The previous A3S tests (2/15/20) showed the minimum SWR on the wrong frequency (especially on 20 meters) and higher than desired SWR. Today, all element lengths were checked and verified as being tuned for mid-band. MFJ told me that the reflector and director should stay with book values. Only the driven element should be adjusted. The reflector and director were left with "mid-band" settings (14.2, 21.275, and 28.350 MHz). The A743 kit, which adds 40 meters to the driven element, was also initially set to mid-band, though the manual does not specify what that mid-band frequency is.
The table below shows the reflector element lengths. These are the mid-band lengths from the A3S manual.
|Boom to TA||8' 1/2"|
|TA to TC||6 1/2 "|
|TC to End||3' 1"|
The table below shows the director element lengths. These are the mid-band lengths from the A3S manual.
|Boom to TA||6' 5"|
|TA to TB||2' 11"|
|TB to End||2' 11"|
The driven element segment lengths were adjusted to get the minimum SWR frequency close to mid-band on each band. Element segments were adjusted as required from the boom out since the segments close to the boom affect all bands, and the outermost segment affects only the lowest band (40 meters).
|Segment||Length from Manual||Length as Adjusted|
|Boom to TA||6' 11 1/2"||6' 10 3/4"|
|TA to TC||6"||5 3/8"|
|TC to TK||19"||17"|
|TK to End||5' 3 1/8"||5' 3 1/8"|
The images below show the resulting VSWR for each band after the adjustments to the driven element. The span of
each sweep was adjusted to keep the VSWR below 2.0.