The C31XR-JK (Tribander) has been re-designed, optimized & Improved from the very popular Force 12 Tribander of all times for contesters and Dx’ers.

3 Elements on 20M / 4 Elements on 15M / 6 Elements on 10M / 30 Foot

Here are the important changes/features from the classic design ….

1. The Boom has been shortened by a foot to make it a 30Ft boom yagi

2. The feed point for 20M, 15M & 10M are connected using a transmission line, the same way as the JK-MidTri & JK-BigTri.

3. The mast mount position is right at the center of the antenna at 180″ with a gap of 25″ on either side for a total gap of 50″, which enables unhindered mounting on ring-rotors or side-mounting on towers.

4. The total number of elements on 10M has been reduced by 1 (one) element while optimizing gain and swr.

5. The overall gain and swr on all bands is consistent & provides excellent performance. (click here)

Price : US$1,895.00 **

Approx wt. = 110 lbs

Wind Area = 12.4 Sq. Ft

Max Wind Speed = 100 Mph

Max Turning Radius = 24 Ft

Feedpoint = Direct 50-Ohm

Peak Gain is shown over a dipole in Freespace
Dipole in Freespace = 2.14dBi

FREESPACE PLOTS – Single Antenna

	10M	15M	20M
Number Elements	6	4	3
Active Boom Length	24 ft	24.5 ft	26.5 ft
Peak Gain*	8+ dBd/10+ dbi	7.5 dBd/ 9.5+ dbi	6 dBd/ 8.2+ dbi
Peak F/B	20+ dB	15 dB	18 dB
Peak F/R	20+ dB	15 dB	18 dB
2:1 SWR Bandwidth	850 KHz	Less than 1.6:1 across the band	Less than 1.5:1 across the band
1.5:1 SWR Bandwidth	650 KHz	450 KHz	350 KHz
Max Element Length	18 ft	24.25 ft	36.5 ft

C31XR-JK : NEC4 – Freespace Gain, SWR & F/B values

Freq	R	X	SWR	Gain	Azimuth Angle	F/B	F/R
14.000	55.38	-23.00	1.561	8.22	0	16.86	16.86
14.025	53.35	-20.02	1.478	8.23	0	17.34	17.34
14.050	51.44	-17.17	1.402	8.24	0	17.75	17.75
14.075	49.63	-14.45	1.335	8.25	0	18.07	18.07
14.100	47.92	-11.84	1.278	8.26	0	18.29	18.29
14.125	46.28	-9.33	1.232	8.27	0	18.40	18.40
14.150	44.73	-6.91	1.202	8.28	0	18.40	18.40
14.175	43.24	-4.58	1.192	8.29	0	18.29	18.29
14.200	41.81	-2.33	1.204	8.30	0	18.08	18.08
14.225	40.45	-0.15	1.236	8.31	0	17.81	17.81
14.250	39.13	1.97	1.283	8.32	0	17.47	17.47
14.275	37.87	4.03	1.340	8.33	0	17.09	17.09
14.300	36.65	6.04	1.406	8.35	0	16.69	16.69
14.325	35.48	8.00	1.479	8.36	0	16.26	16.26
14.350	34.35	9.91	1.558	8.37	0	15.83	15.83

Freq	R	X	SWR	Gain	Azimuth Angle	F/B	F/R
21.000	52.94	-25.35	1.634	9.50	0	15.66	15.66
21.025	54.09	-19.77	1.471	9.53	0	15.62	15.62
21.050	55.30	-14.68	1.344	9.55	0	15.58	15.58
21.075	56.53	-10.09	1.253	9.58	0	15.54	15.54
21.100	57.77	-6.01	1.200	9.60	0	15.49	15.49
21.125	58.96	-2.46	1.186	9.62	0	15.44	15.44
21.150	60.06	0.55	1.202	9.65	0	15.40	15.40
21.175	61.00	3.02	1.229	9.67	0	15.36	15.36
21.200	61.68	4.96	1.256	9.69	0	15.31	15.31
21.225	62.01	6.38	1.276	9.71	0	15.26	15.26
21.250	61.87	7.35	1.285	9.73	0	15.21	15.21
21.275	61.16	7.96	1.280	9.75	0	15.14	15.14
21.300	59.77	8.35	1.264	9.77	0	15.05	15.05
21.325	57.65	8.70	1.240	9.79	0	14.94	14.94
21.350	54.79	9.20	1.219	9.81	0	14.79	14.79
21.375	51.27	10.05	1.221	9.83	0	14.59	14.59
21.400	47.21	11.44	1.273	9.85	0	14.34	14.34
21.425	42.78	13.48	1.390	9.87	0	14.03	14.03
21.450	38.20	16.22	1.576	9.89	0	13.64	13.64

Freq	R	X	SWR	Gain	Azimuth Angle	F/B	F/R
28.000	44.58	-5.84	1.184	10.01	0	16.08	16.08
28.050	46.90	-3.48	1.101	10.05	0	16.50	16.50
28.100	49.15	-1.60	1.037	10.09	0	16.98	16.98
28.150	51.21	-0.22	1.025	10.13	0	17.52	17.52
28.200	52.95	0.70	1.061	10.17	0	18.17	18.17
28.250	54.22	1.24	1.088	10.23	0	18.95	18.95
28.300	54.93	1.56	1.104	10.28	0	19.88	19.88
28.350	55.07	1.86	1.108	10.33	0	21.01	21.01
28.400	54.69	2.31	1.105	10.38	0	22.31	22.31
28.450	53.97	3.05	1.101	10.42	0	23.64	23.64
28.500	53.13	4.12	1.106	10.44	0	24.51	24.51
28.550	52.44	5.40	1.123	10.46	0	24.22	24.22
28.600	52.11	6.56	1.145	10.46	0	22.73	22.73
28.650	52.19	7.01	1.155	10.43	0	20.76	20.76
28.700	52.17	5.88	1.130	10.37	0	18.86	18.86
28.750	50.46	2.44	1.051	10.28	0	17.25	17.25
28.800	44.21	-2.10	1.140	10.12	0	15.96	15.96