New telephone/answering system RFI

[W1RKW]

Had to replace an answering machine because it was behaving erratically lately. It would sometimes record the message or not.  It was an old ATT digital system. So purchased an all in one unit with corded phone and answering system to clean up the office desk per order of XYL. It also came with a wireless phone which I figured would come in handy when out in the yard.

Anyway, it's a Panasonic KX-TG1061. It was recommended by a friend (user's perspective). And I do like how it works. It's nice phone/answering system except for the unexpected RFI. Might explain the low cost.

RFI caused by it is S7 in the shack on 75m and kills 20m. Completely wipes out the beside receiver with birdies up and down 10m.

Both the corded phone/answering machine and cordless phone came with wall-warts. Both wall-warts are SMPSs, ouch. Should've looked into that before purchasing.

So I proceed to build grounded shields for the wall warts. RFI didn't go away.  Wasted an hour.

Hoping that this new phone systems transmitters aren't the source I go a different route first.  Disconnected the phone line from the new corded phone. RFI goes away.  Hmm.  Go around the house and disconnect other phones while the new phone is connected.  Each phone made the RFI go away.  Scratch head.  New phone appears to be emitting RFI on phone line throughout the house and phone line is radiating it. Tried a ferrite bead on the new phone. No perceptible change. Probably don't have the right mix.  Shut-off the DSL modem, no change. Disconnect powered off modem from network, no change.  Turn everything back on and on a hunch insert DSL filter into the new telephones line and viola, RFI disappears.  Go figure.

Removed the wall-warts shielding and everything is still quiet.

Rant mode: ON. So this begs the question, how does one determine if a new appliance is going to be a PITA without having to return stuff and try something else and just plain waste time and money. Are we relegated to having to finishing the engineering to prevent our bands from becoming polluted even within our own confines? Rant mode: OFF.

 

[W3RSW]

Yep, with new amenities come new challenges.  So as it is, so hath it always been.

We now live in a Polluted jungle of EM waves, be they long or short.   Unwanted and background of these can easily overcome the desired tiny slice of the spectrum.

I listen to a Grundig G3 choking on its own spew of computer generated misdirection.

[WD8KDG]

Picked up a Panasonic KX-TG7741 a while back...........no RFI. But it isn't near the shack.

Craig

[flintstone mop]

I have a nice Panasonic TGA??? and it is a DECT6.0 system. 1.9ghz and no interference to it from my QRO HF or from it. I can stand next to our microwave oven and not get blanked out by the leaking RF from the oven as from previous cordless systems.
It was supposed to be the new FCC mandated freq for cordless phones.
Fred

[KB2WIG]

We've got a Panasonic system. I think its a KX-TG7643M , but I know it uses the Dect 6.0 sys. No noise that I can tell. FWIW, the closest unit is about 25' from the closeline dipole and no spew from the wall wart.
There are 6 ht's and I have one next to my computor with the Netgear wireless router. Its 2 inches from the netgear pick up unit.  No problem. Well maybee one -  its got this intercom thing, so the XYL can zip! zip! zip! the phone, and startle the stuffing out of me. Its got a blue tooth, and there's also some way of interfacing 2 cell phones into the unit. I don't know much more about that.


klc

[Jim, W5JO]

Is all your lines in the house in good condition?  Bad connections in the wiring can cause the problem with new systems some times.  My Panasonic KX-TG6071S, about 6 years old is RF immune and causes none.  I used Cat 5E for the cable in the house, professionally installed.  A bad or loose connection at the wall outlet for the phone or somewhere could be the culprit.  Check all your connections.

[flintstone mop]

I caused a little telephone RFI on 80M AM and installed a K-Com filter at the Vonage box and the base unit for the Panasonic and no more KC4MOP in the 'phones.

[Pete, WA2CWA]

I have the Panasonic KX-TG1064. Same as yours except it's 1 base with 4 remotes. No detectable RFI on any frequencies. One remote is in the shack.

[W1RKW]

Jim,
When the qth was being built back in '01 the builder asked what I wanted in the house for wiring. That included electric, phone, cable, E'net, etc. I even had conduits run to various parts so I could run cables in what I considered at the time were hard to reach places. That being said, when the phone wiring went in CAT3 was used initially and it was run from each termination in a series fashion. It was hokey IMO.  I requested that the CAT3 be replace by CAT5 and wired in a star configuration which the builder obliged. Also requested that a 66 block put be in at the service entrance.  So the phone is CAT5 as well as E'net.  Why that base unit is radiating is unknown but a DSL filter dongle shut it up without effecting the sound quality of the phone.  My DSL and phone is separated at the service entrance by a whole house filter. That might have something to do with it but don't know. I sort of doubt it.  All I know is that it's working.

BTW, the phone is one of those DECT6.0 units.  The sound quality is very good on both the corded unit and remote. Good volume too. Aside from the RFI issue I highly recommend the phone to anyone who's looking for a new phone/answering system.

[Jim, W5JO]

Jim,
When the qth was being built back in '01 the builder asked what I wanted in the house for wiring. That included electric, phone, cable, E'net, etc. I even had conduits run to various parts so I could run cables in what I considered at the time were hard to reach places. That being said, when the phone wiring went in CAT3 was used initially and it was run from each termination in a series fashion. It was hokey IMO.  I requested that the CAT3 be replace by CAT5 and wired in a star configuration which the builder obliged. Also requested that a 66 block put be in at the service entrance.  So the phone is CAT5 as well as E'net.  Why that base unit is radiating is unknown but a DSL filter dongle shut it up without effecting the sound quality of the phone.  My DSL and phone is separated at the service entrance by a whole house filter. That might have something to do with it but don't know. I sort of doubt it.  All I know is that it's working.

BTW, the phone is one of those DECT6.0 units.  The sound quality is very good on both the corded unit and remote. Good volume too. Aside from the RFI issue I highly recommend the phone to anyone who's looking for a new phone/answering system.

You did exactly as I did when I built this place except I used the phone company.  Fortunately this company is locally owned and very progressive.  They sent their commercial team out and wired the place like you did because I wanted phone, TV and DSL in each room in the house.  My experience with electicians is exactly as their first attempt and I didn't want that.  The nice thing about the phone company is they had the test equipment to certify the wiring.  I would never have been able to do that with AT&T or any other big company and afford it.  Even though I received a contractor's discount it was costly.

The DSL is stripped at the entrance and brought in on a separate wire like you have and I have never had a problem.  I am not sure if my phone is the detect 6 system or not because I lost the box and it has been so long.  But if that dongle filter did it, I wonder is somehow you have cross couplling somewhere.  But if it is fixed, then why go looking.  Good to know.

[W1RKW]

It is a bit perplexing why the DSL filter is killing the RFI but I'll take it.  As far as I can tell there is nothing else that is affected by having it line. As long as the radios are quiet, that's all I care about. Maybe there is a design difference in the phone that deviates from standard practice that allows it to radiate. Don't know. It's very odd.

[Jim, W5JO]

It is a bit perplexing why the DSL filter is killing the RFI but I'll take it.  As far as I can tell there is nothing else that is affected by having it line. As long as the radios are quiet, that's all I care about. Maybe there is a design difference in the phone that deviates from standard practice that allows it to radiate. Don't know. It's very odd.

Bob I wonder if your DSL stripper outside may have taken a surge of some sort.  Have you had any storms lately?  It is the only remote possibility I can think of.

[WQ9E]

Like Pete I have the Panasonic 1 base with 4 remote system and it has been flawless, no RFI to or from the system. 

[W1RKW]

Jim,
I wondered that.  I did take a look at it and there appears to be no visible damage. At the same time both the DSL and voice are working as they should.  I'm not hearing anything unusual in the phones and DSL is running at 100% rated speed with no connectivity issues.

[Jim, W5JO]

Jim,
I wondered that.  I did take a look at it and there appears to be no visible damage. At the same time both the DSL and voice are working as they should.  I'm not hearing anything unusual in the phones and DSL is running at 100% rated speed with no connectivity issues.

Well unless you can get the phone company to replace the thing to be sure, then what you have works so leave it as is.   That is really a strange thing.

[W1RKW]

yeah it is strange.  I suppose it's possible that the new phone is the problem. I haven't ruled that out despite it working.  I'll go with it and see what happens, if anything. I can live with the DSL dongle.

[W1ATR]

It is a bit perplexing why the DSL filter is killing the RFI but I'll take it.  As far as I can tell there is nothing else that is affected by having it line. As long as the radios are quiet, that's all I care about. Maybe there is a design difference in the phone that deviates from standard practice that allows it to radiate. Don't know. It's very odd.

It's just a simple low pass filter. A very very low, (as in freq), pass filter. POTS voice is up to 4kc, and dsl sigs are 138kc to 1100kc. Switching PS's operate even higher than that, so the nifty little DSL LPF chokes it all away. I have a 5 gallon bucket full of them somewhere around here that I used to give to neighbors that said they can hear me on their phones. Worked like a charm, simple, and can be stacked a couple times for really bad problems.