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Home > Rhombics > W6AM Handout c. 1964
This is KB1SG's W6AM Handout c. 1964. It was written by Ian W. Cummings, KB1SG, and is displayed here with his permission.

W6AM Handout c. 1964

Present W6AM: All #8 copperweld wire, feeders #8, 2 7/8" spaced.

W6AM uses 25 acres for 8 rhombics, 16 directions. The 25 acres is equpped with poles 30' from the property lines.

Antennas tend to be the length or width of the property and adjacent antennas are about +/- 10% larger or smaller to reduce interaction to practically zero. No 8 copperweld wire is used for antennas and feeders. No spacers are in the feedlines. Side poles are not put, the corners are pulled up with a cable to any convenient pole.

Feed lines: 2 7/8" #8 copperweld for 478 ohms. The rhombic transformer is made up by the down lead, 3 1/2 feet at teh top to 2 inches at bottom of pole, i.e. 600 ohm to 468 ohm.

That permits all 16 feedlines to come into the station, each pair 16" from the other. That spacing eliminates reasonable interaction. Sizes (i.e. widths are based on ARRL antenna handbook computed for 14175 kc and drawn on graph paper to determine resultant log lengths. All antennas work fine on 6 to 160 meters.

W6KPC computed sizes on some of the rhombics, and helped put up one of them. All rhombics are best as single wire (1 curtain) for then there is room for more rhombics.

Lengths are based on wherever the poles are; poles are up as high as possible. Antenna heights are 60 ft to 140 ft. The longer rhombics are the best. There are now end poles up for four more rhombics (total 24 directions). When there is time these will also go up.

There are 10 poles 140 ft high and 17 poles 100 to 70 ft high. The rhombics are about as follows tip to tip length:

460', 580', 600', 600', 700', 750', 950', 1050'

and cover 16 directions.

The proposed rhombics to go on poles already up will be:

1350', 900', 1200', 1125' tip to tip length

Then the station will be considerably better for then there will be even more choices as to directions. One direction or one slightly different angle tends to be better at any given time.

Surplus 75 ohm 300 watt non-inductive globar or equivalent resistors are used as terminations, six in series totalling 450 ohms, on each end of each rhombic in the station. The resistor center tap is grounded on all ends at all times, except the one being used, so lightening has never hit due to this up in the air perpetual ground shield. About 100 special home built relays are used for fast small 24 contact rotary switching. Each relay blade is mounted at least one inch from the relay coil, so there is almost zero loss in the relay switching system of about 100 relays.

The rhombics appear to average better than the rotaries in the vicinity as neighboring hams frequently compare weak signals over the land line. Reception paths normally appear to open up 20 to 30 minutes ahead of 100' high rotaries in the vicinity, and reception stays in longer.

W6AM has been on the top of the DXCC a part of each of five consecutive years, has the all time top AM SS contest score, was in three DX contests last year and won first place for the area in the classification used in each contest. It is frequently asked to be used as an emergency station when problems develop at normal stations.

 
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