Author Topic: Helix 9 MSI  (Read 242 times)

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Offline Remington

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Helix 9 MSI
« on: September 07, 2021, 05:57:46 PM »
Hello I am new to this site and my first time posting.
I am in the process of purchasing a new boat and I am putting two Helix 9 MSI units on the boat, the one on the bow will be going to an Ulterra 80 MSI link and will be connected to each other. I have had one dealer tell me that he would not recommend putting two MSI units on the boat due to interference but should put just the MDI as one of the units. I have looked on this site as well as others to try to find any info on this and really haven't seen any info on this happening. Lots of info on interference due to all kinds of other issues but not having two of the same units on the boat. The two transducers should be about 17 feet apart from the transom to the trolling motor. Is this something I should be concerned with or not?
I am new to the Humminbird units and what they can do and will probably be on here asking for help with all kinds of fun questions. Thanks       

Offline rnvinc

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Re: Helix 9 MSI
« Reply #1 on: September 07, 2021, 11:51:40 PM »
There are 2 types of “interference” associated with electronics - RFI and crosstalk  ...

RFI is created by errant electrical currents from items on the boat (trolling motor, wiring harness, etc) that encroach into the electronics - either into the transducer circuit or the power circuit  ... resulting in “noise” on the Sonar views  ...

Crosstalk interference is created when 2 separate electronics units transmit the same frequency at the same time  ... this, in effect, confuses each electronics unit because each unit cannot determine which transmit ping was sent by which unit  ... resulting in “noise” on the Sonar views  ...

Crosstalk interference is the type referenced by your dealer  ...

Most mitigate crosstalk interference in one of 2 ways  ... and one way is more effective than the other  ...

1. Connect the units by Ethernet and choose to allow both units to subscribe to only one unit’s Sonar information (basically shutting off the transmitters to one unit’s transducer)  ...

2. Set transmit frequencies different on each unit (this means 2d, DI, and SI)

Option 1 is more effective than option 2 because HB units transmit the the higher 2d frequency (for digital depth)(in the background) even if one unit is set to transmit the lower 2d frequency  ...

Therefore there may be crosstalk interference in option 2 even if each units 2d frequency is set differently  ... 

But also note : (using option 1) -> With both units subscribing to one units Sonar information - the information displayed on both units is coming from one transducer  ... where ever that transducer is  ..


« Last Edit: September 08, 2021, 12:03:29 AM by rnvinc »

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