295 with cm599lh

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Stevehowlett

Guest
Hi just looking for some info on this setup we fish all depths from 10 to 700m, just wanting to know why on high frequency the bottom shows up as a thin line not showing it thick and also yesterday we went out deep and i left high on to about 150m but was showing any life so flicked over to low and showed fish straight away so i put it back to high and showed nothing again, i then went and changed the frequecy down the 140hz to see if that would help but still the same not sure why i would of thought 2kw high should work out to at leat 200-300m ?
 
Good morning Stevehowlett,

Thank you for your inquiry. You have made an excellent observation. The bottom tail (thickness) is tied to a bunch of factors but we some of the more common concepts include the following: The bottom tail will typically be thicker with a harder bottom composition than with mud or sand. If you take all the other factors out of it this is a pretty consistent. Please see the photo below, you will notice the bottom tail changes this would indicate a harder bottom moving towards a softer bottom.
FCV1200 28khz Q .jpg

Lower frequencies tend to yield a thicker the bottom tail than higher frequencies. You already observed this, we also know that typically the wider the beam angle the thicker the bottom tail. Which works together with frequency, typically the lower the frequency the wider the beam angle hence a thicker bottom. Please see photo below. Comparing low and high frequency and narrow vs. wide beam angle with a fixed frequency.
Low vs High Frequency B265.JPG
Narrow vs wide beam angle.JPG

The "q" rating also can have an impact on the thickness of the bottom tail. It has been our experience that a higher "q" transducer can show a different view of the bottom tail. Please see the photo below. This photo shows two different transducers with the same frequency, same output power, different beam angles but not significantly different, and the same bottom. You will notice the transducer on the right shows the bottom tail much different than the the photo on the left. The photo on the right has a higher "q" value.
Low vs High q 1.JPG
Low vs High q 2.JPG

As far as seeing fish on your meter at depth. Couple things to keep in mind, the higher frequency has a narrow beam angle. So sometimes you might see fish on the low frequency and not the high do to this. Also the larger the beam angle the larger the targets appear on the screen because the fish stays in the beam angle longer making it appear larger or wider.

Can you also verify the Tx power settings, the Pulse Repetition Rate, and the TVG Depth and TVG Level Settings for both the high and low frequencies?

Lastly we have done a sweep test on that transducer please see the photo below. You will see in the photo what frequency responded with the strongest return echos.

R509 sweep test.jpg

Kind Regards
C-Bass
 
Tx power is on 10 tx rate is on max, HF tx pulse is standard and pulse length is 0.05 tvg is set on 4 and distance is set to what im fishing in, LF tx pulse is set to long and pulse length is 0.05 and tvg is set on 6-7 and distance is set to what im fishing in.

On th HF side if we are lowering the hz down to 140hz we should be able to show good bottom out to 250m i would of thought ? Was being weird the other day but might of been out side the blocked zone for the 295 as i think i had it set on 134hz would that make it work less effective ?
 
Stevehowlett,
The only time you can set the TX Pulse Length is when you are in the Manual Pulse Length mode. Also know when you change from a TX rate of 20 to MAX the Pulse Length shortens putting less power into the water.

Snips
 
Good afternoon Stevehowlett,

Can you provide any photos of both frequencies? Or of the high frequency side when in deeper water?
 
Hi guys, finally got back out fishing and took some pics and i figured out what was wrong !, i pulled the cover off the back and had a look and the high frequency plug wasnt plugged in properly so now i have fixed it its working alot better a lot more power what i was expecting.

What do you think now ?
 

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Another pic
 

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Stevehowlett,
Thanks for the screen shots.
What were the sea conditions, looks like you were rolling around quite a bit.

Snips
 
The sea conditions weren’t to bad was 2-2.5m swell and a steady breeze a few of those shots were on the drift and not moving much might explain why it looks like we were rolling.
 
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