[RGK20m3]

My radio is a 38-690 that is located in my basement media room of my condo and is a walkout, approximately 50 miles north of downtown Detroit.  Good reception  is generally limited to the 2 local powerhouses (760 WJR and 950 WWJ, both 50,000 watt 24 hour stations), and my 1/4 watt transmitter using a cheap loop antenna.  Night reception with a 50’ random wire inside allows some listenable stations up to 750 miles away, but with much noise.  Tried the unused telephone wiring with very poor results.
I tried a 20’ random wire in the first floor attic (about 17’ above ground) using a 50’ coax lead in; no matter how I grounded the receiver, coax shield, or un-un the reception was worse and noise increased. I built a milk crate tuned loop with a twisted pair 10’ lead in and get about the same reception as the 50’ random wire....noise is reduced due to the directional/null that is inherent.
My questions are- what is the length of twisted pair lead in before noticeable degradation of performance? What should the twist per inch be for best performance? Would power supply conditioning help? Anyone have any other ideas of something that might work better? Outdoor antenna is not an option.