295 Hondex Transducer options

[spork87]

I have been running the 295/B275 combo for a while now and it has been good to date.

Im wanting to get some better performance for bottom fishing in 5-600m of water. Currently I have no problem reading the bottom in this depth but finding fish and bottom definition is a real struggle.

Im looking at the below options and was wondering if anyone has any thoughts on the best options.

Hondex
TD88- 28khz
TD83- 40/75
TD80- 32/40
TD87- 28/100

My concern with the hondex is the beam angle and the effect it may have on the bottom definition when reading such a large area in 500m

Any help would be greatly appreciated.
cheers

 

[Dean1345]

I have the TD 88 with the fvc 1900 170 fathoms is the deepest I've been but not problem marking fish

 

[Dean1345]

Thats a few pictures hope it helps

 

[jp498]

Beam angles are as follows with a -6db cutoff.
(Airmar uses a -3db cutoff, so it's not apples to apples numbers comparison)

transducer LF HF impedence
TD87 20x32 90 Ω
TD80 12x16 & 11x15 140 Ω
TD83 13x18 & 10x12 120/110 Ω

 

[Tommyryan01]

I have been running the 295/B275 combo for a while now and it has been good to date.

Im wanting to get some better performance for bottom fishing in 5-600m of water. Currently I have no problem reading the bottom in this depth but finding fish and bottom definition is a real struggle.

Im looking at the below options and was wondering if anyone has any thoughts on the best options.

Hondex
TD88- 28khz
TD83- 40/75
TD80- 32/40
TD87- 28/100

My concern with the hondex is the beam angle and the effect it may have on the bottom definition when reading such a large area in 500m

Any help would be greatly appreciated.
cheers

Hi mate I have been running a td73 2.5kw 40/75 for a while now and really happy with it. Let me know if you want any more pics

 

[Fishfiction]

How would you rate the 75khz as a stand alone frequency for bottom fishing? Interested in. 3kw model but am hesitant as to whether the frequency would be to high for bottom fishing in 250-600 meters.thanks

Hi mate I have been running a td73 2.5kw 40/75 for a while now and really happy with it. Let me know if you want any more pics

 

[Deep Blue]

Fishfiction,

Bottom fishing at the depths of 250/600 Meters (820-1968 ft / 136-328 fathoms), most commercial fishing vessels are utilizing frequencies between 38-60kHz for use at those depths. But you can certainly try using 75kHz, it may provide you with better separation of fish targets.

- Deep Blue

 

[Fishfiction]

Would there be that much difference in depth penetration to say 38khz or 50khz and would the higher frequency give better or worse bottom discrimination at those depths as that's what I'm mostly seeking? Thanks for your answers

 

[jp498]

Higher frequency is a finer beam (all other things matching) and finer detail. I would say if you can see the bottom now with 1kw, 3kw will be much nicer. A higher power transducer may have an array of elements meaning a narrower angle (more detail and more physical gain), and if the sounder puts out 3kw, that alone is good for 1.5x more range. With inverse square law, you want 4x the power for twice the range. That can come from kilowatts, or more focused transducers... e.g. a wide beam transducer will need more power to reach the same depth as a narrower beam. Low frequencies carry further, so wide beam and low frequency go together well for economical chirp. 38 and 75 aren't all that different from 50khz, but if 200khz would be a big difference.

In the Furuno world, bottom discrimination as a feature is based on how the two transducer frequencies interact differently with the bottom. You need to choose a transducer off the supported list, not pick another brand of transducer that's single frequency and hope it works.
In the Hondex world, bottom hardness is based on 2nd echo strength, so you'd want enough power to get a colorful 2nd echo on hard bottom and mud would be a reliable single echo only.
Aside from that, bottom discrimination visually is a mix of experience and scientific and non-scientific visually learned things that don't translate if you change sounders or transducers. e.g. people still using a fcv292 because of how the bottom looks.
Some gravel can be seen in any case by off-axis reflections that are below the main echo but less than 2x deep. This sorta explains why it's good to have enough power and transducer to go twice as deep as strictly needed.