Following on from my 2m Band Eggbeater Satellite Antenna here’s the design for the 70cm Band version that will enable duplex satellite operation.
The design is basically the same as the 2m antenna but, with smaller dimensions. All modelling has been done with the antenna at 5m AGL.
Each of the Eggbeater loops has a conductor size of 5mm and a circumference of 73.5cm with the radials exactly 5cm below the bottom of the loops. The 8 radials are exactly 34.15cm long each. The distance between the bottom of the eggbeater loops and the radials must be 5cm to get the best radiation pattern from the antenna.
With these dimensions the antenna has an SWR of <1.5:1 across the whole 70cm band making it ideal for both satellite and general repeater/SSB working.
The 3D far field plot shows that the antenna has a good mix of high and low angle radiation that makes it ideal for working satellites at all elevation angles.
The 2D far field plot shows that the antenna has the following high gain lobes:
6.43dBi @10 Deg
5.15dBi @40 Deg
3.4dBi @60 Deg
4.83dBi @80 Deg
The null at the top of the antenna isn’t as pronounced as on the 2m model and so this antenna should perform better when the satellite is directly above. Just like on the 2m band version, this antenna must also have a feed phase angle of 90 degrees between the two eggbeater elements. It’s very important that the phasing harness is built accurately as it can impact the radiation pattern of the antenna if the phase angle isn’t correct.
ON6WG has written an excellent article on how to create the phasing harness using 2 pieces of coax cable, this is an ideal solution for this antenna.
More soon …