Finally planning to use US2

Background
I've owned Terrovas for many years--all with US2. I also use a HB-1197 so the US2 has been useless because it has no side scan capability. Instead, I mounted a side scan transducer under the motor and snaked the cable through the slot in the Terrova's shaft. Unfortunately, this arrangement causes so much static that a good deal of the side scan detail is lost in the "snow". I'm correcting that problem by making two changes.

First, I moved the side scan transducer (and the GPS receiver) to a stern mount--greatly improving the side scan image, but sacrificing the down view up front. Most of the time, I'm floating 8 corks up front and I really miss the down images that show what's under my feet and the baits.

Second, in order to correct the down view problem, I plan to add a second finder and connect it to the US2. I'm aware of the potential for cross talk between the two finders, but most of the time I'm in fairly shallow water & so the geometry should work in my favor.

Questions
1. Is anyone using a 2-finder setup that makes use of the US2? What finders are you using and how do they work together?
2. Who' run into the crosstalk problem and how did you solve it?
3. Are there any US2-compatible finders that perform poorly and should be avoided?

I believe US2 is 2d sonar only? and mot down view, unless you are mixing up the terminology.

You could put each unit on a separate frequency I would think

On Lowrance 2d is 83/2000 kHz and down imaging is 455/800 kHz. I believe Hummingbird is similar and if that's the case you won't have interference problems. The bow unit on my Lowrance has 2d and downscan in one transducer.
I do have a neighbor that runs both 2d and downscan units on the bow.

I run Lowrance on US2 with 2d and humminbird 998 on rear and have had no problems with cross talk.

As I thought the Minn Kota Universal Sonar transducer is a 200 KHz conventional sonar transducer. Down image will NOT work with it

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Originally Posted by MonteSS

you are mixing up the terminology.

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Very likely. It's been a long time since I studied finders and compared features.

With the 1197 mounted on the back (display unit up front), all I want up front is a simple plain vanilla unit. Originally, the plan was to cull through the lifetime junkpile of old finders & reuse one. For various reasons, none of them are suitable. Before buying one of the 8 expensive US2 adapter cables, I have to decide on the finder.

Sidescan doesn't fire in the direction of the US2, so that's not going to cause interference. Downscan and 2D are the potential problems. The US2 transducer is only capable of 200/83 kHz & they're also the frequencies used by the 1197.

Edit: Looking at the Terrova manual again, I see the 2D-only limitation.

The 200kHz 2d transmit cannot be shut off in any of the CORE series HB units (except by turning off ALL sonar on a specific unit) ...

So it doesn't matter if the 1197 is "viewing" SI/DI ... It's still transmitting 200kHz 2d for digital depth (as has been noted already) ...

There will be crosstalk interference with both HB units sonar on ...regardless if using the stock xducer or the US2 xducer ...

How bad the crosstalk is can only be determined by trying them ...

Rickie

Run a 2d head unit of your choice and the US2 TD at 200hz

Run the 1198 tTD at stern on 83hz (even if it is not being used)

Should be no cross talk

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Originally Posted by MonteSS

Run a 2d head unit of your choice and the US2 TD at 200hz

Run the 1198 tTD at stern on 83hz (even if it is not being used)

Should be no cross talk

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Running a HB CORE unit on 83kHz still does not shut off the 200kHz transmit signal ... It merely only allows the 83kHz 2d view to be seen ...

HB Core units must transmit the 200kHz signal for digital depth ...even if it's in the background where it cannot be seen ...(or chosen to be seen on the display) ...

Lowrance has this option (of selecting 83kHz without transmitting the 200kHz)...

HB core units do not ...

Rickie

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Originally Posted by rnvinc

Lowrance has this option (of selecting 83kHz without transmitting the 200kHz)...

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Very good to know. This puts Lowrance on my list. Originally, HB looked like an obvious choice to minimize the learning curve, but if there's an important performance difference, that changes everything. It would be useful to hear additional experiences with crosstalk. It only happened to me once and the only noticeable problem was that one of the units reported twice the actual depth. When this occurred, the boat was in 65 FOW and the two transducers were about 12' apart. In shallower water, the cones must not overlap.

I run Raymarine front and rear on a 15' boat with no interference. That is chirp tho so dont know if that helps you.

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Originally Posted by Corker

In shallower water, the cones must not overlap.

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Correct ...
http://i477.photobucket.com/albums/r...pshszjsrsu.png

Rickie

After more research, I can see that it's the cone angle that matters, not the frequency of the transducer. Most the HB head units operate at 83/200 kHz & so far it looks like 200 kHz is synonymous with a 20 degree cone angle (for HB.) Moving to Garmin, however, that relationship changes. The bottom end "Garmin echo 100" operates on a single frequency (200 kHz), but the bundled transducer has a 60 degree cone angle! If the head unit also causes the US2 transducer to cover a 60 degree angle, this would cause cross talk as shallow as 10'.

Let me extrapolate a little on how crosstalk inference works ...mainly to identify that "Frequency" is the major factor in possible crosstalk interference ...

A sonar ping of a certain (any) frequency is not proprietary toward brand or unit ... A 200kHz transmit signal has certain specific wave form properties that are the same ...regardless of what unit/brand transmitted that 200kHz transmit signal ...

Brand does not dictate frequency wave form shape properties - Science does ...

If there is a 200kHz sonar ping in the water (transmitted by any unit) ... ANY sonar unit "listening"'for a 200kHz return echo can pick up that 200kHz return echo ...

And that includes any reverberated echo (or stray echo) in that same frequency (double echo, triple echo, echo returns from the outer fringes of the sound pulse, etc,) ...

The problem arises in the scenario of 1 unit "listening" for a 200kHz return echo ... But that same unit did not "transmit" that 200kHz transmit ping ...

This makes it impossible for the "listening" unit to determine how much time has elapsed from the "transmit signal" to the "received return echo" (Duty Cycle)...of that specific 200kHz sonar ping = Unknown transmit start time + Known return time = confused unit = crosstalk interference ...

So while shallow water will reduce the likelihood of crosstalk interference (between 2 separate units transmitting the same frequency) ...and cone angle can have a factor in the likelihood of crosstalk interference ... It does not definitively eliminate the possibility of crosstalk interference ...

Because that 200kHz transmit pulse can be still in the water on the double and triple echo ...and picked up by any unit still "listening" for a 200kHz return echo ...

Rickie

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Originally Posted by Corker

it's the cone angle that matters, not the frequency of the transducer

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Quote:

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Originally Posted by rnvinc

So while shallow water will reduce the likelihood of crosstalk interference (between 2 separate units transmitting the same frequency) ...and cone angle can have a factor in the likelihood of crosstalk interference ... It does not definitively eliminate the possibility of crosstalk interference

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There are several factors at work here and my wording wasn't the best. Let me try again.

Frequency of the transmitter matters if it matches the frequency to which the listening unit is tuned. The best choice for a two-finder setup would be for the two units to share no common frequencies. The 1197 operates at 83/200/455/800 kHz. If the yet-to-be-determined bow unit transmitted at 150 kHz, for example, it would hear the returns but the 1197 would not. Neither unit could be confused by the other unit's signal. Unfortunately, the bow transmitter (the transducer built into the US2) operates at 83/200 kHz and that means there is no way to eliminate 100% of the cross-talk. The best solution, then, will be to minimize cross-talk.

By selecting a new finder that operates on either 83 or 200 kHz, but not both, I will eliminate half of the sources of interference. Further reduction can only be accomplished by reducing the strength of the foreign signal that reaches the listening sides of my two units. I'm not aware of any way to adjust the output wattage of a finder (suggestions are welcome), so the only remaining option is the positioning of the transducers so they are not pointing at each other--either directly or by way of a "bank shot" off the bottom or suspended targets. This is where the cone angles become important.

The 1197's transducer operates with 20/74/84 degree cone angles--the 20 degree angle being the 200 kHz signal. For the sake of discussion, let's say the new unit will also operate at 200 kHz with a 20 degree cone angle. Both transducers will be set as close to a vertical alignment as possible, so each will transmit most of its signal toward a circle on the bottom of the lake. The diameter of these circles increase as water depth increases. At some depth, the two circles begin to overlap and that means each sending unit is now bouncing the edge of its signal directly toward the other unit's transducer--causing a significant increase in cross-talk. My only remaining option is to position the two transducers as far apart as possible and recognize that cross-talk could become a noticeable problem beyond a certain water depth.

Very well said ...

You can aim the xducers away from each other about 5° and reduce the likelihood of crosstalk even more ...

Rickie

Yeah, I thought about that. The US2 won't move unless the entire TM is tilted...not not a good thing. That leaves the side scan transducer. The 2D and down scan views won't be affected too much, but what about the side views?

the more I read about US2 the more I think it isn't worth the trouble to hook it up. I have a Maxumm 80 with US@ and a 'ducer mounted on the bottom of it for a 798 and it can be adjusted up down or rotated side to side, just loosen it a little bit adjust and re-tighten.

The US2 is an example of poor market research. There's no question that it's very desirable to eliminate loose transducer cables. Anyone who's ever broken a cable by over-rotating a TM would love to have the cable safely tucked inside the TM's shaft. Ten years ago, the US2 would have been welcomed with open arms. When it was introduced, however, its plain vanilla sonar transducer was no longer a state-of-the-art feature. Side-scan had arrived. By bundling yesterday's transducer with state-of-the-art top end TMs, M-K created an almost useless combo. Those who could afford the most expensive TMs ever sold were likely to be the same fishermen who could afford the most expensive finders ever sold. US2 would have been a better add-on for TMs with mid-range prices.

After reading all the comments... I run a HB898c HD SI unit on the stern and an older HB 778 for 2d using the US2 (200/83kHz) in my Terrova. I have a 19 ft boat and mainly fish 8 ~ 10 ft water. Occasionally 15 ~ 20 ft. Have never had any issue that I am aware of with crosstalk. Works well and having the Ethernet has been a big help for this rookie.

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Originally Posted by Corker

Yeah, I thought about that. The US2 won't move unless the entire TM is tilted...not not a good thing. That leaves the side scan transducer. The 2D and down scan views won't be affected too much, but what about the side views?

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You can opt for XP 9 20 (shoot thru) or a XNT 9 20 (transom mount) ...along with the AS SIDB Y cable ...

This would allow tilting the 2d without un-leveling the HDSI ...

Rickie

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Originally Posted by rnvinc

the AS SIDB Y cable ...

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This product is news to me...good news! If I understand the product literature, this joiner will let me hook up my two existing transducers: the 1197's original transducer and the US2. Right? Is so, that eliminates the need for a second finder.

Quote:

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Originally Posted by Corker

Background
I mounted a side scan transducer under the motor and snaked the cable through the slot in the Terrova's shaft. Unfortunately, this arrangement causes so much static that a good deal of the side scan detail is lost in the "snow". I'm correcting that problem by making two changes.

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I've been watching this thread all along without realizing what you are actually saying. The "static" you talk about sounds like RF interference and that can be fixed in different ways. Lots of us are running our transducer cables through the slot on the Terrova WITHOUT static. Maybe you don't have to go through all of this work if we can fix the RF issue.

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Originally Posted by vic n

RF interference

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Good to know the proper term and finding other ways to eliminate this interference would be good. I'm only doing something about the interference problem now because I just replaced the old 24v Terrova with a 36v. Moving the 1197's transducer to the stern was easier than taking the new Terrova apart to snake the transducer cable down the slot, but I can do that if it makes sense. To be clear, only the side-scan image was affected by the interference. There was no problem with the sonar or down scan. Moving the transducer to a fixed position also gives me a continuous side view that was not possible when the transducer rotated with the motor.

I put SI on my transom and DI on my Terrova....yes, it is a little hassle to run the cable, but I think it's worth it

Quote:

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Originally Posted by Corker

This product is news to me...good news! If I understand the product literature, this joiner will let me hook up my two existing transducers: the 1197's original transducer and the US2. Right? Is so, that eliminates the need for a second finder.

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The AS SIDB Y cable dis-connects the 2d piezo in the SI xducer ...and routes the 2d channel to a separate 2d xducer (US2 in your case) ...

Rickie

Rickie - I'm ordering the "AS SIDB" cable & will attach its "output" side to the jack on the 1197. The existing SI transducer cable will connect to one of the Y-cables and I'll need a US2 adaptor (MKR-US2-8?) to connect the US2 to the other Y-cable...right? As you explained it above, the AS SIDB cable will ignore the 83/200 kHz signal from the SI transducer and listen instead to the signal from the US2.

Quote:

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Originally Posted by Corker

Rickie - I'm ordering the "AS SIDB" cable & will attach its "output" side to the jack on the 1197. The existing SI transducer cable will connect to one of the Y-cables and I'll need a US2 adaptor (MKR-US2-8?) to connect the US2 to the other Y-cable...right? As you explained it above, the AS SIDB cable will ignore the 83/200 kHz signal from the SI transducer and listen instead to the signal from the US2.

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Correct ...

The AS SIDB Y cable legs are tagged ...:

* The AS SIDB Y cable connects to the HB head unit ...
* The "Side Image" leg connects to your stock SI xducer ...
* The "Dual Beam" leg connects to the US2 adapter (MKR-US2-8) ...
* The MKR-US2-8 connects to the pigtail coming out of the Terrova head ...

* The foot bone connects to the ankle bone ...
* The ankle bone connects to the shin bone ...

Oh wait ... I got carried away ...

Rickie

Also correct ...

The AS SIDB Y cable makes the system ignore the 83kHz/200kHz piezo in the stock SI xducer ... And listen instead to the US2 signal ...

With the AS SIDB Y cable in the wiring ...the 2d sonar images and the digital depth will always come from the US2 ...

There is no switching or changing of menu settings because the wires going to the 2d piezo in the stock SI xducer have been disconnected (in the AS SIDB Y cable) and re-routed to the US2 piezo ...

Rickie

Quote:

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Originally Posted by rnvinc

Also correct ...

The AS SIDB Y cable makes the system ignore the 83kHz/200kHz piezo in the stock SI xducer ... And listen instead to the US2 signal ...

With the AS SIDB Y cable in the wiring ...the 2d sonar images and the digital depth will always come from the US2 ...

There is no switching or changing of menu settings because the wires going to the 2d piezo in the stock SI xducer have been disconnected (in the AS SIDB Y cable) and re-routed to the US2 piezo ...

Rickie

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Maybe I missed something, but this appears that there will only be digital depth available when the TM is in the water, and no depth readings available when running on plane?

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Originally Posted by vic n

Maybe I missed something, but this appears that there will only be digital depth available when the TM is in the water, and no depth readings available when running on plane?

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This is true ...

Depending on how the unit system is intended for use ...the OP may not need digital depth until the TM is deployed ...

Corker ... Do you need digital depth only when the TM is deployed ...??

Rickie

Almost all of my fishing is in TMO lakes or other places where running distances are short enough to get by with the 100# thrust Terrova. The outboard was used so infrequently that I removed it when I swapped in the 36v TM. This should be the perfect solution. Parts are on order & I'll provide an update when everything's installed and working.