05-04-2018, 12:37 PM
The ZigZag antenna is in effect an end fed antenna, in other words a co-linear antenna.
In co-linear antennas the phasing between elements is somewhat important as it determines where the angle of the maximum beam radiation. Thus as the frequency changes so does the beam tilt. Getting this right for the frequency you want may be difficult. This difficulty increases with more elements in the antenna the as beam becomes narrower. Unfortunately the beam cannot be seen and certainly does not show up in VSWR readings. Adjusting the VSWR as suggested in the ZigZag antenna article by altering the length of the end element finishes up playing with the beam tilt. There is no point in having a good VSWR with gain in a direction that is of no use.
Feeding each radiating dipole in parallel ensures that all the dipoles are fed in the same phase and overcomes the beam tilting as the frequency changes. If beam tilt is required with this feed arrangement this is achieved by varying the length of the feeder cables to achieve the desired fed phase difference between the dipoles.
Unfortunately achievable the theoretical antenna gain and pattern can be quite somewhat elusive! I am still looking for an easy solution.
To date I still have not found the ideal antenna, but I am still looking.
PS: Beam skewing is fine. TV stations use it. However it needs to go where it is needed!
In co-linear antennas the phasing between elements is somewhat important as it determines where the angle of the maximum beam radiation. Thus as the frequency changes so does the beam tilt. Getting this right for the frequency you want may be difficult. This difficulty increases with more elements in the antenna the as beam becomes narrower. Unfortunately the beam cannot be seen and certainly does not show up in VSWR readings. Adjusting the VSWR as suggested in the ZigZag antenna article by altering the length of the end element finishes up playing with the beam tilt. There is no point in having a good VSWR with gain in a direction that is of no use.
Feeding each radiating dipole in parallel ensures that all the dipoles are fed in the same phase and overcomes the beam tilting as the frequency changes. If beam tilt is required with this feed arrangement this is achieved by varying the length of the feeder cables to achieve the desired fed phase difference between the dipoles.
Unfortunately achievable the theoretical antenna gain and pattern can be quite somewhat elusive! I am still looking for an easy solution.
To date I still have not found the ideal antenna, but I am still looking.
PS: Beam skewing is fine. TV stations use it. However it needs to go where it is needed!