To put it as simply as I can - an antenna cut to a chosen frequency will " capture" the signal far better then a random length. The radio will never know what di-pole it's receiving from, it's just listening for the strongest signal. A tuner will never improve the signal strength of a station as it is not an rf amplifier. First thing to remember is this is ONLY a receiving antenna, so a tuner will not be required and would only make a slight difference on receive by, maybe reducing some backround noise. I've attached a simple diagram to give you an idea. This worked a treat for me and was for better then any " desk top" antennas or rubber ducks and was as good as a loft mounted discone.
Do this to hook up 4 or 5 different length di-poles and then the last coax length goes to your scanner.
This time connect the coax from the first di-pole to the coax of the second di-pole in the choc block connector and to the relevent upper and lower elements of the di-pole. Cut the coax to a length convinient to connect to the next Di-pole.Do the same again with a longer Di-pole for a lower frequency. Now simply tack the di-pole between your ceiling joist and your roof joist with a nail or drawing pin. Simply measure out the lengths of wire for your interested frequency ( remember you will need 2 of the same length for each di-pole element ) Connect your first di-pole elements into the choc connector ( remember that the centre conductor of the coax connects to the upper element and the outer braid to the lower element. All you need is a quantity of surplus copper wire ( the earth strand from house wiring electric cable was ideal ) ?1's worth of low amp "choc block" connector strip, and some 50ohm coax and a plug to hook it up. That's when I came up with my "Raft of Di-poles" experiment. After studying the photos of one, I had a thought, hang-on, this is no more than a bunch of random length di-poles with a central feed point. Many years ago, when I first started scanning ( with a Bearcat SX200 ) I longed for a Radco " Nest of Di-poles " antenna.