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Old 23 September 2015, 19:46   #1
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Connecting an external aerial to handheld Vhf

Wondering if anyone has experience of connecting their hand held to an external aerial go boost the signal.
I have a 6w Standard Horizon handheld which is decent enough.
Could be doing with a big more oomph though.
What connectors etc would be required and what sort of performance increase is there likely to be?
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Old 24 September 2015, 02:55   #2
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no expert but would say power output would limit its range.
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Old 24 September 2015, 18:00   #3
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My old SH handheld had a mini coax connector just for that. Never used it, as I never bought the adaptor (well, that plus I didn't have a fixed set on the SIB, and never use the HH on the RIB.)
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Old 24 September 2015, 19:48   #4
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no expert but would say power output would limit its range.
Not really. Line of sight is the limiting factor and so height is the priority.

Kaman - you should be able to fit a plug which then lets you fit a cable with fixed antenae. But I think you really want to get the antanae as HIGH as possible. I had a crude approach at Belnahua that you might have spotted - it was just a stainless broom handle zip tied to Willk's seat back with a 3dB gain aerial on top. I've since made that more permanent but it seems to work well - albeit connected to fixed VHF.
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Old 24 September 2015, 20:02   #5
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what I was told before - that loss on the cable will make the signal week and hence any benefits will be lost...

yes I teach it's the higher the antenna the further distance and power is just signal strength....




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Old 25 September 2015, 02:44   #6
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I've used a non-marine 5/8th wave aerial (similar frequency to Marine) with a 5W H/Held. That was mag mounted to the top of a portakabin and compared to an identical H/Held inside the cabin the range to both receive and transmit to other H/Held's in the field was definitely improved. If we'd sat someone on the portakabin roof it probably wouldn't have made any difference.

Good cables, soldered connections, minimising connections (avoid having a Plus A to Plug B and then a Plug B to Plug C type of connection because the coax came with C already fitted.) Try and get the correct connector directly to coax, and solder it. You loose between 1-3dB of "power" through each mechanical coax connection.

Work in where and how to mount the aerial...
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Old 25 September 2015, 02:58   #7
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poly is right picked this off the web.
Say your buddy has an antenna mounted atop his large cruiser at 18 feet above sea level. Combined with the 12-foot height of your antenna, the two of you could converse while about 6.7 miles apart. If the Coast Guard’s antenna is 100 feet tall, you can expect a reliable range of about 13 miles. Your buddy’s 18-foot antenna would net him a range of about 13.3 miles.
The actual distances are a bit farther, due to atmospheric refraction, but these are the distances you can count on, making satellite phones, EPIRBs (emergency position indicating radio beacons) and PLBs (personal locator beacons) very wise for anyone cruising open waters. To see a chart of the Coast Guard’s VHF coverage in your area, visit navcen.uscg.gov.

cheers
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Old 25 September 2015, 05:32   #8
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I've used a non-marine 5/8th wave aerial (similar frequency to Marine) with a 5W H/Held. That was mag mounted to the top of a portakabin and compared to an identical H/Held inside the cabin the range to both receive and transmit to other H/Held's in the field was definitely improved. If we'd sat someone on the portakabin roof it probably wouldn't have made any difference.

...

but if you stood outside portacabin at Same height ...would you get same distance ? what length of the mag mount cable? a few feet ? was the portacabin shielding the signal ...

Higher is better, but was told length of cable will reduce the the power...and as said each connection you lose 3db ...

it's something I have thought of ...and something I was considering doing as backup ...IE when my fix radio went if I needed to try get bigger distance nothing to lose...

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Old 25 September 2015, 06:12   #9
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S,

According to this Coax Attenuation Chart then even the worst coax cable has a loss about 12 dB per 100ft. So in transmission power a 6W handheld with 10ft of cable would have a 1.2 dB loss = 4.5W. Of course if that goes into 3dB gain aerial you are still "up" in relative power (assuming the lobes are pointing at the recipient!). But getting higher will get you more range. Received signals are going to be similarly attenuated - but if the assumption is the receiver has at least a 25W transmitter then its less of an issue than your signal getting to them.

A real comparison would be interesting, but I am not sure how you would set up a trial easily.
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Old 25 September 2015, 08:05   #10
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Insertion loss for a connector (PL259, PL258 etc) at 150 Mhz is certainly less than 0.1dB, some tests show as low as 0.01dB, so not a real concern.
Connecting a HH to an external antenna is of benefit when you can get the antenna higher - height above sea level trumps all other factors for range. The connector at the HH radio is usually either an SMA or the manufacturers own. Most manufacturers will give this information on their spec sheets. You can get adapters from PL259 or BNC to SMA so you can attach your HH to a fixed set antenna (radio or AIS) temporarily if needs be.
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