Quote:
Originally Posted by
jerrisn 
I liked this idea, but took it a step further. In addition to placing the ferrite on the power cord, I thought, what else could be causing EFI? The only other possible cause could be the antenna itself.
I am currently using a
Winegard SquareShooter SS-2000 amplified antenna. I have had this well over a year and it works great. I thought this may be a good source of interference as well. Has anyone thought about trying a ferrite on the coax into the box?
So far, I have had no reboots today even while recording multiple shows simultaneously and watching a 3rd. I had been getting several re-boots prior to this.
Here is my theory. There are many sources of noise in digital circuits. Almost all devices that use digital logic have clock generators that are used to shift data through registers. These clock generators typically are very noisy creating what is sometimes called grass because of how it looks on an oscilloscope. They are very fast rise time spikes. This noise is radiated if the device does not have good filtering and shielding. Now what happens to other devices in the area (like the DTVPal DVR) is the power cord (or other cables that have parallel conductors) act like an antenna and pick up the spikes (RFI). These spikes if not filtered out can get through the power supply and ride on the logic voltage and trigger gates and registers when they are not supposed to be. This can cause the processor to reboot because of an illegal event.
The power cord is the most susceptible to picking up the RFI because it is not shielded. Coax, like the antenna or audio and video cables are less susceptible because they are shielded. Also Ethernet cable is UTP (unshielded twisted pair) and is what is called balanced. Noise picked up on the UTP conductors is canceled because of the twisted balanced pair. So typically you don't need to put a RFI filter choke on Ethernet cable. Now it may be helpful to put it on HDMI cable if your using cheap HDMI cable that is not shielded.
Anyway I counted twenty three digital devices in my house, from microwave oven to two PCs, VCRs, DVD players, TV monitors, and even clock radios. It's now been ten days since I choked my DTV Pal DVR power cord and no reboots. I had previously been getting between 1-3 reboots per day. I'm not saying this is the absolute cause of reboots, there may be many. But so far it is working for me.
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