I have DirecTV. Before anyone asks, yes, I’ve been through every level of their technical support AND had one of their techs come out and poke around.
So, that said… whenever I run my microwave, my DirecTV goes nuts. I get sound distortion, massive artifacting, and after a few seconds the signal cuts out completely as the box struggles to cope. When the microwave goes ping and finishes, everything comes back as normal.
I’ve tried isolating the 'wave to a different circuit - same problem. I’ve pointed the front, back, and sides of the microwave in different directions relative to the DTV box AND dish, just in case. Nope, no fix.
This leaves me to wonder what the cause could be (to say nothing of the technical support team and repair tech). I’m leaning towards ‘my microwave is leaking’, but that seems a bit far-fetched to me. Admittedly, I don’t know exactly how the shielding on them thingies works, but I’ve inspected it and can find no bad connections, broken grounds or leads, etc. (I am certified for TV/VCR repair and have fixed microwaves before, lest anyone shudder in fear that J. Random Homeowner is poking around with a screwdriver in the wrong places)
So, I’m a bit stumped. I haven’t tried giving my DirectTV box a tinfoil hat yet, and doing that to the dish seems like shooting the patient to cure the disease. Any ideas from the Dope?
My guess would be electrical noise being fed into the mains. Could you fit a low pass filter to the microwave that would block higher frequencies than the mains frequency (60Hz?).
Try a different microwave and see if there is any difference?
Oh hey, I didn’t think about noise at the mains level. Hm… I don’t have a filter handy but I could knock on the neighbor’s door and ask to use an extension cord for, uh, scientific research. He’s a nice guy, he’ll say yes.
I forgot to mention but I have tried a different microwave. That’s what’s leading me to think the ‘leakage’ idea is wrong - I mean, chances are that even if I have two defective microwaves, it’s not the same defect, right?
And this is the third box to exhibit the problem, too - the one upstairs does the same thing and the tech replaced the downstairs one last time, with no effect.
It’s fairly likely that his main electrical supply comes off the same line, probably even the same transformer, as the one that supplies your house. So the electrical noise generated by your microwave would just travel back thru the extension cord, out his main house wire to the electric company transformer that also serves you, up thru your main incoming electrical wire, and into your TV box. It might be less, after traveling a longer distance, but probably still there.
You don’t have a filter handy? What about on the computer that you use to post here – don’t you have some kind of a filter/power surge protector on that? You could temporarily remove it from the computer (leaving the computer unplugged) and plug the TV box in thru that, and see if it helps any. It might block some of the noise from reaching your TV box. If it does, then you can solve your problem by buying another power conditioning unit for your TV box.
Another possibility is that your microwave is leaking microwaves around your house, and these are messing up the TV box. If so, this could be dangerous to you or anybody around your microwave. Get it checked! There are ways to check a microwave for leakage (just take it in to nearly any repair place and they will probably test it for free).
Not as such, no. Laptop, which I tend to recharge at work. Heh. At home it gets a Wal-Mart special power strip, along with my cellphone and other rechargable gadgetry.
My workbench has an isolation transformer, which (in theory) should do what’s required, but putting it in the middle (for the box OR the 'wave) isn’t changing much. Then again, I’m not sure if the transformer includes filtering circuitry. sigh It hasn’t come up before. (Most VCRs and TVs which require filtered power do so themselves, within limits, and that’s about all I work on these days.)
Um… perhaps? I’ve worked in a couple of repair places that saw microwaves every day, and not one of them had a way to test for leakage. Could’ve been that the owners were cheap, I s’pose, but I don’t think it’s as widespread as you seem to think.
I’ll call around once places start opening, see if any of them know how to do it. But as before, what’s the likelihood that two microwaves would display the same behavior? I’m willing to admit The Beast is probably defective – it’s probably 15 years old, big enough to cook a turkey in – but the Newer! Faster! Better! model I’ve got does the same thing.
There’s an easy way to test if this may be the problem. Most microwaves have an selectable power level; what this does in the majority of ovens is simply cycle the magnetron on and off with a duty cycle equal to the power level setting, for example, if you set it to 50% power, it will run at a 50% duty cycle (on for a few seconds, off for the same amount of time). If you have a very old oven with a mechanical dial, this will also work if it has a Cook/Defrost selector, since the defrost setting also runs it at less than 100% duty, usually around 50%. In any case, stick a glass of water in the oven and run it for a short time at ~50% power. If the interference comes and goes, the problem is with the HV/magnetron circuit and possibly (but not definitively) a leakage problem.
Also see my Staff Report, What keeps microwave radiation from leaking out the oven door? for some information regarding some possible causes of and solutions to microwave oven leakage. To summarize: keep the door seal CLEAN. The door is the cause of leakage in the vast majority of cases. If it is cracked or otherwise damaged, it should be replaced. The integrity of the door seal is critical to maintaining the integrity of the oven cavity’s Faraday cage.
Damn, missed the edit window. I wanted to add: If it turns put to be a power line noise problem, which is quite likely, you may be able to alleviate or even eliminate the problem by putting ferrite chokes on either the microwave oven’s power cord, or on the cords for the satellite TV receivers or both. They can be had fairly cheaply, so pick up a handful of them and experiment with different configurations. Often, more than one choke on a line may be needed, if the noise level is high.
Just a hunch, but is there any chance that there’s any non-RG6 cable in the dish installation? Or a damaged section of cable? Either could let in enough microwave energy from the oven to swamp out the microwave energy from the satellite.
As for the idea that the oven may be polluting the AC power, a hefty inverter or a UPS could run the oven for a short while on battery power. Or a generator. (Got any RV camping or disaster-prepared neighbors?) If the interference is gone, then you’d know it’s putting garbage into the powerline.
FWIW, all of my home entertainment gear is protected with a Panamax powerline filter, and the satellite box and Squeezebox (an MP3 player) are also protected with a UPS. The Panamax does a fine job of keeping static from things like hair dryers or kitchen mixers out of the picture, and the UPS protects against power glitches - we have more hits on our line than you might expect with underground utilities.
The seal is clean and uncracked (I did check the staff report first, heh).
Looks like it is line noise, though. I scrounged a few chokes from around the shop and played around. With the four I have handy, I get the best results by putting two on the oven and the other two on the signal line from the dish to the DTV box. Even so, there’s still massive artifacting, but the sound is back and the box is able to compensate somewhat for the video signal problems.
I do believe the Dope has solved it. It’s funny; I’ve always been telling people not to bother with the do-it-yourself chokes because I’ve never seen them do anything before. Guess I need to change my tune… :smack:
Well, now I need to go work on that mug of tea that I’ve been reheating over and over again this morning while testing the oven. Thanks, Q.E.D.!
If the through opening in the cores is large enough, you can increase the inductive reactance by looping two or more turns of the cord through it, provided you also have enough excess cord length, of course.
He’s a nice guy, he’ll say yes.
Thanks, Q.E.D.!