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Old 04-28-2019, 05:49 PM   #1
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Vhf antenna question

I want to replace the antenna on my boat. The current vhf antenna is a two piece 16 one that shows some cracking on the coax cable.

My question is this: can I unscrew the antenna coupler and buy an 8 vhf antenna and screw it to the existing base? Is it a height thing or is that a stronger vhf antenna?

To be clear, does screwing a good quality vhf antenna equate to buying a new 9db antenna?

Thanks for your opinions.
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Old 04-28-2019, 06:15 PM   #2
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Nope, not the same thing. You get a lower gain antenna mounted at about the same height.

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Old 04-29-2019, 05:24 AM   #3
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Thank you. That I as the information I was looking for. Very helpful
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Old 04-29-2019, 07:42 AM   #4
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Quote:
Originally Posted by Freespool View Post
I want to replace the antenna on my boat. The current vhf antenna is a two piece 16 one that shows some cracking on the coax cable.

Is it really a 16' antenna... or an 8' antenna on top of an 8' extension base?

-Chris
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Old 04-30-2019, 06:25 AM   #5
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Hello all,

Thank you for the feedback. As a follow up I was considering a Shakespeare Galaxy antenna 5230. It is an 8 DB, not a. 9 DB. Is there much of a difference between an 8 and a 9 DB?
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Old 04-30-2019, 06:42 AM   #6
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Quote:
Originally Posted by Freespool View Post
Hello all,

Thank you for the feedback. As a follow up I was considering a Shakespeare Galaxy antenna 5230. It is an 8 DB, not a. 9 DB. Is there much of a difference between an 8 and a 9 DB?
Is everything else (height) the same? While gain is important, VHF transmissions are mostly line os sight relative to curve of the earth. An antenna with 1 less DB of gain and half the height will be hugely different in transmission at greater distances. Two antennas of the same height with 1 DB of gain difference won't be as much of a difference. How far do you want to be able to transmit a distress call?

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Old 04-30-2019, 07:27 AM   #7
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I just replaced my beat up antenna with a 5230. It is a hollow cored extention with a 8ft antenna. I don't think a normal 8fter will screw in to the base.
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Old 04-30-2019, 08:34 AM   #8
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Freespool,
Yes you could in fact just install a new antenna in the same place if in fact it is the same connector. the issue of 8 or 9 dB is not very critical in fact many boats get by very well with a 6dB gain antenna.
Higher gain not only increases radiated power, but it also flattens out the horizontal beamwidth. In other words if you go as high as 8 or 9 dB, you should really have a pretty stable boat that does not do a lot of rocking.
Shakespeare has a good explanation of this Here.
If you ever have to be concerned about air draft, you should include a ratchet mount so its easy to fold them down.

Another option for high quality antennas is Morad. They have a different look to them but quality is excellent, they're made in the PNW, and they are popular with the USCG.
...and yes antenna height is more useful in increasing range but if you have a 62' boat, i bet the antenna is alread pretty high up...
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Old 05-02-2019, 07:00 PM   #9
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You don't want to spend too much time next to a transmitting VHF antenna so height is important in both cases.
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Old 05-02-2019, 07:08 PM   #10
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The higher the antennae, the longer the range. The small antennae atop my mast has longer range than most.
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Old 05-02-2019, 08:58 PM   #11
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Also, generally, the closer your antenna is to the actual wave length, the more power, I.e. radiated power you get, out. The rule of antenna reciprocity states that more power out also equal greater receive signal strength. I have not computed the wave length of our frequencies (the speed of light in meters per second/frequency in hertz.), but would think that a 16 foot antenna is closer to the wave length than an eight footer.
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Old 05-03-2019, 01:03 PM   #12
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Just under 2 meters. Not so sure about the (actual wave length story). Stacked and phased antennas can get u lots of gain and are mechanically much bigger than 2 meters long.

Look at broadcast UHF TV towers, at the top. Lots of large antennas; TV is about 60 cm wavelength.
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