Connecting an external aerial to handheld Vhf

kaman · 24 September 2015, 00:46

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?

jeffstevens763@g · 24 September 2015, 07:55

no expert but would say power output would limit its range.

jyasaki · 24 September 2015, 23:00

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.)

Poly · 25 September 2015, 00:48

Quote:

Originally Posted by jeffstevens763@g

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.

SPR · 25 September 2015, 01:02

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....

www.firstaidatsea.co.uk
www.SPRmarine.co.uk

ShinyShoe · 25 September 2015, 07:44

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...

jeffstevens763@g · 25 September 2015, 07:58

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

SPR · 25 September 2015, 10:32

Quote:

Originally Posted by ShinyShoe

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...

S.

www.firstaidatsea.co.uk
www.SPRmarine.co.uk

Poly · 25 September 2015, 11:12

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.

Salty John · 25 September 2015, 13:05

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.

kaman · 25 September 2015, 17:06

Wow!
This is getting technical.
I'm toying with the idea of connecting my h.h to an external antenna.
I think the consensus is that this would increase my range.
Also having a look at 2nd hand fixed VHF as well as I may well purchase one 2nd hand and rig it up instead.
Anyone know how long (on average) .a fixed VHF SET would last on standby rigged to a 7ah battery

Poly · 25 September 2015, 17:18

Quote:

Originally Posted by kaman

Anyone know how long (on average) .a fixed VHF SET would last on standby rigged to a 7ah battery

An SH GX1100E claims to draw:
Standby: 0.3A
Receive: 1.0A
Transmit: 5.5A (Hi); 1.5A ( Lo)

Assuming your battery is fully charged and you don't want to drain it below 50% you'll get 11+ hrs on standby. 3.5 hrs on receive or about 30 min transmit on Full power. Bearing in mind that if in distress you will really want that last option I would be looking at a slightly bigger battery.

kaman · 25 September 2015, 18:05

Thanks for that Poly.
I've got a 14ah and a 20ah battery as well that I use for lamping foxes.
Think the 14ah would suffice the 20ah is a beast.
I'm going to keep an eye out for a 2nd hand fixed VHF.
The hand held is permanently clipped to me when I'm out in the sea .
Would be nice to have a bit more range with a fixed set for peace of mind.

Poly · 25 September 2015, 18:35

Quote:

Originally Posted by kaman

Thanks for that Poly.
I've got a 14ah and a 20ah battery as well that I use for lamping foxes.
Think the 14ah would suffice the 20ah is a beast.
I'm going to keep an eye out for a 2nd hand fixed VHF.
The hand held is permanently clipped to me when I'm out in the sea .
Would be nice to have a bit more range with a fixed set for peace of mind.

That's a good arrangement. If your engine has a lighting circuit you could be laughing, but I run a 20Ah on mine (charged off the engine and electric start!) and I feel much happier this year with fixed than handheld (and as you keep the h/held on myself so I still have it if I am no longer in the boat!). You'd get a really cheap fixed unit without DSC I do like the idea of a the big red button and certainly I am happier that the wife/kids would make that work than remember to change to 16 etc in a panic.

jeffstevens763@g · 25 September 2015, 18:46

Quote:

Originally Posted by kaman

Thanks for that Poly.
I've got a 14ah and a 20ah battery as well that I use for lamping foxes.
Think the 14ah would suffice the 20ah is a beast.
I'm going to keep an eye out for a 2nd hand fixed VHF.
The hand held is permanently clipped to me when I'm out in the sea .
Would be nice to have a bit more range with a fixed set for peace of mind.

For piece of mind kaman why not get a PLB as a back up system if line of sight for the radio is blocked or no one in your area or out of range.

kaman · 25 September 2015, 20:51

The PLB is something else I have been considering.
They have come down in price - could be something for Santa time!
This year has seen me set further afield in my Sib.
Been around lots of Scottish Islands this year camping and walking.
Went a few group outing, a few times with my daft mate, but mostly on my lonesome.
You do feel very small out in the blue yonder miles from civilisation.