- Posts: 206
- Joined: Tue Jan 17, 2012 11:51 am
- Closest Airfield: FAPE
- Location: PE
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The reason has been hard to pin point but with much help from Rainier (CEO of MGL) the cause has finally been explained. All EFIS screens emit electromagnetic energy (lots of it). If you want an EFIS then there is no way around this.
The simple dipole aerial uses the lower pole of the aerial as it's "ground plane". This normally works ok and even gives good figures on an SWR meter, BUT the coaxial cable running back to your radio inevitably goes somewhere within a metre or two of your EFIS. The EFIS interference climbs into the coax shield here because it is acting as part of the dipole's makeshift "ground plane".
The solution......an ugly external aerial with a proper multi poled ground plane like the one in the picture.
Use this link to calculate the various lengths:
Fine tune the aerial length using an SWR meter if you can get your hands on one.