Tower #1 - left on the photograph (since 1990) ( lattice steel tower - side length 30 cm (12 inches)) a la ROHN 45, anchored on four sides.
CD-45 rotator, shock absorber, first thrust bearing: Yaesu GS-065 - above shock absorber, second thrust bearing (homebrew, heavy duty) mounted on the top, steel mast OD 2" - 8.5 meters ( 28 ft long).
- 20 - 3 el yagi (old design - W2PV with omega match), boom 5,89 m (19´ 4´´) - left tower @ 17,4 m (57 ft)
- 80 - inverted vee - on the top of the lattice tower @ 15 m (50 ft)
Tower #2 - right on the photograph (since 1984) ( tubular tower), anchored on three sides.
- 160 - inverted L - (55 meters ---> 25 m vertical / 30 m horizontal)
- (wire on the top of the right tower = 15,5 m steel tubular tower (108 mm tube diameter on the top) + 50mm 5m Al tube + fibreglass mast 4,75 m) @ 24,8 m (82 ft) + 1 (one) elevated radial (January 29, 2012). I added second radial (January 26, 2013).
-80 - 1/4 wave vertical + 2 elevated radials (March 7, 2012)
- 40 - 2 element (wire) delta loop with parasitic elements (feeding point is quarter-wavelenght down from the apex - vertically polarized) - hangs on rope between the towers@ 15 m (50 ft). Antenna is fixed to ---> 300 degrees. For receiving antenna on 40 I often use 80m vertical antenna, especially for directions PY, VK, ZL, JA with less noise.
Driver + director, spaced 6 m (20 ft). Driver is tuned on 7100 kc ,
director is tuned 2 % higher --> 7240kc
In "free space"you can cut director wire simply 2 % shorter.
In my case there is impact of surroundings (driven element is 20 centimeters over the top of concrete garage. Very closed to the bases of the both loops). I tuned director on 2 % higher resonant frequency --> 7240 kc.
Procedure - tuning 2 element delta loop with parasitic elements (my case): driven element + director:
1. Mount two pulleys on 6 to 8 mm diameter rope, distance is 6 meters (20ft). In my case, the height of rope was 15 meters (50 ft). Make driven element loop (wire is 1.5 mm diameter Cu). Make 4:1 transformer (1/4 wawelenght of 75 ohm coaxial cable ). Use transformer to make RF choke (turns of coaxial cable, on (aproximately) 11 centimeters diameter, 20 centimeters long PVC tube). Rope which will carry the element draw through a pulley, then pull isolator of the loop (driven element - apex) to the place.
2. Tune driver to the center frequency (7100 Kcs). (I had measured with SWR meter only - without antenna analyzer). Finally tuned antenna element drop on the ground. (Leave it on the ground when tuning second element - director!)
3. Use the 4:1 coaxial transformer from tuned driver and connect it to the director - just for the tuning procedure. Place second element to the final height and tune it 2% higher (on 7240Kcs). (In case that you haven´t possibility to use wooden support to support heavy RF coaxial choke, match 4:1 coaxial transformer (RF choke) in the down corner (on the one end of the base). When director is tuned, disconnect 4:1 75 ohm coaxial cable transformer and short connect the loop (in my case - short connect PL female connector.)
4. Connect 4:1 75 ohm coaxial cable transformer back to the driven element and mount driven element to the final height. Connect antenna to the transciever and enjoy DX-ing.
Driver impendance is transformed down with 4:1 transformer --> quarter-wavelenght 75 ohm coaxial cable.
299.8/ 7.1 = 42.225 m /4 = 10.556 m x 0.82 = 8.66 m long 75 ohm coaxial cable (I used new CATV cable with foam dielectric. For velocity factor I took 0.82 - I didn´t check it with network analyzer.)
RX antena : 30 m long beverage (100 f) ---> 315 degrees (February 26, 2012)
Former call signs: YU3TAQ, YU3SB, YU3SB/2, YZ3AA, S53AA
October 1977: started in amateur radio coarse in third year of secondary school (17 years old ).
First licence - 1978 (C licence in ex YU). I have worked on the club station YU3AIJ; YU3TAQ -my first call sign ( B licence in ex YU) - march 1979; YU3SB (A licence in ex YU) 1986 - ; YZ3AA - June 26, 1991; S53AA June 26, 1991 - 1994;
S57W since January 20, 1994 -
Equipment: ICOM IC-781, Yaesu FT-897, ALPHA 77D, TEN-TEC 715i RF Speech Processor, Heil HC-4 mic..
Vector Network Analyzer (May 5, 2015) N2PK (Many thanks to Robert S57AW for advices and support and Joze S51VJ for help with assembling VNA!)
SW: Logger 32, N1MM
9A/S57W - August 22 - August 29, 2015 from NW Croatia (FT-897 + windom antenna at10 meters).
6697973 Last modified: 2015-09-08 22:15:46, 11964 bytes
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