I plan this out. My rig is an circa 1980s Ten Tec Corsair II.
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Ed
#4 Posted : Monday, January 12, 2009 4:05:06 AM(UTC)
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I can see you'll have the ideal ground plane (half of the ideal lake on top of the mountain) and a new excuse to buy a bigger boat.Do you think the wife will go for a boat to fit the antenna, 160 meters?
Years ago did see a surplus aircraft carrier for sale by one of the brokers.My excuse was I could have my boat and my runway both, but she wouldn't buy it. Literally.
That would work if you can work out a few problems....
I haven't finished moving, my rig is still in storage, 1200 miles away, but maybe you'll inspire me to get it and get back into Ham radio. Not that I don't have plenty to do already. Keep us posted on your project, save us some headaches and inspire us. Maybe hear from you someday. Goodluck with it, Ed KL7YW
BUSIA
32 foot, no flybridge, twin 350 (chevy) Crusaders, closed (freshwater) cooling, 1:1 Velvet drive transmissions.
Proud to be IBEW.
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fastjeff
#5 Posted : Monday, January 12, 2009 8:12:21 AM(UTC)
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Hey, Michael, have you looked into joining the Coast Guard Auxiliary? They are always looking for "watch standers" for patrol activity. Might be something you'd enjoy.

Jeff (Flotilla 10-2 5NR)
"...reality is not nearly as lovely as the world of Liberal Land. No wonder so many people want to go there." - Tom Sowell
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MBHladilek
#6 Posted : Monday, January 12, 2009 8:20:20 AM(UTC)
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Ed, I'd go for the 160 meter boat but I'd have to sell my soul HI. I'll give you my call sign when I get it.
Fastjeff, thanks for the tip. I would enjoy that.
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GB49
#7 Posted : Monday, January 12, 2009 3:33:54 PM(UTC)
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I'm studying for my "General Radiotelephone Operator License" plus "Ship Radar Endorsement". MROP & GROL
There is allot of stuff to remember. Brick wall

Looking forward to doing the FCC inspections on the local commercial boats.
We also handle much of the freighter electronics on the Great Lakes.

-Karl

1986, 32' Sedan, twin 360ci, 275hp Chrysler's w/ K&N flame arrestors
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MBHladilek
#8 Posted : Monday, January 12, 2009 11:20:20 PM(UTC)
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Karl,
That sounds really interesting. What class of commercial boat would require an inspection of that type? I'm also going for my Capitan's license (6 pack), would that be part of my commercial inspection?
Michael
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dougrose
#10 Posted : Tuesday, January 13, 2009 2:11:07 AM(UTC)
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Yes, I connect directly to the hull, as follows:

The tranceiver and coupler are mounted above the windows starboard side (to keep them dry and out of the way) and there is a bulkhead connector above the window going through the horizontal overhang outside the window. I apologize, I have no pictures, and I am in DC and boat is in FL. This "feedthrough" connector is a threaded barrel with a couple of nuts, and is the connection to the hull. Each end of the feedthrough has a connector.

I have an antenna tuner (a must) that has a variable inductor and two variable capacitors in a pi network, along with a meter for SWR/output power. I am sorry that I do not remember the company and model.

There is a short cable from the output of the antenna tuner to the feedthrough connector, and both antenna tuner and tranceiver are grounded by the feedthrough connector through this cable.

Outside, there is a plug with only the center wired, no shield, and the wire goes to the feed terminal at the bottom of the antenna.

I have no photo of the SSB side, but here is a photo of the portside vhf whip (looks the same) showing the swivel connector below the window, and the "wing" out of star-board that extends the flybridge out to hold the antenna mount.



I have, since the photo was taken, shortened the "wing" to straighten the antennas up, for looks. There is a "J" bracket at the aft edge of the cabin top into which the whip is placed when down.

The boat is bigger than the antenna, and should be a good counterpoise. I don't image fresh, salt, or no water would matter, but I haven't tried it.

The whip is a solid conductor fed at the bottom, so you couldn't use half. However, you could get a multiband whip, I just don't need one. Below around 12 meters, a 23' whip will act squirrelly, because the tuner will drive high voltage or high current as needed to match the load. Better to have an antenna made for the wavelength.

Can't image using a directional antenna underweigh or at anchor, but if you use your rig at the dock you could always put your antenna on a nearby piling. Lots of liveaboards do this with their satellite tv.

I am not really a radiohead so I hope some other members will help out here. I have just described what I have actually done and it works.


1975 32' Flybridge Sedan, twin Perkins 6-354 diesels, 1:1.53 velvetdrives, 16 X 19 props. Merritt Island, Florida
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MBHladilek
#11 Posted : Tuesday, January 13, 2009 2:34:27 AM(UTC)
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dougrose,
Thanks for the detailed reply. I've read somewhere that a flat braided cable is draped overboard to act as the counterpoise. However I suspect this is for fiberglass boats. It seems that the hull paint would reduce the coupling to ground (water), but perhaps the sacrificial anodes improve this ???? Guess if I get a could SWR reading I know it's working.
I met a Canadian Ham (no pun intended) on Hamsphere (an on-line transceiver simulator http://www.hamsphere.com/) he has made a lot of 2 meter contacts with boats on Lake Huron. I can't wait until the spring (that is after I install new or rebuild the engines) to get this rig operating on Lake Superior.
What's your call sign?
Michael
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GB49
#9 Posted : Tuesday, January 13, 2009 3:09:32 PM(UTC)
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MBHladilek wrote:
Karl,
That sounds really interesting. What class of commercial boat would require an inspection of that type? I'm also going for my Capitan's license (6 pack), would that be part of my commercial inspection?
Michael


Michael,


The passenger & vehicle ferry boats that run around the Erie Islands require inspection.
I cant say for sure what the 6 pack includes but I'll ask around and try to find out.

So far the Radiotelephone book is common sense. Everything is based on emergency situations and ultimately the safety of lives. The other 1/2 of the book dives into the electrical theory but, if you have some basic electronics like Ohms law and other principles should be ok. Just allot of stuff to read/remember. Prob will never use 1/2 of it after the test.

-Karl
1986, 32' Sedan, twin 360ci, 275hp Chrysler's w/ K&N flame arrestors
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dougrose
#12 Posted : Wednesday, January 14, 2009 2:05:14 AM(UTC)
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Michael, you are most welcome. I can't tell you how much s**t I have avoided by reading this forum.....

A cable draped overboard is a lousy way to get a centerpoise but used to be common on glass and wood boats.

My sailboat had a sintered bronze plate on the hull that made the connection to the saltwater - it is little balls stuck together and has terrific surface area. Don't think you would want one on a Marinette.

Many boats used to use 100 square feet or so of copper sheet inside the hull, which couples capacitively to the water outside. Worked well. Remember, you are not coupling dc. At radio frequencies, the thickness of paint or even of a fiberglass hull just doesn't matter.

The SWR reading, as far as I know, does tell you how well it's working.

2 meters is pretty short and a whip for it is very compact. You might want to check out Amateur Electronic Supply (AES) for multiband antennas, particularly page 56 of their catalog. There is so much stuff available it is unbelievable. When I started in amateur radio back in the 50's you had to build everything for yourself.

My ham license expired years ago, and I think they have reassigned the call sign. The stuff on my boat is licensed as Marine SSB and I only use it as marine communication. But I do love to listen to the radio, and the Yaesu FT747 with tuner really pulls in the stations. I can sit in Florida and listen to the French broadcasts from my hometown (Montreal) or Paris, or even some weird stations in Africa. Every boat should have a good shortwave.




1975 32' Flybridge Sedan, twin Perkins 6-354 diesels, 1:1.53 velvetdrives, 16 X 19 props. Merritt Island, Florida
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dougrose
#13 Posted : Thursday, January 15, 2009 4:44:43 AM(UTC)
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Memory fails me at my age but I believe that the antenna tuner that I installed was an MFJ-969 from MFJ Enterprises.

It tunes from 160 thru 6 meters and, since it uses a continuously-variable inductor rather than switch-and-taps, it can be tuned exactly at any frequency.

It is a manual unit because for Marine SSB you don't often change the frequency. A ham might prefer an auto tuner, but they are a lot of bux.




1975 32' Flybridge Sedan, twin Perkins 6-354 diesels, 1:1.53 velvetdrives, 16 X 19 props. Merritt Island, Florida
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RiverRatt
#14 Posted : Tuesday, January 20, 2009 9:05:02 AM(UTC)
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Good information in the post, Thanks to all
I got my license in 2002.
Antennas and radio equipment will be a project after "sea trials" this spring.

KC9HAX
Robert
"The is no dumb-ass vaccine" - Jimmy Buffet
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