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  1. #61

    Re: Sounder fundamentals for the guys who wanted it

    The diagram.

    I've used a bottom slope of 15 degrees from right to left with 2 similar targets the same height out of the bottom and equidistant from the c/l of the boat.

    With the same angle from the transducer out both sides to the tops of the targets and then beyond to where they hit the bottom. Measuring gives us each shadow length on the bottom.

    The shadow length on the bottom behind Target B is 43% longer than the shadow length on the bottom behind Target A.

    If we put 100 targets like these 2 each side, then the LHS ones would have longer shadows than their counterparts on the RHS.

    Much more black because of more shadows on the LHS (sloping to deeper water).

    Scaled this diagram to about 3m of water.

    As water gets deeper, the shadows get shorter. Like the sun at noon casting short shadows and at sunset casting longer shadows due to the shallower angle of sun's rays. Liken that to transducer beams.


    .Screenshot (268).jpg

    Clear as mud?

  2. #62

    Re: Sounder fundamentals for the guys who wanted it

    Dropped into bcf was a quick walk in and out but got held up by another customer as i dont look around in shops.. so went for a quick squiz at the fish finders/gps first time ever playing with one with all the gizmos was quiet interesting the lowrance hook 7 i think it was was really dark on the sides of the scan i couldnt see anything the pixals were not the greatest for modern technology

    I than had a ply with a 95S or 9S something and it was like a change of world u could clearly see right out to the side, changing screens was very easy got a bit lost with the zoom tho

    Always wanted a 12 inch but after seeing one today that is just massive that size is not needed i reckon i'll be happy with a 9 inch screen

    Sent from my SM-G900I using Ausfish mobile app

  3. #63

    Re: Sounder fundamentals for the guys who wanted it

    Hi Gazz.

    Bit like attempting to learn a new language isn't it? Faltering steps as you learn. I think that's why a lot of people like to stay with the same brand.

    The 95S or 9S was probably a Garmin.

    Guys like Scottar need to be across all of these brands especially those used by people to make their living from (more sophisticated types than the consumer brands made specially for the recreational market). Scott needs that knowledge to make HIS living.

    I recall a trawler guy in Bundaberg called Gollchewsky (Golly) who was a disaster with anything electronic in boat. Local marine electronics dealer/repairer used Golly as a marketing tool. He didn't have to extoll the technical virtues of anything. Most didn't understand those anyway.

    He used to advertise that a piece of electronic kit was " Golly-proof". Locals then knew that it was bullet-proof and simple. Golly didn't seem to mind.

    I have a 4.4m alloy boat and use a 10" screen.

    Just bought a 2nd hand 360 degree transducer. The 455khz version.

    Always have trouble in tidal run when finding a school of king on bottom. Can never find them quickly using the electric "anchor" button or using the waypoint function. The bloody things are never where they are supposed to be when boat stops turning in circles!

    Idea is when the boat settles down, to use the 360 to pinpoint direction and distance instead of turning the boat in more circles looking for them again.

    Spin the transducer instead of the boat in tidal run.

  4. #64

    Re: Sounder fundamentals for the guys who wanted it

    Quote Originally Posted by gazza2006au View Post
    Dropped into bcf was a quick walk in and out but got held up by another customer as i dont look around in shops.. so went for a quick squiz at the fish finders/gps first time ever playing with one with all the gizmos was quiet interesting the lowrance hook 7 i think it was was really dark on the sides of the scan i couldnt see anything the pixals were not the greatest for modern technology

    I than had a ply with a 95S or 9S something and it was like a change of world u could clearly see right out to the side, changing screens was very easy got a bit lost with the zoom tho

    Always wanted a 12 inch but after seeing one today that is just massive that size is not needed i reckon i'll be happy with a 9 inch screen

    Sent from my SM-G900I using Ausfish mobile app
    I hope you had gloves on. Donít want to spread or collect any germs.

    Like people shopping. They pick up a item look it all over and then place back on shelf.

    Just a pet hate during these times.


    Sent from my iPhone using Ausfish mobile app

  5. #65

    Re: Sounder fundamentals for the guys who wanted it

    Quote Originally Posted by shakey55 View Post
    I hope you had gloves on. Donít want to spread or collect any germs.

    Like people shopping. They pick up a item look it all over and then place back on shelf.

    Just a pet hate during these times.


    Sent from my iPhone using Ausfish mobile app
    I didnt even think of that thats probably why most of the screens were turned off bugger

    Sent from my SM-G900I using Ausfish mobile app

  6. #66

    Re: Sounder fundamentals for the guys who wanted it

    I don't know what sort of sponsorships this site has but maybe the organisers need to be aware of this.

    I won't put anything specific up if its deemed best not to by the organisers. There's more than 1 manufacturer involved with various things.

    A couple of days ago I showed you how one particular manufacturer was playing "ducks and drakes" with technical claims about their product. They were upfront it about by telling everybody but very few understood the significance of what it meant.

    Anybody worked out which manufacturer?

  7. #67

    Re: Sounder fundamentals for the guys who wanted it

    OK, you can put up stuff from any manufacturer. I like to use the term... IMO ( In My Opinion ) as that simply states, you have used this and compared it to others. Nothing wrong with that.

    Personally I have used many brands, but still go back to what I know ( language etc ) as you pointed out.

    I remember using my first colour sounder Koden and there were NO words, just symbols on the touch keys.... might have been back in the 80's ?

    IMO......... .......... and because I know how to use them.... Furuno sounders and Garmin GPS's for me.

    I did see the WASSP system when it first came to light many years... mind blowing back then ( 20 years ago now ) https://enl.co.nz/pages/wassp

    .............. continue... ><>

    LP
    Kingfisher Painting Solutions:- Domestic and Commercial.

    For further information, contact details, quotes or advice - Click Here





  8. #68

    Re: Sounder fundamentals for the guys who wanted it

    Koden made good little navigation radars, Phill.

    Popular one was 16nm version for use on yachts mounted about 15ft above the deck.

    However, you could open the case and bridge 2 points on the circuit board and it opened up into a 32nm radar. That meant you could see out to 40nm on the outside of the last 8 mile range ring.

    Installed one on the local ASR boat in 1985 and it gave many years faithful service. This was before the days of GPS when cumbersome old SatNav was the only thing around. There was a a 1200ft mountain with big steel towers (Mt Watalgan n/west of Bundaberg) which reflected radar signals well that we could see on radar @ 40nm. With the bearing to it (compass) and range (radar) we could work backwards for a chart position with very good accuracy.


    The sounder brand doing that is Humminbird. They're still doing it.

    https://www.humminbird.com/sites/hum...ct-catalog.pdf

    page 26 - 27 Look for heading Sonar capabilities on the 2 page specification sheet.

    2nd line is called "Sonar coverage (LHS). The columns to the right contain the different beam angles. Note the words "@ - 10 db". It appears on the spec sheet for ALL Humminbird sounder models in the brochure.

    At least they're telling everybodybut they don't want to talk about it why they do it.

  9. #69

    Re: Sounder fundamentals for the guys who wanted it

    It's something I had totally forgotten about Ron. They were doing it back in the 90's too as sounders developed. From memory the unofficial industry standard was -3db. At the time they were using large coverage angles as a primary marketing tool.

  10. #70

    Re: Sounder fundamentals for the guys who wanted it

    That's right, Scott. The old over-used but much vaunted "broadband" promotions. Humminbird are still doing it.

    The industry convention remains at -3db.

    I don't believe that H'Bird were trying to introduce a new industry "standard" for measurement of bandwidth or calculation of beam angles.

    Simply a "sneaky" product marketing/promotion tool aimed at market advantage.

    Should attempts to change the industry to a new "standard" have been the case, H'Bird would have used the -10db points on calculating the Q Factor of transducers as well (to be consistent).

    Larger divide by numbers in the denominator formula for transducer Q would give lower Q in calculations (desirable for chirp/broadband).

    Had they also used those -10db points in calculating range resolution, H'Bird would also have been able to claim much better range resolution figures than their competition.

    Wonder why they didn't.

    Maybe they simply didn't realise the added advantage in range resolution that they could also claim by that simple bit of specification modification (despite the real rr figure not actually changing).

    About the only thing that I can say about that H'Bird practice is that they at least told people albeit in the fine print.

    I use a H'bird now and am happy with it despite the practice.

    Had a "run-in" with Garmin marketing and promotions staff in the US (2017 or 2018) over some technical stuff.

    They're still quoting those very suspicious specs on their latest models.

    At least Garmin nominates the b/width measuring points as the normal -3db.

  11. #71

    Re: Sounder fundamentals for the guys who wanted it

    Remember this?

    The Garmin GVC20 UHD (Ultra High Definition) Black Box.

    https://buy.garmin.com/en-AU/AU/p/618945#specs

    Click the "SPECS" and look in the Frequencies Supported boxes.

    What's in there was sufficient to raise the question in my mind "what's going on here"? The sums simply didn't add up (and there are only 2 sums there).

  12. #72

    Re: Sounder fundamentals for the guys who wanted it

    My head hurts now................
    Kingfisher Painting Solutions:- Domestic and Commercial.

    For further information, contact details, quotes or advice - Click Here





  13. #73

    Re: Sounder fundamentals for the guys who wanted it

    OK, Phill.

    I not going to put up anything to create sore heads.

    The bottom line is that Garmin put this stuff up in ALL of their advertising. Not just in Aus.

    When challenged about it, the garmin guys in Aus simply did not understand what the problem was. So I ended up with garmin in US (the marketing/promotions guys) who were across the product equally as well as the aus guys.

    The garmin engineers were talking the same language though and agreed there was a problem. They claimed that it was the marketing guys who had stuffed it up. The marketing guys said no, it wasn't them.

    The question of was it simply a marketing/promotions error remained unanswered but nobody within garmin wanted to accept blame for it.

    In the end garmin waited and quietly changed the advertising to what it is now.

    Here's the new advertising.

    Look in the same place for the new info.

    Might'nt look like much of a change but it certainly was to the claimed performance etc.

    https://buy.garmin.com/en-AU/AU/p/626121#specs

    The moral of the story is that these were just 2 of the 4 major suppliers to the rec fishing sounder market.

    The other 2 (Lowrance and Raymarine) also had their moments.

    They all get away with what they are able to and couldn't care less about the confusion they create.

  14. #74

    Re: Sounder fundamentals for the guys who wanted it

    Here's the little interactive xl sheet I told you guys about courtesy of Lucky Phill and the IT backup guys he has working for him.

    Its protected against accidents and you can only input data in the yellow squares.

    You can download the sheet to your computer to use it yourself if you wish.

    There are a couple of things to look at.

    No1 is the minimum size of the targets that the well known frequencies can see. The freq 360khz may not be so well known as that was the freq that Raymarine used on their first little CHIRP sounder the DragonFly.

    Note the minimum size that 1200 khz (Humminbird's Mega) can see. 1.3mm.

    Holy cow, who wants to catch/see something 1.3mm in length?

    Well nobody I guess unless you're in NSW or Vic ('cos that's all that's left ).

    However, if you were looking at a target in the 60cm - 1 metre range, then you'd be able to see it in 1.3mm portions thus showing the shape of every fin on the fish to the stage of recognizing what it is. I've seen

    the feelers on threadfin king with 1200khz. Basically it allows species identification in lots of instances. Turtles, dolphins, sharks, crocodiles, stingrays etc stand out.

    No 2 is how CHIRP makes a dramatic improvement in being able to separate 1 fish from another so that 6-7 fish together or a fish close to the bottom don't show up as 1 single target. They show as separate targets.

    Look at the range resolution that CHIRP can produce ( 94mm).

    You can see separate targets even if they're only 94mm apart.

    Look at the range resolution that a normal pulse sounder produces using a pulse of one thousandth of a second (commonly called 1 millisecond - 1ms). 780mm.

    You can only see single targets if they're a minimum of 780mm apart.

    So CHIRP has a 8 times advantage over a pulsed sounder using a 1 ms pulse in separating targets.

    Sounder calculations.xlsx

  15. #75

    Re: Sounder fundamentals for the guys who wanted it

    Just when you thought that it was safe to go outside again.................................

    I've got a bit more info for those who want to know about choice of freqs to use and depths of water to use 'em in.

    There's a big difference between the needs of blue water use (offshore stuff) , green water (inshore stuff) and estuary stuff (dirty water).

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