I've been playing around and can't really seem to figure out when is the best time to use each?
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I've been playing around and can't really seem to figure out when is the best time to use each?
800kHz will have more detail with less range ...for stuff close to the boat ...
455kHz will have more range with less detail ...for stuff farther from the boat ...
Attachment 274424
Rickie
Attachment 274423
I don't know about SI, and I would defer that to "rnvinc" for his take.
But, when it comes to DI ... as you can see in the picture above ... detail is much better in 800kHz, especially as it defines the fish (white marks) suspended above this dropoff.
I've heard that the 455kHz signal is better in deeper water ... so that may translate to using it when your SI is set for 1/2 to full distance ... and using the 800kHz when your distance settings are less than 1/2 maximum distance. You'll likely have to tweak your sensitivity settings for each kHz setting, as well, so you don't wash out the images or lose them against the background.
Is there a "magic" distance for the 800 say 50'? Or depth?Quote:
Originally Posted by rnvinc
Environmental variables will play a large part in range capability of each frequency ...Quote:
Originally Posted by Tristan Bladon
A hard gravel bottom in deeper water may reflect more sound than a mud bottom in shallower water ...
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Deciding which frequency to use when should be determined by the task at hand ...:
If one wants to see detail of stuff close to the boat = use 800kHz ...
If one wants to find new stuff farther away from the boat = use 455kHz - then drop a waypoint on it and reposition the boat closer to scan it again with 800kHz to see the detail of it ...
Rickie
I understand in Di the difference in 455 and 800 because it changes the size of the cone but in si which is supposedly (as I understand it but I'm still learning) is a thin slice like beam that you are determining how far to the left or right it shoots how it makes such a difference since your not changing the size of a cone.
I think I will try the 800hz on my bow unit. I like the 455hz. best so far on my console unit for finding stuff so far. I have not been to satisfied with the bow unit so far as I troll at much slower speed. Maybe the 800hz will give me better and clearer picture. I am running a 899ci HD SI. Question is what do most of you all use to get clear pictures on your bow sonars while slow trolling?
I almost always use 800 on my bow unit for di.Quote:
Originally Posted by scrat
This is how I understand it ...Quote:
Originally Posted by ccollins
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).
And I believe the actual degrees spread is actually slightly different, by a few degrees, depending on which brand of depthfinder you're using.
But, as always, I defer to Rickie for clarification and/or correction.
This makes since I didn't realize there was an deg change in Si .Quote:
Originally Posted by CrappiePappy
Correct ...Quote:
Originally Posted by CrappiePappy
Attachment 274502
Attachment 274501
Rickie
Also most likely true ... even tho the other brands (besides HB) do not disclose their spec imaging angles ...Quote:
Originally Posted by CrappiePappy
Rickie
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) ?? :scratchheadQuote:
Originally Posted by rnvinc
I have also seen unverified reports of these slice beam thickness but nothing that I recall actually in verified specs by the brands ...Quote:
Originally Posted by CrappiePappy
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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
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 ...Quote:
Originally Posted by Tristan Bladon
Do you know if these lines only occur when the TM is running ...??
Rickie
That's was with the outboard running. Never really noticed it as interference.Quote:
Originally Posted by rnvinc
You might rearrange some cables away from the Sonar power and xducer cables and it might go away ...Quote:
Originally Posted by Tristan Bladon
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
Ferrite ring maybe?Quote:
Originally Posted by rnvinc
That is also an option ...Quote:
Originally Posted by Tristan Bladon
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