A3S Inspection

On 2/15/20, I pulled down the Cushcraft A-3S with A-743 40 meter kit for inspection. The resonant frequency of each trap was checked. Element lengths were changed slightly to move from the phone bands to the center of each band.

Trap Resonant Frequencies

The table below shows the test result of each trap as checked with a Sark 110 antenna analyzer. The resonant frequency (Fo) was determined by looking for the zero-crossing of Xs.

Trap Number	Type	Fo (MHz)	Description	Rs, Xs
1	TK	6.767440	New trap. Used on driven element due to close match with trap 2
2	TK	6.647285	Repaired trap. White insulator on hot side of trap had burned up. This is now used on the driven element since it matches trap 1.
3	TK	7.248060	This is a new trap that had replaced trap 2 when it burned up. Howver, the repaired trap 2 has been put back on the driven element since it matches trap 1.
4	TK	6.887595	This was an original TK that came with the A-743 40 meter kit. However, traps 1 and 2 match better, so they were used instead of traps 3 and 4.
5	TC	11.213175	Driven Element
6	TC	11.213175	Driven Element
7	TA	14.217050	Driven Element
8	TA	13.976740	Driven Element
9	TB	11.693795	Director
10	TB	11.573640	Director
11	TA	14.577515	Director
12	TA	14.096895	Director
13	TC	11.093020	Reflector
14	TC	11.093020	Reflector
15	TA	13.976740	Reflector
16	TA	14.096895	Reflector

VSWR - Antenna on Tripod

After reassembly, the antenna was mounted on the tripod near the bottom of the mast. VSWR sweeps were run from the coax input in the shack. 40 meters looks good. Other bands are tolerable. The minimum VSWR on 20 meter is 1.99 at 13.934 MHz. Other bands have a low VSWR, but it is not mid-band.

VSWR - Antenna at Top of Mast

The antenna was moved to the top of the mast and swept again from the coax input in the shack. VSWR and frequencies are pretty much the same. There's an evaporative cooler below the mast, so tests were done with the antenna pointed a couple directions to see changes in VSWR.

Pointed North	Pointed West