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Hair Dryer interfering with digital TV (HD and SD)

13K views 29 replies 9 participants last post by  Grayed Cogopoly 
#1 ·
I'm having problems with the reception of digital TV on my DVR. Whenever someone uses a hair dryer in the house, the picture/sound degrades dramatically. I am fairly certain that it is with the receiption/decoding of the signal, as it effects recording (so the picture/sound is degraded when watching a recording, even if the hair dryer is not in use at that time).

A brief description of my setup:
Out digital reception is poor in this area, so we have a booster. This is the kind that is plugged into the power next to the TV, and has a wire going into the antena jack in the wall.
From here I have a splitter, with one cable going directly to the computer (some people like to watch analogue TV still), and the other to the PC acting as a DVR.

What can I do about this? Its driving me crazy.

Thanks.
 
#2 ·
Impulse noise is certainly a possibility. This is a form of RF intereference emitted by the electric motor in the hair dryer. You'll probably find that a different hair dryer would help (or possibly be worse!), but there's no way to say for sure until you plug it in and try it.

You could also try insulating the receiver and coax connections, but that would be considerably more difficult.
 
#5 ·
The hair dryer is causing the noise, I guess we're sure of that. Is the dryer plugged into a bathroom GFI outlet? How old is your house/wiring? With that info I can probably tell you something...it has to do with outlets downstream of a GFI one and noise immunity.
 
#7 ·
The house is about 5 years old. I havnt really looked into the circuits (as in, how many their are in the house, if they are on the same one, etc). I had kind of assumed they were on different ones, due to the fact that they are at opposite ends of the house.

I dont know what GFI means, so I cant answer that. But the hair dryer is plugged into a bathroom power plug.

I might see if they are on the same circuit later...
 
#8 · (Edited)
It was a guess, without knowing wiring circumstances.

GFI outlets will be in one or more bathrooms, they have a couple buttons on them. Builders will often use just one GFI outlet to protect all the bathrooms and outdoors too, maybe even the kitchen...anywhere water is likely.

I have spent a lot of time in the past fighting with outlets downstream from GFI outlets. Luckily I work with electricians, and even they were stymied, we had to dig deep into the Code to get some clues. The way they wired my house ('86), circuits snake all over the place. Designed for load balance I guess...things have changed ALOT for the types of electronics we plug in nowadays. You never know where an outlet downstream of a GFI one could be in this house.

Bottom line is, either pop the GFI (you test that monthly, right?? LOL) or open that circuit at the breaker panel and see if your HT gear dies. If so, put it on another circuit. Don't want to share your good "delicate" stuff with a GFI circuit if at all possible, they're designed to protect YOU, and unfortunately make it harder to "protect" equipment downstream on the same circuit (contrary to what "logic" would suggest).

Edit: I just checked a dryer (on low) on the same GFI circuit (but FAR away physically) from a plugged in AVR: HUMMMM. So nothing has changed, LOL. Actually, just the fact they're on the same circuit period is bad enough for hum/noise, GFI or not.

Realised I didn't offer a solution: as JohnnyG says, try another *circuit* (not just a random outlet) for the gear. Another dryer is unlikely to make much diff.
 
#9 ·
Thanks. I'm in Australia - are you sure they use GFI here? To my knowledge, in Australia, they put a single earth leakage switch thing in the fusebox (which is wired to all of the circuits), so if something stupid happens (Person touches live wire, etc) the earth leakage trips and turns off the whole house.

Anyway, I had a quick look at the fusebox, and it seems there are only two circuits for power (according to the labels), which increases the odds the TV and hair dryer are on the same circuit. I'll have to wait a bit to test this though (people will miss their electricity at this time of the morning).

And if I do find they are on the same circuit? I buy a long extensions cord for one of them?
 
#10 · (Edited)
Sorry, I didn't notice your location. So forget the GFI thing I said.

Two circuits? Do you mean two phases? I am WAY out of my league on Australian power/wiring... The way they do "GFI" in Oz sounds like a good idea. Our way is half-assed and cheaper, but easier/safer to retro-fit I guess.

It's probably easiest to see if moving the dryer around makes a diff, instead of moving around where you plug the TV in. I do not like extension cords for HT gear myself, but wouldn't mind quite so much for the TV if I had to do it.

If you do have two phases of wiring coming into your house, and normal stuff only uses one phase (how it is in North America for a normal home), then it's a great idea to put your HT gear on a different phase from equipment with motors that comes on automatically (fridge/freezer) or erratically (hair dryer) or regularly (furnace, if you have them there...). Central A/C is hard to avoid since it uses both phases (here). This would be ideal, but typically you have to "rearrange the circuits" to get this and/or install dedicated HT gear circuit(s).

Edit: well, I see I screwed up again! A quick check shows you use 220-240VAC there. I have ZERO idea how it's provided to your homes, and if you even have two phases delivered to homes (but I bet you do). And you called it a fusebox: is that what it is, not breakers, or is that just the common name?
 
#11 ·
I too missed that you were in Australia, but that just makes it all the more likely that your problem is impulse noise, as your DVB-T/COFDM based digital TV standard is much worse in this regard to the North American ATSC/8VSB standard.

Assuming such a thing exist there, a hair dryer with an AC motor (most are DC motors) should make a big difference as it generates significantly less impulse noise.
 
#12 ·
I appologise to both of you. I only updated my location details before my last post, which would explain why you missed the Australia bit (I really should have mentioned that earlier).

I dont really know the difference between a circuit and a phase I'm sorry. When I say "circuit", I am refering to a single circuit breaker in the fusebox - and everything that is connected to a given breaker is on the same "circuit". Sorry if my bad use of jargon has confused you.

ok - i have done some testing with one hair dryer. It seems that different plugs have different results - the plug for the stove (It has its own circuite breaker in the fusebox) causes no interferance at all, as does another normal plug elsewhere in the house, but it is not practical to use these. Also, running the hair dryer on low (It has two settings - low and high) causes next to no interferance. But I cant guarantee my family will always do this...

I call the box a "fusebox", but we dont use fuses anymore - just breakers (and an earth leakage).

I'll do a bit of research into AC vs DC motors for hair dryers. The one we are using now says it is AC, but that could just be the power it needs - not the type of motor in it.

I was kind of hoping I could just buy some sort of "Line conditioner" or something, to hook up the TV gear to, to ensure it had a good supply of electricity.

Thanks.
 
#13 ·
Most hair dryers have a diode in the circuit to the motor. So though you power them with AC, the motors are actually DC (cheaper). I know nothing about hairdryers with AC motors: how would you know by looking at the labeling etc.? Sounds like a good idea though...hairdresser supply shops would have the better hairdryers, the ones with AC motors probably. I once inquired about a "better" build of hairdryer as I was tired of them burning out so often, and I was surprised how much more expensive they are. Meant for pros and all-day use...

You could no doubt use some type of line conditioner to do what you want. It's usually best to condition the noise source, if you can, to prevent the noise from getting into the system. Rather than to condition everything else to keep the noise out. Again, IF you can.

I can tell you, for instance, that the most expensive APC "filtered" power bars will likely not do it, I used two types of those to do that test I mentioned the other day.
 
#14 ·
I can't say the cause of it for sure (i.e. wiring), but its the massive power draw by the hair dryer (some are like 5000W, or some insane amount..)
I had an old (still works, i just replaced) cheap pair of speakers (there's the problem :p) - but whenever someone would flick on a light/whatever, they would pop, or crackle. I brought them out to use temporarily on another computer, and there's a paper shredder in the room. When you flick it on, the massive draw of power makes the speakers pop, hiss, crackle like crazy.
Your dvr is probably experiencing a similar issue, resulting in degradation of picture. You could try a UPS - this would provide 1) a battery buffer, so you don't lose function, and 2) power conditioning to your electronics.
You wouldn't need a large one, and they're fairly cheap now - often the same price as a high quality surge protector (unless you get into the long-duration ones, they cost considerably more).
 
#15 ·
Thanks again for your replies,

I'm starting to lean towards the UPS idea. Getting a new hairdryer sounds like a bit of hit and miss, and it may be expensive/difficult to get an AC one. UPS's are everywhere, and if I buy from the right place, they'll take it back if it doesnt do what I wanted it to.
 
#16 ·
Some information is missing here. What type of reception is this... OTA, satellite or cable? Signal boosters are next to useless if not mounted at the antenna or dish. Cable amplifiers need to be at the service entrance. They usually cause more problems than they solve otherwise. Coax cables and connectors need to be top quality, minimum RG6 and compression connectors. Poor quality cables and fittings are a frequent source of signal loss and noise introduction.
 
#17 ·
The signal in question is DVT (Terrestial - I think that would be OTA, if that means "over the air").

The signal booster *is* on the antenna (on the roof) - the power supply for it, however, is plugged in next to the TV.

I am unsure about the quality of the cables - in the past I have thrown out one or two cables as they were causing problems.
 
#18 ·
Hmmm, I wonder why this is in *this* section now??

Again, it's usually a much better idea to eliminate noise at the SOURCE. This is optimum if you have that option. If you don't do that, the next time you add some "sensitive" electronics in another location, you'll likely have to suppress the noise there too. Well, I'm speaking from the point that I have 4 systems around the house, so maybe that makes the decision easier for me to attack the source.

I have seen TVs look worse WITH a UPS than without one, under normal use...depends on the UPS type. You will have to try it 1) to see the piccy isn't degraded and 2) it keeps your hd noise out. Depending on TV type and its power draw, and how the UPS provides power (i.e. full time battery or not), the UPS could get a bit pricey. If it's full-time battery there is little doubt it will solve the hd noise problem.

Off-the-shelf brute force filters guaranteed to filter the hd noise at the source would likely be pricey and ugly, so I can't in good conscience recommend that for most people. I'm sure something could be done better/cheaper if you wanted to make this into a scientific experiment...assume you don't. The quality fully-AC hd might just solve the "source" problem and be a nice gift...
 
#19 ·
Well, the reason why I'm leaning towards a TV end solution is because we have one TV/DVR, and two bathrooms each with a hair dryer.

I've had a quick search for hairdryers, and found this site:
http://www.sunbeam.com.au/products/product.cfm?sec_id=22&page=1

As you can see, the Nutrihair one seems to have both an AC and DC version, which would indicate it is what I'm after. Maybe I should try to find a retailer with a generous return policy...
 
#21 ·
This is NOT interference running through the electrical wiring, so no UPS or line conditioner is going to help. It's Radio Frequency interference in the air, generated by the DC motor inside the hair dryer. This RF is entering the receiver through any number of ways. There are definitely some things you can correct yourself, but there are also some that you can do absolutely nothing about as they are design issues within the receiver itself.

For a bit of historical perspective, early DVB-T receivers in the UK would gitch even when a light switch was flicked on/off, or a car with leaky ignition cables would pass by the street outside. It was a very big problem that was largely overcome by improved antenna installation techniques and by improved receiver design.

AC motors simply emit less RF. In my experience, hair dryers so equipped state right on the packaging that they use an AC motor...it's something of a marketing item (although I'm not sure what the real benefits are other than noise emissions). If you look at the boxes, you might find one that says "Powerful AC Motor", etc.
 
#22 · (Edited)
Wow, that is a very important point! I didn't know it was RF interference, I'm more used to dealing with AC powerline noise so erroneously lumped it in. You're sure it's RF eh? I am kinda surprised that type and low level of RF noise would bug a TV much, affecting AM radio I could see. But truthfully I don't know... Still, it seems the better solution is the same in that the source (hairdryer) is best addressed IMO.

Edit: Nope, it's definitely not RF noise here, if we mean RF through the air and not the AC powerline. Plugged the hd and an AVR into the same outlet: noise. Left the hd plugged into the same place, plugged the "line conditioner" back in, AVR into that: no noise. hd is a cheapie Conair. Not saying it *couldn't* be RF noise in some cases, but the hd and AVR were right beside each other here, tuned to an AM station then FM. [don't get hung up on the line conditioner here, it was used just to see if through the powerline, or through the air]
 
#23 ·
COFDM modulation breaks the RF channel into thousands of "slices" with data riding on each one of those. One minor RF spike can disrupt ALL the those slices, so even a millisecond of interference can cause a loss of video because so much data is lost.

North America's 8VSB is more like serial communications where a millisecond of interference will only destroy a comparatively tiny amount of data, and error correction can usually fix it.
 
#24 ·
Wait a minute!. If it was RF, then the results in post 12 about using different power outlets (circuits in the home) contradict this, unless it was because that other outlet put more distance between the dryer and the "TV".

If you use an extension cord from that other outlet and put the dryer in the "normal place", do you still get interference? If not, then it's the power outlets (different circuit) that are the issue, and not RF.

If you do get interference from another circuit (using an extension cord to put the dryer in its usual spot), then it is RF.
 
#26 ·
I had the similiar problem, until I fixed it.
Maybe you can relate.
I use a digital cable provider.
The QAM system has a frequency range that was being interfered with by my hair clipper.
The clipper only interfered with some channels not all. A specific frequency, electric motor(?).
The issue was a bad cable shielding caused by using cheap cable and/or cable connections.
I changed the problem cable. Problem solved.
Hope this helps.
 
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