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Old 01-17-2020, 02:05 PM   #1
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HF Antenna

I am seeking suggestions and information on installing a HF antenna of a fiberglass boat. I will be operating in fresh water only.



The boat is 38ft fiberglass --- I plan to use a Yaesu Ft890 with built in tuner. I also plan to run a 500 watt solid state amplifier. I would like to be able to operate on 15m, 20m, 40m and 80m bands --- 160m would be nice but I realize that may be stretching it.



Any help on an antenna system would be appreciated.


Terry
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Old 01-17-2020, 02:13 PM   #2
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Unlike in saltwater where a sintered bronze ground plate is the norm for HF installations, fresh water is not likely to give your HF rig a very good ground. Assuming you plan to do most of your radio work while at anchor or moored to a pier, you might want to look into a temporary rig like a copper rod speared into the shallow bottom and connected to the rf ground of the radio by appropriately sized cable.
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Old 01-17-2020, 02:17 PM   #3
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Rich, thanks for the reply, but I would rather have the option of using the rig while underway.
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Old 01-17-2020, 02:40 PM   #4
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HF Antenna

I’ve run HF on smaller boats. 27 and 32’. Both down to 3.5MHz.

Have run Hustler whips, 27’ Shakespeare and 32’ whips. Grounding will be the trick in fresh water. Tie in to both prop shafts with shaft brushes. Use the hopefully already extensive bonding system. Include fuel tank, engines, bow rail, transom anode, rudders etc.
I do not value small dyna plates and the like. Problem with in radio tuners is high VSWR on feedline, and feedline radiation. Use an effective CM choke. I like balun designs stuff.

Also, what tuner will the amp feed??
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Old 01-17-2020, 03:32 PM   #5
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I’ve installed several HF radios with the last one an IC-M802. I tie the tuner to the fuel tanks, steering hydraulics, engine and thru hulls. We’ve talked all over the world with people thinking we’re on a sailboat. It might be the radio but I don’t think so. Keep your antenna wire (GTO-15) to tuner as short as possible and don’t cheap out on the 2” copper foil to tie it all together. Some is about as thick as aluminum foil and the good stuff, you’ll need scissors to cut.
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Old 01-17-2020, 06:00 PM   #6
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I know little about building a ground plane. Down in the bilge there's copper straps -- each being about 1.5 inch wide spaced every 3-4' apart. They seem to be connected. Not sure how many but I suspect they from from front to rear. Could this be a ground plane or used as a ground plane?


Thanks
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Old 01-17-2020, 09:57 PM   #7
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Those are likely bonding conductors. You should see a number of offshoots connecting to engines, thruhulls, etc

Yes, they all become part of the antenna counterpoise.
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Old 01-18-2020, 05:44 AM   #8
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IF you are interested I have a WWII life boat collapsible antenna made of monel.


Goes about 25ft when extended
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Old 01-18-2020, 08:08 AM   #9
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A whip antenna is the easiest antenna to implement. Alternatively you could run a wire from bow to a high point then down to the stern. That would give your tuner a bit more of a workout though.


As others have said, the ground plane will be the biggest issue. What I would suggest is that you install as much bronze screen as possible against the hull below the waterline. Connect pieces of screen to each other using 1" or wider strapping (not wire). Also keep the amount of screen to a minimum (preferably zero) in areas that will be occupied when you are transmitting. Remember your ground plane radiates too.


Why do you want to run an amplifier? The 100 watts that most HF rigs put out is adequate for the vast majority of communications, at least in my opinion.


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Old 01-18-2020, 11:03 AM   #10
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HF Antenna

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....Alternatively you could run a wire from bow to a high point then down to the stern. That would give your tuner a bit more of a workout...
Todd (AA1ZS)

If 160m becomes real, u will need more wire to let an internal tuner provide the needed inductance to tune.

External amp is also a complicating factor for tuning. Few remote autotuners take 500 w. I think there is a SCG model for $$

I have done manual tuners aboard, certainly ok for casual use with a real radio operator [emoji41]
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Old 01-18-2020, 11:05 AM   #11
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FF, I'm not familiar with that type antenna, but I could be interested. I'm assuming it to would require a Ground Plane, so I'm still in the same situation. When you have time, PM me with the details. Thanks, Terry



Todd, I could put screening against the inside wall of the hull in the engine room area. it's not likely anyone would be in that area while the radio equipment is in use.

I understand the ground radiates RF. Would this be a safety hazard since I am running gasoline engines and generator?


You asked about the amplifier. I agree the 100 watts most equipment produces is sufficient for general conversation. However, I do enjoy finding me a nice anchorage, kick back, and work some contests. At times, a little help is needed.



Thanks, -- Terry (ko4cx)
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Old 01-18-2020, 11:14 AM   #12
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Dave, If I can get the Ground Plane issue resolved, then I would address the amplifier. As mentioned earlier the radio has a built in tuner. My plans would be to have the radio's tuner tune to the amplifier, and have a manual (high capacity) amplifier on the outboard side of the of the radio, between it and the antenna. Doing this, I can manually tune the antenna. As we all know, these tuners are not really tuning, they are just providing a false reading so as not to damage the equipment.



In your opinion, would this work using a manual tuner?


Thanks,


Terry (ko4cx)
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Old 01-18-2020, 12:08 PM   #13
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High capacity amp? Not sure what that is. Maybe to be a high tuning range manual tuner, I think. Don’t think even a tube amp will have enough tuning range for 80 and 160 with such a short wire.
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Old 01-18-2020, 12:16 PM   #14
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Dave, I didn't mean high capacity amp. I was talking about the manual tuner having enough capacity to handle the 500 amps. (I corrected my screw-up)
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Old 01-19-2020, 08:29 AM   #15
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HF Antenna

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Dave, I didn't mean high capacity amp. I was talking about the manual tuner having enough capacity to handle the 500 amps. (I corrected my screw-up)


I had dreamed of using a weather balloon to hoist a 1/4 wave vertical on the low bands. In settled weather, that may be an option. 160 m would be a short hop daytime or a long hop nite band, I think.
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Old 01-19-2020, 08:44 AM   #16
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Doesn't the hull material affect HF design? Say metal Vs wood Vs FRP.
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Old 01-19-2020, 08:55 AM   #17
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Quote:
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Doesn't the hull material affect HF design? Say metal Vs wood Vs FRP.


If u are blessed with a metal hull, simply connect the tuner return to the hull. Pretty much done.
There is another plastic boat option that others have used, when a mast is used. A vertical loop. Doesn’t require a counterpoise.
Note that using high power transmitters on small boats does expose the boat to corresponding high rf fields. My last home had its garage doors open and close with my 1500watt signal. Yes, there have been times I wished that power level aboard, but 150 watts worked 80% of the time. As a current EMC engineer, I can almost guarantee that running that field strength will affect some equipment on a small boat. But, that is why CM chokes and ferrite exists[emoji106]
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Old 01-19-2020, 11:01 AM   #18
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My gal runs a wire bow/mast/stern on my boat, seems to work OK. Also built a mount for a whip off the stern to port that works OK.
We ran 100w amp only once, it cross talked to the boat wiring, ran the stern thruster.
Biggest complaint I hear is about noise from non-compliant cheap Chinese converters on other boats in harbor.

She goes home to use the big beam/amp/automation for contests.
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Old 01-19-2020, 12:29 PM   #19
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At least in a sparse anchorage, u should be able to control all man made emi. Certainly the case in my experience. That leaves lightning crashes for a thousand mile radius. [emoji30]
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Old 01-27-2020, 01:27 PM   #20
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On SGC’s website you can download a manual on how to setup your boat for HF radio. Go to sgcworld and look under the technical tab.

Are you hooking up a marine radio, or amateur radio?

I use a Yeasu FT-891 and a ATAS-120 screwdriver antenna hooked up to a laptop running Ham Radio Deluxe. I have worked station all over US, Europe, South America, and even Antarctica. All with 100 watts on the Great Lakes from a Tow/Tugboat.

I have a standard model SGC 2000, a 2000 PowerTalk, PowerCube 500 with remote, and SGC Navtex modem. I haven’t messed with any of it yet... still looking for the 235 tuner.
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