Let's answer your questions one at a time.
How does the Humminbird Smartcast work?
Basically the Smartcast system is a miniature fish finder. Now a fish finder uses Sonar
technology which involves a transmitter and receiver. The transmitter is your transducer which bounces the sound off the bottom or fish and then sends it to the receiver which tells you what is below.
I think that is the simplest way to explain it. The Smartcast technology simply does away with the cables.
It is similar in nature to the remote for your TV.
Do you actually attach a sensor to the fishing line?
Yes. There are actually two ways but the one they recommend is to attach your line to the front hole on the RSS (Remote Sonar
Use a heavier line say 10 lb., than attach a 6 lb. line to the second leader hole. This way if the line snags or breaks you don't lose your sensor. You can use a slip line technique which is not really recommended but use a lighter weight line after the lower stop.
Also remember that the MAXIMUM amount of combined weight attached to the sensor is less than 1/4 oz. or 6 grams. This includes hook, swivel, snap, line and bait.
Can you buy more sensors?
Yes. The life expectancy of the sensor is about 3 years on a shelf and will last about 400 hours of in-water use. The RSS will remain ON if it is WET, so wipe it dry when your finished using it and store in a dry place. Also wash it off if you use it in a Saltwater environment.
Do portable fish finders as the Eagle Cuda 168 work the same way?
Similar but not the same. Both are Fish Finders using sonar, both are portable but from here they change. These type of portables have a cable connected from the transducer to the receiver and can be easily mounted and removed from your boat or used for icefishing. So you won't be mounting them to
your fishing line. They cost a bit more but you get a much bigger bang for your buck.
Which one would I recommend for your husband?
In all honesty, I wouldn't be able to recommend because I don't know your husband but my preference would be toward the Eagle Cuda just for the greater amount of features plus the ability of attaching it to a boat, canoe, or just about anything that floats and rig it up for icefishing.
I guess you will have ask yourself if he is a tourist fisherman, one who just
likes to toss the line in the water when on vacation. The average joe fisherman who gets out with his buddies a half dozen times a year or a weekend fisherman or are you a fisherman's widow?
Hope this helps, if you have any other questions, send them my way and I might be able to recommend something.
Thank you for explaining how the fishfinder works. I was leaning towards the Eagle Cuda and you helped me to decide. Thank you very much for taking the time to respond.
Your quite welcome, I just wanted to let you know there are two types of Cuda 168,
Eagle CUDA® 168 FishFinder w/TM Transducer ($70.39 USD).
I think the one below is the one your looking for
EAGLE CUDA 168 PORTABLE FF PTT-WSU DUCER, PPP-12 POWER PK ($100.49 USD).
The PPP 12 or PPP 13 package includes the power pack, battery adapter and portable transducer. Batteries are not included. Each power pack has a storage compartment for the portable transducer.
The PPP 12 can be used with eight AA alkaline batteries. The PPP 13 can be used with eight D alkaline batteries or an optional sealed, rechargeable battery (would be my choice).
The PPP 12 has a quick release mounting bracket built into the case.
The PPP 13 requires you to attach the gimbal bracket to the case and then attach the sonar unit to the bracket. (no big deal).
When the unit is not in use it is recommended you unplug the power connector to reduce the possibility of corrosion or battery drain.
Eagle fish finders are manufactured by Lowrance, the company that originally created the fish finder. They have an excellent service and warranty department if you ever need it.
You can find more information or if you wish to purchase here --> http://notjustfishing.com/eaglefishfinders.shtml