HDS transducer angle

[Pooch]

I can't find any information on the degrees of coverage using the Down Scan feature on the Lowrance HDS units. Lowrance never answered my inquiry.

While I'm thinking of it, is the coverage on the 83 and 200khz transducers both 20 degrees? For some reason I was thinking that the 200 was wider. Not sure where I got that. Probably in a nap..........

Pooch

[LWinches]

Technically the 200 is 20 degrees at -3db and the 83 is 60 at -3db. All this degree business is a bit misleading as Humminbird also advertises 20 degrees and 60 degrees on theirs, but their specification is at -10db. On top of that Lowrance advertises that their fish detection extends to 60 degrees on the 200 khz and 120 degrees on the 83 khz. My experience is that there is something to this. It's not all just hype. I'd say the reality is that their fish detection is real but not that wide.

I've not seen a published degree angle on the down or side scan but Lowrance Customer Service did send me a chart of the measurements of the width of the cones at different depths. This link may help if you can get it to work for you.

http://winchester1.zoomshare.com/fil...m_Lowrance.xls

[Pooch]

What does the negative db mean? Is it the rate at which the cone gets less effective or "weaker".

If I understand sonar correctly, 20 degrees is just a number to estimate the most effective area of coverage. All transducers transmit and receive wider, but are most effective within the 20 degree angle.

Am I thinking straight on this? I guess I am using radio tower thinking as far as "coverage". Gain antennas transmit a more focused signal, but still have a peripheral signal above and below the focused transmission. These radiators have a positive DB gain rating applied to them.

Pooch

[LWinches]

The cone angle means nothing without knowing at what signal strength it is measured. -3db is used by many because that is the point where the power drops to half.

http://primus.lowrance.com/icr/Sonar/Cone_Angles.htm