Placing antennas A-Frame

[Nano]

Hi.

What is the optimal placement of antennas on my A-Frame?

Today i just got navigation lights on my A-frame.
My GPS antenna is placed over the console (see picture)

I just bought me a VHF and also planing to install a FM/AM radio too.

So i want to place all my antennas on the A-frame (and also move the GPS antenna).

So i made a picture of what i think is the best solution. The VHF antenna is placed as far from the other stuff as it could be. Is this right or should i do it another way?

Best Regards
Mårten

[Pikey Dave]

Originally Posted by Nano

Hi.

What is the optimal placement of antennas on my A-Frame?

Today i just got navigation lights on my A-frame.
My GPS antenna is placed over the console (see picture)

I just bought me a VHF and also planing to install a FM/AM radio too.

So i want to place all my antennas on the A-frame (and also move the GPS antenna).

So i made a picture of what i think is the best solution. The VHF antenna is placed as far from the other stuff as it could be. Is this right or should i do it another way?

Best Regards
Mårten

leave the GPS where it is, low down is good, it gives a more stable reading. The vhf & am/fm are ok on the "A" frame.

[Erin]

GPS should not be to the side of the VHF, it should be either above or below it. The manual will give you more info.

[Nano]

Hi. Thanks for the tips. I will just have the two antennas and leave the GPS on the console.

/Mårten

[9D280]

Originally Posted by Pikey Dave

leave the GPS where it is, low down is good, it gives a more stable reading.

If the accuracy due to the extra couple of feet off the water and the roll of your rib is that important I woud suggest you might be better getting someone to look over the bow than you at a plotter screen! Either that or switch on the "track smoothing" option.

Before this turns into a huge debate, my point is that the realisitc accuracy of the GPS is, say, 3-4m. Your console to frame height is going to be , what another half meter at most? If the boat rolls the console antenna will move say 6". the frame mounted one might move a couple of feet. Is that really an issue in a 3m circle? (Especially when you sat there instantly blocks a couple of horizonal satellites that a console antenna might miss that the one on the frame would see that will help to improve your positional accuracy!)





Back to the OP, just make sure that the antenna bases don't obscure the while light to port & Stbd.
(although if you put the antenna on the slope of the frame it shouldn't be a problem)

[Salty John]

Looks good.
Just check that the nav light, if it's LED, doesn't interfere with the radios. If it does you'll need to change to a different type of LED.

[Nano]

I just thought it looked better to have all the antennas including GPS antenna on the a-frame. But i would never do anything so that the reception or accuracy would be bad or worse. That's why i'm asked whats the best placement, and i got great answers. Thanks guys

I will put the VHF antenna on the slope and keep the GPS on the console.

The navigation light is not a LED type, so i hope that there will be no problem

Best regards
Mårten

[Pikey Dave]

Originally Posted by 9D280

If the accuracy due to the extra couple of feet off the water and the roll of your rib is that important I woud suggest you might be better getting someone to look over the bow than you at a plotter screen! Either that or switch on the "track smoothing" option.

Before this turns into a huge debate, my point is that the realisitc accuracy of the GPS is, say, 3-4m. Your console to frame height is going to be , what another half meter at most? If the boat rolls the console antenna will move say 6". the frame mounted one might move a couple of feet. Is that really an issue in a 3m circle? (Especially when you sat there instantly blocks a couple of horizonal satellites that a console antenna might miss that the one on the frame would see that will help to improve your positional accuracy

Room for one more in pedants corner

[Ian M]

Originally Posted by Pikey Dave

Room for one more in pedants corner

Play fair, the OP asked for the best positioning, and 9D280 pointed out that the greater issue is being able to see all the satellites within the viewing arc, and not have one or two blocked by a big chap like yourself if the antenna is console mounted. So, +1 for mounting the GPS antenna on the 'A' frame.

[PeterM]

I would also consider the wiring for a console mounted GPS is less likely to be chaffed, broken etc as it doesn't need to be under the deck or in any water .

I used console mounted more and more recently and work fine (until I put my sarnies on top wrapped in foil ! spent ten minutes trying to work that out ! )

For VHF radio height is a factor - for GPS not as much is my view.

And FM /AM reception - try an aerial inside the console - again less wiring under deck and less exposure to water and will probably pick up 'tunes' fine.

[jyasaki]

Originally Posted by Erin

GPS should not be to the side of the VHF, it should be either above or below it.

Might want to look at a drawing of what your VHF antenna actually has inside. I believe that the actual radiating elements are contained in the upper third to half of the mast. Mounting the GPS and VHF antennae on the same level will keep the GPS out of the VHF radiation.

jky

[9D280]

Originally Posted by Pikey Dave

leave the GPS where it is, low down is good, it gives a more stable reading.

Originally Posted by Pikey Dave

Room for one more in pedants corner

What you got on board? A survey quality reciever???

short version:

GPS antenna height effect on position in a rib is negligible - The s*dding machine can't pin you down to much better than a couple of boat lengths on a good day anyway.


The stoopid thing is - we all agree the console is fine!!!!!!

[Erin]

Originally Posted by jyasaki

Might want to look at a drawing of what your VHF antenna actually has inside. I believe that the actual radiating elements are contained in the upper third to half of the mast. Mounting the GPS and VHF antennae on the same level will keep the GPS out of the VHF radiation.

jky

I'm sure you're right. I was just going by what the manual says. I suppose a metal whip aerial will be radiating along most of its length.

[martini]

I believe the reason for not mounting a gps antenna too high is because it can pick up signals reflected off the water. I'm not sure if the problem is that an antenna mounted high is more susceptible to reflected signals or because there's more time delay in a reflected signal reaching a high mounted antenna.

Either way it's got bugger all to do with your a frame rolling about!

[BruceB]

Console mounted AM/FM aerial is fine, inside the console works fine and picks up anything you wish to hear.
I have a GPS mounted on the a Frame. mainly to ensure the transducer and GPS position are as acccurate as possible and I don't automatically introduce a couple of meters of error automatically.
This is for wreck finding and searching purposes and probably doesn't matter otherwise.

[PeterM]

Just a thought - surely you want the GPS aerial as close to the middle of the boat as possible as in theory if you stick it at the back then on a 7m boat you have just put yourself 3.5m out of position ?(if you want to be really really accurate )

[9D280]

Like I keep saying - you'l be lucky if the machine actually puts you less than a boat's length from reality anyway....

- At 20+ knots, a couple of metres shouldn't be a problem.
- At super close range I'd be relying more on my eyesight or an oar over the bow!

[Cookee]

I'm not going to bother commenting on the GPS debate other than I've never heard so much ..................



Anyway get yourself a VHF/FM splitter to reduce the number of antennas.