Raystar GPS antenna

G

Graham_Wright

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www.mastaclimba.com
Where to place?

I would like to avoid a rail mount as it would act a an effective warp catcher. It is low profile (without the rail mount pod) but I would still like to avoid installing in a walk on area - which excludes virtually every horizontal surface.

Some experiments over the weekend were inconclusive. I gained the impression that a fix was obtained faster if the plotter (E80) was switched off which defies logic. Unfortunately, the signal strengths (according to the plotter) continuously vary. Maybe this is due to motion of the boat but this was very slight.

Bearing in mind that our car satnav obtains a fix in a few seconds, the minute or so taken by the Raystar seems excessive.

I would like to keep the antenna below the deck (in the coaming away from any metalwork).

Any offers on how much attenuation GRP produces?
 
Some. More if wet. Yet more if someone happens to sit there.

When I installed my AIS transmitter I tested the antenna both inside and outside, using the PC setup tool which can show a signal strength graph. There was a detectable difference between the two, but the lower level was still more than comfortably high - I can’t remember the figures now but I looked up a paper from uBlox aimed at product designers which gave some rules of thumb.

By comparison, my elderly Garmin GPS128’s reception was sketchy under GRP; it became adequate but not great when moved to the inside of an acrylic window. The antennas were similar third-party internal ones in both cases. So there is a definite difference between modern receivers and early generation ones. Question is, how modern is the receiver chip inside Raymarine’s mushroom?

Pete
 
prv said:
So there is a definite difference between modern receivers and early generation ones. Question is, how modern is the receiver chip inside Raymarine’s mushroom?
Click to expand...

I guess it depends on which Raystar the OP has. The early Raystar 120 and 125 had 12 channel receivers. The Raystar 130 had a 50 channel receiver. The Raystar 150 has a 72 channel receiver.
 
Not certain the Raymarine 125 is that reliable but ours sits by the sheet winches however location might depend on size of boat but maybe look at photos of others for sale ?
 
pvb said:
I guess it depends on which Raystar the OP has. The early Raystar 120 and 125 had 12 channel receivers. The Raystar 130 had a 50 channel receiver. The Raystar 150 has a 72 channel receiver.
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It's a 12 channel one. The later plotters had GPS built in.

I guess on the cabin roof would be ideal. I could mount a stainless steel dome over it for protection.
 
Not at all sure a S/S dome over the top is a good idea re signal reception. Older Raystar GPS mushrooms were slow to acquire, very slow indeed if the internal battery had died, though would often eventually work if you waited, until powered off again. Changing the internal battery on the older ones often revives them. If your Raystar is the same era as an E80 it's probably a Seatalk 1 type, so not quite a straight swap for a cheap modern Evermore or similar generic replacement that will get a fix far faster, though you can connect one via NMEA. Any modern GPS should work OK inside the cabin. I have one tucked away in the panel behind the chart table, and another about 10 feet away on the pushpit. Funnily enough they usually disagree by about .001 or occasionally .002 of a mile which is 6 to 12 feet.
 
The Countess 33 hull accepts either a sloop or ketch rig. Mine is a sloop leaving the mizzen mast foot space free. That could be the one.

About the battery in the Raystar. I thought there was one. Is it easy to change?
 
Graham_Wright said:
The Countess 33 hull accepts either a sloop or ketch rig. Mine is a sloop leaving the mizzen mast foot space free. That could be the one.

About the battery in the Raystar. I thought there was one. Is it easy to change?
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It's a bit fiddly to change in the 125 so make sure you look carefully how it goes back together or take some photos or mark with a pencil so you can line everything up the same as before. I believe that the 120 is the same but the battery is soldered in rather than slotted into a holder so that's an additional complication.

Richard
 
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If you put the antenna to close to a lump of GRP, it may de-tune the antenna.
When you design a product with GPS, you pick a ceramic antenna tuned slightly high so that the plastic case of the product tunes it right.
As for how badly it works indoors, you'll never really know until it lets you down, like the forumite who hit Cornwall while looking for Plymouth.
My car gps has a very modern chip in it, plenty of channels and all that, but it can still get it wrong, putting the car on the wrong road or a few hundred metres into the fields.
It will always be worst when you need it most, rain on the deck, water in the air for maximum path loss etc.
 
It needs a clear view of the sky, the wider the better. Ours is on the top (and to the side) of the stern arch. Before we had a stern arch it was on the rail in about the same location and far enough out of the way for nothing to catch on it. Instrument poles are also good.

The Raystar models are all designed to be also flush-mountable, so you can do something like this and it won't catch any ropes either (but put it somewhere it won't get stepped on):

https://flic.kr/p/4yZuov
 
Yngmar said:
It needs a clear view of the sky, the wider the better. Ours is on the top (and to the side) of the stern arch. Before we had a stern arch it was on the rail in about the same location and far enough out of the way for nothing to catch on it. Instrument poles are also good.

The Raystar models are all designed to be also flush-mountable, so you can do something like this and it won't catch any ropes either (but put it somewhere it won't get stepped on):

https://flic.kr/p/4yZuov
Click to expand...

Possibly an insoluble equation!
 
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