The K9AY
Reference article by Gary, K9AY himself |
Control box schematics (at the base of the antenna) I like the possibility to adjust the termination resistor through K3/K4/K5. ==> Optimum F/B on 160/80/40m ! This variable resistor is optional, but nice to have in case of multi-band use. Resistor type must be carbon-1 Watt minimum, preferably 2 Watts. |
Controller box (in the shack)
Control K1 and K2 to select the direction of the antenna
1) northeast, when neither relay is energized; 2) southeast, when K1 only is energized; 3) southwest, when K2 only is energized and 4) northwest, when both relays are energized Same "diode matrix" principle usable to control the resistors. ==> 1 rotary switch for direction, 1 for resistor adjustment |
Common mode & noise incursion
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Full-size K9AY is a low-gain antenna : -23dBi of gain on 160m, -13dBi on 80m; And its performances are ground dependant.
==> As for all low-gain antenna, there could be some noise incursion (common mode issues).
Remember, in the antenna control box, there are 2 grounds : Antenna ground, station ground.
By default,
- Antenna and station ground must be separated/isolated.
- Relay ground is connected to station ground.
==> Ideally, both coaxial cable and control cable should have ferrite beads (type 71 for instance) to prevent common mode noise.
For the antenna ground, minimum is to place a 6 feet ground rod. Additional radials may help, and must be connected only to the antenna ground point.
Checking procedure :
1. Disconnect loop wires and find the strongest Broadcast signal, measure it.
2. Connect loop wires and measure the new signal level ==> there should be a ~ 40dB difference.
If not, try to connect relay ground to the antenna ground instead of the station ground and/or add 2 to 4 radials
==> As for all low-gain antenna, there could be some noise incursion (common mode issues).
Remember, in the antenna control box, there are 2 grounds : Antenna ground, station ground.
By default,
- Antenna and station ground must be separated/isolated.
- Relay ground is connected to station ground.
==> Ideally, both coaxial cable and control cable should have ferrite beads (type 71 for instance) to prevent common mode noise.
For the antenna ground, minimum is to place a 6 feet ground rod. Additional radials may help, and must be connected only to the antenna ground point.
Checking procedure :
1. Disconnect loop wires and find the strongest Broadcast signal, measure it.
2. Connect loop wires and measure the new signal level ==> there should be a ~ 40dB difference.
If not, try to connect relay ground to the antenna ground instead of the station ground and/or add 2 to 4 radials
Results on the air
160 SSB : K9AY versus inverted-V @ 105feet high !
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W0ANT K9AY front-to-back ratio test on AM broadcast
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