Why would a DECT Panasonic cordless phone keep losing the wireless link?

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Any idea why fully-charged DECT Panasonic cordless phones would keep losing their wireless link lately?
http://farm4.staticflickr.com/3720/11812145904_ab84d957e3_o.gif
They're not at all far (fifteen feet) from the base and, this loss of signal only started happening about a year ago (the phone is probably about three or four years old).
So, something clearly aged (but the batteries show as fully charged and I've changed them between handsets anyway).
The error I keep getting (on multiple handsets) is: No Link. Reconnect base AC adapter.
This happens after, say, a few minutes of talking time, but, it's erratic. Sometimes I can be on the line for an hour before it happens; other times it happens within five minutes.
What frustrates me is the lack of debugging techniques.
Reconnecting the phone to the charger doesn't change anything; nor does placing each of the handsets back into the mother phone to reinitialize them.
Here's the DECT Panasonic KX-TG6441 phone & handsets:
http://farm4.staticflickr.com/3779/11811980883_f540a29bee_o.gif
Here's the model number plate:
http://farm6.staticflickr.com/5539/11812098283_c1f2dc22f0_o.gif
Googling for that error message, I see it's pretty common; but I already tried the little that Panasonic suggests: http://eng-na.faq.panasonic.com/app/answers/detail/a_id/12927/~/my-handset-displays-no-link-to-base.-reconnect-ac-adaptor.-what-should-i-do%3F
The outlet is working fine; the phone works fine from the base; it's just the handsets that keep losing their wireless connection.
Anyone else resolve this problem before? Any debugging hints?
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Have you added anything like a wireless router for the internet ? Sometimes phones and other wireless devices will interfear with other.
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On Tue, 7 Jan 2014 04:28:02 +0000 (UTC), Danny D'Amico

Since it happens with multiple handsets, it's a fair assumption that all of the handsets did not simultaneously fail. Therefore, whatever is wrong is at the base unit.

Clue. The transmit power of the base is only about 10 mw of RF. It doesn't take much to ruin that. I suggest you open up the base unit, and see if there's anything amiss inside. Look for loose screws, corroded connections, bad connectors, critters, liquid spill residue, mechanical damage, cracked PCB, bad solder connections, bad crimps, and a bad standby battery. The last is a bit problematic as I don't know if that model uses a battery to retain the settings and messages, or if it uses flash ram. If you find a battery, test it. If not, don't worry about it. Also, if it uses the same charger as the remote chargers, try swapping the charger. If you only have one charger, measure the voltage under load or just replace it.

These days, everything is throw away and few devices are made to be repaired. If you can find a schematic, it will be both a bonus and a miracle.

Only one charging base?

Yes, but not on a Panasonic phone. I think it was a Uniden. It turned out to be corrosion residue caused by an unreported milk shake spill several months previously. The outside had been wiped clean, but the inside was a mess. On an other phone, it was a loose screw and lug to the antenna wire causing an intermittent antenna connection.

Tear it apart and look inside.
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On 1/6/2014 8:28 PM, Danny D'Amico wrote:

Sounds like interference.
I recently switched to a high-power router and Wi-Max wireless internet. One or both drove my 2.4GHZ wireless phone crazy. Hardly worked at all, even up close. I powered up the spectrum analyzer. Yep they were right on top of one another. I switched to a DECT phone, which, as I recall, works on different frequencies. Problem got a lot better. I still can't stand too close to the router.
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mike wrote:

There are three kinds of interference that can happen in this case.
The first is direct interference, where your WiFi unit operates on 2.4gHz and your cordless phone also operates on 2.4gHz. The old 2.4gHz phones did not listen for activity on a channel before transmitting on it, and often would wipe out Wifi.
The newer DCT phones listen, but there is only so many channels and eventually they overlap.
Since 2.4gHz is 1/2 of 5.8 gHz, the second harmonic of WiFi can interfere directly with 5.8gHz phones and so on.
The second is intermodulation, where two signals combine and the difference or sum causes interference. Not likey in this case.
The third is desensitization, where a strong signal on a relatively near frequency overloads the receiver in a device. So a WifI router can cause DECT phones to stop receiving, even though WiFi is 2.4gHz and DECT is 1.7gHz.
That's why you can't talk on the DECT phone near your WiFi device.
It's very likely that the OP is experienceing desensitazation or direct interfernce.
Another thing they can try is to move the base station. Especially if it is sitting next to another wireless device.
Geoff.
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"Geoffrey S. Mendelson"

** That some new kind of math ???
ROTFL
... Phil
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On Tue, 07 Jan 2014 08:19:18 +0000, Geoffrey S. Mendelson wrote:

This is very useful information, an applicable to the WiFi group as well.
My DECT Panasonic KX-TG6441 phones & handsets apparently operate at 1.9 GHz, according to page 6 of this PDF: http://service.us.panasonic.com/OPERMANPDF/KXTG6431-MUL.PDF "The product operates in the frequency range of 1.92 GHz to 1.93 GHz, and the RF transmission power is 115 mW (max.)"
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Don't you have a voltmeter? You shouldn't be depending on the base to inform you as to whether the batteries are actually being fully recharged.
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On Wed, 08 Jan 2014 02:50:41 -0800, William Sommerwerck wrote:

I was remiss in not mentioning that I tested the voltage with my fluke but the problem, as always, with testing open circuit no-load voltage is that without a load, a battery that tests good isn't necessarily good.
However, all the handsets are now reading full bars in battery voltage, so, I'm inclined to assume that the battery-charge indicator on the handsets isn't really a voltage indicator - but some sort of integrator.
The good news is that it hasn't happened since re-registration; but I also haven't been on the phone a lot either. I will report back in a few days to let you know if the problem is solved by the re-registration or not.
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On Mon, 06 Jan 2014 23:48:17 -0500, Ralph Mowery wrote:

Yes. There is lots of WiFi in the house.
There are also other cordless bases and phones on other lines, e.g.,
http://farm3.staticflickr.com/2873/11811729095_cafdd2467b_o.gif
For example, this Panasonic KX-TG6671 seems to work just fine though:
http://farm3.staticflickr.com/2806/11812266724_b252b01faf_o.gif
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On 01/07/14 12:59 am, Danny D'Amico wrote:

Our Panasonic DECT phones are on 1.9GHz, I'm almost certain -- not on the common 2.4GHz WiFi frequency.
Perce
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Percival P. Cassidy wrote:

DECT phones are on 1.9gHz (1.7 in Europe), DCT phones at 2.4gHz.
They are similar, and of course, incompatible.
Geoff.
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On Tue, 07 Jan 2014 14:52:02 -0500, Percival P. Cassidy wrote:

My problematic Panasonic KX-TG6441 cordless phone is also on 1.9 GHz, as described on page 6 of this PDF:
http://farm4.staticflickr.com/3786/11829460325_b34ca30a30_o.png
http://service.us.panasonic.com/OPERMANPDF/KXTG6431-MUL.PDF
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On Mon, 06 Jan 2014 20:52:27 -0800, Jeff Liebermann wrote:

Hi Jeff,
Googling, it says the error indicates the base station loses its power, but, that's just not happening, at least not from a loose power cord.
The reason I know that's not happening, other than it's not, is that not all of the handsets fail at any one time. Only one handset fails at a time.
So, if it was the base failing (which is what the error indicates), then all the handsets should fail simultaneously, I would think.
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On Tue, 7 Jan 2014 06:01:50 +0000 (UTC), Danny D'Amico

Nope. If it's a loose antenna connection on the base, the handsets close enough to get a minimal signal from the base would still work, while those far away would loose the signal.
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On Mon, 06 Jan 2014 22:21:07 -0800, Jeff Liebermann wrote:

This is a good point!
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On Mon, 06 Jan 2014 20:52:27 -0800, Jeff Liebermann wrote:

As someone suggested, I guess it could be my 2.4GHz WiFi antenna that is causing problems; but why would that be intermittent?

This is likely. The error indicates a lack of power at the base, but, there isn't any overt lack of power at the base.

This makes a lot of sense - and it's a good idea, especially since the error indicates a lack of power at the base.
I'll try that and re-test & report back.
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Danny D'Amico wrote:

It may not be YOUR WiFi that is causing it. Unless you live in a single family house about 1/2 km from anyone else and a road, you could have problems with interference from other WiFi devices, cordless phones, cell phones, and so on.
I live in a steel and poured concrete building, and away from the center of it (I'm on a middle floor), say my bedroom, I can only "hear" my Wifi. In my living room which is in the center, I can "hear" 8 unprotected WiFi networks, and a few protected ones. It's a miracle I can use my WiFi there.
Geoff.
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On Mon, 06 Jan 2014 21:04:17 -0800, mike wrote:

It could be. There's a lot of WiFi floating around my house these days.

I had to look up WiMax: http://en.wikipedia.org/wiki/WiMAX

I hadn't thought of aiming my spectrum analyzer inside (mine is pointed outside). What I may try is setting up a spectrum analysis where I run a 1000 frames without any devices plugged in, and then another 1000 frames with all my WiFi devices plugged in to see if there is a big difference.

I don't know what frequency DECT works on, but, two of my four phone bases are DECT.
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On Tue, 7 Jan 2014 06:10:11 +0000 (UTC), Danny D'Amico

In the USA: 1920 to 1930 MHz. 5 channels, spaced 1.728 MHz apart. 4 mw average tx power. 100 mw maximum. <http://en.wikipedia.org/wiki/Dect>
In the USA, there's no GAP support, which means that phones from different manufactories not only will not talk with each other, but also can interfere with each other. You might try your problem phone with the other DECT phones and base turned off.
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