Ping pong balls, panty hose, and DSP

Furuno 620 and Ray DS500X 2 BenE

I’m guessing that title got your attention? You see I’m trying to compare a Furuno FCV-620 fishfinder with the Raymarine DS500X which is already installed on Gizmo (and which the idiot thieves failed to strip off). Airmar kindly made me a patch cord so that the same transducer works with both machines (and the Navman 8120 I’m also testing). I can’t run them simultaneously (the DS500X is locked up in above photo), but can switch the transducer quickly. You can see in the bigger picture how noise-free both units are, apparently thanks to Digital Signal Processing, and note that both are in full auto mode. What I’m having a hard time determining is if one or the other is actually better at finding fish. So far the Raymarine IDs more fish on screen, but I suspect that it is being ‘optimistic’. It’s hard to get trained fish for this purpose, which is why someone suggested that a few ping pong balls held underwater with panty hose and a rock could simulate fish bladders. I’m not sure I’ll find time to try that, but would appreciate other suggestions on how to compare the units.

In the meantime, the difference in interfaces is much more obvious and quantifiable. I quite like the 620’s knobs for controlling manual gain and screen mode (below, bigger here), a much more tedious process on the DS500X. Knobs, as noted yesterday, are old fashioned, but they sure can be useful.

Furuno FCV-620 BE test

Ben Ellison

Ben Ellison

Panbo editor, publisher & chief bottlewasher from 4/2005 until 8/2018, and now pleased to have Ben Stein as a very able publisher, webmaster, and editing colleague. Please don't regard him as an "expert"; he's getting quite old and thinks that "fadiddling fumble-putz" is a more accurate description.

4 Responses

  1. Ben,
    Testing sounders is always a nightmare but when i do it i try and do it over a bank or reef / wreck.

  2. Walter Guinon says:

    Ping Pong balls will crush at shallow depths but you don’t need to sim the air bladders since an acoustic reflection will arise from any object with acoustic impedance different from water.
    Try throwing your tools overboard.

  3. Ron Rogers says:

    Golf balls maybe. Part of sounder capability is selecting and using different frequencies – which might require different transducers. But your focus on software interface and ergonomicis is more important.

  4. The FCV-620 (at least in the UK) comes with a 50/200khz transducer from airmar (pretty much standard for the class)

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