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Old 27 August 2010, 16:47   #1
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High Power VHF Radio (25 watt+)

Evening all,

I'm curious, is there anyway to boost the output of a marine VHF radio on a RIB? (Yes I'm aware there are licensing issues that would accompany any such modification but I'm wondering if it can actually be done before talking to Ofcom and/or buying any kit)

It seems technically feasible to do it for CB radios which are lower output (4w up to 20w) and there are various schematics to home build boosters.

Does nobody offer off the shelf equipment that would not allow higher output?

Chris
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Old 27 August 2010, 17:22   #2
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Originally Posted by CJL View Post
Evening all,

I'm curious, is there anyway to boost the output of a marine VHF radio on a RIB? (Yes I'm aware there are licensing issues that would accompany any such modification but I'm wondering if it can actually be done before talking to Ofcom and/or buying any kit)

It seems technically feasible to do it for CB radios which are lower output (4w up to 20w) and there are various schematics to home build boosters.

Does nobody offer off the shelf equipment that would not allow higher output?

Chris
I've a booster that I used to use on the CB, same connections so in theroy it should work the same.

Never tried it though.
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Old 27 August 2010, 17:32   #3
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Quote:
Originally Posted by treerat View Post
I've a booster that I used to use on the CB, same connections so in theroy it should work the same.

Never tried it though.
27Mhz versus 150Mhz, I dont think so... there miles apart!!
You'll need a Ham Band 2m linerea amp for 150Mhz, then though there is still a few Mhz out.
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Old 27 August 2010, 17:34   #4
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An interesting subject. Only of use if you're talking to the CG (or another similarly equipped craft).

You might be best to "optimise" your (legal) setup before trying this. Have you tried all that malarky first?
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Old 27 August 2010, 17:36   #5
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if you needed the extra power to contact someone (range?) then how they going to answer back if they don't have the extra power too?

and i'm no expert but wouldn't a taller aerial give more range due to the curvature of the earth and the whole line of sight issue?
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Old 27 August 2010, 19:43   #6
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The easiest road to higher power output would be to use one of the ham band VHFs which are 50-55w and can be opened up to the marine band though that won't be waterproof so no use on an open boat ... I have a collection of ham sets which we use on marine band because the Mrs requires it for her job though of course I always make sure we are transmitting on the middle power rating not on high power

The ones I have are Icom IC-2000, a few IC2100 and an IC2200 plus an Alinco DR140 and an old Icom IC229H at work, they all operate happily in the marine band for transmit and receive, and all except the last one are 50w+

3DB gain on the aerial is worth twice the power output so may be an easier solution? Conversely some crap coax or a dodgy aerial or connections will cut the performance in half just like that.
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Old 28 August 2010, 04:21   #7
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Transmitting with more power than the license specifies is illegal and I doubt OffComm will allow exemptions unless you have good reason. The best way to improve the transmit and receive performance of your VHF is to install a higher gain antenna. As mentioned, a mere 3db gain will double your effective radiated power and provide benefits when receiving the transmissions of other stations. Just buying a new antenna per se will probably help anyway as most of us pay little attention to coax degradation and the quality of our PL259 fixtures.
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Old 28 August 2010, 04:28   #8
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Quote:
Originally Posted by ashbypower View Post
27Mhz versus 150Mhz, I dont think so... there miles apart!!
You'll need a Ham Band 2m linerea amp for 150Mhz, then though there is still a few Mhz out.
I think the booster works though by taking in a signal and running it through its board and boosting it up. It should work with the marine as well, actual mhz in shouldn't matter too much.

But I'm no enginier.
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Old 28 August 2010, 04:51   #9
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Originally Posted by treerat View Post
I think the booster works though by taking in a signal and running it through its board and boosting it up. It should work with the marine as well, actual mhz in shouldn't matter too much.

But I'm no enginier.
It won't work. Trust me, I've been a Ham for 25 years; the amplifier needs to be tuned for the frequency band in question.
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Old 28 August 2010, 07:16   #10
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From what i remember the maximum allowed for marine vhf is or was 25 watts,
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