PL-360 radio tuning series connected  twin stranded wire 74 uH  coils over separate ferrite sleeve tests. Connected they measure 147 uH. Radio connected  between coils and jumper across the outer ends of the coils, per Polydoroff.

First I tried one contra wound coil and one wound in the opposite direction. Poor results with ETM scan station counts, and pattern appeared to be oval with the less rounded ends at the ends of the forms.

Then I tried same direction winding of the two coils-

First experiment was spacing between coil/ferrite assemblies by ETM scan counts First number is inches apart between windings. Second number is how many stations the ETM scan found MIDDAY.

11" -34 stations
9" -33
7" -33
5" -32
4" -29
3" -29
2" -32
1" -33

Second experiment I tuned three stations across the MW band and noted the best RSSI readings, then rotated the loop 90 degrees to compare the null. at 1 inch spacing and again at 11 inch spacing

560 WHYN best RSSI 49-53 & 18-22 @1 inch, 32-36 & 18-21 @ 11 inches
        90 degrees off    38-40 & 16-18 @1 inch, 26-28 & 15-18  @ 11 inches

1080 WTIC best RSSI 53-55 & 16-19 @ 1 inch, 49-51 & 18-22 @ 11 inches
         90 degrees off    44-46 & 11-13 @ 1 inch, 40-42 & 10-14 @ 11 inches

1600 KHz   best  RSSI 36-38 & 13-17 @ 1 inch, 39-43 & 13-17 @ 11 inches
         90 degrees off    33-36 &   8-12 @ 1 inch, 38-42 &  8-16 @ 11 inches
-FARMERIK