CM The K9AY Receiving Loop (optimized for 160 m)
CM by Gary Breed, K9AY
CM first published in QST (ARRL), Newington, Sep 1997
CM The matching transformer is a 9:1 impedance, 
CM 3:1 turns ratio type that should be familiar to many readers. 
CM Five trifilar turns of ordinary hookup wire are wound 
CM on a 3/4-inch diameter (0.825 inch) 43 material toroid. 
CM The terminating resistor (Rterm) value will be between 
CM 390 to 560 ohms depending on your band preference. 
CM With average ground conductivity, a value of 390 ohms provides 
CM the optimum F/B at 160 meters, while 560 it optimizes the loops 
CM for 80 meters. A value of 470 W splits the difference for 
CM "pretty good" performance on both bands. I chose to optimize 
CM the antenna for 160 meter operation, so used a 390 ohms resistor. 
CM Use an Rterm power rating of at least 1 W in case some transmitter 
CM power ends up being coupled to the loops. I use a 2-W carbon  
CM resistor, but two parallel 1/2 W or four 1/4 W units of  
CM appropriate ohmic value can also be substituted.
CM Addition of another K9AY loop may significantly improve
CM the performance.
CM Converted with 4nec2 on 11-jan-03 by OK1RR
CE
SY rt=300
GW 	1 	11	-11.5	0	4.0	-8.5	0	0.01	#12
GW 	2 	11	-8.5	0	0.01	-5.5	0	4.0     #12
GW 	3 	11	-5.5	0	4.0	-8.5	0	6.0     #12
GW 	4 	11	-8.5	0	6.0	-11.5	0	4.0     #12
GW 	5 	11	15.0	0	0.01	18.0	0	4.0     #12
GW 	6 	11	15.0	0	0.01	12.0	0	4.0     #12
GW 	7 	11	15.0	0	6.0	12.0	0	4.0     #12
GW 	8 	11	15.0	0	6.0	18.0	0	4.0     #12
GW 	9 	11	-8.5	0	0.01	-3.0	0	0.01       #12
GW 	10	11	-8.5	0	0.01	-14.0	0	0.01       #12
GW 	11	11	15.0	0	0.01	21.0	0	0.01       #12
GW 	12	11	15.0	0	0.01	15.0	-5.0	0.01       #12
GW 	13	11	15.0	5.0	0.01	15.0	0	0.01       #12
GW 	14	11	-8.5	0	0.01	-12.0	4.0	0.01       #12
GW 	15	11	-8.5	0	0.01	-5.0	-4.0	0.01       #12
GW 	16	11	15.0	0	0.01	19.0	4.0	0.01       #12
GW 	17	11	15.0	0	0.01	19.0	-4.0	0.01       #12
GW 	18	11	15.0	0	0.01	11.0	-4.0	0.01       #12
GW 	19	11	15.0	0	0.01	11.0	4.0	0.01       #12
GW 	20	11	-8.5	0	0.01	-12.0	-4.0	0.01       #12
GW 	21	11	-8.5	0	0.01	-5.0	4.0	0.01       #12
GW 	22	11	-8.5	0	0.01	-8.5	-5.0	0.01       #12
GW 	23	11	-8.5	0	0.01	-8.5	5.0	0.01       #12
GW 	24	11	15.0	0	0.01	9.5	0	0.01       #12
GE	1                                                        
EX	0	6	1	00	1.0	0.0              
EX	0	1	11	00	-0.866	-0.5	'phase angle 210 degrees
LD	1	5	1	0	rt	0	0'terminating resistor 300 ohm
LD	2	2	1	0	rt	0	0        
GN	2	0	0	0	13	.005             
FR	0	1	0	0	1.825                    
EN