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Dual frequency Fish Finders?

Old 01-20-2003, 04:46 PM
  #1  
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Default Dual frequency Fish Finders?

Im considering a few different fish finder / gps combinations. It seems that one big jump in price comes when you go from single (200mhz) to dual (50/200mhz) frequency. The $300 question is "Is it worth it?"

Id love to hear your thoughts. I'll be putting it on a scout 185sf.

Thanks
Dave

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Old 01-20-2003, 05:17 PM
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Default Dual frequency Fish Finders?

If you fish deeper than a 100' to 150' then yes it's worth it, otherwise no. The beamwidth of the 50khz signal (it's khz not mhz) is way too wide for shallow water.

Fish reflect differently at both frequencies, so although one frequency may miss it, the other will most likely see it.

What ever you buy, get one with "A-Scope" this is invaluable to know what is happening in real time under the boat.

Color is the holy grail. You can understand much more information if it's presented in color.
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Old 01-20-2003, 05:49 PM
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Default Dual frequency Fish Finders?

i had dual frequency on my last rig. i bottom fish at max depth of 125 ft. i never used the 50. i dont know the depth you will be fishing, but the first guy is right about which to use. good luck
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Old 01-20-2003, 09:36 PM
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Default Dual frequency Fish Finders?

I like the duals, even in 30-50'. Sometimes one just works better. The 50khz has a wider beam, shows more bottom, just not as detailed as 200khz. Fish not near bottom can show up better. Any day I might switch several times. Most units will display both at the same time in split screen, or in the case of a Raymarine L750 on the same screen with different fish echos for each frequency.

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Old 01-21-2003, 06:13 AM
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Default Dual frequency Fish Finders?

nichnet,
You didn't say what type of fishing you do. If you are a serious salt water bottom fisherman, no question, go with the best dual you can afford. The least expensive dual color with good features would probably be the Furuno 600L. A better machine would be the 582L. Just my opinion. I would spend a little less on the GPS to get a good bottom machine unless your primary boat use is not fishing. The color units are worth the money once you understand how to use them.
Joe

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Old 01-21-2003, 06:51 AM
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Default Dual frequency Fish Finders?

Dave -

I, too, own a Scout 185SF and had these same questions about sounders.

I ended up with a Furuno 600L with the transom-mounted tri-ducer. The unit is simply awesome, and I can't recommend it highly enough. The color display is very nice, and I have no visibility issues in direct sunlight. The xducer is great, holding bottom at WOT as well as providing 2 frequencies, water temp, and speed (which isn't very useful if you have a GPS).

I've been out as deep as 120' and as shallow as 2' with no issues. It is important to learn how to tune the FF appropriately to the depth you are working, but this takes an hour or so of fiddling with it.
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Old 01-22-2003, 01:30 PM
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Default Dual frequency Fish Finders?

Thoughts on the dual frequency sounder "200 kHz works great in shallower water but has a depth limitation of roughly 450 – 550 ft. Make sure you operate in the 50 kHz mode in deep water." Taken from the si-tex website.
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Old 01-22-2003, 03:00 PM
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Default Dual frequency Fish Finders?

I usually switch over from 200 to 50 in around 250 feet of water or so. But that's just for our sort of boat use. If you don't much ever get out into deeper water there wouldn't be much of a reason to have a dual frequency sounder I 'd say.

One thing is though, and I don't know if you've paid any real attention to this or not, but while its true that the more expensive sounders' are dual frequency, but that's not the only thing that makes them more expensive, they are a lot better in other ways too. So something you tend to see is that any fish finder that is worth having is going to be dual frequency no matter if you need it or not. That wasn't true when Furuno was still makeing the old LS6000, which was a single frequency unit that could be had in either 50 or 200 KHz. Now days the best deal going on a fish finder is the Furuno LS6100. Its not color but if you are trying to keep the price within reason this really is the unit for you. Just take it for its great quality and consider the dual frequency a bonus.

Thom

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Old 01-22-2003, 03:46 PM
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Default Dual frequency Fish Finders?

Thanks for all the replies. I've pretty much decided I want to go with a combo unit GPS Chartplotter / Fishfinder.

First of all - Im not much of a fisherman - yet. I'm a long time sailor (stop the booing and hissing) and I've bought the scout to get out onto the bay and am determined to start catching some fish. I've trolled behind the sailboat for years with some luck - but now its time to get serious. I do plan to get outside of the bay from time to time - probably out to Cuttyhunk or Block Island. When I get out there the depth will be an issue - but in reality 95% of the time I'll be in water <100ft.

I've decided to go with the combo unit to save space because I love having a chartplotter (i have one on the sailboat).

So far I've narrowed it down to the garmin 188 (50/200 khz) approx $775 or garmin 168 (200khz) approx $775.

If you have other suggestions for a combo gps/ff unit I'd love to hear them

Thanks

Dave

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Old 01-22-2003, 03:55 PM
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Default Dual frequency Fish Finders?

oops - make the price on that garmin 168 = $475

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Old 01-22-2003, 04:51 PM
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Default Dual frequency Fish Finders?

200 khz will suit your needs fine.

Dont venture to far out in that scout.
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Old 01-23-2003, 06:34 AM
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Default Dual frequency Fish Finders?

I copied this post from another board. It was written by someone involved with Great Lakes Angler Mag and I found it very informative...

"Generally speaking, the higher a fish finder's frequency the closer targets can be in a vertical plane and still be shown as separate objects. You get better screen detail overall, the screen picture looks sharper and you can see subtle changes in the bottom and structure.
The lower a fish finder's operating frequency the deeper it can reach. Unfortunately, the lower the operating frequency the more suspended objects tend to merge together on the screen in a single, bigger mark instead of being shown as separate, individual marks.

The industry standard frequency for fish finders has settled at around 200kHz because it seems to deliver the best balance between detail and depth reach. I've seen cone angles from 6-8 degrees on up to about 30 degrees for 200kHz units with the overwhelming majority at about 20 degrees. In contrast, most of the 50kHz models I've seen have cone angles from 30 to 50 degrees. The low frequency units' wider cone angle contributes to the problem of blobbing fish together instead of showing them separately. A fish finder converts the three dimensional area inside its cone into a two dimensional screen picture. A cone that is twice as wide contains lots more stuff at any given depth so it is going to have more trouble separating everything into individual marks. That's not the only reason, low frequencies just can't separate targets as well.

You should be able to see fish about as well at 50kHz as you can at 200kHz, although with 50kHz tight groups of fish may look like single big fish arches and fish close to the bottom may tend to blend into the bottom contour. Try turning the sensitivity up a bit when 50kHz isn't showing you fish that 200kHz does show you right in the same spot. Remember that when the dual frequency split screen is used on Lowrance units(50kHz on one side and 200kHz on the other) you have to adjust the sensitivity for each side separately.

In a nutshell, use 200kHz when detail is important and use 50kHz when depth penetration is your main concern. You can also use the wider cone angle common with 50kHz as a tactical advantage, say when you want to see your full spread of downrigger weights or are looking for a prominent piece of structure - the wider cone will find it faster then you can swtich to 200kHz and its narrower cone for a more detailed look."
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Old 01-23-2003, 09:36 AM
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Default Dual frequency Fish Finders?

Hey Dave,
Garmins are very popular here on THT, and there have been some negative comments about Lowrance. However, I have been using a Lowrance LCX-15MT since last February (over 200 hours of use) with NO problems. It is a combined GPS/Chartplotter/Sonar (i.e. fishfinder), with dual 50/200KHz transducer.
GPS is WAAS and accuracy is fantastic. Unit holds two Multi-Media Cards (MMC) and I purchased the entire Chesapeake Bay and entire North Carolina coasts from Navionics for $200 each.
Fishfinder is great at both frequencies, although I have not been in any "deep" water.
Best of luck.
Brian


quote:Originally posted by nichenet:

First of all - Im not much of a fisherman - yet. I'm a long time sailor

When I get out there the depth will be an issue - but in reality 95% of the time I'll be in water <100ft.

So far I've narrowed it down to the garmin 188 (50/200 khz) approx $775 or garmin 168 (200khz) approx $775.

If you have other suggestions for a combo gps/ff unit I'd love to hear them
Thanks
Dave


2002 GW Islander 270 - 2001 Yam 250 OX66. Fishin' & cruisin'

[This message was edited by ocnslr on 01-23-03 at 11:53 PM.]
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Old 01-23-2003, 06:49 PM
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Default Dual frequency Fish Finders?

i have had great luck grouper fishing with the lcx 15 mt
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