Furuno 1870

[profisher]

Mine is just a 2 piece unit..here are a few pics...have posted them before

 

[Sr SQ]

I think you may be confusing the transducer's transmitter side with the receiver side.

No........I understand both sides.
Its only transmitting 10% of the time.....the other 90% its listening
Thats why the Q factor of the ducer is so important, if the element spends a large period of time ringing after the ping it effects the return echo.

 

[Sr SQ]

I had also looked at one of these Airmars in 1kw

The TM260 is a great ducer but not the best unit for our application of trolling for salmon because it has a pretty narrow cone width, the 200hz side at 100' is only showing you a cone 11' across.
The ss270w has a cone 45' across at the same 100' on the 200hz side and a slightly better Q factor.

 

[ziggy]

No........I understand both sides.
Its only transmitting 10% of the time.....the other 90% its listening
Thats why the Q factor of the ducer is so important, if the element spends a large period of time ringing after the ping it effects the return echo.

Are you talking reverberation level or pulse length? I'm not familiar with q factor.

 

[profisher]

The wider the cone the more power you need from the sonar itself to keep your sensitivity up. I prefer the dual frequency models 50 & 200hz. Narrow beam with good single fish definition abilities and a wide beam for locating bait balls.

 

[ziggy]

The old adage was always low frequency longer range, higher frequency better target definition. And yes beam width makes a difference, much like if you took two flashlights out and one had a concentrated beam, the other a wider beam. With the same power you would see farther with the concentrated beam, but a lot more with a wide beam. In sonars that is directivity index. Pretty easy to see that transmission power is only part of the equation, but easy to understand and measure so usally a major part of any sales pitch. Power output, frequency,directivity index and receiver sensitivity all are factors. While not as big a factor in low power units, the ocean environment plays a huge role in military grade sonars. As such they adjust power,frequency, pulse length etc to get the best results.
It's hard to get a lot of the technical info and sometimes it's of dubious quality. I think the best thing is to poll the users, which is why these forums are great.

 

[profisher]

Sounds like we should be shopping military surplus!!! lol

 

[ziggy]

Sounds like we should be shopping military surplus!!! lol

Depends on what you're looking for. Lol. Wouldn't advise it in 200 ft of water in any case.

 

[Sr SQ]

Are you talking reverberation level or pulse length? I'm not familiar with q factor.

Yes the reverberation, tough for me to put in words but........
Q is the transducers quality factor, all Airmar ducers have a Q rating.
Q describes the amount ringing the ceramic element ( piezoceramic ) undergoes when power is applied to the transducer.
Ringing is not a positive because the element should have the ringing dampened out for best results in target separation and bottom imaging.
The lower the Q number the less ringing in the transducer and thus the higher the quality of the unit.
A single element 600 watt transducer may have an average Q of around 25-35, where as the average multi element 1 kw transducer will have a Q of around 6-12.

 

[Sr SQ]

The old adage was always low frequency longer range, higher frequency better target definition. And yes beam width makes a difference, much like if you took two flashlights out and one had a concentrated beam, the other a wider beam. With the same power you would see farther with the concentrated beam, but a lot more with a wide beam. In sonars that is directivity index. Pretty easy to see that transmission power is only part of the equation, but easy to understand and measure so usally a major part of any sales pitch. Power output, frequency,directivity index and receiver sensitivity all are factors. While not as big a factor in low power units, the ocean environment plays a huge role in military grade sonars. As such they adjust power,frequency, pulse length etc to get the best results.
It's hard to get a lot of the technical info and sometimes it's of dubious quality. I think the best thing is to poll the users, which is why these forums are great.

Agreed, ping output power has been grossly over marketed and not the whole picture.

As with everything in life he quality of the build is always more important than the sum of the parts IMO

I was amazed at the improvements I seen when I hooked my 270w to my HDS, even though the HDS output is only 250w........ definition was hugely noticeable over the stock unit.