RF Ingress and some report back from the field..
Posted: Tue May 01, 2007 7:21 am
A while ago I started a thread as a response to certain GPS and electronic instruments and their related feedback into radios. I have spent many hours with certain suppression "beads" loops, caps, coils and anything that I (we, Brian Eaton) and myself thought would work. The biggest culprit of ingress is the Garmin 196/296 series and some Rotax Skydats. I may add also that certain MP3 players also give a rf ingress, namely the Telefunken and certain Game products. The only real solution with these is to increase the squelch (or buy an iPod). The Apple ipods do not give ingress.
The rf comes in to the radio and is independent of the intercom, some intercoms in the field do not have rf inhibiting circuitry and will give some problems, this may be easily overcome with suitable suppression devices.
Radios have a base frequency, Icoms (except the ICA200) are the biggest problem and we focused primarily on the ICA4 as this covers the rest of the range. A Garmin 296 being the rf weapon in question.
As most readers will probably already know; the polarisation of radio waves is either horizontal or vertical..quite standard practice and schoolboy physics. Interference takes the same attitude...
So after failing miserably with suppression the only route to travel is the antenna, physically move it away from the source as far as possible. This only leaves the King Post as the furthest point. Antennas are available for this purpose, no problem they work fine..BUT they are either horizontal or vertical. The desire was to break the interference so we made the antenna out of phase completely. So we tested and made a Vee dipole, this creates other problems with capacitance and other things. The device worked after wearing out my hang point removing it so many times. So in short and nearly 30 sold..the answer may lie in our new antenna. It has also fixed Henks rf induced noise from his skydat in the GT450.
But Rf is a black art and no firm guarantee is given but to date each one has solved the problem with smiling faces. However I may add Brian has a topless wing so we are still trying other means.
Comments on the design is that its rather "Agricultural" but you need a tractor to plough fields..not a Porsche. And they do not look very pretty on the King post..
The performance exceeds the standard 1/4 wave whip antennas.
See attached pics and will keep the forum posted on further trials.
We are making new brackets for three axis aeries, these will be ready in the next two weeks, they also are not very pretty..
Jabula Zulu1
The rf comes in to the radio and is independent of the intercom, some intercoms in the field do not have rf inhibiting circuitry and will give some problems, this may be easily overcome with suitable suppression devices.
Radios have a base frequency, Icoms (except the ICA200) are the biggest problem and we focused primarily on the ICA4 as this covers the rest of the range. A Garmin 296 being the rf weapon in question.
As most readers will probably already know; the polarisation of radio waves is either horizontal or vertical..quite standard practice and schoolboy physics. Interference takes the same attitude...
So after failing miserably with suppression the only route to travel is the antenna, physically move it away from the source as far as possible. This only leaves the King Post as the furthest point. Antennas are available for this purpose, no problem they work fine..BUT they are either horizontal or vertical. The desire was to break the interference so we made the antenna out of phase completely. So we tested and made a Vee dipole, this creates other problems with capacitance and other things. The device worked after wearing out my hang point removing it so many times. So in short and nearly 30 sold..the answer may lie in our new antenna. It has also fixed Henks rf induced noise from his skydat in the GT450.
But Rf is a black art and no firm guarantee is given but to date each one has solved the problem with smiling faces. However I may add Brian has a topless wing so we are still trying other means.
Comments on the design is that its rather "Agricultural" but you need a tractor to plough fields..not a Porsche. And they do not look very pretty on the King post..
The performance exceeds the standard 1/4 wave whip antennas.
See attached pics and will keep the forum posted on further trials.
We are making new brackets for three axis aeries, these will be ready in the next two weeks, they also are not very pretty..
Jabula Zulu1
