Re: [OT] Locating source of FM radio interference
It's also entirely possible that there is a pirate broadcaster - Heh. I'm pretty sure it's not a pirate broadcast station unlesss their demographic studies indicate there's a market segment that's fond of the sound of motor noise or arcs discharging. (And, yes - I realize that the former is likely just a special case of the latter...) The interference in question is a motor-like thrumming with ragged, nerve-jangling overtones. It seems pretty clearly localized to one of several rows of buildings in our condo since it swamps all other signals around 89MHz when you're within about 100 yards of that locale. The jazz aficionado who first reported it has been very patient but is talking about bringing in the FCC - I'd love to avoid that and solve it locally, if possible. ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss
[OT] Locating source of FM radio interference
Michael ODonnell writes: Something near our house has recently started generating spectacular amounts of radio intereference that's most noticeable around 89MHz. I have no portable radio equipment of any kind except a humble little $10 handheld with a normal telescoping antenna that seems not to be very directional, or at least I don't understand its directionality. Is there some way I can use it to do some sort of triangulation on the source of interference? Maybe some particular way of holding/orienting it, or selectively/partially shielding it, or tuning it, or... ? A particular problem with an FM receiver is that its response to signal strength may seem counter intuitive. As the desired signal gets weaker, it doesn't get quieter (at least until the very end), but rather noise gets louder. Of course, your particular noise might be serving as a signal, rather than the white or background noise that indicates weak signal. If your portable also receives AM, and if the interference is broadband enough to be received in the AM mode, then the results may be easier to interpret. AM antennas in portables also tend to be fairly directional, though in the sense of having a bilateral null, rather than a peak. In either case, however, a strong enough (interfering) signal will give no audible change in response over a fairly broad range of signal strengths (unless it has an S meter). For work close to the source, then, you need a means of seriously attenuating the signal. Your portable is unlikely to come equipped with one, so you have to fabricate your own. This probably takes the form of a shield with an aperture. If you have one of those metalized plastic bags in which you are supposed to put your speed pass if you don't want to use it at the moment, that's a good start. Put the portable inside, fold over the closure a few times, and see if it behaves like a radio between stations. If this isn't enough, try a metal foil bag (though making a good connection where you want to edges to act like a continuous side could be as difficult as making the bag hold water). If this works then partially open the bag, making the opening progressively larger, until you hear the interference. Then keep the opening that size while you walk around to try to get a feel for a constant signal strength contour. This may give you a better idea of the source location. You may need to repeatedly close down the aperture and make another contour for a greater signal strength as you close in. Note, however, that the spot you find may be, rather than the source, a piece of metal that is coupled to the actual source (fence, roof flashing, rain gutter, phone line, power line, etc). Coupling can be via actual electrical contact, such as a bad cordless telephone base injecting noise into the phone line, or simply by proximity. Being able to work in both AM and FM modes can be valuable here, since coupling may be quite different between the two. A good test is to have someone not holding the portable in the bag touch the fence, etc., (but not a power line), which should make a marked difference in the signal. Finally, if you can track it to one or a few dwellings, and if you have the social skills to persuade the owner to unplug things one at a time, you may not need to pinpoint things more closely. If there is some new appliance that is causing the problem, the manufacturer is usually legally bound to fix the issue, though this is still a pain. Bill ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss
Re: [OT] Locating source of FM radio interference
A google search for 89MHz reveals below. Gotta wonder if a fellow geek in the area is hacking a linux box and leaving running in the open air (no case). :-\ Can you record the audio and make a wav file? Someone on this list might be able recognize the 'noise' and narrow the search for its potential source. http://www.anandtech.com/printarticle.aspx?i=1384 Finally, the BX chipset has been around for quite some time and was not originally intended to be used in conjunction with a 133MHz front side bus. As a result, there is no 1/2 multiplier for the AGP bus (although there is a magical 1/4 multiplier for the PCI bus). As a result, the BX benchmarks listed in the forthcoming pages are somewhat misleading because the AGP bus is actually running at 89MHz while the other two boards are running at 66MHz. The 89MHz bus translates to 712MB/s of bandwidth, a 34% increase over the 533MB/s of standard AGP 2X. Note that AGP 4X yields a peak transfer rate of 1.06GB/s. For further discussion on AGP standards and performance considerations, see our article http://www.anandtech.com/showdoc.html?i=1250p=4 on BX chipsets at 133MHz FSB speeds. We don't consider this to be a major problem, however, as this is still a common setup for gamers wishing to stick with their current BX boards, enjoy the extra performance with minimal overclocking, or take advantage of the tried and true nature of the chipset. Further, most cards work fine at 89MHz. The only exception that comes to mind is Matrox's new G450 http://www.anandtech.com/showdoc.html?i=1315. Michael ODonnell wrote: It's also entirely possible that there is a pirate broadcaster - Heh. I'm pretty sure it's not a pirate broadcast station unlesss their demographic studies indicate there's a market segment that's fond of the sound of motor noise or arcs discharging. (And, yes - I realize that the former is likely just a special case of the latter...) The interference in question is a motor-like thrumming with ragged, nerve-jangling overtones. It seems pretty clearly localized to one of several rows of buildings in our condo since it swamps all other signals around 89MHz when you're within about 100 yards of that locale. The jazz aficionado who first reported it has been very patient but is talking about bringing in the FCC - I'd love to avoid that and solve it locally, if possible. ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss
Re: [OT] Locating source of FM radio interference
Bill Freeman wrote: In either case, however, a strong enough (interfering) signal will give no audible change in response over a fairly broad range of signal strengths (unless it has an S meter). For work close to the source, then, you need a means of seriously attenuating the signal. Your portable is unlikely to come equipped with one, so you have to fabricate your own. This probably takes the form of a shield with an aperture. I used to do tracking on radio signals years ago... There is a technique that works without going to RadShack or the local supermarket for parts... Though, as has been pointed out, it works better for AM than FM... but it should work in FM. It's called Body Shielding. Your body can act as a shield. Tune the radio so you can hear the interferance, but *just* barely. Put the (probably not-fully-extended) antenna up against your chest and slowly turn around, listening carefully. You are looking for the absolute *worst* reception where you can still make out a signal. If you do it right, there will be a direction in which the signal fades out. At that point, the source is likely to be right behind you. This is obvious in AM signals, but probably pretty subtle in FM... You have to tune off-frequency till you barely hear the signal. Note, however, that the spot you find may be, rather than the source, a piece of metal that is coupled to the actual source (fence, roof flashing, rain gutter, phone line, power line, etc). Coupling can be via actual electrical contact, such as a bad cordless telephone base injecting noise into the phone line, or simply by proximity. Being able to work in both AM and FM modes can be valuable here, since coupling may be quite different between the two. A good test is to have someone not holding the portable in the bag touch the fence, etc., (but not a power line), which should make a marked difference in the signal. Excellent point. I used to have a hell of a time with transmitters near train tracks. Brian ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss
Re: [OT] Locating source of FM radio interference
There is a technique that works without going to RadShack or the local supermarket for parts... Though, as has been pointed out, it works better for AM than FM... but it should work in FM. It's called Body Shielding. Your body can act as a shield. Tune the Beauty! I suspected that sort of technique could be used - I'm eager to try it when I get home. ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss
Unkillable processes?
Okay, here's a strange one. On a Red Hat 9 system I've encountered a situation where there are two processes that I cannot kill when using kill -9 (or any other value, for that matter.) What's the deal with that? The only kind of process that I've ever run across that I could not kill was a zombie and neither one of these is a zombie. Just to add more confusion to the mix, or maybe a useful clue, the system load average is about 4 but top shows 97% system idle time. Strange. Any ideas? Dan ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss
Re: Unkillable processes?
On Friday 17 February 2006 01:58 pm, Dan Coutu wrote: Okay, here's a strange one. On a Red Hat 9 system I've encountered a situation where there are two processes that I cannot kill when using kill -9 (or any other value, for that matter.) The processes could be in an IO Lock, maybe trying to access an NFS share with hard locking and not INTR option set? Just to add more confusion to the mix, or maybe a useful clue, the system load average is about 4 but top shows 97% system idle time. Strange. That's suspicious, but I suppose not entirely impossible. Have you done anything like chkrootkit on it, just for kicks? -Neil ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss
Re: Unkillable processes?
On Fri, Feb 17, 2006 at 02:35:15PM -0500, Neil Schelly wrote: On Friday 17 February 2006 01:58 pm, Dan Coutu wrote: Okay, here's a strange one. On a Red Hat 9 system I've encountered a situation where there are two processes that I cannot kill when using kill -9 (or any other value, for that matter.) The processes could be in an IO Lock, maybe trying to access an NFS share with hard locking and not INTR option set? Just to add more confusion to the mix, or maybe a useful clue, the system load average is about 4 but top shows 97% system idle time. Strange. That's suspicious, but I suppose not entirely impossible. Have you done anything like chkrootkit on it, just for kicks? IO locks will cause the load to be high with a low idle time. -Mark signature.asc Description: Digital signature
Re: Unkillable processes?
On 2/17/06, Dan Coutu [EMAIL PROTECTED] wrote: On a Red Hat 9 system I've encountered a situation where there are two processes that I cannot kill when using kill -9 (or any other value, for that matter.) Do a ps aux and note their status. It's D, right? That means they're in uninterruptable sleep -- waiting for system call to finish something that cannot be interrupted. The D stood for driver or disk originally. Bad hardware or buggy device drivers are the most common cause of a process stuck in this state. The only thing you can do is wait or reboot the system. If the syscalls ever complete, the kernel will immediately process the kill signals you sent, so those processes are dead, they just don't know it yet. :) -- Ben ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss
Re: Unkillable processes?
On Friday 17 February 2006 1:58 pm, Dan Coutu wrote: Okay, here's a strange one. On a Red Hat 9 system I've encountered a situation where there are two processes that I cannot kill when using kill -9 (or any other value, for that matter.) What's the deal with that? The only kind of process that I've ever run across that I could not kill was a zombie and neither one of these is a zombie. Just to add more confusion to the mix, or maybe a useful clue, the system load average is about 4 but top shows 97% system idle time. Strange. We ran into the same type of thing on a RHEL 3.0 Update 4 system a few weeks ago. I think we decided that it was waiting on I/O that did not complete. -- Jerry Feldman [EMAIL PROTECTED] Boston Linux and Unix user group http://www.blu.org PGP key id:C5061EA9 PGP Key fingerprint:053C 73EC 3AC1 5C44 3E14 9245 FB00 3ED5 C506 1EA9 ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss
Re: Unkillable processes?
Ben Scott wrote: On 2/17/06, Dan Coutu [EMAIL PROTECTED] wrote: On a Red Hat 9 system I've encountered a situation where there are two processes that I cannot kill when using kill -9 (or any other value, for that matter.) Do a ps aux and note their status. It's D, right? That means they're in uninterruptable sleep -- waiting for system call to finish something that cannot be interrupted. The D stood for driver or disk originally. Bad hardware or buggy device drivers are the most common cause of a process stuck in this state. The only thing you can do is wait or reboot the system. If the syscalls ever complete, the kernel will immediately process the kill signals you sent, so those processes are dead, they just don't know it yet. :) -- Ben Hmm, the I/O wait seems likely. We've been having trouble with an IOMega REV 10 disk autoloader ever since we bought the thing. Even swapped it out for a new one but still get flaky behavior. Maybe it's time to send the thing back... Dan ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss
Re: Unkillable processes?
On 2/17/06, Dan Coutu [EMAIL PROTECTED] wrote: Hmm, the I/O wait seems likely. We've been having trouble with an IOMega REV 10 disk autoloader ever since we bought the thing. Yikes! I've never, ever encountered an IOMega product that didn't suck in some major way. No wonder it doesn't work. Maybe the kernel is just refusing to have anything to do with such a crummy product on principle. -- Ben Click of death Scott ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss
Re: Unkillable processes?
On Feb 17, 2006, at 15:55, Ben Scott wrote: 've never, ever encountered an IOMega product that didn't suck in some major way. No wonder it doesn't work. Hey, my first linux box ran off a 150MB Bernoulli drive hooked up to my soundblaster. That was before Iomega gave up on Bernoulli effect media for the mass market, of course. -Bill - Bill McGonigle, Owner Work: 603.448.4440 BFC Computing, LLC Home: 603.448.1668 [EMAIL PROTECTED] Cell: 603.252.2606 http://www.bfccomputing.com/Page: 603.442.1833 Blog: http://blog.bfccomputing.com/ VCard: http://bfccomputing.com/vcard/bill.vcf ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss
Re: [OT] Locating source of FM radio interference
It's called Body Shielding. Your body can act as a shield. Tune the Yes. Advanced body shielding involves a secondary conductive shielf. You put the radio in Pringles can, or other deep open-top conductive case, antenna up, and using a lanyard (string) to pull up (and let gravity pull down) to adjust how close to the mouth it is, thus providing a variable attenuation to get it just on the edge so you can hear it change as you turn it around your body, the body shield. This technique will work with weak VHF FM signals, we use it in VHF FM foxhunting in ham radio. (It's hardly the preferred technique, but it will work for close-in if you don't have specialty gear.) [ I heard of someone wrapping himself in aluminum foil to do advanced body shield, but the cops questioned him quite a while (post 9/11, alas). Not a recommended variation. ] -- Bill [EMAIL PROTECTED] [EMAIL PROTECTED] ___ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss
