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General Questions/Information

Emissions from your AVR

I thought I would summarize for folks this whole issue in the hope that a million new threads on the same topic will not be suddenly spawned based on the posting over at Industry Canada. The information contained herein is culled from numerous boards and Internet sites and my own electronics knowledge in an effort to present facts, not myth. I've done my best, but the truth is out there [and maybe slightly off in this doc!] :)

Additionally, I did not want to get too technical here, so I've included some links at the bottom to help with terminology and concepts of RF/EMI

What are EMI and RF?

Almost all electrical and electronic devices in use today give off some sort of Electro Magnetic Interference (EMI) when in operation. A common form of this EMI is Radio Frequency Emissions (RF) AKA Radio Frequency Interference (RFI). Theses emissions can be purposeful or a by- product of operation. A couple of purposeful examples would be your cordless fone (900MHz or 2.4Ghz) or your microwave (2.4GHz). Your computer is a great by-product type emission. Many of the components of a PC (CPU, keyboard, video card) all contain an oscillator, which is a device that produces a sine wave. Attached to these devices are cables, which will act as an antenna and (passively) amplify this RF output. That is why you will find bulbs or bumps at the end of your keyboard/video (and others) cables. Contained in these bumps is a ferrite bead or ring which acts like a sponge in sucking up RF and turning it into heat in the bead. In order to preserve radio spectrum so it can actually be used, all these devices are required to shield against these emissions (including your IRD!).

What is this 121.5Mhz of which you speak?

121.5MHz is the frequency of the sine wave (and part of the radio spectrum) that has been reserved by many countries around the world for aircraft emergency beacons. By triangulating on the signal, rescuers can locate downed aircraft.

How is it produced?

The jury still seems split on how this RFI from your AVR is produced, but suffice to say that by having an external device that is working with the internal clock (oscillator) of your IRD, you are in effect transferring the RF from inside your protected IRD case to the outside "air". Once "outside", the RFI can travel. The IRD oscillator works at 4.5MHz and through the magic of physics, is transformed into an RFI radiating at 121.5MHz.

Range?

We're not dealing with huge voltages here (think of some AM radio stations that produce 5000Watts or more of output power and now we're talking!), but it has been shown that the AVR output can be detected outside the home and the frequency it emits is 121.5MHz.

Solutions? - Feel free to PM me with any ideas!

Couple of possible options:

1) quit testing and return to CAM and sub
2) move your AVR internal (inside IRD) and connect using RJ11 fone jack (this option is not for the electronic faint of heart and it requires modifications to your IRD that could render it inoperable!)
3) use copper tape (that is grounded) around the contacts of your AVR and IRD to deflect the emissions.
4) Arm yourself with knowledge and assess the threat yourself. There are alot of factors to consider with RF and RFI and it is very possible that you are already in a situation that any risks are low to none.
5) do #4 and sit tight!

Tinfoil is not such a good idea as it can act like an antenna and make things worse.

Panic?

At this point, NO! Please read all that you can on this subject so we can all help to prevent folks from freaking. The game has taken a new twist however: the AVR and it's cousins have been deemed harmful by the Fed's and this changes things a wee bit.

Bottom Line:

Hang tight! This is a hobby for many of us and as such, there are folks who are constantly trying this and that. A definitive solution (be good or bad) will be found. Touring around and trying to trace all of this 121.5MHz that seems to be out there would be a monumental task, and while proof of emissions could conceivably be used against an individual, I'm highly skeptical that this alone would cause the "trucks" to show in your neighbourhood.

Some other notes:

Cable companies routinely drive and scan their coverage area. The are looking for leaks in their cable network that are causing emissions. Theses leaks produce scorn from the Fed's and result in fines...no need to go running for the shelter if seen! :)

I have a friend in another part of the country who lives across the street from an airport. She has been testing for a couple of years now with no issues whatsoever!

Here is another trick: copper tape! Hava look at this pic:



Note the copper tape touching the ground pad!!

Links for more info:

Industry Canada

Oscillators
How Radio Works
Sine Wave/Waveform