I have 2 locators mounted on my boat, one on the back transom, the 2nd is on my trolling motor. The one on the trolling motor has taught me that the non-mounting side of the transducer is what is reading the water depth/column. I figured that out by spinning the motor near shore. What I have to determine is how close to the transducer is the reading? Is it straight down  - or does it broadcast forward (or backward on the transom mount) and how far?

20 degree cone, aprox 1/3 of depth.

http://fishinweb.com/messages/messages/13028/13028.html?1254779454

The transducer signal is like a flash light beam or your shower water; it's about 1" diameter at the transducer face and spreads out in a cone shape. Most fresh water transducers use a 20 degree cone angle some are wider 38 degrees.

Yes your transducer signal is pointed straight down. It's true the signal diameter, like the flash light spot size, is about 1/3 as wide as the water is deep; 15 foot water depth, the signal spot on the bottom is about 5 feet in diameter. Keep in mind the cone gets smaller the closer the return signal is to the transducer. At 15 foot depth, the bottom signal is 5 feet in diameter and if the fish is 10 feet deep, the cone is only 3 feet in diameter where the fish is located...small area!

Also keep mind your sonar screen only shows you a history of what you have passed over; everything displayed is behind you!*

I didn't read the link offered and it may define all this more clearly.

Don Iovino's book Finesse Bass Fishing and the Sonar Connection is written for bass fisherman, easy read and very informative.

Tom

* the far right edge of the screen is in real time.

The transducer signal is like a flash light beam or your shower water; it's about 1" diameter at the transducer face and spreads out in a cone shape. Most fresh water transducers use a 20 degree cone angle some are wider 38 degrees.

Yes your transducer signal is pointed straight down. It's true the signal diameter, like the flash light spot size, is about 1/3 as wide as the water is deep; 15 foot water depth, the signal spot on the bottom is about 5 feet in diameter. Keep in mind the cone gets smaller the closer the return signal is to the transducer. At 15 foot depth, the bottom signal is 5 feet in diameter and if the fish is 10 feet deep, the cone is only 3 feet in diameter where the fish is located...small area!

Also keep mind your sonar screen only shows you a history of what you have passed over; everything displayed is behind you!*

I didn't read the link offered and it may define all this more clearly.

Don Iovino's book Finesse Bass Fishing and the Sonar Connection is written for bass fisherman, easy read and very informative.

Tom

* the far right edge of the screen is in real time.

Wait, are you saying that there aren't little fish symbols down there happily swimming right to left going beep, beep, beep?....Oh the humanity!...