From: gary@ke4zv.uucp (Gary Coffman)
Newsgroups: rec.radio.amateur.packet
Subject: Re: What is packet radio?
Date: 7 Sep 92 12:24:39 GMT
Reply-To: gary@ke4zv.UUCP (Gary Coffman)
Organization: Gannett Technologies Group

In article <4879@daily-planet.concordia.ca> yau@cs.concordia.ca (Joseph K. K. Yau) writes:
>I have been a Usenet news reader for 1 years now. During reading news from
>other newsgroups, sometime I heard about packet radio but not in detail.
>I have several questions about packet radio and what it can do. I hope 
>some one from this newsgroup can give me an answer or point me to the FAQ
>file. 

I'm posting this answer since more than one person has posted similar
requests today.

>1) What is packet radio ?

Packet radio is a method of transmitting digital data via radio. It
sends information in "packets", or short bursts, and then waits for
an acknowledgement. This is known as an ARQ protocol. There is a
check sequence in each packet that allows the receiver to determine
if a transmission error has occurred. The system works somewhat like
an Xmodem file transfer in that it resends packets that aren't positively
acknowledged. In addition, each frame has an address header that identifies
the sender and the intended receipent. Unlike telephone transfers, packet
is used on shared broadcast channels so some means of identifying the
sender and receiver of each frame is required. 

Packet radio, as it is usually practiced, is a half duplex system. The
common speed is 1200 baud. But because it is half duplex, and because
it is a stop and wait for acknowledgement protocol with considerable
overhead in each frame, it's thruput is considerably less than a common
1200 baud telephone connection. Real direct point to point connections
generally have an effective thruput of less than 300 bps. There are
faster systems available, 9600 baud and 56 kilobaud, but they aren't
in common use yet. These are all VHF/UHF systems with limited range.
At shortwave, the baud rate is restricted to 300 baud or slower, and
the thruput is very low, though the range can be worldwide.

Packets are often relayed through other user's stations to extend
range. Normally each relay step will halve effective thruput. Paths
with more than four relay steps are generally unusable.

>2) Can someone use packet radio to read, or post Usenet news ?

Yes and no. *Amateur* radio has content restrictions and third party
restrictions that limit it's usefulness for Usenet access. No commercial
content, and no profane or indecent language can be transmitted. In 
practice this means that a gateway station must manually screen traffic
*from* the Usenet. Traffic sent *to* the Usenet is the responsibility
of the amateur sending the traffic and places less of a burden on the
gateway operator. Third party rules are also a problem. International
messages for or from a third person can't be passed between amateur 
stations, except if the countries involved have international third 
party agreements. There are only a limited number of countries that 
have such agreements with the United States. This is only an issue
if the amateur stations involved are in separate countries.

>3) What about email, telnet or rlogin ? Is it possible ?

All of this is possible, with the same restrictions listed above for
general Usenet news access. No commercial use, no profanity, and
no international third party messages except where authorized. The
generally slow speed of packet makes interactive usage painful in
most cases. Use of 56 kilobaud systems, however, is nearly as good
as a wireline 19.2 kb connection. Even interactive editors are
easily used under these circumstances.

>4) What kind of equipment is need to get into packet radio ?
>   IBM-PC ? DOS/UNIX ? MODEM ? RADIO ?

In the simplest case, a terminal, or terminal emulator program, a
TNC (Terminal Node Controller), and a radio are all that is required
to become active on packet. Most users prefer more sophisticated
software with a PC of some sort. The KA9Q TCP/IP software for example
is available for DOS, Mac, and Unix systems.

>5) How much will it cost (minimun) ?

This is highly variable. A (free) junked terminal, a used TNC ($70),
and a surplus radio ($50) can get you on packet. Or, you can spend
much more for new PCs, TNCs, and radios. The average price for new
equipment, excluding the PC, is in the $500 to $700 range. In the 
most advanced cases, some of us use Sun workstations and 56 kb RF 
modems, you could spend several thousand dollars, most of that for
the workstation. A 56 kb RF modem costs $250 and a transverter to
shift it to a UHF frequency costs between $150 and $350. Then there
are antennas, feedlines, power supplies, etc for any of the above
combinations.

>6) Where can I find a source for newsfeed ? Is there any money involve for
>   newsfeed ?

It's illegal to charge money for any amateur radio activity. Finding 
someone local to give you a feed may be difficult as few hams are
gatewaying the Usenet to amateur radio.

>7) I may move to Toronto or Montreal or Hong Kong. Is it possible to use
>   packet radio to access newsgroup at these cities ? 

Amateur radio laws, and activity, vary from country to country. Canada
has more liberal rules than the US. I can't advise about Hong Kong.

If all this sounds negative, it is. Amateur packet radio is fairly 
new, in a constant state of flux, and is saddled with many outdated 
regulations and practices.  It's basically an experimental service 
at present with much hope for the future, but little current practical 
use for people needing either high speed or high volume service. If
you want to be a ground floor developer, it's wonderful, but if you
have a current practical communications need, I'd suggest the telephone
network. Finding a dialup Usenet feed is not difficult.

Gary KE4ZV