"tg" <tg@[EMAIL PROTECTED]
> wrote in message
news:48416796$0$2482$da0feed9@[EMAIL PROTECTED]
> I know about the following frequencies for DECT cordless phones:
> 1881.792 MHz
> 1883.520 MHz
> 1885.248 MHz
> 1886.976 MHz
> 1888.704 MHz
> 1890.432 MHz
> 1892.160 MHz
> 1893.888 MHz
> 1895.616 MHz
> 1897.344 MHz
>
> but I fgured there might be more. Are there?
> The reason I ask is because I have a philips dect phone and when I use
it
and run my
> scanner on the above frequencies I get nothing. Before you jump on me I
know that you
> can't listen to dect phones on a scanner and I know about the
encryption,
but I just
> wanted to find out what frequency my phone used (if not one of the
above).
I did try
> contacting philips but they don't respond andthe above numbers are all I
could find on
> google.
> Thanks for any help.
>
>
>
>
The reason for this is that the signal is time division multiplexed (up to
12 calls sup****ted per channel at any given time!), and as the
transmission
switches on briefly and then off again for the majority of the time, i.e..
it has only a few percent duty cycle, the transmissions are too short
lived
for your scanner to open squelch. In fact, the base and handset take it in
turns to transmit, the switching happens thousands of times per second;
this
is what allows the base and handset to use the same frequency to
apparently
provide a full duplex link. This method of transmission is known as
'digital
ping pong'. Also, remember that the channels have a bandwidth of over
1MHz,
and that your scanner can only (even in WFM mode) hear less than 10% of
the
channel at once, so most of the signal always falls outside of its
passband.
You may hear something though if you open the squelch fully, go close to
the
phone or base station whilst a call is in progress, and try tuning each of
the 10 centre frequencies. Remember, you will hear a slight electronic
buzz
mixed with the background noise. That's your lot!
By the way, 3G phones use Wideband Code Division Multiple Access, and
channels 5MHz wide in the 2100 MHz area. I won't go into how WCDMA works
as
it's tricky to explain, but don't expect to hear even this much if you
tune
into a frequency which is part of a WCDMA channel even if your scanner
tunes
this high, you can detect these of you have a radio with a bandscope
allowing you to sweep at least several MHz of the spectrum, a strong WCDMA
channel shows up as a wide pulse above the noise floor since the base
stations continuously transmit throughout the 5MHz of spectrum.
Anyway, I hope I have explained?
David, G7VDI
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