Topic: What to do with dummy transducer with SIDB Y

[country water]

I have a new Helix unit I plan to use as a dedicated SI/DI viewer.  I picked up a cheap transducer and SIDB Y cable to ensure the 83/200hz frequency doesn't interrupt my other unit.  Is there a best practice for how to store and locate the dummy transducer in the boat?

[rnvinc]

The HB SI units use the 200kHz 2d for depth readings ...even when viewing the SI or DI ...

The 2d must be in the water for the HB SI unit to operate correctly ...

Rickie

[country water]

I ran the boat Sunday with the SIDB cable installed with the dummy transducer and was able to view SI and DI.  This is my first time with SI so I'm not exactly sure what I'm supposed to see but it looks like a SI view.  I drove by a bridge and was able to make out the pilings and what looked like fish on SI.  I had to manually adjust the lower depth range of the DI views but that was it.  What sort of problems am I supposed to experience with a bad depth reading coming from the other transducer?

[bobcoy]

I seem to remember that you cannot accurately mark waypoints in SI screen without an accurate depth.

[rnvinc]

I'm waiting for Greg to respond in this one ...

Rickie

[country water]

I saw this post on another forum where Greg seemed to indicate there wasn't an issue doing it. 

http://bb.sideimageforums.com/viewtopic.php?t=4010

I haven't tried adding waypoints to SI so I can't speak yet on whether it is a problem.  I'm not sure if I would even be able to tell it was inaccurate.

[bobcoy]

Click on a brushpile and see if you can get on top of it using the waypoint. Unit needs to know depth to figure out using geometry to the spot. Don't ask me the math used. Not my job! Bob

[country water]

I have no idea how the math is done in the Humminbird units but I'm not sure the depth under the boat is relevant since the depth of the spots on the left and right of the SI may be significantly different.  I would assume the best way to calculate the location would be based on the distance to the point on the SI and the angle of that return with respect to the water.  With those two pieces of info you can calculate the distance offset.  The depth below the boat could be used as a relative measurement so it may be important.  We won't know unless someone with Humminbird engineering expertise weighs in.

[bobcoy]

I have no idea how,but I don't think you can know the angle,only distance. You sound more math savvy than I. Bob

[rnvinc]

I found this posting from Greg in my saved archives ...(Greg must be covered up with training duties)..

The 200kHz depth data helps in some of the automatic SI sonar functions like the Auto Sensitivity but not a whole lot besides that.

The 200kHz depth data will control how often the unit pings the 200kHz sonar as long as the Max Depth is set to "Auto". 

Setting the Max Depth to any manual setting controls the maximum amount of time that the unit will wait until pinging again (it will ping sooner if it gets a bottom reading).

The only tie-in between the 200kHz depth data and the Si sonar data is in how often the unit can ping the Si sonar.  This can be slowed down if the unit is having to wait a long time as the unit searches for the bottom reading.

The water column area is a product of the Si sonar data - not the 200kHz sonar data.  This is why someone with bad 2D sonar data can still have good Si sonar data.

So it seems as long as the unit is not losing bottom ...the unit will perform normally without the 2d xducer in the water ...

The un-answered question would be ... How often does the unit lose bottom ...(pinging at 30-60 times per second)...which would hinder the function of the unit when set to "Auto" ... (as I'm sure most use the "Auto" Max Depth setting anyway) ... ??

Rickie

[Humminbird_Greg]

I’m not sure of the total answer to this either as the newer units (and units with newer versions of software) have several features that need the water depth to work correctly.  I guess as long as you keep everything that can be set to manual as possible it should work.  I haven’t tried this myself but you definitely need to set the Lower Range and Max Depth menus.

I would try it with the other unit and the 2D transducer firing into the water just to see if you get any interference or not.  What make/model is your other unit and what frequency(s) does it use?

[country water]

My primary unit is a Lowrance HDS with a 83/200 transducer.  The next time I'm out I'll try using it without the splitter and check for interference and see if there are any differences in the way things get displayed.

Is there any setting in the Helix that allows you to dial down the intensity of the 200kHz signal that could help cut the interference if it occurs.  I'm worried that if I cut down on the sensitivity of the Lowrance I'll be missing fish.

[Humminbird_Greg]

About the only way to “dial down the intensity of the 200kHz signal” would be to set the Max Depth menu to a minimum setting.  This should keep the unit transmitting at a lower power.  However, I’m not sure what setting the Max Depth menu to less than the actual water depth would do to the Di sonar.  The Di sonar comes from the left and right Si sonar but there are ties between it and the 2D sonar, so you may just have to try it see what happens – you won’t harm the unit by doing this.

[Brunswick]

I guess lowering the insity is okay, but the bigger issue is your trying to listen to two radio stations independently on the same channel.

 Turn off the 200khz on one and just use 83kHz, vice versa.

Either unit will be screwing up, as their signals are being traded.. Entirely too much noise coming in on the correct rythm . if I'm understanding you correctly?

[Brunswick]

As far as well the math on the SI to waypoints. The way I interpreted is that its from the transducer to the way point gives you the distance (slant range) so the closer you are the more error unless contour mode is on and that helps the deviation. With unknown depth, its using speed(chart speed) over time to dictate how far back and horizontal distance to left or right.. Giving you a GPS point that is "x" deviations from x- axis and "y" deviations from y-axis. There is a z-axis that'd have to be the same as the depth the boat was in, so marking waypoints on ledges turns into trig on the fly vs pythagreous theroem. (Line out to target/waypoint differing from boat on target/waypoint).

Can Greg check me on that?