The old transducers were round and placed inside the boat sending out a cone shaped beam.  Now they are rectangular and on the back of the boat.  Do these transducers send out a 'rectangular" pattern to the lake bottom?

Most modern transducers can send multiple beams of various shapes.  Both old school cone shapes and beams that are wide from side to side and very narrow from front to back.  These are used to provide very detailed images and side imaging.

 

Here's a diagram of the various beams and frequencies that my transducer is capable of sending.

 

 

Its still a radio wave of some frequency sent out in a very thin plane.  Old transducers were the same (and not a cone per se).  The longer transducers of today have multiple beams coming out of them- one for side imaging, one for down imaging, one for 2D imaging.  Some have many multiple frequencies available in the same transducer.

1 hour ago, casts_by_fly said:

Its still a radio wave of some frequency sent out in a very thin plane. 

No. It's a SONAR, and S is for?...

Just now, Deleted account said:

No. It's a SONAR, and S is for?...

Actually...the SO goes together.

SOund NAvigation Ranging

49 minutes ago, Deleted account said:

No. It's a SONAR, and S is for?...

 

It is in the radio wave part of the electromagnetic spectrum.  1 megahertz (mega imaging) is a wavelength of about 300m.  Older sonar at 80 khz is about 3700m.  Pretty much all other sonar is between the two.  The radio portion of the spectrum is 10^-3m out to 10^8.

8 minutes ago, casts_by_fly said:

 

It is in the radio wave part of the electromagnetic spectrum.  1 megahertz (mega imaging) is a wavelength of about 300m.  Older sonar at 80 khz is about 3700m.  Pretty much all other sonar is between the two.  The radio portion of the spectrum is 10^-3m out to 10^8.

Can't compare SONAR and RADAR

 

Yes, RADAR uses radio waves..which is part of the electromagnetic spectrum - which includes visible light, microwaves, gamma rays, etc.

 

SONAR is pure sound waves - NOT part of the electromagnetic spectrum. Reason you don't hear anything? Average human hearing only goes to around 20khz - 80khz is way beyond what we can hear.

There's still a difference between a mechanical wave and an electromagnetic wave. 

Edit: MN got it before me, lol

1 hour ago, casts_by_fly said:

 

It is in the radio wave part of the electromagnetic spectrum.  1 megahertz (mega imaging) is a wavelength of about 300m.  Older sonar at 80 khz is about 3700m.  Pretty much all other sonar is between the two.  The radio portion of the spectrum is 10^-3m out to 10^8.

I had heard Jersey had good schools...

1 hour ago, Deleted account said:

I had heard Jersey had good schools...

It must for what I pay in taxes.  I wouldn't know though as I've never set foot in one.