From: Ed Switalski <E.Switalski@bnr.co.uk>
Date: Fri, 18 Mar 94 01:09:37 PST
To: Matthew J Ghio <mg5n+@andrew.cmu.edu>
Subject: Re: Radio Networking
In-Reply-To: <8hW8cKi00WAu0UsEso@andrew.cmu.edu>
Message-ID: <199403180908.13234@bnsgs200.bnr.co.uk>
MIME-Version: 1.0
Content-Type: text/plain


Hi,



   >Ed Switalski <E.Switalski@bnr.co.uk> wrote:
   >
   >>*** Quite Far !
   >>
   >>    With coherent CW you can key morse Japan/US i.e cross the Pacific
   >>    on a few watts.
   >
   >If so, this might make a very convienient email/chat system... and with
   >encryption, a great way to hide our anonymous remailer connections from
   >'Big Brother'.

*** you said it, only prob is that a slow signalling method is ungood for 
    cryptoprotocols with lots of overheads! e.g RSA wil take 512/1024 bits
    to encrypt just a single session key.  Such efficiency considerations
    might temp users to change keys on a per-day rarther than per-message
    basis 

   >I must admit I don't know much about radio hardware...  But would it be
   >possible to link up a large metropolitan area via radio links of this
   >type and transmit email and such?  I think I could find a lot of sysops
   >interested in that... no more waiting until night to get netmail!

*** probably, the slow signalling means very narrow bandwidth per station
    so you could pack lots into any unused slice of RF spectrum.
    I would use gaps in your local cellular 'phone system (etc!) as then
    the spooks would be hard pushed to even find the traffic and could not
    jam without annoying/alerting every local yuppie.   

   >If the system worked at 300 bps, you could transmit a 2K message in
   >about one minute.  That would allow over 1000 messages per day, much
   >less than most small BBS networks, and certainly enough to keep up with
   >this list.  (Not to mention that ASCII text is very compressable, 50% or
   >more compression is not difficult in many cases.)

*** Sounds OK.  Disguise the receiver and antenna (my Polish partisan mama's
    washing line with wire plaited all along the length of the string)
    and leave it on all day.  save the days messages to protected RAM 
    and read out at will.

   >How hard would it be to build a small transmitter/receiver system to
   >handle data at low bps rates?  And how much would it cost?

*** Incoherent - QRP (ham-speak for low power) TX/TX transevivers cost
    50-80 pounds for a shortwave kit in the UK -VHF/UHF bands maybe more.
    Low power means no exotic transistors, no big power supplies, 
    no noisy cooling, fancy protection etc -the ouput tranny might need
    a modest heatsink -thats all. A data modulator woul be 20-30 pounds extra.
    Coherent addons  bit probably 100 pounds (quessing here)  

    As electronics are cheaper in US, so for sterling read dollar.

    Stay Cool, Hang Loose, Hack Crypto.

  Ed