🚀 go-pugleaf

In article <52@bootsie.UUCP>, olson@bootsie.UUCP (Eric Olson) writes:
> I've got a few simple questions about cordless phones:
> 
> 1.  About 5 years ago, they started selling "new freqency" phones.
>     What was new, compared to the old phones?

The old phones used several frequencies around 1.7 MHz for the base
unit to transmit to the handset.  They used channels around 49 MHz
to go from the handset to the base.  The 1.7 Mhz band was phased
out, and now the base units operate at 46 MHz.
> 
> 2.  What frequencies are used by modern ("new frequency") phones?
>     AM or FM?  Sidebands?  Are they all exactly the same frequency,
>     or do some have different or multiple frequencies?

The MODE (which has nothing to do with FREQUENCY) is FM.  There
are ten channels, and here they are:

 
Base         Handset
 
46.61 MHz    49.67  MHz
46.63 MHz    49.845 MHz
46.67 MHz    49.86  MHz
46.71 MHz    49.77  MHz
46.73 MHz    49.875 MHz
46.77 MHz    49.83  MHz
46.83 MHz    49.89  MHz
46.87 MHz    49.93  MHz
46.93 MHz    49.99  MHz
46.97 MHz    49.97  MHz


If you listen with a VHF scanner radio, the best listening is on
the base unit side, as this side transmits BOTH sides of the call.

Several handset freqs, including 49.83, 49.845, 49.86, and I think
49.89 MHz are shared with kids walkie talkies, real CHEAP radio
controlled toys, and those wireless "nursery monitors" used in baby's
room.  In fact, if you drive around any residential area with a
scanner, there is a continuous carrier on 49.83 and 49.86 MHz from
all the nursery monitors.
> 
> 3.  My roommate has an AT&T cordless phone with 3 "channels".  I
>     guessed that they were upper SB, lower SB, and main band.  He
>     claimed they were separate frequencies.  What's the scoop?

Yes, it uses three of the channel pairs on the list above.  There
are no tricks with upper and lower SSB.

The FCC recently ruled that the manufacturers do not have to stick
to the assigned channels anymore, as long as they are within the
band, so things should get a LOT more chaotic soon.
> 
> 4.  (Not really a question)  I know there are security codes sent
>     between base & handset, my questions don't pertain to those.

The security code prevents folks from using another cordless phone
to make calls on your base unit.  It does nothing for voice
privacy.  Cordless phones are NOT private.  It is legal to listen
to them, and quite easy.
> 
> Thanks for any info you might have!

You're welcome!



Tad Cook
Seattle, WA
Packet: KT7H @ N7HFZ.WA.USA.NA
Phone: 206/527-4089 
MCI Mail: 3288544 
Telex: 6503288544 MCI UW  
USENET:...uw-beaver!sumax!amc-gw!ssc!tad
or, tad@ssc.UUCP