Mounting pole for GPS antenna etc.

[lw395]

It should really be on the centreline at deck level to stop the boat's rolling adding to the signal.

Given that the radio waves are coming in at the speed of light, how much do you estimate that the rolling motion at say a couple of feet per second is going to influence things?
You can work out from the bit rate and modulation scheme that it is pretty resistant to the effects of the boat rolling.
At that level, there is often more modulation imposed on the signal by atmospheric effects.

 

[FWB]

Given that the radio waves are coming in at the speed of light, how much do you estimate that the rolling motion at say a couple of feet per second is going to influence things?
You can work out from the bit rate and modulation scheme that it is pretty resistant to the effects of the boat rolling.
At that level, there is often more modulation imposed on the signal by atmospheric effects.

My LGC4000 updates 5 times a second. It could measure the speed of the roll.

 

[BERT T]

I want to get my GPS antenna and Navtex aerial up off the pushpit out of the way. Who supplies the brackets, poles etc.?

I made up my own for less than £50. 2m of 25mm x 1.5mm stainless pipe, a stanchion base from Seascrew, a piece of 2mm stainless 450mm x 80mm with holes drilled to suit the various antennas welded to the top of the pole to form a T bar; a piece of 3mm stainless plate 80mm x 40mm with 4 holes drilled to suit 25mm U bolts welded to the side of the pole with the centre at the same height as the push pit rail. Mount the stanchion base on the deck and secure the pole through the 3mm plate with 2 25mm x 5mm U bolts.
Simple.

 

[lw395]

My LGC4000 updates 5 times a second. It could measure the speed of the roll.

That shouldn't cause it a problem with averaging the position. Most GPS's spend their time working out the speed at the same time as the position. In fact it could make life easier for the signal processing.
Not ideal if you are using it for surveying and want centimetre accuracy. If the averaging time for the speed is badly set up, it might be all over the place, but on a boat COG and SOG should be averaged over a few seconds at least. The same thing is going to happen if you sail over any waves.

 

[Caer Urfa]

Made my own pushpit mast 6 years ago and it's still going fine with no reception problems from the GPS antenna.

You can get the swivel fittings easy on line to make up the mast and I just purchased the 1" bore SS tube, also mounted the wind sensor which has also worked fine and it took me 20 minutes to replace the cups last year .

View attachment 35185

In the absence of a suggestion for an "off the shelf" solution, that's what I want, hence my original post.

 

[sailorman]

Made my own pushpit mast 6 years ago and it's still going fine with no reception problems from the GPS antenna.

You can get the swivel fittings easy on line to make up the mast and I just purchased the 1" bore SS tube, also mounted the wind sensor which has also worked fine and it took me 20 minutes to replace the cups last year .

View attachment 35185

How well does the wind transducer work with the main set & going to windward

 

[Caer Urfa]

How well does the wind transducer work with the main set & going to windward

Good question!

I have monitored this over some time, years ago I ask Nasa, Raymarine and Tick Tack before I mounted the wind cup sensor on the pushpit mast top which is approx 8' above the water and 6' away from the end of the boom as to how much differance in wind speed reading I would expect to get as opposed to mounting it 'ontop of the main mast' which I agree is the best place, but I noted most systems have one main weak point 'the wind indicator or cups' and at 68 I have no intensions of going up the mast to change the cups!.

All three came back and said under normal sail conditions on a beam reach I 'could get' up to 2/4mph differance, at that little differance I am very happy as I have a motor sailer not a racing yacht , checking with other boats closeby my wind speed has been roughly 2/3 mph differance to their readings.

As I am not always a 'fair weather' sailer and sail all the year round my main interest apart from knowing the wind direction is the wind speed as an indication of when to 'start reefing' which I do at 20mph winds.

Mike