My dedicated MythTV computer has now been removed from its cardboard box and has been put into a proper case.
However when it's running it causes interference on medium wave on my wife's radio. Her own computer, which is nearer the same radio, does not cause any interference.
What component could it be, in the MythTV box, which is causing this interference?
The only obvious item that's different would be the TV card, try taking it out and seeing if that fixes it...
Matt
-----Original Message----- From: main-bounces@lists.alug.org.uk [mailto:main-bounces@lists.alug.org.uk] On Behalf Of Barry Samuels Sent: 10 February 2008 21:02 To: Alug Subject: [ALUG] Radio interference
My dedicated MythTV computer has now been removed from its cardboard box and has been put into a proper case.
However when it's running it causes interference on medium wave on my wife's radio. Her own computer, which is nearer the same radio, does not cause any interference.
What component could it be, in the MythTV box, which is causing this interference?
On Sun, 2008-02-10 at 21:01 +0000, Barry Samuels wrote:
My dedicated MythTV computer has now been removed from its cardboard box and has been put into a proper case.
However when it's running it causes interference on medium wave on my wife's radio. Her own computer, which is nearer the same radio, does not cause any interference.
Did it do this when also in the cardboard case ? I presume so
What component could it be, in the MythTV box, which is causing this interference?
I have had this before with things like Studio PC's causing problems with audio equipment and have always managed to trace it down to one of the following.
Bad earthing, either mainboard to case or mains earth to case at high resistance.
Missing EMI shields in empty drive bays etc...usually they are punch out when drives are fitted so a secondhand case may have some holes here, missing pci slot blanks can also make a surprising difference (and also bugger up the airflow in your case)
The ATX connector backplate (where the audio and vga, serial, parallel connectors are) yes they are earthed to the case and it makes no sense..but they have little fingers on the inside that should touch metal parts of the connectors on the mainboard..make sure they do...if the mainboard is earthed down via the mountings you can be forgiven for making the assumption that this isn't relevant but earth paths don't always work quite like that so check em.
Cases like those with perspex windows in the side etc...it is pretty much impossible to get good EMI performance out of a PC built from generic components unless it is in an earthed metal tin
As Matthew suggested a peripheral component like your TV card.
On 10/02/08 23:56:43, Wayne Stallwood wrote:
On Sun, 2008-02-10 at 21:01 +0000, Barry Samuels wrote:
My dedicated MythTV computer has now been removed from its cardboard box and has been put into a proper case.
However when it's running it causes interference on medium wave on my wife's radio. Her own computer, which is nearer the same radio, does not cause any interference.
Did it do this when also in the cardboard case ? I presume so
Yes it did. I thought that putting it in a proper case would cure it but it didn't.
I have had this before with things like Studio PC's causing problems with audio equipment and have always managed to trace it down to one of the following.
Bad earthing, either mainboard to case or mains earth to case at high resistance.
Dunno about that.
Missing EMI shields in empty drive bays etc...usually they are punch out when drives are fitted so a secondhand case may have some holes here, missing pci slot blanks can also make a surprising difference (and also bugger up the airflow in your case)
Not guilty m'lud.
The ATX connector backplate (where the audio and vga, serial, parallel connectors are) yes they are earthed to the case and it makes no sense..but they have little fingers on the inside that should touch metal parts of the connectors on the mainboard..make sure they do...if the mainboard is earthed down via the mountings you can be forgiven for making the assumption that this isn't relevant but earth paths don't always work quite like that so check em.
Cases like those with perspex windows in the side etc...it is pretty much impossible to get good EMI performance out of a PC built from generic components unless it is in an earthed metal tin
Steel case with no windows.
As Matthew suggested a peripheral component like your TV card.
I'm going to try it first with the TV card removed. If the interference is still present I shall remove everything except the power unit and mainboard. If it is still present I shall then assume the PSU is the cause. I want to get another PSU anyway with a large fan to make the whole box quieter.
Many thanks to everyone for the various suggestions.
On Monday 11 February 2008 16:51, Barry Samuels wrote:
On 10/02/08 23:56:43, Wayne Stallwood wrote:
On Sun, 2008-02-10 at 21:01 +0000, Barry Samuels wrote:
My dedicated MythTV computer has now been removed from its cardboard box and has been put into a proper case.
However when it's running it causes interference on medium wave on my wife's radio. Her own computer, which is nearer the same radio, does not cause any interference.
Hi Barry Just checked the ATX power supply which caused interference (when new) Very high level of broadband noise on Spectrum Analyser from 200kHz to approx 18MHz
Kind Regards -Nick Daniels
On 11/02/08 19:07:09, Nick Daniels wrote:
On Sun, 2008-02-10 at 21:01 +0000, Barry Samuels wrote: My dedicated MythTV computer has now been removed from its cardboard box and has been put into a proper case.
However when it's running it causes interference on medium wave on my wife's radio.
It turned out to be, mostly, the TV adapter. Removing that removed 80% of the interference leaving a little which must be one of the other components.
That really doesn't help of course as the whole idea is to have a TV adapter. I'm surprised manufacturers can get away with that these days.
On Tuesday 12 February 2008 15:09, Barry Samuels wrote:
On Sun, 2008-02-10 at 21:01 +0000, Barry Samuels wrote: My dedicated MythTV computer has now been removed from its cardboard box and has been put into a proper case.
However when it's running it causes interference on medium wave on my wife's radio.
It turned out to be, mostly, the TV adapter. Removing that removed 80% of the interference leaving a little which must be one of the other components.
That really doesn't help of course as the whole idea is to have a TV adapter. I'm surprised manufacturers can get away with that these days.
Hi Barry Glad you found the source, the Radio Society of Great Britain advises you contact the manufacturer, although it quotes Ham radio it is I believe even more applicable to domestic services
6.1 Contacting manufacturers If you prove conclusively that a certain piece of equipment is producing RFI, it is worth trying to find out full details of the make, model number and date of purchase so that a complaint can be made directly to the manufacturer or importer. A polite and technically well-informed approach is recommended when dealing with manufacturers. The equipment probably met a necessary standards at the date of manufacture so the only way forward is on a good will basis. The best approach when dealing with manufacturers is usually to phone first and find out the name of the person responsible for EMC then follow up the phone call with a letter, fax or e-mail. It is also worth finding out whether a newer model is available with reduce RFI. In some cases, the manufacturer may be prepare to provide a filter or exchange the equipment in question for a newer model at a reduced price.
http://www.rsgb.org/emc/pdfs/leaflets/emc4interferencetoamateurreceptionmemb...
Kind Regards - Nick Daniels
On Sunday 10 February 2008 21:01, Barry Samuels wrote:
My dedicated MythTV computer has now been removed from its cardboard box and has been put into a proper case.
However when it's running it causes interference on medium wave on my wife's radio. Her own computer, which is nearer the same radio, does not cause any interference.
What component could it be, in the MythTV box, which is causing this interference?
Hi
Are you using the "HomePlug" type networking? The ones two doors from me are preventing me from using any band on my ham radio from 7Mhz downwards, and also MW radio. they generate an incredibly strong broadband "hash" over a very very large part of the spectrum
Kind Regards - Nick Daniels
Nick Daniels wrote:
Are you using the "HomePlug" type networking? The ones two doors from me are preventing me from using any band on my ham radio from 7Mhz downwards, and also MW radio. they generate an incredibly strong broadband "hash" over a very very large part of the spectrum
As a reseller of those devices this is news to me and merits some investigation.
If they're 2 doors down from you there's a good chance they're on the same phase as you which would in principle make it more likely they'd cause you problems than if they were next door, but all the same I've not heard of this happening before.
Do you know the brand of homeplug, or their speed (14, 85 or 200Mbps)? Any idea what the distance is between you and them? Have you done any tests that confirm the homeplugs to be the problem?[*]
I know practically nothing about ham radio, but can I assume that the interference is via mains and not radio? (Ie that your radio equipment isn't battery powered and therefore isolated from mains?)
[*] Please don't mistake any of this for "I'm sure the products aren't at fault and you've misdiagnosed it". You sound like you know what you're talking about and I've got no reason to believe that you're wrong. I just like to know about the products I sell, good or bad. If this is a brand of homeplug we have dealings with I'll talk to the manufacturer/distributor and find out if this is a known issue, or perhaps indicates a fault. In fact I'll probably ask the people we deal with anyway, but a little more info would be useful first.
If this is of no interest to the list I'm happy to take it off-list.
On Monday 11 February 2008 09:54, Mark Rogers wrote:
Nick Daniels wrote:
Are you using the "HomePlug" type networking? The ones two doors from me are preventing me from using any band on my ham radio from 7Mhz downwards, and also MW radio. they generate an incredibly strong broadband "hash" over a very very large part of the spectrum
As a reseller of those devices this is news to me and merits some investigation.
If they're 2 doors down from you there's a good chance they're on the same phase as you which would in principle make it more likely they'd cause you problems than if they were next door, but all the same I've not heard of this happening before.
Do you know the brand of homeplug, or their speed (14, 85 or 200Mbps)? Any idea what the distance is between you and them? Have you done any tests that confirm the homeplugs to be the problem?[*]
I know practically nothing about ham radio, but can I assume that the interference is via mains and not radio? (Ie that your radio equipment isn't battery powered and therefore isolated from mains?)
[*] Please don't mistake any of this for "I'm sure the products aren't at fault and you've misdiagnosed it". You sound like you know what you're talking about and I've got no reason to believe that you're wrong. I just like to know about the products I sell, good or bad. If this is a brand of homeplug we have dealings with I'll talk to the manufacturer/distributor and find out if this is a known issue, or perhaps indicates a fault. In fact I'll probably ask the people we deal with anyway, but a little more info would be useful first.
If this is of no interest to the list I'm happy to take it off-list.
Hi Mark I do not know the brand or speed at the moment, but I know as soon as I took them out (with their permission) the interference ceases I only started looking into this this weekend, There have been articles in Radcom, the journal of the Radio Society of Great Britain concerning this interference, I will try to find them this week if you are interested? Allegedly they have a 25dB notch? in the ham bands?? but my receivers have a sensitivity of 0.05 microvolts. Will contact you off list, Mark when I find articles, and make and model of homeplug (cannot get to neighbours house until next weekend) I will be able then to find out if interference is mains or RF Distance from my house approx 100yds, on same phase. Distance from my antennas to their house approx 150yds Many thanks for your interest.
Kind Regards - Nick Daniels
Nick Daniels wrote:
Will contact you off list, Mark when I find articles, and make and model of homeplug (cannot get to neighbours house until next weekend
Thanks for the info so far and quite happy to continue this off-list.
Just as a postscript, I did a quick Google for the Radcom articles (didn't find them)but it lead me to this interesting Homeplug + Amateur Radio thread: http://www.digitalspy.co.uk/forums/showthread.php?t=477821 (The thread is about homeplugs, the radio part of the thread starts in the last couple of posts on the first page (of three)).
Interesting that there are some people who would be affected if there were a general problem saying that they use them without problem, so I suspect that any problem will relate to manufacturer+model, or maybe a manufacturing fault, but that makes me no less intruiged to follow this up. (Interesting thread on Homeplugs anyway.)
On Mon, Feb 11, 2008 at 11:59:17AM +0000, Mark Rogers wrote:
Nick Daniels wrote:
Will contact you off list, Mark when I find articles, and make and model of homeplug (cannot get to neighbours house until next weekend
Thanks for the info so far and quite happy to continue this off-list.
Please don't take it fully offlist, at least put a reply here with some findings and further links and a summary.
Even though this isn't strictly on topic for the list it is interesting to some people here and if someone searches the internet for this problem in the future and finds this list it will be a major annoyance for them to find the thread stops dead.
I've had a fair few times where I've had a problem and found a mailing list archive where there was some conversation about the problem only for them to have offlisted the conversation.
Adam
"I've had a fair few times where I've had a problem and found a mailing list archive where there was some conversation about the problem only for them to have offlisted the conversation."
I'd agree with that view. Slightly different from the original post but on the topic of homeplugs - why is there encryption software (winblows use only). The only point i can see of encryption is in some school or office buildings where homeplug was used and certain individuals wanted complete security. Using it in a house with a wired router - how can anyone use that connection?
james
On 11/02/2008, Adam Bower adam@thebowery.co.uk wrote:
On Mon, Feb 11, 2008 at 11:59:17AM +0000, Mark Rogers wrote:
Nick Daniels wrote:
Will contact you off list, Mark when I find articles, and make and model of homeplug (cannot get to neighbours house until next weekend
Thanks for the info so far and quite happy to continue this off-list.
Please don't take it fully offlist, at least put a reply here with some findings and further links and a summary.
Even though this isn't strictly on topic for the list it is interesting to some people here and if someone searches the internet for this problem in the future and finds this list it will be a major annoyance for them to find the thread stops dead.
I've had a fair few times where I've had a problem and found a mailing list archive where there was some conversation about the problem only for them to have offlisted the conversation.
Adam
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member jessejazza wrote:
I'd agree with that view. Slightly different from the original post but on the topic of homeplugs - why is there encryption software (winblows use only). The only point i can see of encryption is in some school or office buildings where homeplug was used and certain individuals wanted complete security. Using it in a house with a wired router - how can anyone use that connection?
Unlike wireless connections, where unique encryption is essential, it is less important in homeplug setups due to the fact you need to connect to the mains to pick up the signals. But there is the potential for a nearby house (usually not your direct neighbour) who is on the same phase supply as you, if the distance is not too great, for them to plug in a homeplug and get onto your network. If you encrypt the data that can't happen. You're right that the potential for easy access to your network is massively lower, though - not least because it's not so easy to scan the area to find houses that have homeplugs installed.
The newer homeplugs (the Solwise ones we sell anyway) have a push button on them that you use to regenerate encryption keys therefore not needing Windows.
On Monday 11 February 2008 13:46, Adam Bower wrote:
On Mon, Feb 11, 2008 at 11:59:17AM +0000, Mark Rogers wrote:
Nick Daniels wrote:
Will contact you off list, Mark when I find articles, and make and model of homeplug (cannot get to neighbours house until next weekend
Thanks for the info so far and quite happy to continue this off-list.
Please don't take it fully offlist, at least put a reply here with some findings and further links and a summary. .........
Hi Adam
Will keep you up to date, The articles in Radcom are not available online and I will have to go back through several years issues to find them. A quick search in Google "homeplug ham radio interference" gives
"In 2004, BBC researchers conducted an investigation into Homeplug-compliant power line communications, to see whether they did affect radio reception. They found that as soon as data starts flowing, the radio signal is obliterated. It turns out that the Homeplug standard only requires that devices avoid using radio frequencies that are used by amateur radio enthusiasts. It does not mention anything about all the other frequencies that are used by broadcasters around the world. This interference might not be restricted to just your home." http://news.bbc.co.uk/1/hi/programmes/click_online/4080566.stm But it is a bit ambiguous, not sure if they mean real PLT also: http://p1k.arrl.org/~ehare/bpl/Testing_HomePlug.htm
Also if as I "believe" there is a 25dB notch in the hamradio bands this is inadequate, as it would still interfere with low signal strength communications. And if the interference ever went up to VHF where moonbounce transmitions are used and computers are often used to extrapolate the the received signals from noise, this would be impossible.
RE original problem - I had the same a few years back, and traced it to the PSU, replaced PSU cured, common with switched mode PSU's, an inline filter helps, but a lot of PSU's radiate RF badly
Kind Regards - Nick Daniels
Adam Bower wrote:
I've had a fair few times where I've had a problem and found a mailing list archive where there was some conversation about the problem only for them to have offlisted the conversation.
Point taken, I'll summarize here if/when there's something to say.
For the benefit of anyone reading this in the archives: By all means contact me off list to find out where this lead if I forget to summarise here. Ideally retain the subject (or something similar) if doing so.
On 11/02/08 09:09:31, Nick Daniels wrote:
On Sunday 10 February 2008 21:01, Barry Samuels wrote:
My dedicated MythTV computer has now been removed from its cardboard box and has been put into a proper case.
However when it's running it causes interference on medium wave on my wife's radio. Her own computer, which is nearer the same radio, does not cause any interference.
What component could it be, in the MythTV box, which is causing this interference?
Hi
Are you using the "HomePlug" type networking? The ones two doors from me are preventing me from using any band on my ham radio from 7Mhz downwards, and also MW radio. they generate an incredibly strong broadband "hash" over a very very large part of the spectrum
I am using a Solwise Homeplug link on part of the network but that is on all the time and doesn't cause interference on medium wave at least.
In any case (no pun intended) when the MythTV machine is turned off the interference stops.
-
Adam Bower -
Barry Samuels -
Barry Samuels -
Mark Rogers -
member jessejazza -
Mephi -
Nick Daniels -
Wayne Stallwood