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Antenna System Details
My antenna system covers HF and VHF from 160M to 6M and is composed of a Force12 C4E for 10M thru 20M a Cushcraft A503S A503S for 6M, a bent inverted vee for 80M and 160M Tx and a K9AY loop for 80M and 160M Rx. All antennas except the K9AY loop are mounted on an Aluma Tower T-50H crankup tower. This tower only weighs about a 100 lbs and is very easy to crank up and down. The complete system, including the tower, antennas, mast and rotor only weighs a total of about 180 lbs including 21 pounds of coax and rotor control cable.
The Bent Inverted Vee uses 14 gauge stranded wire and is fed with 450 ohm 14 gauge stranded ladder line. It is supported at the top of the tower at a height of 47 feet. The legs are not equal length and are bent back on themselves because of lack of real estate and available supports. One end runs 72 feet north from the tower to a 24 foot pole attached to a fence and then back to within about a foot of the tower for a total length of 144 feet. The other end runs 56 feet south from the tower to a tree that supports it at 25 feet and then back to within 1 foot of the tower for a total lenght of 112 ft. I use it primarily for 80M and 160M although the ladder line and my antenna tuner allows me to use on any band from 160M to 10M. Because of the less than optimal SWR on the WARC bands on the C4E, I made gain and pattern comparisons between this inverted vee and the C4E. These patterns can be accessed via the link below. It is interesting to note that the C4E beats the inverted vee in gain on all the WARC bands (even 30M) even though the C4E has additional SWR coax losses that the ladder line does not. The C4E and inverted vee have about the same gain on 40M except that the C4E is rotatable, so the C4E wins again. Take a look at the comparisons.
The C4E has 2 full size elements on 20 and 15 meters, 3 full size elements on 10 meters and a single linear loaded element on 40 meters. I also use it for the 17 meter and 12 meter WARC bands. The SWR is not that good on the WARC bands but it works with an antenna tuner. I have an EZNEC model of sorts for this antenna that seems to predict its performance fairly well. The patterns predicted by this model for the various bands as well as the measured SWR curves are shown in the links below. All gains are in dBD The SWR is 2.6:1 and 5:1 on 17M and 12M respectively. This yields an SWR related loss of about 0.7 dB on 17M and 2.0 dB on 12M. Note that the gains shown in the patterns has this SWR loss included.
The pictures to the right and below show the arrangement of the antennas on the tower as well as how the coaxs and rotor control cable are routed and attached. The 6M antenna is located about 5 feet above the C4E. There are two aluminum supports attached to the tower. A 4 foot support is centered and attached to the top section of the tower. The left side supports the cables. The right side supports the inverted vee using a pulley. You can see the ladder line sloping off to the right. A second 3 foot support is attached to the top of the lower section of the tower to route the coax and control cables. The two pictures below show the arrangement at the top of the tower in more detail. The coaxs are threaded through a rubber hose and clamped to the top support using aircraft clamps and cable ties. I have found that simply taping the coax does not last. A simple U-Bolt is used as a guide for the cables on both the upper and lower supports. As the tower is cranked up or down the cables just thread through these U-Bolts. I use an old hose reel attached to the house keep the coax orderly when the tower is cranked down.
A K9AY loop is used for 80M, 160M and broadcast band receive. It provides a cardiod pattern that is switchable in 4 different directions using remote electronics containing relays and a transformer in conjunction with a control box located at the operating position. I have oriented the loop so I can point it NE, SE, SW or NW. Although it does not have much gain, it provides QRM and QRN cancellation that is more important than gain for low band receiving.
Schematic for my Remote Electronics
Schematic for my Control Electronics
A Spreadsheet that shows some simulation and actual test results
The picture at the right shows the loop in my backyard. You can see that my yard is not exactly huge and that the antenna takes up a substantial portion of it. I erected a PVC mast guyed in two place with the loops supported at the top. There are a number of metal objects near the loop including: 1.) my tower which is about were I was standing when I took the picture, 2.) a 20ft pole bolted to the back fence that supports the end of my inverted vee, 3.) a utility power transformer on the other side of the block wall, and 4.) the clothes line in the forground of the picture.
Coax and control cables are buried. The coax is RG-213. For the control cable I used 5 wire sprinkler cable.
This picture is a closeup of the remote portion of the K9AY loop electronics that I built. It is attached to a 3/4" copper pipe that I pounded into the ground to provide the necessary earth ground. The wires from the antenna are plugged into the box using banana plugs. When the grass needs to be mowed, I simply unplug the wires from the box and slide the ropes that hold the insulators to the mast up. This allows me to just duck under the antenna wires when mowing the lawn.
The control unit is shown below. The toggle switch at the left switches between 80M and 160M. The rotary switch controls the loop selection and direction with the direction indictated by the four LEDs.
