PTP watts and RMS watts

[High Bidder]

I want to install a new FF/GPS unit and am trying to decide which Humminbird unit( I have a Airmar B60 Thru hull trans with Humminbird cable) will work the best. My present 778c unit only works on 200kHz. The 859ci HD XD unit has 8000PTP and 500 RMS. The 788cxi HD XD unit has 4000 PTP and 500 RMS. Both these units I think will work with my 50/200 transducer. But I don't know what is the advantage of a higher PTP rating if any. I believe the B60 is rated at 600 watts. Or should I save more money and go with a unit that has a RMS greater than my transducer? The only reason I am considering the 788 unit is that it would not require me to reposition my current GPS unit to fit in a larger FF unit on my limited space dash. I called Humminbird Customer service about this but they won't discuss hooking a unit to an Airmar transducer so I have to go to the real experts here.

 

Thanks.

 

 

[Sk8man]

Rather than get tangled up in the transmission  power issue (RMS vs. PTP) which primarily is a technical measurement/design decision issue I'd be looking at whether the units you are considering will match up to that particular transducer properly and that the transducer is functioning properly to begin with. Rather than dealing with the Humminbird folks I'd contact the Airmar tech folks (very good at what they do) and tell them which models you are considering and ask whether that transducer will match up OK with them. Most units today have enough power to do the job correctly and high power itself does not not guarantee a better result from a unit (target separation etc. also important design factors in a particular unit) and unless you are doing very deep water fishing (e.g. ocean) most units will have the right composition for your needs in terms of showing fish, structure, and bottom features provided they are properly matched to the transducer and the transducer is installed and placed properly for optimal results (may be especially critical for through hull situation).

Edited February 6, 2014 by Sk8man