Why can't I find my cordless phone with my scanner ?

[Rodo]

Hi all,

I have a scanner that goes all the way to 2 GHz. I also have a couple of
cordless phones. Both Panasonic, one says "900 MHz digital", the other does
not have the word "digital" in it. I thought maybe I can find them with the
scanner. I could not. Maybe the "digital" is not rally analog so I can
understand. I thought I should be able to find the non-digital. I swept the
900 MHz range with no luck. Am I missing something here ? Do they really use
900.000 MHz ? what about modulation (FM, USB,LSB,etc) ?

Thanks

 

[Joel Kolstad]

I have a scanner that goes all the way to 2 GHz. I also have a couple of
cordless phones. Both Panasonic, one says "900 MHz digital", the other does
not have the word "digital" in it. I thought maybe I can find them with the
scanner. I could not. Maybe the "digital" is not rally analog so I can
understand. I thought I should be able to find the non-digital. I swept the
900 MHz range with no luck. Am I missing something here ? Do they really use
900.000 MHz ? what about modulation (FM, USB,LSB,etc) ?

If they're digital, there's a decent chance that, even if you do find it,
it'll just sound like background noise. Also, if your units were advertised
as being "spread spectrum," effectively all your scanner will see is a small
increase in the noise floor of the entire band and you'll never find it.

The tool you really need is a spectrum analyzer or perhaps a service monitor.

 

[qrk]

Hi all,

I have a scanner that goes all the way to 2 GHz. I also have a couple of
cordless phones. Both Panasonic, one says "900 MHz digital", the other does
not have the word "digital" in it. I thought maybe I can find them with the
scanner. I could not. Maybe the "digital" is not rally analog so I can
understand. I thought I should be able to find the non-digital. I swept the
900 MHz range with no luck. Am I missing something here ? Do they really use
900.000 MHz ? what about modulation (FM, USB,LSB,etc) ?

http://electronics.howstuffworks.com/question320.htm

 

[JeffM]

I also have a couple of cordless phones.

I thought maybe I can find them with the scanner. I could not.
Rodo

Heddy Lamar doesn't want you to.
http://www.google.com/search?q=Heddy-Lamar+frequency-hopping

 

[Mark Zenier]

Hi all,

I have a scanner that goes all the way to 2 GHz. I also have a couple of
cordless phones. Both Panasonic, one says "900 MHz digital", the other does
not have the word "digital" in it. I thought maybe I can find them with the
scanner. I could not. Maybe the "digital" is not rally analog so I can
understand. I thought I should be able to find the non-digital. I swept the
900 MHz range with no luck. Am I missing something here ? Do they really use
900.000 MHz ? what about modulation (FM, USB,LSB,etc) ?

Off the top of my head, the band is 902 to 928 MHz. Some non-digital
ones use several channels of wide band FM at two different (handset,
base) frequencies in the band. Digital ones can be either frequency
hopping or spread spectrum or a combination of both. A spread spectrum
signal would sound like digital hash spread out over some MHz of the band.

Mark Zenier [email protected] Washington State resident

 

[Mebart]

Or, they could be in tthe 2.4 Ghz ISM band, whcih isn't covered by
your scanner.

Slightly more expensive phones can operate as high as 6 gHz too.

Just a short time ago, 900 Mhz was common....with recent advances in
technology, the frequencies have gone up too.

As others pointed out, they could be spread spectrum. If carried to
the limits of technology, you would have to put the phone in a
shielded room and use a wideband spectrum analyzer to even have a hint
of where they are operating in frequnecy.

People that do FCC certification have shielded rooms, just for this
purpose.

M

 

[Mebart]

Did some ebay checking right afteer I sent the message.

Here's a 5.8 Ghz phone:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=75450&item=5779146040&rd=1

and, another one:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=48504&item=5779147355&rd=1

'nuff said.

M

 

[Mebart]

If you aren't sure about your particular phone model, and the
manufacturer does not have info...

You can search the FCC type acceptance database to get alot of info.

I used it to find technical info on my vlf wireless dog fence
manufactured by petsafe. IN my case, there were high res pictures, a
full schematic, theory of operation and similar info. It was a
goldmine of info and helped me alot.

Regards,

M