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Old 2008-06-09, 07:36 PM   #16
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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.
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Old 2008-06-09, 07:52 PM   #17
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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.
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Old 2008-06-09, 07:55 PM   #18
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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...
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Old 2008-06-09, 08:07 PM   #19
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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/p...c_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...
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Old 2008-06-09, 08:25 PM   #20
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The $100 one with the "Italian leather" handle? To me $100 for a hd is expensive compared to what I use...probably still cheap for a female...
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Old 2008-06-10, 03:00 PM   #21
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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.
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Old 2008-06-10, 04:54 PM   #22
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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]

Last edited by cfraser; 2008-06-10 at 05:14 PM.
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Old 2008-06-10, 05:06 PM   #23
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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.
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Old 2008-06-10, 05:17 PM   #24
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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.
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Old 2008-06-10, 05:47 PM   #25
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Well, as 57 said, there is an easy way to test JohnnyG's theory. I'll whip out an extension cord and give that a go today.

The wife had just OK'ed the UPS idea (this house has two bathrooms & two hair dryers, but only one DVR)
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Old 2008-06-10, 09:13 PM   #26
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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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Old 2008-06-11, 01:03 AM   #27
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OK - another update. I tested JohnnyG's theory, and it appears that he is right - the location of the hair dryer is significant - by moving the dryer as little as 3 metres, the interferance dissapeared. This was the case for two different circuits (or are they phases?) - one that previously showed no signs of causing interferance.

I also tested SonyWE610Owner's theory, that it is the cabling. The cables I'm using right now were given to me by the guy who installed the arial (and booster thing), after I complained that I was having reception problems. He made them using that heavy duty coax cable. He also gave (or maybe sold) me a 3 way splitter (I need to split the signal to go to the TV, and two cables to tv TV cards in the computer/media centre).

I removed all this from the equation by replacing it all (4 heavy duty cables and 3 way splitter) with a single (more lightweight) cable. The result was no change.

I also noted during these experiments that it does not cause interferance to all channels - at least one channel does not suffer from the interferance at all.

So, a quick recap of the facts:
- A hairdryer is interfering with TV reception.
- Reception is digital over the air (DVT).
- I am in Australia.
- Not all channels are effected.
- Physical location of the hair dryer is significant.
- Power plug (Phase/circuit??) does not appear to be significant.
- Running the hair dryer on low reduces the interferance to a barely noticable level (the odd artifact in the picture)
- Aerial has a booster. Booster is on the actual aerial (On the roof), but the power supply is plugged in next to the TV, with power supplied to the booster via the TV cabling in the walls.
- Beleive quality of cables (from wall to TV) is not the issue.
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Old 2008-06-11, 07:13 AM   #28
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Did you try a different hair dryer?

Your hair dryer is giving off EMI from the sparking brushes in the DC motor.

http://en.wikipedia.org/wiki/Electro...c_interference

Try a better brand of hair dryer and I bet the EMI stop.


Since we're on this subject......
My sister brought back a hair dryer she bought in Thailand. Since Thailand uses 220 Volts it was useless here. I cracked it open to see what it was like inside. Since Thailand has no electrical standards the hair dryer had no thermal fuse or even an over heat cutout. It was actually made this way... since it's not required in Thailand... so be careful with stuff like this brought back from Asian countries.
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Old 2008-06-18, 09:10 PM   #29
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I have just had an opportunity to use a second hairdryer (I live in a two hairdryer household). The second hairdryer does not interfere with reception. So it appears it is this hairdryer specifically.

Such a simple test, I'm kicking myself for not trying it earlier. I was just assuming that it was both of the hairdryers...

I think I'll have to buy a new hairdryer from a retailer with a very generous return policy.

Thanks for all your help everyone. (I'll post a final message with the ultimate outcome - how hard it was to find a hairdryer that didnt interfere)
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Old 2012-02-16, 12:35 PM   #30
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Default Had same issue with my in GH antenna....

A few hair dryers, extension cords and "noise suppressing" power centers yields....

Interference isn't a problem through the power lines. 20feet/17 feet off-axis from my DIY GH antenna makes the OTA signal drop completely.

+++++Distance is the only solution++++++

Readers should probably be warned about installing an antenna adjacent to a room where a hair dryer will be used since I believe this is a well known issue for OTA. Interestingly, a common table fan didn't affect signal reception, neither did my laptop or laptop "brick" untill they were 2 feet in front of antenna; YMMV. No permutation of "Power center" type noise suppressing bars did anything at all (including on antenna amplifier). Also, on topic, 9 years ago I dabbled with SACD and spent many, many hours researching speakers, room set-up, intercnnects, etc; basically all that could affect the fidelity. Ended up with a 1 second tick comming through my stereo, caused by my TV(internal clock circuitry I suppose). I was shocked when a 180$ monster power cleaner did diddly! All those hours reading about impact on bass response from cable length or speaker wire gauge etc, yet noboby advised the most basic set-up detail: keep your amp/receiver away from the tv no matter the impact on cable length!
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