"tg" wrote in message
...
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 supported 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