Does anyone have the "Noise Filter" in the triple prong SimNet connector under the mast step?

Mine looks like a regular terminator, the "noise filter" is supposed to also have a capacitor.  Curious if anyone has this and what theirs looks like?

I'm having an issue with my 508 wind sensor (new) where it doesn't come back to life after the power to the SimNet network is turned off.  The only solution is to disconnect and reconnect it, where it then comes back to life.  It's a brand new sensor replaced in the fall...

Should not need any kind of 'noise filter' in Simnet. Simnet is an industry standard CANBUS protocol that is very robust providing installation guidelines have been followed.

Basically it is only a Resistor.

Sure the 508/608 has built in termination resistor; you do not need an extra termination resistor at mast base.

It you connector multi-meter across SIMNET L/H, A/B or data+/- connection (whatever they call it in your system) with everything switched off, you should measure ~60-Ohms (two end termination resistors in parallel). If you measure ~40-Ohms them you have an extra termination resistor. If ~120-ohms then you are missing an end termination or there is a break in your SIMNET network. 

Cheers.

I am wondering why newer boats still need a noise filter.

My boat from 2008 has one under the mast. The reason was, that they used the wrong cable in the sparcraft mast, and we got strange readings from the windvane. Later boats should have the correct cable......

This is how my noise filter looks like:

If you zoom in on the mast area diagram:

Refer to this article in Panbo (ok, from 2011)

https://panbo.com/impedance-driven-nmea-2000-simnet-gets-a-noise-filter/" rel="nofollow - https://panbo.com/impedance-driven-nmea-2000-simnet-gets-a-noise-filter/

In one of the comments:

"I’ve been told it contains a 120 Ohm termination resistor as well as a 220 μF capacitor. So it is completely passive. It lowers total impedance to 120/3 = 40 Ohm instead of the standard 120/2 = 60 Ohm.

Thanks Peter.  Mine definitely doesn't look like that - that looks like the pictures i've found.  Mine looks like a regular terminator.  I believe the longer part is the capacitor.

Mine looks like this:

I've also got to check the voltages under the mast step in that 3-prong connector, as that may contribute to the issue as well.

But the bottom line is that at least in this diagram, the total resistance across the H/L on the bus would actually measure 40 ohm, not 60 ohm, and that apparently was by design.  Additionally there should be some capacitance as well.

SIMNET is 250kbs CANBUS which 'should' be good for a 250m cable length although SIMRAD quote 120m in their specification. Running cable up a 20m mast should be no problem at all.

Capacitor cannot be 220 μF; that would kill the bitstream dead. Might be 220 pF or 220 μF across the DC rather than data. Either way, have you tried removing it?

Actually it's the opposite.  Right now there is no "filter", just that thing I posted (the small "plug" with the red end, which i suspect is just a termination resistor).

From the pictures it definitely looks like a 220uF capacitor (the shape is consistent, it's not a small pico cap).

I'll know more when it shows up - as I think you mentioned, it's not a very common part and was difficult to find.

So with or without the additional terminator that is currently installed, the 508 acts the same.  Its solid while the SimNet is powered up, but will not come back to life after a power cycle.  Makes no discernible difference if that plug is installed in the 3-prong connector under the mast step.

The very curious thing is that without that terminator installed, powering down the network takes a very long time.  I have an extra Triton2 at the Nav station (that is powered only by the SimNet bus) and when you turn off power to the network, it remains on for a long time (minutes).  If the terminator is installed, the network powers down "faster" in less than a minute.  But either way it seems strange?  This is the red-tipped terminator, so I don't believe it has any capacitance, and technically shouldn't touch the power side of the bus cables.  But that is the observed behavior.

So when i'm back on the boat this weekend, I need to get out the multimeter and see what's going on...

Totally agree.  There is something fishy going on.

I'm curious to your statement about the bus vs voltage?  I guess since it's working the implication is that there is sufficient voltage getting to the mast top?

Why should it "come to life" when you un-plug/plug it in, vs just turn the power on...?

Yes, the B&G's have a diagnostic page.  It shows single digit "fastpacket errors", everything else is 0 and the bus load is around 17%.

I guess I can measure the voltage at the bottom and assume a certain voltage drop.  So it would only really be an issue if the voltage at the bottom was pretty low (like 11v).

My noise filter is arriving today, I'll swap that in first and see what happens.

I'm still also going to verify one, robust N2k power tap.

I have a N2K ShipModule to USB adapter (not installed), so theoretically I could examine it further on a laptop (I assume there are some pc based diagnostic tools?).  I also have an oscilloscope so I could really get all technical on it and see the shape of the signal.  That panbo article goes into it a bit:

... screen #1 shows a very short, simple network with no terminating resistors — which at least partially accounts for the ringing that follows the nice square NRZ waves, as demonstrated in screen #2, in which the same backbone has some terminator-style resistance added. Screen #3 shows what’s actually happening with 13 active sensors and about 60 meters of SimNet cabling. Apparently it works, but those waves are looking a little raggedy. Or were until he installed a SimNet Noise Filter as seen in screen #4...

SIMRAD break some CANBUS rules which can have detrimental affect on data quality. For example, CANBUS spec states maximum dropper length (distance from device to main backbone) of 0.3m where my SIMRAD compass came with 5.5m cable which I cut back to minimum. We have 18 SIMNET/NMEA2000 devices over ~40m backbone with no problems so it is possible to make it work effectively.

Be interested in you experience with that new filter.  

So I definitely don’t have the filter.  The one I ordered just arrived and looks like this:

The filter just arrived and it doesn’t look anything like the termination plug that’s in there now.

The other part was definitely another terminator only, no capacitor.  Strange.

I realize this is water under the bridge. But just wanted to say that I was measuring 42 ohms across my simnet network, but when I pulled out that «filter» from the simnet «3-way strip» in salon below mast it read 60 ohms as it should.

So my thoughts are that when Hanse installed this filter thing, then they in fact violated the 60 ohm «rule» in order to get their top of the mast instruments working. That being said, everything was working on my boat with the mentioned 42 ohms, but from what I’ve been told this third resistor will cause hell when installing my fancy Zeus and Halo+ radar which is less tolerant to out of spec values. Hanse 2012 385 here.