View RSS Feed

the dream of dawn

Gadgets Gone Wild

Rate this Entry
Well this has gotten a bit out of hand. Arcturus' Electronics mash-up was collected piece by piece over the years. More than half of it from Craigslist or Ebay. This all started from a depth sounder and an iPhone! But it's OK, because Arcturus is my toy and one of his legitimate primary functions is to be a toy-bearing platform.
At the request of EM-Trak customer service, to help troubleshoot a problem, I drew up a schematic for them. I didn't think I'd be doing this so soon after seeing the one posted by "kiwisailor!" Every time I thought I was done, I remembered another gadget that's connected in there. Looks dreadful. If one went to purchase a system that did the same thing, from scratch, lots of these little black boxes would all fold into one of the main head units. And of course there are extra headaches trying to mix components from different vendors - everybody blames the other guy!

Name:  Navcom diagram.jpg
Views: 173
Size:  81.5 KB

The current problem is a bit vexing. The EM-Trak B100 AIS transceiver serves AIS data and GPS data to the radios and computer/chartplotters. The only problem is that it causes severe radio interference in the 2 - 4 MHz bands of the SSB radio. You know, the ones that are actually used most of the time! It's not actually the AIS transmissions, but sounds like the NMEA 0183 data output that's the problem, any time the AIS is powered up. For most gadgets, that would be annoying, but not fatal. You'd just turn off the offending device. Except that the radio requires GPS input to function correctly, so I can't do that. Plus downloading a full set of weatherfax broadcasts off the radio can take a couple of hours - you wouldn't want to go without navigation for that long, I think. (I know... people did it all the time, only a couple of decades ago...)

Hmm... looks like we can't upload video clips, but the interference basically sounds like a loud continuous riff of chirps in 2/4 time. The sea talk instruments put out a similar riff, but 1000x quieter, and that was easily snuffed with ferrite chokes.

I've spent most of my time so far powering up everything on the boat in isolation, one device plus the radio at a time. The B100 is definitely the culprit. I've installed a king's ransom in ferrite chokes on every wire in sight, double-checked that all the shields are grounded, and everything is connected correctly. Next I'll try replacing cables, but of course, they've all got fussy unique connectors. The EM-Trak customer service is in Bath, half a day out of synch, so they won't get my response to their questions for another couple of days.
I could fiddle with it some more or just leave it for the weekend and go dig out the SUPs. Supposed to be 103F tomorrow

Submit "Gadgets Gone Wild" to Digg Submit "Gadgets Gone Wild" to del.icio.us Submit "Gadgets Gone Wild" to StumbleUpon Submit "Gadgets Gone Wild" to Google Submit "Gadgets Gone Wild" to Face Book

Updated 06-24-2017 at 06:15 PM by toddster

Tags: None Add / Edit Tags
Categories
Uncategorized

Comments

  1. kiwisailor's Avatar
    WOW!! That is a great schematic and it's got me all excited to add a few more pictograms to my one. Once you start networking everything on board a boat you really need a schematic for reference. Regarding RF noise I think I'm dealing with some of that as well from my iMux as well as the 12V USB outlets...next step ferrite chokes.
  2. toddster's Avatar
    Drawing everything out like that did help to find a couple of improper connections. I rushed to the boat to fix it, but alas, it did not solve the interference.
    To wit: even with the MUX, one cannot just hook up all the TX ports to input and all the RX ports to the output. The AIS unit also has a limited multiplexing function, so it might be possible to set up an infinite loop. Although in this case, no such signal should be present, but it might feed more data into the VHF radio than it can parse.
    As one might expect, EM-Trak customer service just says "it must be one of those other devices, not ours." Despite the fact that for testing purposes, the system was reduced to only their device plus the radio.
  3. toddster's Avatar
    Quote Originally Posted by kiwisailor
    WOW!! That is a great schematic and it's got me all excited to add a few more pictograms to my one. Once you start networking everything on board a boat you really need a schematic for reference. Regarding RF noise I think I'm dealing with some of that as well from my iMux as well as the 12V USB outlets...next step ferrite chokes.
    I seem to recall hearing a RF noise complaint about the USB outlets sold at West Marine. Possibly on their product review page. There is one of these on the I/O and power outlet panel, just next to my M802 head unit. I haven't noticed any problem so far, but will double check.
  4. toddster's Avatar
    Making progress...?

    Disconnecting all of the NMEA inputs and outputs from the AIS unit seemed to eliminate the interference. So, likely the problem is in the cabling.

    Reconnected all the AIS I/O wires to the multiplexer breakout, testing after each connection. All is still quiet!

    Reconnecting the special coax cable I bought from Dockside Radio to connect to the M802 GPS input port, even when not connected to the M802, brought back the interference. Despite being laden with ferrite chokes. I'll try making up one from scratch - maybe with a shielded twisted pair.

    Then I discovered that I could eliminate most of the interference on the 4 Mhz band by connecting the shield of the AIS cable to the chassis ground of the M802, but not the shield of the multiplexer. Still as strong as ever on the 2Mhz band though. Oddly, adding a ferrite choke to this grounding jumper made the interference come back on 4 MHz. (And no, stripping all the ferrites off of the offending cable did not help.)

    Hmm... I guess I also didn't check back in step one whether interference was gone at 2Mhz. *Sigh* Time to start all over again.

    The dog was whining at this point, so we had to go.
  5. toddster's Avatar
    I happened to see that Brian on S/V Delos just posted his new electronics scheme today. https://youtu.be/FJUSrbKS1-A
  6. kiwisailor's Avatar
    I just noticed that too and he is using the iMux and Actisense bridge. That Maretron ultrasonic motionless wind sensor looks like an interesting option to replace traditional wind anemometer.
  7. toddster's Avatar
    Quote Originally Posted by kiwisailor
    I just noticed that too and he is using the iMux and Actisense bridge. That Maretron ultrasonic motionless wind sensor looks like an interesting option to replace traditional wind anemometer.
    Yes, looks pretty sweet. I actually "bought" a similar unit for much less money through indiegogo, but it's been more than a year and they still haven't shipped them. Not sure if it will have NMEA integration, but the APIs are available. It's from the same company as "sailflow" and "ikitesurf" so I think they will eventually deliver. Knock on wood.
    https://www.indiegogo.com/projects/w...s/x/14634868#/
  8. toddster's Avatar
    Argh. Nope. Still got interference on 2Mhz with all the I/O cables disconnected. Installing a new GPS cable didn't really change anything.