Questions on fish finder
 

Can anyone tell me how beneficial a "dual beam 24/60 would be vs. a single
24deg?
Also, any opinion on the Hummingbird Matrix 17/20/25 finders?
Thanks,
LD
ì

Questions on fish finder
 

Depends exactly what you use your sounder for.
The narrower the cone the more detail you'll read of the bottom. If you are
looking for "holes" to place cray pots etc then you need a narrow beam. On
the other hand to look for fish maybe a wide beam will give you more info of
what is "around" the boat & not just under it. Some of the wide ones will
even let you know if the fish is on the right or left side.
Therefore if you want both then get a "dual" beam one for sure.
Imagine a flat bottom with a 100 ft deep hole in the middle of it that is 10
ft across. If a "ping" from your sounder won't fit "inside" the hole then
you won't see it at all. The echo will return from the edge of the hole. Now
if you have (say) a one degree cone & it fits inside, then you'll see it. A
bit clearer?
BruceM


"LD" wrote in message
ink.net...
Can anyone tell me how beneficial a "dual beam 24/60 would be vs. a single
24deg?
Also, any opinion on the Hummingbird Matrix 17/20/25 finders?
Thanks,
LD
ì

Questions on fish finder
 

Good explanation -
Could you explain why if I have a 240 Blue 200/50/dual, why I would use it
on anything but dual - if this apparently gives the best of both worlds - or
is there an advantage to one of the specific freq. thanks

"BruceM" wrote in message
...
Depends exactly what you use your sounder for.
The narrower the cone the more detail you'll read of the bottom. If you
are
looking for "holes" to place cray pots etc then you need a narrow beam. On
the other hand to look for fish maybe a wide beam will give you more info
of
what is "around" the boat & not just under it. Some of the wide ones will
even let you know if the fish is on the right or left side.
Therefore if you want both then get a "dual" beam one for sure.
Imagine a flat bottom with a 100 ft deep hole in the middle of it that is
10
ft across. If a "ping" from your sounder won't fit "inside" the hole then
you won't see it at all. The echo will return from the edge of the hole.
Now
if you have (say) a one degree cone & it fits inside, then you'll see it.
A
bit clearer?
BruceM


"LD" wrote in message
ink.net...
Can anyone tell me how beneficial a "dual beam 24/60 would be vs. a
single
24deg?
Also, any opinion on the Hummingbird Matrix 17/20/25 finders?
Thanks,
LD
ì

Questions on fish finder
 

Do you want me to repeat all I wrote?
200 (ithink) is narrow for better bottom reading.
50 is wider & better for reading fish in area.
Both together will not be much dif that 50 on it's own.
On some sounders 50 will be limited in ability to go DEEP & read bottom. So
in deep water using both (dual) might increase bottom echo.
The main dif is your ability to use & read the sounder.
For the few bucks more, I reckon you should maybe get it & learn how to get
the maximum out of it.
BruceM


"wg992000" wrote in message
t...
Good explanation -
Could you explain why if I have a 240 Blue 200/50/dual, why I would use it
on anything but dual - if this apparently gives the best of both worlds -
or
is there an advantage to one of the specific freq. thanks

"BruceM" wrote in message
...
Depends exactly what you use your sounder for.
The narrower the cone the more detail you'll read of the bottom. If you
are
looking for "holes" to place cray pots etc then you need a narrow beam.
On
the other hand to look for fish maybe a wide beam will give you more
info
of
what is "around" the boat & not just under it. Some of the wide ones
will
even let you know if the fish is on the right or left side.
Therefore if you want both then get a "dual" beam one for sure.
Imagine a flat bottom with a 100 ft deep hole in the middle of it that
is
10
ft across. If a "ping" from your sounder won't fit "inside" the hole
then
you won't see it at all. The echo will return from the edge of the hole.
Now
if you have (say) a one degree cone & it fits inside, then you'll see
it.
A
bit clearer?
BruceM


"LD" wrote in message
ink.net...
Can anyone tell me how beneficial a "dual beam 24/60 would be vs. a
single
24deg?
Also, any opinion on the Hummingbird Matrix 17/20/25 finders?
Thanks,
LD
ì

Questions on fish finder
 

In article ,
"BruceM" wrote:

Do you want me to repeat all I wrote?
200 (ithink) is narrow for better bottom reading.
50 is wider & better for reading fish in area.
Both together will not be much dif that 50 on it's own.
On some sounders 50 will be limited in ability to go DEEP & read bottom. So
in deep water using both (dual) might increase bottom echo.
The main dif is your ability to use & read the sounder.
For the few bucks more, I reckon you should maybe get it & learn how to get
the maximum out of it.
BruceM

Actually your conclusions above are a bit missleading.
200 Khz will actually deliniate individual targets
much better than 50Khz due to it's higher frequency and
shorter wavelength. The Rule of Thumb for sonar is:
The higher the frequency the better resolution of targets.
The lower the frequency the deeper the signal can go.
200 Khz machines can't see down farther than 100 Fathoms
in most cases, but can resolve individual fish easily.
50 Khz machines can see down to 1000 fathoms but can't
resolve anything smaller than a cabin. North Pacific
Crab fisherman use 28 Khz machines so as to get excellent
bottom resolution at extreme depth, but they don't expect
to actually see anything other than the profile of the bottom.

Bruce in alaska
--
add a 2 before @

Questions on fish finder
 

Woops.......... knew I'd get it the wrong way.
BruceM



"Bruce in Alaska" wrote in message
...
In article ,
"BruceM" wrote:

Do you want me to repeat all I wrote?
200 (ithink) is narrow for better bottom reading.
50 is wider & better for reading fish in area.
Both together will not be much dif that 50 on it's own.
On some sounders 50 will be limited in ability to go DEEP & read bottom.
So
in deep water using both (dual) might increase bottom echo.
The main dif is your ability to use & read the sounder.
For the few bucks more, I reckon you should maybe get it & learn how to
get
the maximum out of it.
BruceM

Actually your conclusions above are a bit missleading.
200 Khz will actually deliniate individual targets
much better than 50Khz due to it's higher frequency and
shorter wavelength. The Rule of Thumb for sonar is:
The higher the frequency the better resolution of targets.
The lower the frequency the deeper the signal can go.
200 Khz machines can't see down farther than 100 Fathoms
in most cases, but can resolve individual fish easily.
50 Khz machines can see down to 1000 fathoms but can't
resolve anything smaller than a cabin. North Pacific
Crab fisherman use 28 Khz machines so as to get excellent
bottom resolution at extreme depth, but they don't expect
to actually see anything other than the profile of the bottom.

Bruce in alaska
--
add a 2 before @

Questions on fish finder
 

OK, I see the differences but I'm unlikely to need a finder to look deeper
than 100' (in the Gulf of Mexico). Out of Pensacola, you have to go 15 to
20 miles out to get over 100' and I wouldn't do that very often in my 20'
runabout. SO, is a dual beam, 24/60deg for example, needed or useful at
these depths?
thanks, LD

"BruceM" wrote in message
...
Woops.......... knew I'd get it the wrong way.
BruceM



"Bruce in Alaska" wrote in message
...
In article ,
"BruceM" wrote:

Do you want me to repeat all I wrote?
200 (ithink) is narrow for better bottom reading.
50 is wider & better for reading fish in area.
Both together will not be much dif that 50 on it's own.
On some sounders 50 will be limited in ability to go DEEP & read
bottom.
So
in deep water using both (dual) might increase bottom echo.
The main dif is your ability to use & read the sounder.
For the few bucks more, I reckon you should maybe get it & learn how
to
get
the maximum out of it.
BruceM

Actually your conclusions above are a bit missleading.
200 Khz will actually deliniate individual targets
much better than 50Khz due to it's higher frequency and
shorter wavelength. The Rule of Thumb for sonar is:
The higher the frequency the better resolution of targets.
The lower the frequency the deeper the signal can go.
200 Khz machines can't see down farther than 100 Fathoms
in most cases, but can resolve individual fish easily.
50 Khz machines can see down to 1000 fathoms but can't
resolve anything smaller than a cabin. North Pacific
Crab fisherman use 28 Khz machines so as to get excellent
bottom resolution at extreme depth, but they don't expect
to actually see anything other than the profile of the bottom.

Bruce in alaska
--
add a 2 before @

Questions on fish finder
 

In article ,
"LD" wrote:

OK, I see the differences but I'm unlikely to need a finder to look deeper
than 100' (in the Gulf of Mexico). Out of Pensacola, you have to go 15 to
20 miles out to get over 100' and I wouldn't do that very often in my 20'
runabout. SO, is a dual beam, 24/60deg for example, needed or useful at
these depths?
thanks, LD

Ok, now we have enough information to expound on the question at hand.

If you never expect to look below 100 Ft the a nice 200Khz
sounder/fishfinder will work great in your application. 200Khz will
give you excellent small target definition, and good target
discrimination, if you use a very narrow tranducer like maybe 12 degrees
or better.
Most of the small sounder outfits don't spec the transducer's beamwidth,
and just sell a generic transducer with an average 25 degree beamwidth.
This will work ok for most applications , but will tend to not provide
individual fish discrimination, that can be obtained with a narrower
beamwidth. Power output for depths of less than 100 Ft at 200 Khz
doesn't need to be more than 50 watts PEP. More will tend to fill the
area with reverberations that just fog up the return signals, and reduce
system clarity.

Bruce in alaska
--
add a 2 before @