Topic: A few more HB SI questions

[bigkahuna]

1.  I noticed that the HB 798ci HD si is the only current model HB SI unit that has a "HD" designation, what does that mean?

2.  I'm going to want to extend the cable to the transducer to a total length of 250 feet.  I noted that the 798ci HD si emits at 500 watts while the 800, 900, and 1100 series are all 1000 watts.  has anyone tested a cable extension of this length on a 798?  My concern is that because it starts with half the power and then attenuation over the longer cable length may render it useless.

3.  I'd like to display the SI display in real time on my notebook computer, ie. use the computer as a large screen sonar repeater.  The only software capable of connecting to the HB SI unit's ether port that I am aware of is DrDepth.  Are there any others?

4.  Will the 800/900/1000 HB SI units operate without the external GPS connected?  This will be used as a semi portable station so GPS data will be meaningless and the GPS antenna would just be something else to carry.

[ITGEEK]

1) HD means high-definition.  I think this is an upgrade to the previous
model, but with a higher screen pixel count and brighter screen.

2) I have no idea.

3) If you are just using your computer screen to show what's on your
HB screen, if a unit has a video out, you could probably use that.
But, your PC won't be capturing any sonar data, just echoing what you
see on the HB screen.

4) I think the units will physically work, since GPS is an option.
But, you won't be able to use any of your maps.
Also, you won't be able to save any waypoints.

[bigkahuna]

1) HD means high-definition.  I think this is an upgrade to the previous
model, but with a higher screen pixel count and brighter screen.

Ok, so it refers to the LCD screen and not the resolution of the SI image then?

3) If you are just using your computer screen to show what's on your
HB screen, if a unit has a video out, you could probably use that.
But, your PC won't be capturing any sonar data, just echoing what you
see on the HB screen.

Unfortunately the video out will only display at the same resolution as the HB unit, which in the case of the 798ci HD si is pretty low res.  The nice thing about DrDepth (as I understand it at least) it displays the full resolution of the SI scan which is what I'm after.

4) I think the units will physically work, since GPS is an option.
But, you won't be able to use any of your maps.
Also, you won't be able to save any waypoints.

I won't need maps or waypoints as my station won't be moving only the transducer will.  I plan on mounting the HB transducer on a remotely operated vehicle (ROV) that I will (more often than not) be operating from the shore.  The ROV has a tether of 250 feet so I plan on mounting the transducer to the bottom of the ROV and taping the transducer cable to the ROV cable.  What I want displayed on the screen is an image of what is directly under the ROV.  The ROV normally moves at about 1 kts so I'll set that manually in the settings.  The heading and position is almost irrelevant as once we find the target we'll dive straight down to the bottom until we see it.

I've got a couple other ideas on how to use the HB SI with our ROV that I'm toying with, but I'll save them for later. 

[Bob B]

1.  I noticed that the HB 798ci HD si is the only current model HB SI unit that has a "HD" designation, what does that mean?

2.  I'm going to want to extend the cable to the transducer to a total length of 250 feet.  I noted that the 798ci HD si emits at 500 watts while the 800, 900, and 1100 series are all 1000 watts.  has anyone tested a cable extension of this length on a 798?  My concern is that because it starts with half the power and then attenuation over the longer cable length may render it useless.

3.  I'd like to display the SI display in real time on my notebook computer, ie. use the computer as a large screen sonar repeater.  The only software capable of connecting to the HB SI unit's ether port that I am aware of is DrDepth.  Are there any others?

4.  Will the 800/900/1000 HB SI units operate without the external GPS connected?  This will be used as a semi portable station so GPS data will be meaningless and the GPS antenna would just be something else to carry.

I can answer part of your question, but there are others who can answer better....I'll give it a shot.
1.  The HD designation for the 2011 year 798 is more of a marketing identifier that a change in resolution.  The screen resolution is the same as it has always been.......It does have the highest resolution / inch of any of the HB side image units.
The 2011 unit is also supposed to have an LED backlight which will give it a wider range of brightness adjustment.
If Wayne checks in, he can give you all the facts on this.
2.  The 798 has the same power as the other HB SI units when using the side imaging transducer.  The increase power of the other units is only available when using a special 2D transducer.
The standard transducer does not give as high of resolution as the other HB SI units, but can be utilize the HDSI transducer that comes standard with the other units.
3.  I have seen a fairly recent post by Robert Gecy about Dr Depth now supporting the ethernet connectivity of HB to send data directly to it.....this would be another reason to use the HD version of the 798 instead of the older one since the older 798 also doesn't have ethernet.
You might search for the post, since Robert also explained how to make your own cable to accomplish the Dr Depth ethernet tie in.  I think this is sending the RAW data, and that would be totally independent of screen resolution,but not sure about that.
4.  I would think the SI would still work fine without the GPS antenna, but since the units software is execting the GPS to be available and sends the GPS data along with the SI data, I would probably connect the GPS antenna to the unit just to prevent potential problems with the unit trying to process data that doesn't exist.

Sounds like a very interesting way to use the SI, and I am sure there are a lot of people on this site that will be eager to see your results.

[bigkahuna]

2.  The 798 has the same power as the other HB SI units when using the side imaging transducer.  The increase power of the other units is only available when using a special 2D transducer.
The standard transducer does not give as high of resolution as the other HB SI units, but can be utilize the HDSI transducer that comes standard with the other units

That's an important bit of information, thank you.  I was leaning towards the 898c si because of the higher power output so you just saved me some money.    So if I'm reading this right, the 798ci HD si with the better transducer and DrDepth running on a PC will give me the same SI performance as any other HB SI unit.  That's what I was hoping.

[Bob B]

I know the 798 can use the HDSI transducer, and those that have say that they notice increased resolution.

I can't say for sure that the RAW data from the 798 will be the same as the other SI units, only HB Greg or someone more knowledable that me could say that for sure.

[bigkahuna]

Thanks.  Another thing I see is that the 798ci HD si doesn't support 800 khz SI which I'm guessing gives shorter range, higher definition imaging.  For the price difference, I might just go with the 898c SI anyways as the 798ci HD si + the HD transducer is only a couple hundred $ less.

[Bob B]

I personally think the 898 is the best "price break" when you look at normal pricing.  The 798 is sometimes put on sale at an VERY good price.  I think it was Cabelas who had the old version of the 798 on sale for $699 at the end of last year.  We are getting into the time of year when new models are being rolled out and there could be some good sales.

When I was seriously looking to buy, one other advantage of the 798 that had me conflicted is that you have the option of an internal GPS antenna.  I was considering it because of the improved portability that would offer....in your case it would save some inconvenience also.

In the end, I bought an 1197 when they went on a big sale last year end when the 1198 was being introduced.

I don't think you could go too far wrong with either the 798 or the 898.  It is just a matter of boiling down the differences and deciding which features are most important to you.
Wayne, who posts on here quite a bit, has posted some very impressive images that he got while using a 798 with the HDSI transducer.  You don't see too many people using the 800Khz, but some side by side image comparisons I have seen do show better resolution......depends on what you are looking for with your ROV.

[bigkahuna]

Thanks Bob.  I wonder if signal loss will be a greater issue for the 800khz signal vs the 455khz signal when sending it down a 250 foot extension?

I looked at the wiring diagram for the transducer and it looks like 4 of the 7 leads are for the SI / DI signal and 2 are for power.  What are the power leads for?  Any idea what the volt / amp levels are coming out of the topside unit?  With that info I can calculate voltage drop which will help me find a cable that will (hopefully) reduce loss a bit.

[Bob B]

I am not an expert on the cable extension, but there are quite a few posts on this forum from people who have built a towfish and quite a bit of cable discussion in those posts.  I think most have settled on a high quality network cable with various way of doing the strain releif.

With my background in electronics, it does seem that there would be greater impedance losses with the 800Khz.

Did you see the post from Kondamigos selling the used 898?

[bigkahuna]

My knowledge of electronics is only sufficient to make me dangerous.     I've got a sneaking suspicion that the attenuation losses at 800khz of a 250 foot extension might render it next to useless.

Didn't see the used 898 for sale but I'll probably stick with new and just shop for the best price I can find.

[bigkahuna]

Two more questions before I pull the trigger:

1.  Is anyone using the 798 with a towfish and, if so, what transducer and cable length are you using?

2.  Is anyone using the 800 khz SI sonar in a towfish and, if so, what cable length are you using?

[Humminbird_Greg]

You will probably get a better response for your last two questions if you posted them in the DIY Towfish section of the web site.

FWIW: the 798 units have always been built with the same 640 X 640 display.