Mast wiring

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Tomfoolery
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Re: Mast wiring

Post by Tomfoolery »

BOAT wrote:With all that jazz I'm getting here about my radio signals falling out of the wire because it's bent too sharp (so don't bend it real tight) or wrong wire (see my links above) and "base loading" (that's just the antenna construction - the lump at the bottom so the whip can be short - see links above) and fabricating antenna mounts (I can't even weld!) (I put up a link to a ratchet mount, but just a common 90 degree fixed antenna mount is fine) it's scaring me (no reason it should) so I'm thinking of just replacing my existing radio and giving up on the idea of having two radios. ( :| )
As to 3dB being 'best' for a sailboat, the reason is that the vertical azimuth gain pattern of any single whip antenna looks like a donut centered on the wip. A flattish donut (think Frisbee), like a 9dB antenna, is strongest in a horizontal plane with the antenna vertical. Stray above and below the horizontal, and the gain drops off fast. But it's very strong in or near that horizontal plane (9dB). Drop down to a lower gain, and the donut pattern gets thicker, and a 3dB sailboat mast antenna has a fat donut (think Dunkin' Donuts brown sugar), with lower gain in the horizontal plane, but the gain doesn't drop off as fast as you move above or below horizontal - or tilt the antenna from vertical, as sailboats do when heeled. :wink:

So a reduced gain, but an increase in elevation plus less reduction in transmitted signal strength due to heeling is why they're what's normally used on sailboat masts. Power boats don't heel under normal conditions, and they don't have much elevation, so a flatter pattern and higher transmitted signal strength makes more sense.

And a 6 ft or more white fiberglass antenna on top of a mast would look funny.

The first graphic (that I found by sniffing around) shows the relative signal strength at various angles (though actual azimuth angles aren't shown). You can see that where the envelope of the red 6dB meets the yellow 3dB, an increase in heel angle would render the 6dB just about useless, but the gain of the 3dB is still high, and doesn't drop off much with greater heel angle, up to a point. The blue 9dB is out of the running long before that angle.

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Like this one - heel the boat a bit, and where a horizontal line intersects the 'envelope' would be in the negative gain region, depending on heel. That's why you don't use a high-gain antenna on a mast - tilt it even a little, and it's mostly going into the water or up to an airliner. Like a directional TV antenna, when aimed away from the transmitters - it can't grab much signal, and can even reject it with prejudice. :wink:

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So you want your antenna 'aimed' at the other guy's antenna, and unless you have a way to manually tilt the antenna on top of your mast to compensate for heel, it's best just to have one with a 'wider' up/down patten, at the expense of lower power in any direction overall. Because you never get something for nothing.

Like a floodlight vs a spotlight, both with the same wattage. Spotlight has brighter light at it's best angle, and floodlight covers a broader angle at a lower intensity. :wink:
Last edited by Tomfoolery on Sat Jan 28, 2017 4:55 am, edited 1 time in total.
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BOAT
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Re: Mast wiring

Post by BOAT »

Does wattage come out of the radio antenna?

So if it's a 50 watt radio I can "see it" (hear it) just like I would a 50 watt light from the distance?
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grady
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Re: Mast wiring

Post by grady »

BOAT wrote:Does wattage come out of the radio antenna?

So if it's a 50 watt radio I can "see it" (hear it) just like I would a 50 watt light from the distance?
Yes wattage comes out of the antenna. It also reflects back to the radio. AKA what does not go out the antenna goes back to the radio. That is why if you want your radio to operate at maximum performance you need to tune your antenna to the radio, wire, with a watt meter. That is about depth of my knowledge on the subject.

Call this guy if you need more information.
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BOAT
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Re: Mast wiring

Post by BOAT »

grady wrote:
BOAT wrote:Does wattage come out of the radio antenna?

So if it's a 50 watt radio I can "see it" (hear it) just like I would a 50 watt light from the distance?
Yes wattage comes out of the antenna. It also reflects back to the radio. AKA what does not go out the antenna goes back to the radio. That is why if you want your radio to operate at maximum performance you need to tune your antenna to the radio, wire, with a watt meter. That is about depth of my knowledge on the subject.

Call this guy if you need more information.
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Is that what Tom says too? I always trust Tom because he is smart.
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Tomfoolery
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Re: Mast wiring

Post by Tomfoolery »

In very crude terms, yes. In a way. Wattage isn't a 1:1 comparison, but VHF radio waves are both electro-magnetic (as are visible light waves), and line-of-sight (as are visible light waves, but a little more so). So if the horizon blocks the line-of-sight path, it will bend very slightly, but mostly be blocked.

Think of a light house. The Fresnel lens aims the light into a narrow band vertically (vertical azimuth)*, so if you tilt the lighthouse, a boat on the water will be out of the strong beam. If you widen the beam, you can tilt it more, but the max intensity at the horizon will be reduced. That's not something you need in a lighthouse, but it is something you need in an antenna if the boat heels. Flood light vs spot light when you need light far off-axis.

Reception works the same way as transmission. A 3dB antenna has a wider pattern (vertically) than a 6dB, so on-axis gain is less, but doesn't drop off much over a wider vertical azimuth as a higher gain antenna, for both transmitting and receiving. Same with light - collecting light and focusing on a point using a Fresnel or other lens (or parabolic dish like in a flashlight) is the same as shining it from a point and focusing to a narrow band.

In the end, a 3dB antenna mounted to the top of the mast and driven by a 25W marine VHF radio connected with good quality coax should have no trouble reaching the horizon and beyond to another antenna mounted high above the water (signal skipping over the surface of the horizon). You'll lose nearly have the signal in the cable alone, so good cable is a must, as short as reasonable (don't use 100 ft with the excess coiled up), quality soldered terminations, and you'll have a nice setup.

*And as an interesting aside, navigation lights for sailboats have more stringent requirements than nav lights for power boats. For both sailboats and power boats they have to maintain 100% intensity (at whatever distance) for a +/- 5 degrees vertical sector. Power boat nav lights have to maintain at least 60% intensity at up to +/- 7.5 degrees vertical sector, but sailboat nav lights are required to maintain a minimum of 50% intensity at up to +/- 25 degrees vertical sector (or heel angle). Power boat nav lights have no intensity requirement beyond +/- 7.5 degrees, so mounted on a sailboat heeled to 25 degrees, there may be essentially zero intensity to the side.

Nav lights with Fresnel lenses are usually only certified for power boats, by the way. Like these Aqua Signal Series 20's.

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Last edited by Tomfoolery on Fri Jan 27, 2017 6:45 am, edited 3 times in total.
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Sumner
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Re: Mast wiring

Post by Sumner »

Hugh wrote:....I'm pretty sure Shakespeare makes an AIS/VHF antennae design for lightweight mast installation.
https://www.westmarine.com/WestAdvisor/ ... HF-Antenna...
I have a 3dB Shakespeare 5215 ( http://shakespeare-ce.com/marine/produc ... y-antenna/ ) on the Mac and when I switched to the radio with AIS it worked just fine. It is designed to work with AIS.

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I could see AIS targets miles away, way further than I actually needed to. Above you can see that I changed course after seeing and being able to communicate with .....

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....the large ship, thanks to the AIS. As I mentioned above was able to pick up NOAA weather well over 100 miles from the coast. I'm using RG-8X coax and it has worked well also.

I use a handheld in the cockpit for most of my boat-to-boat communication. A Standard Horizon HX851 ( http://www.standardhorizon.com/indexVS. ... Archived=1 ) It floats, has GPS and DSC if I go overboard and have it with me, though I doubt the range is much if you are down in the water and it doesn't have the wattage of a fixed radio.

If I went back out in shipping lanes I'd give real consideration to spending the money for an AIS transponder also. It is nice to see them but our little boats don't always show up well on their radar. A transponder would help to rectify that a lot.

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The boat above, by Nassau, didn't see me until I called him and asked if he saw me, as he was bearing down on me faster than I could move out of the way. He replied, "now I do" and adjusted his course,

Sumner

============================
1300 miles to the Bahamas and back -- 2015

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The Endeavour 37

Trips to Utah, Wyoming, Idaho, Canada, Florida

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BOAT
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Re: Mast wiring

Post by BOAT »

Lights, cable, ACTION! and fabricating metal things or store-bought metal holder things and base antennas along with (SOMEDAY) I sure would like to get a mast head electronic wind instrument up there!! (I mean like, that's what the MAST on a sailboat is for - SAILING, . . in the WIND! By the time I get all though this I'm gonna have 20 pounds of crap on top of the mast!!! (Well, forget about getting a camera on top!)

There has got to be a better way.

I think I see where this is going - it's obvious I will not be getting a camera on the top of the mast - not with all the other junk that is going up there.

Okay, so I already have one of these on the way going on top:

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And I guess I need to make room now for this Shakespeare thing too:
I guess this one that Sumner uses has a bracket on it already so I don't have to weld if I get this one.
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That just leaves the cable? What else am I forgetting?


Do I need one of these up there too?

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I guess I'll go shopping for a radio.

.
K9Kampers
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Re: Mast wiring

Post by K9Kampers »

BOAT wrote: That just leaves the cable? What else am I forgetting?
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Re: Mast wiring

Post by BOAT »

.
.
Okay, fine - I guess after I install the Coffee maker and the Crows Nest I can hang a sign too:

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Re: Mast wiring

Post by Highlander »

Boat
this one comes with 60ft of coax cable !
http://shakespeare-ce.com/marine/produc ... s-antenna/

J :wink:
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Re: Mast wiring

Post by Highlander »

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Re: Mast wiring

Post by BOAT »

Thanks John, I think that anntena might work.

Can I ask another question of you guys? Is there such a thing as a 12 volt cofee maker? (I doubt it - the amperage needed to heat water that hot would kill the battery in one brew!). Or do they make a drip coffee maker that goes on top of the stove that works like the electric ones?

I already have one of these old ones that I have used for camping for 30 years and I don't even know how old it was when I got it:

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These old percolators recycle coffee from the bottom back into the top thus burning the coffee and it's a hassle to deal with the coffee grinds and cleanup because percolators have a tube going up thru the middle of the grounds making it impossible to use a filter - the grounds are a mess to clean up. Also it's hard to tell when the coffee is done because the little lighthouse on top gets cloudy and you cant judge the color of the coffee well. (Am I the only one that has these problems? :( )
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Re: Mast wiring

Post by Tomfoolery »

I use one of these.

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Plop it on top of my mug or disposable cup, boil water in a small pot on my little butane camp stove (very hot, so very quick), and pour into the cone with enough ground coffee for one cup.

They make bigger ones, too, with a carafe of some sort. http://www.melitta.com/en/Products-1790 ... 72583.html

But mine takes almost no space, the filters store in the cone when not being used, and I can even put the whole thing into the plastic 2 lb coffee canister (as long as it's less than half full) to save even more space, which is way more coffee than I could ever use on a typical week long trip. And it's all plastic, so I can't break it. :wink:
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Re: Mast wiring

Post by K9Kampers »

BOAT wrote: Image

These old percolators recycle coffee from the bottom back into the top thus burning the coffee and it's a hassle to deal with the coffee grinds and cleanup because percolators have a tube going up thru the middle of the grounds making it impossible to use a filter - the grounds are a mess to clean up. Also it's hard to tell when the coffee is done because the little lighthouse on top gets cloudy and you cant judge the color of the coffee well. (Am I the only one that has these problems? :( )
I use one of these everyday at home and on the boat. I don't watch the color of the perking brew but rather let it perk a few minutes on high, then a couple more on a lower setting. I do get some grounds, especially on the last cup but it's not a big issue for me. For cleanup I just hang over the stern and wash out the ground in the ocean.

I've also used the filter style above and a french press both at home and on the boat, but the perk style has suited me well for the past few years.
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Re: Mast wiring

Post by BOAT »

Thanks guys, I know this is not really about wiring up the mast unless we do somthing like this:

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So sorry if I am going off subject but you can drink coffee up there so I guess it's okay. :(

Hey K9, Yes I agree with you - when you get the brewing time right the percolator makes a really good coffee - I too like the coffee in that thing when i am out camping - it's still the mess I have a hard time with because in the camper I am not on the water. I also like the percolator in the camper because sometimes I make coffee while we are on the road (on the freeway - cross country like stuff - get sleepy) and the percolator sit's nice and stable while driving down the road BUT that's where the boat becomes a problem - I tried to make coffee in the boat underway and the galley is tipped over too much and the pot will slip off the burner - so I held the pot on the burner, but then the hot water all percolated onto one side and the coffee came out weak. ( :( what a complainer, right?)


But, this thing that Tom suggested looks like it just might be the answer! I can boil plain water at ANY angle in my big flat tea kettle on the boat and then pour it into this thing!! And it has A FILTER!! So the California EPA will not throw me in jail for dumping my coffee grounds.


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I am going to buy this thing that tom suggested - I think it might solve the problem - thanks very much - I will do my mast wiring AND get my coffee thanks to you guys!

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