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Old 14-04-2019, 15:49   #16
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Re: Removing antenna from mast, good move?

https://photos.app.goo.gl/TUgWCFGzzJny8BQg7

https://photos.app.goo.gl/Dn7roSbrZfHwPrzz7

Haven't figured out pics yet, sorry. Ya, that would be a good way to go as well especially since I plan going offshore at some point, just not sure it's worth the added expense. Also, I have a handheld for a backup. I guess when we drop the mast I'll take a look at the feasibility of adding one on top.
At 26', I don't have any lights at all on the mast. I like that. Adding stuff that's hard to get to is against my nature but I want to have an idea of what I'd be giving up. Thanks for you opinions and suggestions, I'm listening.
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Old 14-04-2019, 16:03   #17
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Re: Removing antenna from mast, good move?

No one so far has stated that they had done it, just the theory of it. I did this many years ago and got better results. Removed the mast top aerial and placed a long whip on the targa (arch or whatever you want to call it) Did it on the advise of a very practical experienced marine electronics professional who stated I would loose nothing. His reason was that the cable run to the targa of 5 meters would give a better signal output than the loss over 20 meters of cable to the mast top regardless of the height of the aerial. He was right. In open ocean we expect and are able to communicate 40nm easily. Often we can communication at 50nm plus but at that distance its not something that I could rely on. Theory and what happens in the real world are two different things.
We have a steel vessel with a 15 year old inexpensive standard VHF.
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Old 14-04-2019, 16:12   #18
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Re: Removing antenna from mast, good move?

Wow..that is interesting. Aesthetics aren't a first priority but I was trying to stay away from a 15' fiberglass whip with tennis balls on it, lol.
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Old 14-04-2019, 16:56   #19
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Re: Removing antenna from mast, good move?

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Thanks Alchemy! I think you answered my question before I was able to formulate it.

No problem. When I redid my mast wiring last year and put in a radar, I had to solve all these options. I went for a VHF on the mast top with far better coax, and a AIS whip on the first spreader and a radome between them. We can see tomorrow now! https://alchemy2009.blogspot.com/201...ng-around.html
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Old 14-04-2019, 17:01   #20
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Re: Removing antenna from mast, good move?

One important consideration not mentioned here thus far is interaction with other stuff in the same plane. For example, putting a vertical antenna lower on the mast will cause significant interaction, the result being detuning the antenna and screwing up the omnidirectional radiation pattern. Two things you don’t want.

Higher is always better as long as you use good quality coax and connectors.
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Old 14-04-2019, 17:44   #21
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Re: Removing antenna from mast, good move?

Ya, begs the question why put it there in the first place? I assumed it was factory but I could be wrong. The coax going thru the cabin top looks factory and old.
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Old 14-04-2019, 17:53   #22
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Re: Removing antenna from mast, good move?

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One important consideration not mentioned here thus far is interaction with other stuff in the same plane. For example, putting a vertical antenna lower on the mast will cause significant interaction, the result being detuning the antenna and screwing up the omnidirectional radiation pattern. Two things you don’t want.

Higher is always better as long as you use good quality coax and connectors.

That is true and is why I chose to keep the VHF antenna atop the mast and the AIS antenna farther down. Both are supplied with LMR-400UF-grade coax and Amphenol PL-259s.

I consider the VHF a higher priority than AIS transmit, so it gets the highest position. In addition, my VHF, like many these days, does AIS receive, so I have desirable redundancy. And if my AIS antenna goes, I can switch to a deck-level antenna.

It's a good point you raise, to be aware of the mast's effect on the transmission pattern. Should I lose either antenna, however, I have a switcher that would allow me to use the remaining antenna for both purposes. If I did not have a pilothouse, this sort of setup would be harder to pull off.
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Old 14-04-2019, 17:57   #23
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Re: Removing antenna from mast, good move?

If I had that setup, I'd be interested in deleting it as well. It is just not optimal in so many ways. Your easy solution which loses a few feet seems all the better if you don't want to stick it on top of the stick.

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Old 14-04-2019, 17:58   #24
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Re: Removing antenna from mast, good move?

"Higher is always better.."

That was my assumption as well but given Fine Tolerance's experience, I'm not so sure. It really is about a third of the cable to go to the tower.
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Old 14-04-2019, 18:14   #25
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Re: Removing antenna from mast, good move?

On our Bristol 29.9 the antenna cable is run up the inside of the mast exiting about six inches from the top then running up to the antenna, which is about eighteen inches long maybe a bit longer, we are keel stepped. In theory you could run your cable through the center of the mast step, ( drilling a hole of course) like our B-24 anchor light was set up. That way you would get maximum vhf range and it would be a reletivly clean way to run your antenna cable.

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Old 14-04-2019, 18:24   #26
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Re: Removing antenna from mast, good move?

The thing I don't like is on the inside. ..comes out of the ceiling in the head and stapled down the wall. Easy to remove, pain to replace.
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Old 14-04-2019, 18:30   #27
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Re: Removing antenna from mast, good move?

Quote:
Originally Posted by 1camper View Post
"Higher is always better.."

That was my assumption as well but given Fine Tolerance's experience, I'm not so sure. It really is about a third of the cable to go to the tower.
Don't know who you refer to, however, it's simple to do that math. Coax cable loss tables are ubiquitous on the internet. See for yourself. Generally, the extra loss of good coax is trivial even at VHF. The indiscernible power loss through coax is more than offset by height.
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Old 14-04-2019, 18:43   #28
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Re: Removing antenna from mast, good move?

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The thing I don't like is on the inside. ..comes out of the ceiling in the head and stapled down the wall. Easy to remove, pain to replace.
You might be able to use a bit of trim covering and route the cable to the closest bulk head, and then along the edge of the bulk head and ceiling to were the cable goes out of sight. Don’t know if that would work for you or not. But if the trim covering over the calble was wood and pleasant looking it may just work. Just a thought, 🧐

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Old 14-04-2019, 19:07   #29
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Re: Removing antenna from mast, good move?

I had an old antenna (and cable) at the top of the mast on my C&C25. The cable made a horrible noise at night, slapping around inside the mast. So I removed the antenna and cable entirely. Instead I used a handheld VHF. It worked much better than the old set/antenna ever did. Range was not an issue...it was mostly for calling marinas before entering, or bridges.

I removed a ton of unnecessary wiring and plumbing from the boat. Instead I used a few LED flashlights, handheld VHF, handheld GPS, etc. Kept the running lights of course.
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Old 14-04-2019, 19:08   #30
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Re: Removing antenna from mast, good move?

Quote:
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"Higher is always better.."

That was my assumption as well but given Fine Tolerance's experience, I'm not so sure. It really is about a third of the cable to go to the tower.
Higher is always “better” if better means reaching farther away ships. Radio theory and practice agree on this. VHF can reach slightly beyond the so-called “line of site” distance but once you reach line of site the signal strength drops exponentially fast. A short antenna can reach far away vessels if the distant vessels have high antennas. But two “low to the water” antennas will be very limited in range. That’s why you get some anecdotes like FT. But that does not mean radio theory is wrong.

The “best” system is a VHF radio antenna at the mast head and AIS antenna down lower. You want the DSC distress call to reach as far as possible which dictates putting the radio antenna highest for furthest coverage. Use low loss coax but really that is less important than height. VHF radios are over powered at 25 watts to make up for cable loss. But it takes massive power to make up for height.
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