Hello Alan and happy holidays.
1st..you really don't need a tuner.. Basically what you have is a antenna 
used for listening, not transmitting as I first thought.
2nd, Yes a tuner would help for receiving by providing a resonant tuned front 
end for the untuned ant, etc. I would use a store bought type preselector 
which has a front stage amplifier, etc.
3rd a simple circuit would be a "T" network such as ;
                on the antenna side of the "T", a variable cap
                on the rcvr side of the "T", a variable cap
                in the middle of the "T", a coil, tapped to ground
                caps could be approx 250mfd
                coil approx 28uh or 2- 2 & 1/2" dia 6-8 tpi 5" long, top part
                to the "T" and tapped bottom end to ground.
To use, set caps mid point, try various setting on coil, then rotate ant cap, 
and then rcvr end for max signal.
 let me know how you make out.... 73's larry.. WB2LBF .
       -----|(-----|------)|-----
                        |
                        )
                        (<-|  tap with aligator clip
                        )  |
                        (  |
                        ) --
                        |
                        -gnd
--- QuickBBS 2.80 GoldBase (Zeta-1)
---------------