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Old 17-05-2012, 15:58   #31
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Re: SSB Antenna Question

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Originally Posted by deckofficer View Post
Bill,

Since your on this thread, may I hyjack it for a second? I'm the nut case that hoists a trapped inverted vee up my mast at anchor and use telescoping fiberglass masts to get my 90* on the legs. As I said earlier, I'm building another and my question is, would you use 1/2" wide braided wire (typically used as a grounding strap) for the legs? I know it is costly, but for uhf and vhf yagis I have found the larger diameter elements give a larger low SWR bandwidth. Never tried this out on HF, probably won't make the big difference as it did on the higher frequencies.

Thanks.
Bob,

I'm probably not the right guy to ask about this, mainly because I have a couple of strong beliefs about antennas on sailboats:

1. they must be able to withstand the harsh marine environment -- salt air, strong winds, sometimes violent movement, etc.; and

2. they should be practical.

A trap dipole with legs made of 1" copper ground straps, alas, doesn't meet criterion #1. The wind and sea air working on those legs is gonna be quite a sight, and they're very likely to corrode into nothing within a few months, if not weeks. Moreover, you've got to feed the damned thing, and that means a coax running up the mast somehow. More to flop about in the wind and seas.

I know you said "at anchor", so maybe this would be fun to play with for awhile. But as a practical matter, I don't think it will pass muster.

What are you trying to accomplish with a trap dipole, anyway? I assume you want multiband performance better than the traditional backstay antenna/automatic tuner combo. That's hard to do with a wire antenna.

Screwdriver verticals might do the same for you, with pretty good signals on multiple bands and with much better survivability and practicality in the marine environment.

JMHO,

73,

Bill
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Old 17-05-2012, 22:19   #32
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Re: SSB Antenna Question

Thanks Bill, I have a screwdriver antenna I'm not using. So no advantage on HF with a wider "element" as on UHF for bandwidth? What would your choice be for a resonant antenna for 10,15,20,40, and 75 that doesn't need a tuner and can handle a minimum of 600 watts. I hold your expertise in high regard, so if you have the time, I'm all ears. Also will use it at my home for awhile and will run 1500 watts.
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Old 18-05-2012, 04:12   #33
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Re: SSB Antenna Question

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Originally Posted by bcripps View Post
Thanks again, guys. I agree with everything folks are saying here. What I can't understand is why I'm the only person in the harbor who can't receive Chris Parker's weather forecast each morning. I was lead to believe that the Palstar Radio is a top end receiver. Other boaters are using the ICOM SSB radio and are having no trouble. I am at anchor in Luperon's harbor in the Dominican Republic and it is not overly crowded. But this problem didn't start here. I have never been thrilled with the performance of my system since installing it over two years ago in Florida. Initially, in the Bahamas, I could copy Chris Parker's signal but could never hear the boats responding to him. Not unless they were anchored very close to me... within two or three miles!


I know it will end up being something simple but tracking it down is making me old. When I listen to the radio, all my breakers are off. With the exception of the fan, the light, the stereo and the shortwave that all share the same breaker, all power is off... to everything. I am now thinking about dedicating a circuit for the shortwave but I'll do some more fiddling tonight and tomorrow.


Best,
Bryan
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Originally Posted by Jim Cate View Post
FAN??? did you say that there was a fan running? Depending on the type of motor, fans can be VERY RF noisy. Try disconnecting/switching it off.

Cheers,

Jim
There is a surprising amount of stuff still connected to the average boats electrical system even when one thinks everything is turned off and a lot of it will produce RFI way out proportion to it's size or current draw. A permanently connected digital voltmeter can kill a HF receiver with RFI.

If you are serious about tracking down RFI (and all the obvious sources have been eliminated), disconnect the battery bank right at the battery terminals and run a temporary lead direct to the radio receiver, note its performance and then reconnect battery bank and note the receivers performance again and compare. You may be surprised.
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Old 18-05-2012, 05:23   #34
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Re: SSB Antenna Question

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Originally Posted by deckofficer View Post
Thanks Bill, I have a screwdriver antenna I'm not using. So no advantage on HF with a wider "element" as on UHF for bandwidth? What would your choice be for a resonant antenna for 10,15,20,40, and 75 that doesn't need a tuner and can handle a minimum of 600 watts. I hold your expertise in high regard, so if you have the time, I'm all ears. Also will use it at my home for awhile and will run 1500 watts.
Ah, yes.... that would be the little known "Zippy Truly Stupendous Miracle Antenna" :-)

Sorry, my friend, but aside from a screwdriver antenna what you're looking for doesn't exist....at least not for a boat, IMHO.

Yes, a trap antenna on a large enough boat with traps carefully tuned could be multi-band ready, but traps are lossy and they flop around in the wind and seas and I just don't believe they're suited for the marine environment.

BTW, on a boat with an efficient antenna, it's rarely necessary to run high power. For 11 years in the Caribbean I carried a 500-watt amp but almost never used it. Ran phone patches home often with just 100 watts and a monoband vertical dipole on 20. The secret was the dipole.

Basically, to operate multiband on a boat you're going to need an end-fed something or other (backstay, alternate backstay, random wire, etc.) or maybe a G5RV-type dipole with a tuner. You can get away with a manual tuner at the rig if you use an Un-Un at the base of the antenna, with coax from there to the tuner. Otherwise, I think you're stuck with a screwdriver or other vertical antenna with a tunable loading coil.

JMO,

Bill
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Old 18-05-2012, 05:34   #35
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Quote:
Originally Posted by deckofficer
Thanks Bill, I have a screwdriver antenna I'm not using. So no advantage on HF with a wider "element" as on UHF for bandwidth? What would your choice be for a resonant antenna for 10,15,20,40, and 75 that doesn't need a tuner and can handle a minimum of 600 watts. I hold your expertise in high regard, so if you have the time, I'm all ears. Also will use it at my home for awhile and will run 1500 watts.
There is still a bandwidth advantage at HF with wider/larger diameter antenna elements, but practicality on a boat is still a big issue.
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Old 18-05-2012, 11:08   #36
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Re: SSB Antenna Question

SoonerSailor, thanks, I didn't know if it translated to HF as well as it increased the bandwidth on VHF and UHF.

Bill, your still the guy that knows this stuff inside out. What if I just went with the tried and true 28' Shakespeare whip and auto tuner at its base? I have used this before on a 32,000 ton steel vessel and it worked OK, nothing great, but on a glass pleasure boat I'm concerned about degraded performance without using a crazy amount of counterpoise. I think you know where I am coming from, I'm a long time HAM that wants the best signal I can muster in the MM setting. You have authored tons of antenna articles, what would you construct for the big MM signal?

Also, whatever you suggest should be usable off the balcony of my 2 story home before I transfer it to the boat. In all my experimenting, I have yet to use someone's backstay that I was impressed with it's performance. Maybe there were other issues with my friends antennas, but to date I have not heard a backstay "sing" very well.
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Old 18-05-2012, 12:10   #37
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Re: SSB Antenna Question

BOAT ANTENNAS

As I've said many times, backstay antennas are decent radiators on all bands, but not great antennas. Nevertheless, because of their versatility when matched with a good autotuner, and their robust construction, every boat ought to have one as a starting point.

Big signal antenna on a boat? That's real easy for 30m, 20m, 17m, 15m, 12m, and 10m ham bands: construct monoband vertical dipoles (from s/s insulated lifeline) for each intended band. Ain't nothin'....nothin' gonna equal the DX signal from such antennas.

For 40m and below, it's a different story though. Most boats aren't big enough for a vertical dipole and they don't have the same signal multiplying effect on the low bands anyway.

A good screwdriver antenna can give decent performance, maybe even edging out the "just OK" backstay antenna on some bands. A G5RV might be OK, but with it's feedline and general construction it's not really what I'd call "marine ready"....at least not for long :-)

An inverted-Vee is fine on 40, but inverted vee's have a high angle of radiation, so they're not great performers for DX.

A quarter-wave tuned vertical, with no traps or resonator or loading coil (or tuner) could work well, but that's a pretty big stick on 40m and impractical below that band.

An "alternate backstay" antenna made of s/s lifeline could work very well if it's long enough. A friend on a 46' boat experimented at my dock a couple of years ago and found that he could best work England on 75m with a really long alternate backstay antenna: at least 55' long.

For an RF ground system on a boat, I'd not worry about heroic ones you hear about ("100 sq feet of copper", tanks, keel, wide copper straps, external ground plates, etc., etc.). Some or most of that is bunk anyway. A simple KISS-SSB radial ground system works very very well, as do other solutions I've written about for years.

The thing is, you really have to experiment on your own boat. Each boat is different, and even boats of the same make and model differ one from the other because of installed equipment, etc.

HOME ANTENNAS

Almost by accident, as well as by circumstances, I put up an inverted-L antenna at my home about 6 years ago. It's about 85-90' long, about 55' at the peak, and slopes a bit on the short side. It's fed directly from a Palstar tuner near my radios, and works like gangbusters on almost all bands. Much better than I had hoped. The RF ground consists of a whole bunch of insulated wire scraps thrown into a window well. I put about 600 watts into it, and am told consistently that I have a whopping signal under most conditions.

I believe it's a mistake to aim for an antenna which can work well at home as well as on the boat. In each circumstance -- and they're very different -- you want to put up the optimum antenna for the situation.

Wire antennas are cheap to construct and can work very well. For the home, I use THHN electric wire found in any Home Depot. While any size will work, I've found AWG10 lasts a lot longer, though for short lives (say, 2-3 years) smaller AWG12 or even 14 would be OK. Buy a big roll, and experiment away: dipoles, inverted vees, long wires, inverted-L's, wire beams....the list is endless.

But, on the boat, you won't have anywhere near the same freedom to experiment or to use cheap materials.

Have fun.

73,

Bill
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Old 18-05-2012, 12:41   #38
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Re: SSB Antenna Question

I tried the new straight wire antenna this morning and bounced back and forth between it and my 65-foot inverted L. I couldn't tell any difference between the two. Not sure what this means... probably that I spent money I didn't have to.


I couldn't pick out Chris Parker's broadcast on 4045 from the noise. Sounds like a waterfall. I think he was there, but couldn't be sure. On 8173 it was much the same but he was definitely speaking in the background and for a brief minute or two, I got light copy and could make out the conversation.


I did better with the Water Way Net on 7268. Unreadable copy for the first twenty minutes or so, then light, readable copy. Nothing heard on Cruizheimer on 8152 except the waterfall.


Could the fact that the Water Way Net is on Lower Sideband have anything to do with anything?


I'll go through this procedure again tomorrow morning with the Palstar wired directly to the boat's batteries. See if that makes a difference.


Regards,
Bryan
Luperon, Dominican Republic
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Old 18-05-2012, 12:47   #39
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Re: SSB Antenna Question

No, LSB has nothing to do with it.

Stations at different distances from you has a lot to do with it, as does propagation at the time and frequency you're listening to.

Again, try listening to the weather broadcasts from the USCG and WLO on different frequencies. That gives you much more time to evaluate the strength and readability of incoming signals, as contrasted with nets on which you might hear a strong signal for a few seconds, then weaker ones, then none at all.

Keep at it...you'll sort it out eventually :-)

Bill
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Old 18-05-2012, 15:33   #40
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Re: SSB Antenna Question

Bill,

So I guess there is a reason the masses use the backstay. The SG-230 auto tuner (the original) at just a 200 watt rating would probably be the best, as it will tune down to 1.8 mhz still using a 23' wire, whereas the 500 watt auto tuner at 3X the price needs a minimum of 300' for 1.8 mhz. I'll just have to set my drive to stay below 200 watts.

On your monoband vertical dipoles, are they center fed, and what is the impedance? They sound like a fun, low angle antenna that I can use my full output on.

Also, what do you think of using telescoping aluminum tubing that you can adjust the vertical element and 4 radials length for different band operations? Should be a 50 ohm antenna and take the legal limit with the low angle radiation of a vertical.

Thanks again Mr. antenna guru.
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Old 18-05-2012, 15:41   #41
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Re: SSB Antenna Question

Yes, they're center-fed. No balun needed. Feed with RG8X coax. Tune for desired center of band. I usually cut my 20m dipoles for lowest SWR on about 14250kHz.

Construction details are here: Marine Antennas

Click on each pic twice for full resolution.

Suggest you make a cheapie one first out of any available materials. Once you're convinced, then spend the time/bucks required to make a real marinized vertical dipole!

Have fun.

73,

Bill
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Old 18-05-2012, 18:20   #42
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Re: SSB Antenna Question

Consider boats next to you for RFI. Go sailing and see what you can receive.
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Old 19-05-2012, 14:37   #43
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Re: SSB Antenna Question

A direct power feed from the battery to the radio didn't change anything and my results (or non-results), were the same as yesterday. One interesting thing happened while trying to listen to Chris Parker on 8173. A boat by the name 'Atlantica' came in as sweet and as clear as a bell. Should have because she is anchored about 200 yards from me. The woman was asking Chris for sailing directions to Puerto Rico. I could not hear Chris but twice during her conversation with him, she said, “Thanks Chris, good copy!”


Well hell! Now I am mad. What do you make of that?


Cheers all,
Bryan, still with his ears on!
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Old 19-05-2012, 16:57   #44
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If attaching and detaching the antenna to the radio results in a change in the volume of background static, then I really think you have a local noise source problem on the boat, and not a problem with your antenna or radio.
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Old 19-05-2012, 18:11   #45
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Re: SSB Antenna Question

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Originally Posted by bcripps View Post
A direct power feed from the battery to the radio didn't change anything and my results (or non-results), were the same as yesterday. One interesting thing happened while trying to listen to Chris Parker on 8173. A boat by the name 'Atlantica' came in as sweet and as clear as a bell. Should have because she is anchored about 200 yards from me. The woman was asking Chris for sailing directions to Puerto Rico. I could not hear Chris but twice during her conversation with him, she said, “Thanks Chris, good copy!”


Well hell! Now I am mad. What do you make of that?


Cheers all,
Bryan, still with his ears on!
Just to confirm, when you say "direct power feed from the battery", does that mean that the battery (or batteries) were disconnected at the terminals for the rest of the ship?

There are only four possibilities for poor receive performance.

1. No signal available - unlikely given good signal available 200 yds away
2. poor antenna - again unlikely given what you have posted
3. High noise locally (therefore poor signal to noise ratio) - likely unless ALL power is removed from boat including dry cell batteries from portable devices and remote controllers. Even then it is still possible for RFI to be a problem from nearby boats or shoreside devices. Are you anchored out or in a marina?
4. Poor / faulty receiver itself - possible, can you have it checked at a local radio repair shop?

Is it possible to take the receiver to a completely different location (non boat) and try it elsewhere?

Don't let it beat you
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