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Marine VHF base station antenna/cable

Old 07-19-2013, 10:25 AM
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Default Marine VHF base station antenna/cable

Marina wants to upgrade their base station and antenna. They were more concerned with receiving range increase as they only transmit local. I told them that an antenna upgrade would most likely help both anyway. I don't know a whole lot about them but I was told a "Yagi" might be good for reception and to use good quality cable as the "run" is about 75' or so. I know the higher height the antenna is mounted the better but does anyone have any other recommendations as far as a good receiving antenna and good cable? TIA
Old 07-19-2013, 02:21 PM
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A Yagi is going to be very directional.

Antenna height is going to give you the best performance, there are no 'special' antennas.

For the cable I would use something like LMR-400, about 1.5 dB of loss per 100' versus 4.7 dB for RG8X.
Old 07-19-2013, 02:59 PM
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Originally Posted by Crabpot Man View Post
A Yagi is going to be very directional.

Antenna height is going to give you the best performance, there are no 'special' antennas.

For the cable I would use something like LMR-400, about 1.5 dB of loss per 100' versus 4.7 dB for RG8X.
Maybe a dual or quad adjustable dipole antenna that you could adjust the pattern on. There not cheap tho. Check tessco.com
Old 07-19-2013, 04:26 PM
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Originally Posted by john1sr View Post
Maybe a dual or quad adjustable dipole antenna that you could adjust the pattern on. There not cheap tho. Check tessco.com
Yea, a $1500 antenna for RX only is a little pricey.
Old 07-19-2013, 04:43 PM
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List is more like $800. There are idiots that pay that much for a cooler.
Old 07-19-2013, 06:15 PM
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9 or 10db 17 ft fiberglass antenna as high up as allowed (60ft to the top I believe) using RG-8 coax. Reasonable cost and relatively simple installation will give high bang for the buck.
Old 07-23-2013, 07:03 PM
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Will a longer coax run cause poor reception, or does that only apply to when transmitting ( db loss) ?? Like i said they are concearned with reception more than trans.
Old 07-23-2013, 07:49 PM
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The dB losses in a coax run apply to both reception and transmission. There are several good low-loss lines available, but they are not cheap and are large, like 1/2" diameter. Hardline is another option, but with added costs, including specialized connectors. Are coast stations allowed to run more than 25 watts? Andrew's Heliax is the most available hardline...some of their larger lines (nearly an inch in diameter) have almost zero attenuation at marine band frequencies , but are expensive with very expensive connectors.

A directional antenna would be beneficial, too, especially if only 180* coverage is needed, but you're getting into expensive territory there. These are "sector" antennas and are pretty rare and expensive.

It all comes down to cost/benefit ratio...I used to play with this stuff for the 2mtr. amateur band, which is very similar in frequency to the Marine VHF band, but I think with marine stuff, you're limited to type-accepted antenna components to remain legal, a constraint not imposed on ham operations.
Old 07-25-2013, 10:06 AM
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ok I have a mounting area I would like to use (top of an abandoned chimney so no heat smoke etc.) but the run will be about 175-200'. Is this way to long? What would the best cable be for the $$ ? I looked at the Heliax but its about $3.50/ft and they wont approve $700 for cable only not to mention the connectors are like $30 each. I could prolly get them to pay maybe half that. I was going to use a shakespear galaxy 8' as an antenna and the best cable I can buy for $300-$350. What would be a good cable/connection that would cost maybe $1.50 ft or so?. Is the galaxy the best fit for this application. Im looking for most bang for the buck. Sorry for all the questions but you guys have prolly forgotten more than I know about this stuff. Thanks
Old 07-25-2013, 10:47 AM
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LMR600 coax is often used as an alternate to hardline...a 200' run will cost around $400. BUT, a 200' run will attenuate your signal by over 3db, both send and receive, effectively cutting your signals in half.

Could be justifiable if you were able to use a 180* sector antenna, but it sounds like you are on a tight budget.
Old 07-25-2013, 11:39 AM
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Originally Posted by enzoforza View Post
ok I have a mounting area I would like to use (top of an abandoned chimney so no heat smoke etc.) but the run will be about 175-200'. Is this way to long?
You are probably going need a shore station amendment to do what you're talking about legally. Also, I believe you are able to run more than 25 watts with authorization. Typically it would be a regular fixed-mount with weatherproof amplifier mounted at base of antenna, eliminating all feedline losses.

I also have doubts that 200' above surrounding terrain will get approved.
Old 07-25-2013, 01:46 PM
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No its not going to be over 25W or nearly that high. its only like 40 to top of chimney, its just where the office/basestation is located is about 100 feet+ to the other side of the house so the cable run will be like 175' or so. top of antenna will be about 45' from the ground or so.
Old 07-25-2013, 02:38 PM
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RG213 or 9913 will be fine. Here's a good discussion on the subject
http://forums.qrz.com/showthread.php...213-or-LMR-400

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