Mixing brands

[cspierings]

I'm thinking of giving Hummingbird's SI locators a try on my boat. I have been running a Lowrance 520C and was planning on keeping it and running it on the trolling motor.

Is there any known issue with running a Lowrance and a Hummingbird 798 or 997 SI on the same boat? I'm specifically concerned about interference if both are running on opposite ends of the boat.

Thanks,

[hondo]

I think the only advantages to running one brand of unit are if you network them together, or if one unit craps out and you can move the other(s) around as necessary to fill in where needed until they're all up and running again.

In terms of having one transducer on your bow motor and the other on your transom, you won't run into any interference until you get in deep enough water for the transducer cones to overlap, typically about 30 fow depending on various factors. You'll run into that with any units that operate at the same frequency. One way around it, with dual beam or dual frequency units, is to change the frequency on one of the units.

Since you mentioned adding an SI unit ..... and getting back to networking units together ..... I'll point out that with the Lowrance HDS units you can add the StructureScan module and network the side-scanning function to 3 HDS units. It won't work with the 520 you're moving to your bow, but if you were to replace that 520 with an HDS unit you could have side-scanning with both your units with one module. Not sure if that is of interest to you or not but it might be something to consider when you're deciding which new unit to get.

[VernH]

......

In terms of having one transducer on your bow motor and the other on your transom, you won't run into any interference until you get in deep enough water for the transducer cones to overlap, typically about 30 fow depending on various factors. You'll run into that with any units that operate at the same frequency. One way around it, with dual beam or dual frequency units, is to change the frequency on one of the units.

....



Sorry I disagree and I think others will jump in also.

Running a transducer in the front of the boat and the back, when on the same or close frequency can and most likely will cause problems even when in shallower water. That's why Pinpoint networked their units together and synchronized the ping between the two units Both fired simultaneously)

If the units are not synchronized and depending upon the bottom hardness (more problems in a harder or rocky bottom,) the units will get confused by sonar returns from the other unit.

Remember that the common 20 deg transducer's cone can put very usable signals into a 50 deg cone. That outer edge signal will hit bottom and reflect back at roughly the same angle off perpendicular as it hit the bottom and that reflection will be heading toward the other Transducer. If you draw it out on graph paper, you'll see that it can happen easily in less than 10 ft.

If Unit "A" pings and then switches to receive mode, it is very likely that the "B" ping energy reflected from the previous ping will reach the "A" transducer while it is in the receive mode.

The vertical lines commonly seen when you pull up along side another boat to chat are caused interference from the other person's sonar.

Sitting next to other boats on an underwater rock pile is a sonar nightmare

Vern

[hondo]

I agree that hard bottoms and rocky bottoms will cause interference to show up sooner, ie. in shallower water. Even so, you should be able to run bow and transom mounted units on the same frequency at the same time with little to no interference problems until you start getting into "deeper" water. I don't recall ever seeing interference on my units in less than 25 fow and usually it has to be deeper than that.

[VernH]

Here's some posts from the past:

If you're running both units on 200 kHz they will interfer. HB and Low both have options for dual frequency transducers, such as 50 kHz or 83 kHz, so you could use one unit on 200 kHz and the other unit on 50 or 83 kHz and not get interference ....... but 200 kHz is going to give you the best display for typical inland waters.

The side-scanning transducers operate on different frequencies than 200 kHz, so if you planned to use one unit for side-scanning and the other for down-viewing sonar then you wouldn't have interference issues either.

Just my opinion, but I expect it's the two sonars interfering with each other. Lowrance/Eagle "20 degree" transducers see a much wider angle than you might think. For example, I have mounted two different transducers on the transom of my 16' boat and both marked the bow-mount trolling motor. I have an Eagle in the bow using a TM-mounted puck and a Lowrance on the console using a transom-mounted Skimmer. In 15' of water they will interfere with each other if I run both at the same time. The interference is one transducer picking up sonar pulses from the other one.

If you want to run both sonars at once and the interference bothers you, use a narrow-beam transducer, say 12 degree, on the Eagle. That will stop the interference in depths of 15', but you'll still see interference in deeper water.

Hawgeye - try setting the ping rate on your units to different levels, that is usually successful. Sometimes, it will again cause interferance at some depths, but not others. For that you will have to experiment on the water.

US? If it's a 2007 trolling motor, the US is working much better. Previous models have not been so friendly. I'd forget about the US on earlier motors (2006 and earlier) and wire an external. There were all kinds of grounding issues with earleir models - not really worth the frustration to fix. Good news is the new ones are working.

And yes, you are right. They should just come out with a 120-150 kHz option and be done with this issue. I run a different brand on my bow (120 kHz) partly due to eliminating cross talk.


You are right.
The only real good solution is what Pinpoint did with their units.
They did a lot of testing and experimenting and found that the only way to really be 100% guarenteed of not having interference from close proximity transducers was to have the frequencies different by at least 20K"HZ.
That is why they sold two models of each of their depth finders.
One for the console and one for the bow or stern.

I believe that one was on 200KHZ and the other on 220Khz. They were able to network the trandsucers etc. with never any interference.

--
From a design staindpoint - it is really a trivial solution to have a unit on a slightly different frequency.
A couple of different tuning capacitors and tuning coils. The same transducer and display could be used with no issues.

It really would be a nice solution to this very common problem that is well known and well documented.

Take care
REW


Try it. It may work for you. It appears that it has for some.

Vern

[acar555]

[quote=hondo;1138941] You'll run into that with any units that operate at the same frequency. One way around it, with dual beam or dual frequency units, is to change the frequency on one of the units.quote]

The Humminbird do not stop pinging the 200khz frequency no matter what frequency is selected. If you set it 83 khz it still uses the 200 khz for the depth reading.

[REW]

ACR
Does your statement make sense?

i.e. if you select 200 khz, the unit will transmit a 200khz pulse and receive a 200 khz pulse to check for depth and bottom conditions.

However, if you select an 83 khz function, the 200 khz pulse is turned off and only the 83 khz pulse is transmitte and received back at the unit for bottm and depth information.

I assume that this statement is correct.

If not, I stand corrected.

Take care
REW