I live at 8000' in the Rockies. We have lots of woodpeckers--they especially love to drill 4" holes in the north side of my house. They also like to drill on the arial telephone cables. Water then gets into the cable and causes a partial grounding on the circuits. This causes 60Hz hum to be heard on the line as well as a loss of amplitude. Qwest says tough s--t. All three of my POTS lines have hum. They are connected to an Adtran 750 and my asterisk system (a testbench for commercial endeavors.) The hum has always been bad on my end. Since I installed *, several of my callers have remarked about the hum. So here's the question: Could a notch filter of sorts be installed in the codecs I use? Filter-out everything between, say, 55 and 65Hz? Alternatively, is there a feature on the Adtran FXO card that deals with this? Thanks for your help, Mike
> They also like to drill on the arial telephone cables. Water then gets > into the cable and causes a partial grounding on the circuits. This > causes 60Hz hum to be heard on the line as well as a loss of amplitude. > Qwest says tough s--t.Dump a bottle of cayenne pepper into some shelac and paint the house where they like to peck -- This saved a beautiful willow tree from sapsuckers for my grandfather. Qwest should be held to some standard of audio quality on their lines -- I am surprised it's not easier to armour the lines. Regards, Andrew
I would have thought that should have been gotten rid of... Notch filter would only get rid of the fundamental frequency unless you notch at the harmonics also. Best bet I would say is a high pass filter at say 500hz. Reasonably simple to make with a resistor and capacitor... I think Sound On Sound magazine (which has archives on the web) had an article on how to build one... The thing is, most of the codecs available in * should be high and low pass filtering it anyway... Matt Michael Welter wrote:> I live at 8000' in the Rockies. We have lots of woodpeckers--they > especially love to drill 4" holes in the north side of my house. > > They also like to drill on the arial telephone cables. Water then > gets into the cable and causes a partial grounding on the circuits. > This causes 60Hz hum to be heard on the line as well as a loss of > amplitude. Qwest says tough s--t. > > All three of my POTS lines have hum. They are connected to an Adtran > 750 and my asterisk system (a testbench for commercial endeavors.) > > The hum has always been bad on my end. Since I installed *, several > of my callers have remarked about the hum. > > So here's the question: Could a notch filter of sorts be installed in > the codecs I use? Filter-out everything between, say, 55 and 65Hz? > > Alternatively, is there a feature on the Adtran FXO card that deals > with this? > > Thanks for your help, > Mike > > > > _______________________________________________ > Asterisk-Users mailing list > Asterisk-Users@lists.digium.com > http://lists.digium.com/mailman/listinfo/asterisk-users > To UNSUBSCRIBE or update options visit: > http://lists.digium.com/mailman/listinfo/asterisk-users >
Hi Michael, Michael Welter wrote:> I live at 8000' in the Rockies. We have lots of woodpeckers--they > especially love to drill 4" holes in the north side of my house. > > They also like to drill on the arial telephone cables. Water then > gets into the cable and causes a partial grounding on the circuits. > This causes 60Hz hum to be heard on the line as well as a loss of > amplitude. Qwest says tough s--t. > > All three of my POTS lines have hum. They are connected to an Adtran > 750 and my asterisk system (a testbench for commercial endeavors.) > > The hum has always been bad on my end. Since I installed *, several > of my callers have remarked about the hum. > > So here's the question: Could a notch filter of sorts be installed in > the codecs I use? Filter-out everything between, say, 55 and 65Hz? > > Alternatively, is there a feature on the Adtran FXO card that deals > with this?Notching may not be that effective, as it will not deal with the harmonics. The analogue to digital converter should already be filtering below 300Hz, so you probably have quite a lot of hum if it gets through that. There isn't much you can do to eliminate the hum your callers hear. For your own hum, additional filtering may be beneficial. This could be implemented by analogue or digital filters. Simple RC analogue filters probably would not be sharp enough to give much benefit, so you would need a more complex active analogue filter. A digital filter would require no hardware changes, but you need someone who knows what they are doing to implement it for you. Regards, Steve
> I live at 8000' in the Rockies. We have lots of woodpeckers--they > especially love to drill 4" holes in the north side of my house. > > They also like to drill on the arial telephone cables. Water then gets > into the cable and causes a partial grounding on the circuits. This > causes 60Hz hum to be heard on the line as well as a loss of amplitude. > Qwest says tough s--t.Fairly common problem, but you can put some pressure on them by escalating to the public service commission.> All three of my POTS lines have hum. They are connected to an Adtran > 750 and my asterisk system (a testbench for commercial endeavors.)The public service commission can suggest/force various work arounds at no cost to you (regardless of what it might cost Qwest). Example, might suggest iax2 connection to a colocated * server within the qwest CO to bypass the local plant problem.> The hum has always been bad on my end. Since I installed *, several of > my callers have remarked about the hum.Having worked as an engineer for a different telco for many years and worked with various customers on the same type of problem, there are things the telco can do to correct the problem and/or minimize it. However, one individual complaining generally does not cause the telco to react unless some other pressure is applied (eg, multiple customers, public service commission). The hum is actually caused by imbalance between the tip/ring and ground. The tip/ring could truly have 50 volts of AC induced into it, and if the tip/ring pair were balanced you would never hear it, period. Some tricks to reduce the problem have involved installing devices that essentially adds the equivalent resistive imbalance to one side or the other of the tip/ring pair causing the exact imbalance on both tip & ring. When the correct values are found (and years ago it was simply a twist of knobs on the passive devices), the problem is essentially equalized and the hum disappears (even though there could still be 50 volts of AC induced on the pair). Other work arounds have included the use of subscriber carrier systems, etc.> So here's the question: Could a notch filter of sorts be installed in > the codecs I use? Filter-out everything between, say, 55 and 65Hz?Nope, will never work. There are more harmonics and other non-60hz signals on the wire that almost makes it impossible to filter.> Alternatively, is there a feature on the Adtran FXO card that deals with > this?No, what you're suggesting is finding a problem-bypass and not solving the root-cause. Wouldn't even attempt to go there as you'll be constantly having to dick around with the bypass. It is amazing what happens when pressure is applied at certain points. Write the public service commission and copy senior customer service mgmt and see what happens. Be accurate and detailed, leaving out all adjectives and adverbs. Rich
You may try bridging the tip and ring of each pots line with a .01 microfarad capacitor. You can pick up a pack of the ceramic type at radio shack for a few bucks. Good luck, Luke ----- Original Message ----- From: "Michael Welter" <mike@introspect.com> To: <asterisk-users@lists.digium.com> Sent: Thursday, February 19, 2004 5:00 PM Subject: [Asterisk-Users] Woodpeckers> I live at 8000' in the Rockies. We have lots of woodpeckers--they > especially love to drill 4" holes in the north side of my house. > > They also like to drill on the arial telephone cables. Water then gets > into the cable and causes a partial grounding on the circuits. This > causes 60Hz hum to be heard on the line as well as a loss of amplitude. > Qwest says tough s--t. > > All three of my POTS lines have hum. They are connected to an Adtran > 750 and my asterisk system (a testbench for commercial endeavors.) > > The hum has always been bad on my end. Since I installed *, several of > my callers have remarked about the hum. > > So here's the question: Could a notch filter of sorts be installed in > the codecs I use? Filter-out everything between, say, 55 and 65Hz? > > Alternatively, is there a feature on the Adtran FXO card that deals with > this? > > Thanks for your help, > Mike > > > > _______________________________________________ > Asterisk-Users mailing list > Asterisk-Users@lists.digium.com > http://lists.digium.com/mailman/listinfo/asterisk-users > To UNSUBSCRIBE or update options visit: > http://lists.digium.com/mailman/listinfo/asterisk-users >
The low "B" string on a 5-string bass guitar is approx. 31 Hz....>> >>> A power spectrum plot will tell him he has a 60Hz hum. I think he >>> already knows that. I think he can definitely consider solutions >>> without >>> following your suggestion. :-) >> >>> No, It's not a "60Hz hum". Yes, 60Hz is getting into the line >but the existing filters are removing the 60hz. What he hears >is most likely 120Hz, 240Hz or something else or most likely >a combination of various multiples for 60hz. > >I'd bet that the tiny speaker inside a telephone handset can not >even reproduce a 60Hz tome. Yes you can hear a hum but it's >the overtomes of 60 that you hear. Many people can not even hear >down to 60Hz, some can but not everyone.