Scx-20 Mounting Questions

[eheffa]

1. I have just ordered an SCX-20 Sat compass for installation on my Nordic Tug 37 Pilot house roof. I had intended to mount it in the location of a now defunct GPS puck (gray puck on STB side of roof) but reading the manual, I see that location is less than 1 m from the STB side VHF antenna. How significant a problem is proximity to the VHF? Should I look to a more midline location?

2. Is there any advantage to a true mid-line location for the Sat Compass vs mounting it off the mid-line?

3. If I mount the unit directly in the midline close behind the searchlight, would it still have enough access to the sky or should I look to a short pole mount? (not too high so as to not get into the radar beam..). How close can I mount it behind the searchlight before there is potential obstruction to the sky?

4. The manual says that the unit must be mounted level but my pilothouse roof is canted back about 2 degrees from level. I see that the software allows for some pitch offset. Is it OK to rely on that offset rather than create some sort of levelling shim for a base?

Thanks in advance for any information and clarification.

-evan

 

[eheffa]

1. I have just ordered an SCX-20 Sat compass for installation on my Nordic Tug 37 Pilot house roof. I had intended to mount it in the location of a now defunct GPS puck (gray puck on STB side of roof) but reading the manual, I see that location is less than 1 m from the STB side VHF antenna. How significant a problem is proximity to the VHF? Should I look to a more midline location?

2. Is there any advantage to a true mid-line location for the Sat Compass vs mounting it off the mid-line?

3. If I mount the unit directly in the midline close behind the searchlight, would it still have enough access to the sky or should I look to a short pole mount? (not too high so as to not get into the radar beam..). How close can I mount it behind the searchlight before there is potential obstruction to the sky?View attachment 4759

4. The manual says that the unit must be mounted level but my pilothouse roof is canted back about 2 degrees from level. I see that the software allows for some pitch offset. Is it OK to rely on that offset rather than create some sort of levelling shim for a base?

Thanks in advance for any information and clarification.

-evan

Here is another view.

I'm thinking that this location (marked with orange X) might serve very well as it has easy access from below?

Is there enough distance from the searchlight?

 

[gtstang462002]

Based on the images provided, I would think that you are about in the correct region and should have no issues mounting it in the location indicated. I do not think that the searchlight would create enough EMI to cause any issue with the compass at that distance and it appears to be well out of your radar beam. I wish I had that much space to work with on my roof when laying everything out.

 

[eheffa]

Based on the images provided, I would think that you are about in the correct region and should have no issues mounting it in the location indicated. I do not think that the searchlight would create enough EMI to cause any issue with the compass at that distance and it appears to be well out of your radar beam. I wish I had that much space to work with on my roof when laying everything out.

Thank you gtstang.

After considering the question further, I think the midline placement would be best but would prefer to move the SCX unit as far forward as possible without negatively impacting the SCX performance. I would prefer to mount the unit as a roof mount.

I rarely need to use the searchlight so am not so concerned about the rare occasions of EMI. I am just not clear on how much clear sky the SCX unit needs to operate optimally; ie how far away from the housing of the searchlight does the SCX need to be to not be obstructed?

I do not see any recommendations in the manual as to how much exposure to the sky is optimal...

-evan

 

[Magnetron]

I agree with Gstang462002's assessment. With regards to the VHF antenna proximity, it concerns introducing strong RF (e.g. when keying the mic) into a satellite receiver. Regarding the top canter, it doesn't take much clear view to constitute clear view - if you need a baseline than it's a clear view of the horizon. I think your placement as indicated in the last photo is a good placement. However, if you are concerned about reception relative to placement than it's possible just to mock up our product on the roof and use the GPS Status from our MFD (for example) to monitor satellite reception. If you're getting a good HDOP value after the GPS cold start finishes indexing the satellites - it's a good spot.

- Maggy

 

[eheffa]

I agree with Gstang462002's assessment. With regards to the VHF antenna proximity, it concerns introducing strong RF (e.g. when keying the mic) into a satellite receiver. Regarding the top canter, it doesn't take much clear view to constitute clear view - if you need a baseline than it's a clear view of the horizon. I think your placement as indicated in the last photo is a good placement. However, if you are concerned about reception relative to placement than it's possible just to mock up our product on the roof and use the GPS Status from our MFD (for example) to monitor satellite reception. If you're getting a good HDOP value after the GPS cold start finishes indexing the satellites - it's a good spot.

- Maggy

Thank you Maggie.

That's a very helpful and constructive suggestion. I will mockup the placement and look at the HDOP values in varying proximity to the searchlight before committing to a final installation location.

I will report back if that's of any interest to people.

-e

 

[Magnetron]

I'm interested -e, please when you decide upon a placement spot on that beautiful 37 Nordic Tug let us know. It is always helpful to see other's successful installation of our products.

- Maggy

 

[eheffa]

I installed the SCX-20 in the location as noted above.

I tested the unit before committing to drilling holes. The Sat Compass latched onto the current position very quickly and had consistent HDOP values around 0.5 which is excellent and significantly better than any of the other 3 GPS antennas in the system (Airmar WX-150, Furuno 330B and a Vesper Unit) which all had values in the 1 - 1.5 range.

Very pleased here...

-evan

 

[Johnny Electron]

Great example of measuring thrice and cutting once. Well done!

 

[eheffa]

Further testing today shows a rock solid GPS position and better detail in radar imaging. It seems that there is less smudging and sharper discrimination of the less reflective objects like crab pot floats and other debris in the water that were previously lost in the stutter (?). The Radar overlay on the chart plotter is now dead accurate.

I'm very pleased.

Thank you for the good help in answering my installation questions.

-evan