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Old 06-07-2022, 08:47   #1
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Radar Reception Range / Radar Plugin

Hi,

we just crossed the bay of Biskay and had the first in earnest use of our new installed radar.
Unfortunately it seems to have some reception issues we like to solve.

It's the, by the OpenCPN Plug-in apparently well supported B&G 4G radome.
The radome is mounted about 8m above deck on our mast.
We ran the supplied radar cable uninterrupted all the way to the nav station where we attached 12V to it and added a 250mm long crossover cable to plug in into the Ethernet port of our laptop.

Heading sensor is a Quark-Elec QK-AS08-N2K attached to a serial port via USB. On a side node I have to wake the relevant connection up each time I start OpenCPN. To do this I call up connections and click apply. The tick mark is there before but OpenCPN does recognize it only after hitting apply again.
We connected this via USB because it seemed the simplest way to do.
The radar Plug-in shows the heading from start but does not have a checkmark on it.
Dashboard shows it only after apply is hit.

The laptop runs the latest OpenCPN and radar Plug-in on windows 10.
No other displays or plotter attached. No interface box either.

Only local interference can be our own aluminum mast and the stainless inner forestay which is passing about 300mm before the unit.
Only the forestays are stainless all other rigging is synthetic / Dyneema.
There is an unused wire in one of the running backstays, but it is not connected to anything below or above deck.

The B&G 4G should have a range of 36nm according to the manual.

At close range (say 2-3nm) we could see all steel cargo vessels, but the fairly high Spanish coastline was only visible once we could see it with the naked eye from deck level.
We did detect an, according to AIS, 18m catamaran at less then 2nm distance but none of the fishing vessels at 4-5nm range.
Most of them likely from metal construction.

So, this seems odd. Maybe it's not, I am ready to learn more.

We had some swell overlayed with a bit of wind induced waves.

I played a lot with the settings, and tried with the following settings amongst others:

Target boost was high
Target seperation was off
Gain I played with 63 worked best
Sea clutter was on auto offshore
Rain clutter was off

See attached images. Images attached show the different settings.

Maybe someone can help to find out what is going on?

Thanks.




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Old 06-07-2022, 18:15   #2
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Re: Radar Reception Range / Radar Plugin

I regularly saw cargo vessels at 8 NM and coasts at 20+ with my 4G.

Sea or Rain clutter set too high might explain this. Other settings donít have influence on distance of detection. The other answer you will like less: your 4G might be broken.
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Old 06-07-2022, 23:14   #3
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Re: Radar Reception Range / Radar Plugin

Quote:
Originally Posted by merrimac View Post
I regularly saw cargo vessels at 8 NM and coasts at 20+ with my 4G.



Sea or Rain clutter set too high might explain this. Other settings donít have influence on distance of detection. The other answer you will like less: your 4G might be broken.
Thanks.

That sounds not good, I had rain clutter off (we had no rain) and tried sea clutter in Auto offshore, Auto harbour, 100% and 0% no big difference.

If it's faulty not sure how to approach this, we are in another country now, actively cruising.

Does one deal with B&G directly or does one need to do this through the actual dealer who sold the unit initially?
We bought ours brand new about 3 months ago.
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Old 06-07-2022, 23:19   #4
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Re: Radar Reception Range / Radar Plugin

Turning sea clutter off completely would be worth a try.
Effect would typically be that targets under a mile would be lost in the clutter but you wouldn't be suppressing targets 4 miles or more away.

You radar may have a 36 range but even the best and most powerful radars rarely see targets over 16 miles away* - I doubt yours is that powerful.

*unless ducting is involved.
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Old 07-07-2022, 00:02   #5
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Re: Radar Reception Range / Radar Plugin

Quote:
Originally Posted by El Pinguino View Post
Turning sea clutter off completely would be worth a try.
Effect would typically be that targets under a mile would be lost in the clutter but you wouldn't be suppressing targets 4 miles or more away.

You radar may have a 36 range but even the best and most powerful radars rarely see targets over 16 miles away* - I doubt yours is that powerful.

*unless ducting is involved.
Thanks, that sounds a bit more reassuring. I'll try your suggestion on the next leg.

Why do they claim 36nm then, is that a theoretical value?
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Old 07-07-2022, 01:18   #6
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Re: Radar Reception Range / Radar Plugin

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Originally Posted by Franziska View Post
Why do they claim 36nm then, is that a theoretical value?
36 nm = 66.67 km. The earth is round, you have to believe me. After ~20 km "the other" ship is behind the horizon when you look from the deck level. Now your radar dome is 8m in the mast so you can see "the other" ship a bit further, but still. So, from 8m up in the mast theoretically you should see high rise buildings on shore from 20-25km but a sailing vessel, a small trawler I guess no way. This is for a radar as well. It has the calculated energy to see 36nm, and it might get a reflection when it is up in a mast of 150m but at a height of 8m... it will overshoot targets I think. I bet you can find some formulas on-line for answers.

But, I agree, 2-5nm should work
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Old 07-07-2022, 02:24   #7
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Re: Radar Reception Range / Radar Plugin

Quote:
Originally Posted by champ8242 View Post
36 nm = 66.67 km. The earth is round, you have to believe me. After ~20 km "the other" ship is behind the horizon when you look from the deck level. Now your radar dome is 8m in the mast so you can see "the other" ship a bit further, but still. So, from 8m up in the mast theoretically you should see high rise buildings on shore from 20-25km but a sailing vessel, a small trawler I guess no way. This is for a radar as well. It has the calculated energy to see 36nm, and it might get a reflection when it is up in a mast of 150m but at a height of 8m... it will overshoot targets I think. I bet you can find some formulas on-line for answers.



But, I agree, 2-5nm should work
Thanks for explaining.

Absolutely agree on the round earth!

What made me curious though, was that the mountainous coast here did not kick in earlier.

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Old 12-07-2022, 00:41   #8
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Re: Radar Reception Range / Radar Plugin

Hi,
The 36 mile range is very useful for looking at weather, squalls, rain, etc. as they are very high and over the curve of the earth. It is not just a sales gimmick. Things on the ground (even mountains) can get lost in the clutter.
-E
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Old 13-07-2022, 08:06   #9
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Re: Radar Reception Range / Radar Plugin

The maximum range to the radar horizon is:- D= 2.22√h
D= 2.22*2.8284
D=6.3naut miles
So you should not have targets at much more than that range, unless it is a large high target.
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