400hz vs. 800hz si

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Originally Posted by CrappiePappy

This is how I understand it ...
In DI the single beam is directed downwards (only), and the difference between the two kHz settings is the angle spread (45deg & 75deg). When using SI, the beam is projected from both sides of the transducer (and also down), so the 455kHz spread is nearly 180deg (greater distance coverage), while the 800kHz spread is over 100deg (better defined images within the beam).

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Correct ...
Attachment 274502
Attachment 274501

Rickie

Quote:

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Originally Posted by CrappiePappy

And I believe the actual degrees spread is actually slightly different, by a few degrees, depending on which brand of depthfinder you're using.

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Also most likely true ... even tho the other brands (besides HB) do not disclose their spec imaging angles ...

Rickie

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Originally Posted by rnvinc

Also most likely true ... even tho the other brands (besides HB) do not disclose their spec imaging angles ...

Rickie

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Rickie ... I thought I saw somewhere that HB's beam was 1.7deg thick, and Lowrance was something like 3deg thick. But, wouldn't the SI angles be the same, since they're using the same kHz ranges (455 & 800) ?? :scratchhead

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Originally Posted by CrappiePappy

Rickie ... I thought I saw somewhere that HB's beam was 1.7deg thick, and Lowrance was something like 3deg thick. But, wouldn't the SI angles be the same, since they're using the same kHz ranges (455 & 800) ?? :scratchhead

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I have also seen unverified reports of these slice beam thickness but nothing that I recall actually in verified specs by the brands ...
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Beamwidth is a factor of piezo shape and piezo size ...

Frequency applies to the resonate (natural) vibration "frequency" that the specific piezo "vibrates best at" ...

In other words - a piezo will vibrate at any frequency of electrical pulse sent thru it ... but each piezo will have a resonate (natural) tendency to vibrate best at certain frequency (or 2 frequencies) ...

Piezo manufacturers know how to control the criteria (during the manufacture process) to create a certain piezo that "vibrates best" at a certain frequency (or frequencies) ...

Interesting reading here ...:
http://www.airmar.com/uploads/instal...Operations.pdf

Rickie

Thanks alot everyone. I got a chance this weekend to play around with the 455 vs. 800 and got some good results. Attachment 274843

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Originally Posted by Tristan Bladon

Thanks alot everyone. I got a chance this weekend to play around with the 455 vs. 800 and got some good results. Attachment 274843

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You have a very small amount of interference in the right SI ... indicated by the parallel faint horizontal dashed lines in the lower half of the right SI ...

Do you know if these lines only occur when the TM is running ...??

Rickie

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Originally Posted by rnvinc

You have a very small amount of interference in the right SI ... indicated by the parallel faint horizontal dashed lines in the lower half of the right SI ...

Do you know if these lines only occur when the TM is running ...??

Rickie

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That's was with the outboard running. Never really noticed it as interference.

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Originally Posted by Tristan Bladon

That's was with the outboard running. Never really noticed it as interference.

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You might rearrange some cables away from the Sonar power and xducer cables and it might go away ...

There is a "Noise Filter" under the Sonar tab that would filter that out ... but I don't really advise that because the Noise Filter also filters out softer returns that you may want to see ...

Rickie

Quote:

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Originally Posted by rnvinc

You might rearrange some cables away from the Sonar power and xducer cables and it might go away ...

There is a "Noise Filter" under the Sonar tab that would filter that out ... but I don't really advise that because the Noise Filter also filters out softer returns that you may want to see ...

Rickie

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Ferrite ring maybe?

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Originally Posted by Tristan Bladon

Ferrite ring maybe?

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That is also an option ...

Always install a ferrite core as close to the head unit as possible to arrest errant RFI before it gets into the head unit ...

Rickie