Raymarine Dragonfly

Chemdawg

Petty Officer 2nd Class
Joined
Aug 31, 2013
Messages
112
Hello everyone. Just looking for some info. I have a really old Humminbird graph in my boat, and want to upgrade it to something with GPS and Sonar. My boat is a 17.5 foot fiberglass boat, with 3.0L Mercruiser. It's kind of a combination boat for fishing, and having fun with the family.

I have been doing some research here on different graphs, and I see this dragonfly. I went to cabellas, and saw it in person, and the display is just amazing. I found one for 560.00 with free shipping, and with the gold maps, and transducer. That is about what I'm looking to spend, and from what I'm reading, bang for buck, it's a good unit. I don't need any of the fancy radar stuff, or anything in that nature. Just something that shows a good picture of the bottom, and can plot charts, etc....

So what do you all think?

Pat
 

dingbat

Supreme Mariner
Joined
Nov 20, 2001
Messages
15,416
Re: Raymarine Dragonfly

What is your criteria for "bang per buck"? I wouldn't judge a unit's performance by the looks of the demo screen.
 

Pez Vela

Chief Petty Officer
Joined
Dec 4, 2004
Messages
504
Re: Raymarine Dragonfly

I think it would be an outstanding choice for your application because it incorporates some of the most recent technologies at a surprisingly low price point.
 

dingbat

Supreme Mariner
Joined
Nov 20, 2001
Messages
15,416
Re: Raymarine Dragonfly

I think it would be an outstanding choice for your application because it incorporates some of the most recent technologies at a surprisingly low price point.
The surprising low price point is because they're playing games in their advertising. It's nothing but conventional "dual beam" sonar with a lower resolution DI
 

Pez Vela

Chief Petty Officer
Joined
Dec 4, 2004
Messages
504
Re: Raymarine Dragonfly

How do the RM advertising claims differ from the reality? I have been a victim of some RM advertising shenanigans with my own gear, but I hoped those days were in the past. What are the specifics?
 

dingbat

Supreme Mariner
Joined
Nov 20, 2001
Messages
15,416
Re: Raymarine Dragonfly

How do the RM advertising claims differ from the reality? I have been a victim of some RM advertising shenanigans with my own gear, but I hoped those days were in the past. What are the specifics?

They imply that the unit uses "CHIRP processing", which is true in the narrow definition of CHIRP, but its not the same technology being marketed as CHIRP sonar in other units.

CHIRP is better described as spread spectrum sonar. Instead of sending just 1 single frequency, CHIRP sends a continuous sweep of frequencies ranging from low to high then interprets frequencies individually upon their return. This continuous sweep of frequencies provides a much wider range of information giving a much clearer, higher resolution image. The technique requires a special transducer to broadcast and receive the wide spectrum of signals. CHIRP transducers start @ $400 and go up from there.

Then there is "Dual beam". Dual beam is a software function. All transducers produce a secondary, lower frequency (wider beam, lower resolution) as a side affect of the primary frequency. Whereas a conventional sounder would filter out the secondary returns as noise, the dual beams listens to both returns and uses software filters to “fit” the secondary, lower resolution returns into a viable, "higher" resolution data package for display.

Spread spectrum and Dual beam are miles apart from a performance standpoint and the cost reflects this.
 
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Pez Vela

Chief Petty Officer
Joined
Dec 4, 2004
Messages
504
Re: Raymarine Dragonfly

Interesting ... thank you. The first thing I just did is to check the specs on the Dragonfly transducers, to see what the frequency spread was, if any. I could not find such a specification, which is in keeping with your explanation. Then I found this in the FAQ's:

"CHIRP sounders are normally much more expensive, does Dragonfly truly use CHRIP?

Yes. Both channels use CHIRP signals to produce exceptional resolution and low noise."

If RM wants to confuse me, they're doing a pretty good job.
 

dingbat

Supreme Mariner
Joined
Nov 20, 2001
Messages
15,416
Re: Raymarine Dragonfly

Interesting ... thank you. The first thing I just did is to check the specs on the Dragonfly transducers, to see what the frequency spread was, if any. I could not find such a specification, which is in keeping with your explanation. Then I found this in the FAQ's:

"CHIRP sounders are normally much more expensive, does Dragonfly truly use CHRIP?

Yes. Both channels use CHIRP signals to produce exceptional resolution and low noise."

If RM wants to confuse me, they're doing a pretty good job.

If you go to the specification page in the manual they state the frequencies are "centered on 200kHZ" and "centered on 350kHZ". If you go to the tech info for Ray's "real" CHIRP sounder, they give a frequency range of 25-250KHz. The "wide" cone angles they advertise alone are a pretty good indication that they're using "dual beam" processing of the secondary emissions.

The processing of the secondary emission is by definition "CHIRP" but the technology is far cry from the "Spread Spectrum" technology known as "CHIRP" .
 
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Pez Vela

Chief Petty Officer
Joined
Dec 4, 2004
Messages
504
Re: Raymarine Dragonfly

Sounds like a true CHIRP vs. a quasi-CHIRP distinction, not likely to be understood through all the marketing hype, certainly not by me until now. Thanks for the education. This situation is analogous to the early HDTV marketing hype in which shoppers wanting an HD set found some great price points, only to later find out that they had purchased a 720 set (by definition HD because it surpassed the STD sets they had at home). They swallowed hard when I told them they could have had a 1080 set for a couple of hundred more. "But the salesman said ours was a hi-def set."

Well, it was, sorta.
 
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