CV52 vs GT52

[LWINCHESTER2]

Okay guys. I'm taking suggestions on how to compare the CV52 vs the GT52. What do you want to see? How do you want me to do it?

ifishinxs is loaning me a CV52. I'll have a GT52. It's not the same one I used before that had the weird double lines (probably due to mounting), but I talked a friend of mine in the next county into swaping with me for a while. I'm going this evening to pick it up.

Other than the standard stuff of repeated passes and screenshots on 455 and 800 using side and down, I thought I would take Vik's suggestion about turning up the settings on the CV some for some comparisons. I can check shallow to deep. We do have standing timber at least 150 ft deep so I can push them to the limit.

[mjk1210]

Please do something like I did to block the different signals and see what results you get on the screen.

[Schins]

[Larry3215]

I would do it both ways.

1) Follow viks recommendation to keep him happy :)

2) Do it the way most folks do - brightness, contrast etc, set on both to show bottom detail clearly and to more or less the same level of brightness - without the washout effect. Thats how the vast majority of users will want them set.

The trick will be to pass over the same exact ground on the same exact path as close as possible.

Hmmmm..... It occurs to me that with the tilted elements, this may be a very difficult comparison to evaluate. With the DI elements tilted, you are going to get some bias to one side with the GT down element which will make interpretation of the effects tricky. Since Garmin has refused to answer my questions, we dont know the exact results of the "shading effect" they talked about. I also am not sure if its the element thats tilted to port or the beam thats tilted to port.

How are you going to know if its the tilt or the DI element itself or some other factor making things look the way they do?

I would suggest you mount the transducers so that one is right behind the other on a board ( just like in the Lowrance video) and record both units running at the same time. You may need to run one on 455 while the other is on 800 then switch them around to avoid interference.

Also - what exactly is the goal? Vik has left me confused as to what he is claiming - its changed too many times. Are you trying to find some setting so that the CV can produce pics as good as the GT or?

[MROBIT294]

The novice that I am, I would just like to see the DI comparison. And I wouldn't even need it to be an exact cruise by...just in the general vicinity. My concerns with the CV are that right now, what I see is, as stated by mjk1210 on another thread, cartoonish. Or another way to put it, imagine 2D SONAR with the DI color palette. My selfish side would ask that you perform one test in shallow water (<12') and either of a weed edge, timber or rocks. I just want to see what a dedicated DI beam would look like compared to the blended.....I have played with the settings and cannot seem to get it any better. Also, I would be interested in knowing the conditions you perform this in (windy or calm)(or both!) Thanks!

[LWINCHESTER2]

1. I want to check out Vik's claim and as I understand it, in shallow to medium depth water the blended DI from the CV52 should be better than the GT52. I will make many passes to get a bunch of screenshots so that I can cherry pick the best shot from the set. Then I'll do the same for the GT52. I feel like I already know and/or have shown using the GT/CV22 that the CV is not as good using the same settings. That was one of Vik's criticisms. I should have used different settings. Also the tilt business on the GT will require multiple passes to get its best image. On a side note, some time ago I suggested to Garmin that when a screenshot was done that a second file with the same name be created (.txt) containing the unit settings for that screenshot. That would be real handy to have right now, but my suggestion was not implemented. I thought it would also be valuable for their tech support people.

2. I'd like to know if the tilt from horizontal of the side elements is different. I really don't have a clue on how to test that.

3. Something possibly could be gained comparing the SI screenshots, maybe. Again I'm not so clear on how to determine with any degree of certainty if the elements ping in unison or alternately. Vik seems to be quite confident of determining this from the screenshots.

I am hopeful that Vik will make some suggestions on this.

I will not be doing this on windy days. The ripple on the water surface is picked up by SI and gets messy. Another good selling point for Panoptix.

[Larry3215]

1. I want to check out Vik's claim and as I understand it, in shallow to medium depth water the blended DI from the CV52 should be better than the GT52.

I thought he backed off from that claim, but I could be wrong. I had trouble keeping up and we wandered around a lot. Still worth testing though to see if the results are consistent using different transducers.

If you're not going to mount them one behind the other, how are you planning to do it? It sounds like you're planning to mount one, do a bunch of passes, then mount the other one and repeat?

Oh, silly me - I guess if you dont have two Garmin MFD's thats the only option.

[LWINCHESTER2]

I'm concerned about the mounting. Neither is mounted right now. Transom mounting could work but to put them on different places on the transom adds another variable. I'll go through the garage tomorrow after I get in from fishing and see what I can scrape up. The Lowrance method you mentioned seems to have some promise. I am running 2 7610's right now, so I could run them both at the same time. You know how much I like the 7610 and how much I utterly despise the screenshot function on it, but I'll not go on that rant right now except to say it would be near impossible to get two screenshots at the same time,

[Larry3215]

How close together are the 7610's mounted to each other? Maybe you could try a two finger screen touch and grab them both at the same time :)

Even if the screen shots were 5-7 seconds apart, that would still be better than completely different passes. You would see more history on one, but there should still be plenty of over lap. Plus you could better gauge the relative brightness/contrast settings on the different transducers in real time.

If you are looking at woody, branches, etc, even a slight difference in the path could make for very different details on the screen. Its going to be bad enough trying to allow for the tilted elements....

Oh - when you're recording the DI, be sure to have the depth on at least some of the passes set extra deep so we can see the bottom return fade out. That will help with some things vik brought up. However, that may be difficult with the CV - the effective cone angle is going to be huge, so the bottom return is going to be very thick depending on brightness settings.

[vik]

1. I want to check out Vik's claim....

Thank you very much for doing this comparison - a lot of users wanted to see it. Please see my comments in red color below:

... as I understand it, in shallow to medium depth water the blended DI from the CV52 should be better than the GT52 - I hope it will be as good as GT52 in about 95 -98% of cases, because GT52 has a single dedicated DI view, but CV52 DI should be better than triple overlaid DI at GT51 and TotalScan.

I will make many passes to get a bunch of screenshots so that I can cherry pick the best shot from the set. - completely agree, the more screen shots you show from different passes the better for comparison and seeing some hidden moments.

Then I'll do the same for the GT52. I feel like I already know and/or have shown using the GT/CV22 that the CV is not as good using the same settings. That was one of Vik's criticisms. I should have used different settings.- yes, that's the point, looks like CV automatic settings for deeper water are not sufficient and require some adjustment by Garmin engineers, but actual unit can properly work at deep water.

2. I'd like to know if the tilt from horizontal of the side elements is different. I really don't have a clue on how to test that. - if you show many screen shots going directly above the goal and a bit aside, I think we will see the difference in tilting and overlapping of the side beams.

3. Something possibly could be gained comparing the SI screenshots, maybe. Again I'm not so clear on how to determine with any degree of certainty if the elements ping in unison or alternately. Vik seems to be quite confident of determining this from the screenshots. - yes, I saw it , and it is would be seen if you set bigger depth range on GT52 DI view, as Larry suggested, to see bottom fading out. No need to do this with CV52.

[LWINCHESTER2]

Looks like I have an option for the mount - maybe. Many years ago, during my Hbird days, I had my son-in-law craft a transducer stick to use in connection with Hbird Side Imaging so I could rotate it. I've looked it over and it may work. Still working on the transom concept. Dreading it a bit as there's no question that putting them on the transom means removing some others that would be in the way.

[Schins]

Regarding the wider cone angle, isnt it a difference of only a couple degrees? I thought the CV was about 53 deg

[LWINCHESTER2]

I've never seen spec's published on any CV. The GT-52 published specs are 2.0x50@455 and 1.0x30@800. You're thinking about the GT-40 and GT-50.

Generally it's supposed that the CV is just like the corresponding GT but without the down element. Now the following I just made up. But I figured that knowing there was no down element and still wanting to do down imaging by blending, that instead of the standard 30 degree tilt of the side elements from horizontal that they would be tilted at least to 45 to give a little stronger signal to blend for the down. The sacrifice would be the stuff on the surface and in my mind that wouldn't be much of a sacrifice. But that's just me and my imagination.

[Schins]

I think I was going by the gt20 as it had the exact part number as my cv20 and that angle was 53 iirc

then i I looked up Humminbirds specs and it was like 75 on 455 for blended DI

[Larry3215]

In theory, the difference in DI "cone angle" between the CV and GT transducers is HUGE.

Someone posted a link from Garmin showing the cone angles and how different they were. This was a picture actually from Garmin.

The CV transducers are using the sidevu elements, and they point out to the sides with only a small overlap in the center normally. That means the CV transducers will have a very very wide cone angle for the DI view. It will be as wide as the total sidevu cone angle or close to 180 degrees depending on the Brightness/gain setting.

In contrast, the GT transducers have a DI element that points (almost) straight down. Its actually tilted 16 deg because of Garmin trying to get around the law suit, but its still more or less down rather than to the sides.

Also, the cone angles listed on Garmins website do not really match up to what you see on the screen. In reality, they are much wider.

I cant find the link to the Garmin page right now it now, but here is roughly how it looked.








GT.jpgCV.jpg

[Larry3215]

That said - remember that in my tests the actual real world cone angles are much larger than Garmin specs would indicate - depending on Gain settings. Also, it looks like Garmins GT transducers fire the side elements at the same time as the down elements. That means that, if you have the SI and DI on the same frequency, then real world cone angles on DI are going to be closer to the CV cone angle even with a GT transducer.

Thats not necessarily a bad thing.

Confused? :)

[vik]

...it looks like Garmins GT transducers fire the side elements at the same time as the down elements. That means that, if you have the SI and DI on the same frequency, then real world cone angles on DI are going to be closer to the CV cone angle even with a GT transducer.

All looks correct, but not for GT52 - it's DI cone is about 50-60 degree at 455kHz, looks like there is no SI returns on it's DI view as it is done on other three elements Garmin transducers, and units of other companies.

[Larry3215]

All looks correct, but not for GT52 - it's DI cone is about 50-60 degree at 455kHz, looks like there is no SI returns on it's DI view as it is done on other three elements Garmin transducers, and units of other companies.

What makes you think the GT52 is different from all the other GT transducers?

As far as I know, the sonar power, frequency, etc, is controlled by a module within the MFD on most of our units or by an external module like a GSD24/25/26, not the transducer.

[LWINCHESTER2]

Tell me how, by looking at a down image that you determine whether or not it contains returns from the side elements. Is it simply a matter of measuring the distance from where the bottom appears to the distance under it that it is still showing some detail. Then using that to calculate the estimated cone width. And then if that cone width is larger than the stated width of the down element, then the conclusion is that the down element is picking up returns from the side elements. And if so, then they are pinging at the same time.

Do I have that straight?

What makes you thing the GT52 is different from all the other GT transducers?

I'm not sure which Garmin transducers Vik puts in the category of pinging alternately. In the GT22/CV22 comparison. he noted that the side views showed fish that were not in the down view and so the DI view was "pure". So it's GT52 and GT22 and ????.

I'm trying to get a handle on the types of screenshots I need to get and how to know if I've found something that would be revealing.
I get the part about making sure the depth is set to manual and extended enough. Then getting shots of underwater structure. There will be no problem finding some trees partially submerged 0-20 ft. I do know of a specific tree standing upright that should top out at about 40 ft. And I know of some really deep ones at likely top out at about 150 ft deep (maybe more).

Then there is getting screenshots on the GT52 where the DI is the same frequency as SI and others where it is different.

I also feel like I need to get some screenshots of known suspended targets. Meaning, that I put them there. I can't guarantee that fish will be active where and when I'm getting the screenshots and on SI you don't know their depth, only their distance from you.

Vik. I don't fully understand your ranking of the different types of DI. It is clear that you believe single element DI is best. On the rest would you put them in order from best to worst.
A. Single element DI.
B. Blended DI from two side beams (no down element), some Hbirds and all CV models
C. LSS1 (which you call triple overlaid).
D. GT22 and GT52 which have three elements but supposed not overlaid.

[Larry3215]

Thats going to take a lot of typing and a drawing or two to answer fully. Its going to take me a bit to get it all together - Im babysitting a demanding 7 yr old at the moment, so Im a bit distracted.....

The short version - seeing fish on SI but not on DI means nothing either way as far as DI being pure or not pure. The fish on the SI only could be off to the side and near the surface, which would make them completely out of the DI cone. Remember your logs on the surface showing up on both sides but not in the DI?

As far as telling if SI signals are showing up on the DI screen, your almost there, but its a bit more complicated.....