Maritime Mobile questions

[VK3LAJ]

Hi All -

I have a fibreglass boat that i take out on port phillip bay - And I recently purchased a Kenwood TS50 S to take out on the boat for some DX work in between tide changes (fishing).

I've got an auto tuner etc and i was thinking of setting up an antenna as follows:

Stainless steel wire up a 9M fibreglass squid pole, and then another 9m stainless steel radial wire with a sinker on the end overboard underwater.
Connect this up like a vertical antenna into the tuner and bobs your uncle.

Can anyone see anything wrong with this idea that i'm missing?

I've done something similar on land before with a few more radials and it worked a treat..

[VK3DXE]

That should work Anthony. The only thing I'd suggest is to be aware of where the major lobes will be on the different bands. You may find yourself with most of your signal going straight up in the air on the higher bands...

I'd also suggest keeping the radio's power system completely separate from the boat's - it's really hard to push start a boat with a flat battery

[VK3LAJ]

Thanks for the tip! Yes i have dual batteries with an isolator so push starting a boat shouldn't be required.
The other option for a counterpoise/radial i guess would be 10m+ of stainless wire with a float on the end dragging behind the boat.

Not sure which would work better, straight down (vertical dipole) or horizontal - L

One way to find out!

[VK4TI]

Hi All -

I have a fibreglass boat that i take out on port phillip bay - And I recently purchased a Kenwood TS50 S to take out on the boat for some DX work in between tide changes (fishing).

I've got an auto tuner etc and i was thinking of setting up an antenna as follows:

Stainless steel wire up a 9M fibreglass squid pole, and then another 9m stainless steel radial wire with a sinker on the end overboard underwater.
Connect this up like a vertical antenna into the tuner and bobs your uncle.

Can anyone see anything wrong with this idea that i'm missing?

I've done something similar on land before with a few more radials and it worked a treat..

Here , interesting read http://www.accidentalcruiser.com/featur ... Radio.html , best to try and get the feed point as high as able

[VK2AVR]

Not sure which would work better, straight down (vertical dipole) or horizontal - L

Try both, but I suspect you are better off hanging a metal plate over the edge and letting it couple into the seawater. You really want the ocean to act as your ground plane, and surface area is your friend.

[VK4TS]

Of the fibreglass boats I have owned - I had satisfactory performance by running "radial" wires around the boat under the gunnel held in place with silastic..and then using a tuner directly at the feed point to a marine 9 foot whip.

Just being on the sea gives you an advantage

[VK4WDM]

9m stainless steel radial wire with a sinker on the end overboard underwater.

Add a couple of hooks on the end and you can fish AND radio. If you run a decent amount of power you might not need the hook

Seriously though, I used a "backstay wire" on a wooden boat with the metal keel as the ground and it worked extremely well.

73

Wayne VK4WDM

[VK5ZD]

another 9m stainless steel radial wire with a sinker on the end overboard underwater.

The length of wire in the water will not be critical.
I like the idea of a plate; go for the greatest area in contact with the seawater.

[VK3YE]

Hi All -

I have a fibreglass boat that i take out on port phillip bay - And I recently purchased a Kenwood TS50 S to take out on the boat for some DX work in between tide changes (fishing).

I've got an auto tuner etc and i was thinking of setting up an antenna as follows:

Stainless steel wire up a 9M fibreglass squid pole, and then another 9m stainless steel radial wire with a sinker on the end overboard underwater.
Connect this up like a vertical antenna into the tuner and bobs your uncle.

It will work fine from 7 to 28 MHz. The radiation pattern will be fairly low angle from 7 to 18 MHz (ie roughly 1/4 to 5/8 WL) but as mentioned before may break up above that. So it would be interesting to take along a 5 or 6m wire as well to compare for 21 MHz and up.

Last weekend I took a 5m end fed wire vertical on a squid pole and tried making contacts on 20m. None were made there due to a fade out but some were made on 10 MHz (ie 1/6 wavelength only). Also did some tests with chucking the counterpoise into the water. At least on 10 MHz there was a large increase in noise when the wire was making contact with the water.



The one that follows, made a week before demonstrates the success of a 5m wire on 15 metres. Again from the shores of Port Phillip.



Some people go on about resonant antennas and so forth, but provided that you're on a great ground (eg salt water) and the antenna is more than (say) 1/6 or 1/4 wavelength long then you'll be OK provided the tuner handles it. Even lesser lengths will work well on bands like 160m, though top loading and capacitance hats etc will help.