[PCR-1000] 900 Mhz Cordless freq??

24 Mar 2002 11:29:27 -0500

Spread spectrum signals are modulated in such a way that they cover a
larger bandwidth than they would normally occupy.  Spread spectrum comes
in two basic flavors.

FHSS - Frequency Hopping Spread Spectrum - The frequency of the signal
is changed rapidly.  The frequency is hopped by a psuedo-random (PN)
sequence.  You can gain some security if the PN sequence is only known
to the stations communicating in the network.  

DSSS - Direct Sequence Spread Spectrum - The overall bandwidth of the
signal is spread by appling another PN sequence.  This time it is simply
used to "chip" the frequency up/down at a rate higher than the
modulating signal.  If you are carrying a 5Khz digitized signal the
signal might be chipped at a 20-25Khz rate.  This may primarily give
more immunity to noise.

FHSS may qualify as LPI (Lower Probability of Intercept) since it can be
much harder to fully recover the signal if the PN sequence isn't known.
It wouldn't qualify as LPD (Lower Probability of Detection) since each
hopped frequency is at full narrow band (usually) strength.

DSSS (which is what 802.11b radios utilize for high speed modes) might
be harder to detect, but it certainly isn't buried in the noise.  I can
be seen on a spectrum analyzer.  The key is that again you must know the
PN code to be able to recover the modulating data.

		THX/BDH

On Sat, 2002-03-23 at 15:15, Chastain wrote:
> This is may be a very basic question, but exactly how is spread spectrum
> different from non-spread?
> 
> Clint
> 
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Scanner Enthusiast
> Sent: Saturday, March 23, 2002 12:52 PM
> To: [email protected]
> Subject: RE: [PCR-1000] 900 Mhz Cordless freq??
> 
> 
> Understood - but there must be more than just 10 discrete frequencies?
> 
> I have a spread spec and a non-spread; can't hear the non one.
> 
> Adrian
> 
> 
> >From: "Trish & Carla" <[email protected]>
> >Reply-To: [email protected]
> >To: <[email protected]>
> >Subject: RE: [PCR-1000] 900 Mhz Cordless freq??
> >Date: Sat, 23 Mar 2002 10:44:37 -0800
> >
> >Many "900 MHz" phones are spread-spectrum units
> >operating on the 902-928 MHz .. band..
> >
> >If a particular phone is spread-spectrum, your
> >scanner will not even detect a signal..
> >
> >Trish.
> >
> >--
> >Patricia E. Gibbons & Carla Satra
> >Tactical Link Systems
> >In California:
> >"She sells D-cells by the seashore"
> ><ICQ#: 72818195>
> ><http://www.tactical-link.com>
> >  see my comvan at:
> ><http://www.tactical-link.com/wa6ube.htm>
> >......................................
> >My Public Key is available at: 
> >http://wwwkeys.pgp.net:11371/pks/lookup?op=index&search=0xedecb44f
> >Key ID: 0xEDECB44F
> >This key is RSA, NOT Diffie-Hellman !!
> >
> >
> >-----Original Message-----
> >From: [email protected] 
> >[mailto:[email protected]]On Behalf Of Scanner Enthusiast
> >Sent: Saturday, March 23, 2002 10:38 AM
> >To: [email protected]
> >Subject: [PCR-1000] 900 MhZ Cordless freq??
> >
> >
> >
> >Does anyone know the 900 MHz cordless phone frequencies?
> >
> >I have a list of 10, but my Canadian (unblocked) pcr100 doesn't hear my
> 
> >own cordless phone.
> >
> >
> >73, Adrian
> >
> >
> >_________________________________________________________________
> >Chat with friends online, try MSN Messenger: http://messenger.msn.com
> >
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> 
> 
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