Long story short: put FERRITE COREs on your IR blaster wires, close to the MRF.

(Duplicate posting over in the other URC forum)

Here's my sad story:

I've had severe RF interference for some time now on my MRF-250. Seems like no matter where I placed the MRF, there would be some new interference cropping up over time causing intermittent operation. To make matters worse, I have the Motorola DVR from Comcast which is notorious for periodically going non-repsonsive to input commands (either IR or front panel) while queuing up those commands and then finally getter around to executing them more or less all at once.

It was so bad that I had decided to just forget about the whole RF thing and go back to IR exclusively. I just purchased the Spearkercraft IR repeater kit with the intention of converting everything back to IR. Being the engineer that I am, I just couldn't admit defeat and let this damn RFI problem kick my butt. It's just RFI, people have been effectively dealing with RFI for decades. So before I ripped out my existing MRF blasters, I thought I'd give one more shot to isolating the source of the RF in my case.

I first eliminated the power supply path by wiring up a 9V battery on a short cable into the MRF - no change there. Still a bunch of RF interference.

I even tried the whole tin foil thing with the intent of reducing the effective sensitivity of the MRF RF receiver. Figuring the remote control RF signal was hot enough to overcome the attenuation from the foil. Very marginal results here as well.

Then it finally occurred to me... what about all those long IR blaster wires running all over the place? So I began to disconnect them one by one while watching the MRF RF activity LED (in the channel-0 position). Sure enough, there was a direct correlation between those blaster cables and the degree of RF interference. The long IR blaster cables are acting like a bunch of antenae, picking up all kinds of RF noise and apparently injecting that noise into the MRF unit.

OK, I thought, now I'm getting somewhere. So, how do you reduce RF being introduced on these cables? Filters. Either capacitor to ground or series coil. I first thought about getting a small enough capacitor that would act as a high-pass filter, and just effectively short all that high frequency to ground. Probably would work. But then I realized the URC engineers must surely have thought about that and include those small and inexpensive parts internally in the MRF. Right? Anyway, after talking to some other colleagues, they suggested ferrite cores on the cables.

Duh. Simple and cheap solution that wouldn't require ugly soldering and stuff. So I just found a few of these <$1 goodies and looped each IR blaster wire around each core a couple times. This creates a series inductor. BAM - RF interference is gone completely. It's actually hard to get any RF interference now. The whole thing just became rock solid. While your mileage may vary, this certainly has worked for me. And it's a mystery why the talented engineers at URC haven't thought of such a simple solution for their products.

So I"m passing this info along to the experts in this industry. I urge you to try this simple and CHEAP solution. You can find cores like this at your local electronics parts store, or online at places like digikey:
[Link: dkc3.digikey.com] (clamshell type at bottom of page).


URC - if you happen to be reading this and would like to thank me for solving your design problem, I would be happy to accept upgradeable software for my MX-850. I purchased LOCALLY (not over the internet) from a custom installer who I later discovered is not an authorized dealer. This only recently became an issue for me when you made your liveupdate policy change :)