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ungrounded HUM/static sound with new router

Started by Stephen, January 29, 2012, 02:52:23 PM

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Stephen

Hi,

My Obitalk has worked great with a clear sound for about a month now.

But, the wireless part of my $20 router is going out, so I needed to switch to a new one.

The new, $120, router has QoS that is supposed to make VOIP even better.  However, I get a HUM on the line that sounds like analog hum of an line that is not properly grounded.

I don't see how the router could induce an analog hum sound since the connection to the Obi is ethernet/digital.

Any thoughts on what may be happening here?

Thank you,
Stephen


Stephen

forgot to note: Turning off the QoS feature improves a little.

Another sound analogy - it's very similar to the sound that would occassionally arise on a landline ("I think we got a bad connection, let's hang up and call back")

lk96

Are you using cordless phones? if so, try to connect a corded-only phone to the PHONE port
and see if you have the same noise.

If you are not using cordless phones, try to move your phone handset further away from the router/antennas or
try to turn off the wireless interface of your router as a test.

Also, you may want to change the channel/band that the wireless part of you router is using
just in case it interferes with a cordless phone.

Some routers allow you also to adjust the transmitted power: that will depend on the range you
want to cover, walls/obstacles (ie walls, etc).

BTW as a side comment on Qos: that will help if you mark traffic coming off the Obi with
the appropriate DHCP/TOS marking. You can set to your liking the DSCP value for each
ITSP. But you will have to make sure that lower priority traffic in your network doesn't
use same value, and that your router is configured accordingly on how to handle that DSCP value.

L.


Stephen

L - thank you for the great guidance.

1) I am using a cord-only phone.

2) The router does not have a means to turn off wireless.  However, i plugged my old router back in to test for the 'clear' quality - still there.  And, while doing this test, the new router was still turned on and transmitting (eg, my wireless gear was all still connected  to it, though it was not currently connected to the internet).

3) my handset has a 20' cord and i moved closer and further away from the antenna - no affect - the hum stayed the same.

Is this type of hum common on some routers?

The QoS note is appreciated - though I'll have to do a lot of research to understand what means :)

Thank you!
Stephen

lk96

Quote from: Stephen on January 29, 2012, 03:40:39 PM

2) The router does not have a means to turn off wireless.  However, i plugged my old router back in to test for the 'clear' quality - still there.  And, while doing this test, the new router was still turned on and transmitting (eg, my wireless gear was all still connected  to it, though it was not currently connected to the internet).

when you say "still there" you mean that the good quality was still there ? so you are saying
that with both routers present/powered but with your old router handling the network traffic, you
don't get the hum ?

Which interface are you using? SP1, SP2? what services they have on them?

What do the statistics of SP1 and SP2 look like ?
Status-> SP1 & SP2 stats

can you cut/paste the data? do you see any abnormal stats when you use the new router ?

Quote
Is this type of hum common on some routers?

No. Your experience sound a bit strange.

so that the source of the issue is isolated, make sure you don't have any cellphone
near the phone handset. 

L..

gearblok

i got the same noise when i first hooked up--it was the phone.

Everton

Quote from: gearblok on January 29, 2012, 06:12:05 PM
i got the same noise when i first hooked up--it was the phone.

I'm not sure I understand you clearly, given your abbreviated way of writing.  Are you saying you have isolated the problem and that the source of the hum/noise was the corded phone itself?  If so, why was it not a problem when  the previous $20 router was in use?

Stephen

Sorry, the last post was not clear.  The phone being used is solid, high quality - 18 years old and the best audio of any phone I've ever used.  The phone is not the problem.

When going back to the old/$20 router, I get crystal clear audio over the Obi - nearly as good as my previous landline.  This high quality remains even with the new router being turned on (though not connected to the internet, it is still broadcasting).

The hum problem only exists when connecting the Obi to the new router.

Having a cell phone nearby or not, has no impact on this hum problem.

Status->SP1 SP2 - I'm not sure what this refers to.  Is this on my router, on the Obi somewhere?





lk96

Quote from: Stephen on January 29, 2012, 08:13:51 PM
Status->SP1 SP2 - I'm not sure what this refers to.  Is this on my router, on the Obi somewhere?

It's from the Obi management page. You can access it by pointing your browser to
the IP address of your Obi. One way to find it by dialing ***1 from the attached phone.

The part that is puzzling is that routers don't/can''t alter in any way audio quality:
they merely transport it in IP packets.  By accessing the stats page I mentioned in the previous msg
i wanted to see if somehow you face packet losses.

BTW, does the other side also hear the noise? or it's only on your side ?

L.

Stewart

Quote from: Stephen on January 29, 2012, 08:13:51 PM
Sorry, the last post was not clear.  The phone being used is solid, high quality - 18 years old and the best audio of any phone I've ever used.  The phone is not the problem.
IMO, that's not obvious.  Some phones are sensitive to common-mode AC voltage on the line; the new router may have more leakage, which is being conducted over the Ethernet cable.

If this is the case, you will hear the hum, even when there is no VoIP.  Pick up the phone, hear dial tone and press one digit to stop the dial tone.  Do you hear hum?  If so, does it get louder if you grasp the coiled handset cord with your hand?  If so, that's likely the problem.

If the above is your issue, possible fixes:  If the power plug for the new router is not polarized and does not have a ground pin, try plugging it in "upside down" (with the plug blades swapped).  If no luck, try connecting the old router behind the new (OBi to LAN port on old router, WAN port of old router to LAN port of new router, WAN port of new router to modem).  The old router must be set for DHCP addressing.  Or, if you have an old Ethernet switch or hub, try connecting it between OBi and new router.  If none of this helps, please post make and model of both routers.

Stephen

Lk96,

I got the IP address, but not sure where to find the Obi management page with a Status taht i can click.

From the Obi Dashboard there is a status field that shows my home phone as being active.

when clicking on my Home phone, it takes me to a page that has Service Provider 1 and 2.

Only #1 is configured and i can click to edit this, but this doesn't show statistics and nothing that indicates I'm on the Management page.

Thank you,
stephen

Stephen

Stewart,

Voltage leakage makes sense.

YES, I hear the hum even not going over VoIP.  The hum is there even with the dial tone, then after selecting 1... and, the hum does get louder when I grasp the coiled handset cord.

I tried flipping the power supply upside down - same hum.

In this situation, both modems need to be returned.  The "Old" modem is still within refund period as well as the "New" one.  The problem with my "Old" one is that it intermittently drops wireless signal throughout the day (sometimes works all day, sometimes can't connect for 5-20 minutes at a time - this is the 2nd replacement and all had the same problem).

Model of the "New" - Belkin N750 DB
Model of the "Old" - Monoprice MS-WN512N1

Now to find another "new" modem.  Maybe one that supports Tomato (that seems a popular topic on this forum).

Any recommendations on a reliable modem appreciated.

Thank  you,
Stephen

Ps: also tried D-link Xtreme N+300 – it had several problems and very low signal strength


lk96

Quote from: Stephen on January 31, 2012, 02:14:20 PM

I got the IP address, but not sure where to find the Obi management page with a Status taht i can click.


You just point your browser at the IP address you got. So if your Obi is at 192.168.0.10,
then at the place where you normally enter an http address to go to a web page, you just
enter the IP address.