fishfinder confusion

[--GQ--]

Re: fishfinder confusion

<br /><br />Note: equations above may not be used for the sole purpose of financial gain with out MY written permission.

 

[Paul Sullivan]

Re: fishfinder confusion

Nice square wave .... problem is that wave creates an enormous amount of noise (electrical) i.e., odd harmonics ... so really it isn't the wave used to create the sonar image. One would have to filter the heck out of it(cleaning away all of the odd harmonics) adding to the total power usage of the sonar equipment and the signal attenuation. <br /><br />Rather the wave is a very large narrow pulse followed by a relative long off period off then followed by another pulse. <br /><br />Why? because you need to send an enormous(relative) signal through the transducer into the water then allow for it to return and then simultaniously convert the acoustic wave into a digital signal and then transmit it to the FFinder .<br /><br />Listen to your transducer click away while it is working .... notice the acoustic profile of it ....pulses not regular square waves.<br /><br />Now the W rms to transmit the signal to the FF from the transducer is critical since it is the driving energy behind the components size and ability to handle the I^2*R...<br /><br />Also just like an RF signal the image information sent from the transducer has a carrier component ...this is where the rms value would be of great importance. However to drive an acoustic signal down into the water and then have enough signal return is the peak to peak value ....this is the critical parameter in selecting a quality sonar system...IMHO

 

[Paul Sullivan]

Re: fishfinder confusion

I have a Garmin 178C ... 4000 W peak ..this is the signal used to produce the acoustic signal into the water ... the 4-500 W rms is the transmitting strength of the transducer to the FFinder. <br /><br />Hint look at the components of your transducer ...cheep plastic (usually) with a very small cable feeding it usually ~ 20-22 awg. Pushing more than 500W through that cable will greatly increase the attenuation of the signal through heating and voltage drop ....remember that cable is ~ 25 ft long. The peak output gets you a better acoustic image back.<br /><br />Besides if what you say is true explain this on my Garmin I have peak Watts 4kW ptp ... the effective watts are 500 dual and 400 single freq. ....no matter how hard you try you are not going to get 400 watts out of 4kW by <br /><br />W(eff)= W(max)/ 1.414 or .707xW(max)<br /><br />thats because it is not a sinusoidal wave form be it square,triangular, of sine .... it is a series of pulses...

 

[tangent]

Re: fishfinder confusion

Sounds like we need a different way to measure effectiveness. Stealing ideas from Mythbusters, we could create some simulated fish, put them in a tank under all sorts of conditions (bottom conditions, false targets,etc.) and find out how good the return signal works. Then look at how well the whole system works (on screen & fish recognition software). <br /><br />Or maybe we could just go fishing and have a beer or two.

 

[Boatist]

Re: fishfinder confusion

The two standards have been around for years. You can use either one to compare units and as long as you know the 8 to 1 ratio you can compare Peak to Peak to RMS. The top of the line high power units usually use RMS. The low power unit seem to use Peak to Peak to make them sound more powerfull to people that do not understand the difference.<br />I hope everyone now knows how to compare RMS to Peak to Peak.

 

[Paul Sullivan]

Re: fishfinder confusion

There is a reason why the specs read peak to peak and why they read RMS ...being an electrical engineer myself I'm pretty sure it isn't a marketing ploy per se'. <br /><br />In general you buy the most engineering you can afford for your application. Example on saturday I went out on my 20' cuddy searching for a wreck off of San Diego harbor. I use a Garmin 178C fish finder w/a in hull transducer(BTW everyone told me not to buy a in-hull-sure am glad I didn't listen to them) and found the reef where the vessel lies as clear as any image I've seen on more expensive units. When we dove the site we were within 50yds of the wreck ...not bad for a 400W RMS 4000W ptp unit - eh? ...and dead reconing off of a few bouys and landmarks. <br /><br />Learn how to use your tools effectively even if they aren't the high end models.

 

[Boatist]

Re: fishfinder confusion

You need to convence all the major company to agree with you. For me All I want to do is help people looking for a way to compare units to each other. By the way 400 watts RMS is 3200 Peak to peak.<br /><br />Depth Sounder features (GPSMAP 178/178C Sounder only) Frequency: 50/200 kHz or 200 kHz <br /><br />Transmit power : <br /><br />500 watts (RMS), 4000 watts (peak-to- peak) w/ dual frequency transducer <br />400 watts (RMS), 3200 watts (peak-to- peak) w/ single frequency transducer

 

[--GQ--]

Re: fishfinder confusion

HUH ???

 

[--GQ--]

Re: fishfinder confusion

Originally posted by Parisitic:<br /><br />Or maybe we could just go fishing and have a beer or two. <br /><br /><br />Count me in. You bring the beer, I'll bring the girls. You find the place and i'll find the time... <br /><br />And leave the girlfriend/wive at home cause we won't be fishing.

 

[Paul Sullivan]

Re: fishfinder confusion

you're right ... I did have it set at 500W dual freq 4kW ptp ...<br /><br />point I'm trying to make is don't get hung up on the power ratings ..for most boaters it is over kill.. <br /><br />I use a 20' cuddy in SoCal waters ...usually chasing surface fish like yellowtail, albacor, ahi, and dorado, also I use mine for finding good dive sites < 130'fsw. How do I justify a $2600.00 Interscope with a trailing fish-several hundred more .Specially when the tell tail sign for these palegics is diving birds,boiling water, bait balls, and floating kelp patties. <br /><br />I like the GPS on the 178C and the sonar once again for looking for sea floor reefs, or stucture, its all about knowing what you are looking for. Understand what your FFinder can do and maximize the efficiency of your unit ... having a more powerful sonar doesn't necessarily translate into a more efficient system ... just a bigger badder system ....kinda like Boom Boxes -eh? If you're 16 yrs old that overdriven bass sounds hot ... but for us middle aged guys and you slow breathers ... that high gain output doesn't do much for us does it....<br /><br />Buy a unit and learn how to use it and don't get caught up in the power game ....We ain't out there searching for submarines ... just reefs, temp breaks, holes, structure and maybe a few nice fish echos.<br /><br />Then again if you want to dump a few grand into a fishfinder who am I to lecture you otherwise ...and mount it on your boat to use it 10 times a yr.

 

[Paul Sullivan]

Re: fishfinder confusion

Oh yea who is it that is claiming they use a DC-DC converter on these production sonar units. Have you guys seen the transducers ... again they are cheep plastic units feed by a 24-20 awg cord. Even most thrue hull models are cheap the bronze sink is for stablizing the unit to reduce cavitation primarily and as a heat sink secondarily ...look at the cord feeding it that is the telltail as to how much energy it can handle. The cords can hardly handle 500 W rms. My guess is they put a cascading amplifier inside made of transistors and a few zenor diodes(voltage multiplier) and a big capacitor to drive the sonic unit. Thus you get a big ptp rating while maintaining a relatively low rms rating.<br /><br />Go to your local boat store..look at a 700W inverterDC-AC ..essentially a DC-DC source without the final stage. See how big these guys are ... now look at your sonar is it even remotely as big (ability to disipate heat) ? Now look at the remote sonar units ...now do you get it.<br /><br />Again don't get hung up on power issues. The signal generated by the sonar unit that drives to bottom and then recieved is the critical parameter in how "powerful" your system is.<br /><br />Finally if you got the use for a big thrue-hull and a powerful remote ...knock yourself out as you're chasing bottom fish. Seems to me to be overkill ...but hey to each their own

 

[Boatist]

Re: fishfinder confusion

Today I would agree with you on the power issue since for the last few years can only fish 20 fatoms or 120 feet. However in the past fishing bottom fish or rock fish at 450 feet of salt water you needed a lot of power and a high resolution. Also needed bottom track or bottom lock to expand the bottom to see fish. I hopefull that some day we will be able to once again fish off the California Coast.

 

[--GQ--]

Re: fishfinder confusion

Originally posted by PSulli5494:<br />[QB] Oh yea who is it that is claiming they use a DC-DC converter on these production sonar units. Have you guys seen the transducers ... again they are cheep plastic units feed by a 24-20 awg cord. <br /><br /><br />I think it was me. I'm not so sure of anything as of late. True enough with the wire gauge thing, but I don't think power is measured at the transducer. Rather at the main unit on the secondary side of the DC-DC converter. And I'm positive that converters are used on high powered model. Correct me if I'm wrong.

 

[Paul Sullivan]

Re: fishfinder confusion

guys I'm not trying to beat up on anyone or "be right" ..all I'm saying is buyer be informed. <br /><br />Besides the technology going into these fish finders is making them incredibly powerful tools for the weekend warriors out there ...<br /><br />Again I'm happy with my mid priced unit ....so far.<br /><br />However the Interscope side scanning sonar gives an incredible picture of the bottom and what's in front of your boat but 3 G's is a bit much for my little tuna chaser. Over on a scuba forum a guy posted pics of what it can do as far as looking at the bottom... you can actually see a car submerged in 100' ffw ....amazing but very exensive

 

[Realgun]

Re: fishfinder confusion

My fish finder has so much power I run the boat over the lake and the fish float to the top already cooked. <br /><br />Oh thats the Atomic Power rating never mind. <br /><br />Depending on the area you fish is how much power you need. <br /><br />Salt or deep you need more.<br /><br />RMS is 1 way to compare however some finders cheat on this information.<br /><br />If you have less power but a better reciever then your in the same boat again.