Antenna wire should be a half wave (468/f ) based on a frequency in the middle of the lowest band to be used. Note: due to design limitations, transformers that cover 80-10m will not work on 160m.
The counterpoise should be .05 wavelength of the lowest band. So for 80m this would be 936/3.75 MHz x .05 = 12.5 feet. When a wire counterpoise is used, a choke balun is best placed right behind the 49:1 transformer.
In lieu of a wire counterpoise, you can allow the coax shield to act as one. When used in this manner the choke should be inserted in the feedline at a distance from the transformer equal to the calculated counterpoise length, i.e. 12.5 feet. This portion of the feedline must also be up off the ground and can be in any orientation but should not run under the antenna wire.
If your feedline is above ground and runs under or parallel to your antenna wire, another 1:1 balun is recommended in the feedline as it enters your operating position.
