24.pdf

(2044 KB) Pobierz
Chapter 24
Web, Wi-Fi, Wireless
and PC Technology
The personal computer (PC) and
Internet have surely changed many
lifestyles — young and old and those in
between. Hams have always embraced
technology, and they have used the PC
and Internet to greatly enhance and im-
prove the ham radio experience in many
ways! Hams with an interest or passion in
virtually all interests (homebrewing,
DXing, contesting, digital modes, satel-
lites are but a few examples) now take for
granted nearly instantaneous access to in-
formation and specialized Web sites. Com-
puters are routinely used for operating
digital modes, logging contacts, tracking
satellites, controlling stations locally or
remotely, software defined radio and a host
of other applications.
In this chapter, in addition to touching
on how hams are using PCs and the
Internet, we will also review the personal/
commercial
wireless
world around us that
is extraneous to ham frequencies, equip-
ment or operation. This chapter was writ-
ten by Donald R. Greenbaum, N1DG, and
Dana G. Reed, W1LC. It also includes ad-
ditional contributions from John J.
Champa, K8OCL, Reed E. Fisher,
W2CQH, Howard S. Huntington, K9KM,
and Ronnie P. Milione, KB2UAN.
The Internet and World Wide Web
SEARCH ENGINES
The Internet encompasses millions and
millions of pages of information. Unless
you know exactly what you are looking
for, there is simply too much information
on the subject of ham radio to find without
properly using search engines. There are
countless ham radio Web sites created by
individuals, clubs, organizations and com-
mercial vendors. The Web sites listed in
the sidebar “A Ham’s Guide to Useful
Internet Sites” offer just a small taste of
what’s available.
In any event, the best way to locate ham
radio Web sites for your particular interest
is to use one of the popular search engines:
Google, Yahoo, Ask, Alta Vista, Dogpile
and
Look Smart
are among the more popu-
lar. The secret to a successful search is to
be specific by limiting the results or
hits.
Although most search engines are pretty
good at ranking results in a useful order,
simply typing
ham radio
as the topic of
Search Engines — Electronic Parts and
Cross Referencing
A QRP list member was trying to search, or cross reference, a semicon-
ductor in Google, but without success. He had probably only entered the
exact part number. The part was described as possibly of one family of
semiconductor, but apparently in Google he used the part number “IRF331A”
which indeed comes up blank.
However, a knowledge of manufacturing prefixes or numbering systems
used for semiconductors or other components can be very valuable. Origi-
nally, IRF was the prefix for International Semiconductor Parts. Entering that
in Google.com, I came up with a Web page:
www.irf.com.
From there, I
came to a search engine on the page that eventually led to their cross
reference guide — and the fact that the IRF331A can possibly be replaced
(depending on the application) by the IRF330. However, an upgraded part is
the IRF440, or the 2N6760.
Knowing a general supplier of replacement semiconductors, my next stop
— had this not worked out — would have been
www.NTE.com.
The main
point here is to study distributors catalogs, for knowledge of part-numbering
conventions for whatever electronics you might need. Get to know company
logos that are applied to parts as these will shorten your searches if the
company still exists, using that logo. For the totally unfamiliar part, a logo can
be very helpful to focus your search.—Stuart
Rohre, K5KVH
Web, Wi-Fi, Wireless and PC Technology
24.1
A HAM’S GUIDE TO USEFUL INTERNET SITES
The Web is all about change, so it’s difficult to present a comprehensive list in
an annual print publication. Here are a few general ham-related sites to get you
started. Many more are linked from these sites. If you don’t find what you’re
looking for, try your favorite search engine.
ARRL:
www.arrl.org
Where else would you go for ham radio news?
AC6V:
www.ac6v.com/
Rod has links to over 6,000 other radio related sites
covering all topics imaginable.
AA1V:
www.goldtel.net/aa1v/
Don has the usual DX links plus some pretty
good NASA links not found on other sites.
DX Zone:
www.dxzone.com/
A good commercially-run site that is well laid
out providing 7000 links to other commercial and private ham run sites.
425 DX News:
www.425dxn.org/
Good Italian non-commercial site for DX
News and links to DX-related sites.
K4UTE:
www.nfdxa.com/K4UTE/K4UTE.HTML
One of the best sources of
QSL routes and links to other DX-related activities.
NG3K:
www.ng3k.com/
Want to know who’s going where and the link to
their Web site? Since 1996, Bill has been keeping track of these things on this
Web site and has everything archived for searching.
QSL.NET:
www.qsl.net
Al, K3TKJ, provides free hosting to thousands of
hams for radio-related Web pages.
K1BV Awards Directory:
www.dxawards.com/
Are you into wallpaper? Ted
has one of the best sites for award information and links to those offering them.
MODS:
www.mods.dk/
Modifying your radio? Find hundreds of links com-
piled over the last eight years by Erik, OZ2AEP.
VOICE OVER INTERNET
PROTOCOL — VOIP
Like our airwaves, the Internet can carry
our transmissions over great distances. Un-
like ham radio, the Internet offers only digi-
tal transmission. If we are using an analog
mode like voice or video, those modes must
be converted into that digital format before
sending and converted back to analog upon
receipt. Two software packages have
emerged to allow hams to converse over the
Internet in what is known as
Voice over
Internet Protocol,
or
VoIP.
ARRL offers a
publication titled
VoIP: Internet Linking for
Radio Amateurs
by Jonathon Taylor,
K1RFD (check with your favorite ham radio
dealer or visit
www.arrl.org/shop).
The
book discusses Amateur Radio VoIP opera-
tion in great detail.
EchoLink
Recognizing the growing use of the
Internet by hams, Jonathon Taylor, K1RFD,
wrote a software program called
EchoLink.
Now even antenna restricted hams can en-
joy the fun with a computer, a microphone
and an Internet connection. You can con-
nect via EchoLink to other licensed hams on
computers, mobiles transmitting through
repeaters linked to the Internet via connected
VHF repeaters, and even nodes connected
via HF. There are well over 100,000 regis-
tered users worldwide using EchoLink.
There are also conference nodes, some spe-
cific to other hobbies such as aviation. It is
the ultimate party line encompassing com-
puters, radio and the Internet. Like radio, it
is not a duplex mode; both stations cannot
talk at once. The software is free (you must
have a ham radio license) and is
downloadable from
www.echolink.org.
The software is very user friendly, and all
control features are click-of-a-mouse en-
abled. The only requirement of your PC is a
sound card and microphone.
IRLP
Unlike Echolink, which allows two hams
to communicate without either having a ra-
dio, the
Internet Radio Linking Project
(IRLP)
takes a different approach to VoIP.
David Cameron, VE7LTD, designed the
software to provide a simple and easy sys-
tem to link radio systems together using the
Internet as the communications backbone.
The system is
Linux
based and requires
a
Linux-based
Pentium PC running
Speak
Freely
software, an interface card (purchased
inexpensively from VE7LTD), your radio
and a sound card. Your sound card takes the
analog audio from the radio, converts it to
compressed digital packets and sends
short streams over the Internet to the con-
nected nodes via the interface card. The
control software controls the packets
Linux
Ham Radio Software Directory:
radio.linux.org.au/
Do you prefer
Linux
to
Windows?
This site lists Perl scripts ranging from modeling antennas
to European Microwave Beacon propagation forecasting.
Satellite Tracking Software:
www.satsignal.net
QSL Museum:
www.hamgallery.com/
In addition to one of the most com-
plete online QSL collections, Tom (K8CX) has one of the more complete ham
radio link sites on the Web.
interest to you is not sufficient. For ex-
ample, a query on
ham
yields links to Web
sites mentioning ham radio, ham (the
food) and other hits totaling more than 100
million pages! A more specific search of
ham radio
reduces the page count to 25
million pages. Narrowing and refining
your search is as simple as adding more
specific words, sometimes called
key-
words.
and choosing them wisely will re-
duce the page count to manageable levels.
Ham radio software
reduces our search to
19 million pages while
ham radio dsp soft-
ware
reduces it to 500,000 pages.
You can keep refining your search by
adding keywords. Most search engines
offer various options to help narrow your
search. These are found in a section called
something along the lines of
advanced
search.
For example, searching for the
exact phrase
“ham radio software”
returns
40,000 hits and
“ham radio dsp software”
brings it down to a handful.
24.2
Chapter 24
Search engines are a great help for locat-
ing parts and component data for construc-
tion projects. For example, later in this
chapter we discuss isolation transformers
and specify a RadioShack part. A search for
radioshack 273-1374
brings you right into
the RadioShack online catalog with infor-
mation on ordering this part. It’s possible to
be too specific in searches. Sometimes the
part number can be too exact, and adding
either a manufacturer or looking up the de-
scription of
isolation transformers
are a
broader alternative that will help if the spe-
cific part search comes up negative. See also
the sidebar, “Search Engines — Electronic
Parts and Cross Referencing.”
Another way to find ham radio related
Web sites is to browse one of the link sites.
A number of good sites like the one shown
in
Fig 24.1
are run by hams and dedicated
to collecting thousands of links to Web
sites of interest. They are usually arranged
by topic as well as alphabetically by name.
Fig 24.1 — AC6V’s collection of links to thousands of ham
radio Web sites can provide hours of exploration.
Fig 24.2 — IRLP links radio systems together via the
Internet.
along with continuous tone coded
subaudible squelch signals (CTCSS) to
start and stop the streams. CTCSS is also
used to pass commands that specify which
node to connect to, start and stop the con-
nection and a host of other settable param-
eters to control the process. Streams can
be sent to one or many nodes.
The software, interface cards and all
manuals are available from
www.irlp.net
(see
Fig 24.2).
PROPAGATION FORCASTING
One of the most valuable pieces of infor-
mation available on the Web is the various
real time propagation statistics and tools.
Current gray-line paths are vital to the LF
operator. MUF values are helpful to HF
operators. Current observed sunspot activ-
ity, solar storm indexes and other data are
posted on various ham and government
Web sites. Current solar flux numbers are
published by the Canadian Space Agency
as monitored at its Penticton Observatory:
www.drao-ofr.hia-iha.nrc-cnrc.gc.ca/.
Since auroral activity is harmful to HF
transmissions over the globe, NOAA pro-
vides both North and South Pole real time
auroral maps:
sec.noaa.gov/pmap/.
Knowing which frequencies are usable in
real time is also as handy a propagation
tool as a ham could want. As shown in
Fig
24.3,
a real-time graphic can be found at
the Solar Terrestrial Dispatch Web site,
www.spacew.com/.
INTEREST GROUPS
No matter where your ham radio inter-
ests lie, there’s likely one or more Web
sites or discussion groups dedicated to
your topic. Looking for a new rig? You’ll
find Web sites and discussion groups
where owners share opinions, tips and
information on most current radios. Are
you collecting or restoring vintage gear?
The ‘net has a wealth of information from
individuals and clubs interested in similar
radios (Fig
24.4).
Sites devoted to DXing,
Fig 24.3 — Maps like this one from
www.spacew.com display maximum
usable frequency in real time.
Fig 24.4 — The Internet is home to the Web sites of
countless clubs and organizations like the Collins
Collectors Association.
Fig 24.5 — Contesting.com is but one example of the many
Web sites devoted to specific Amateur Radio modes and
activities.
Web, Wi-Fi, Wireless and PC Technology
24.3
contesting (Fig
24.5),
emergency commu-
nications, digital modes, QRP, AM, VHF/
UHF, ATV and just about any other activ-
ity will help you get started or become
more proficient. It’s never been so easy to
explore the many and varied ways that hams
enjoy their hobby.
VIRUS PROTECTION AND
FIREWALLS
No Internet user should be connect-
ing to the Web without up-to-date virus
protection. Norton Antivirus and
McAfee are the two most popular com-
mercial products. There are also some
shareware products available.
Virus protection alone does not offer
full protection from intruders. Hams in-
crease the risk of being infected by open-
ing ports to allow IRLP, Telnet, Instant
Messenger, VoIP or FTP applications. The
solution here is installing a
firewall.
Firewall and other security features are
built into later versions of
Windows XP
or
you can choose third-party software from
a number of vendors. They detect both
internal and external attempts to compro-
mise your personal computer (PC).
A more expensive but more capable so-
lution is a hardware-based device com-
monly known as a
firewall appliance.
In
addition to the simple intruder detection
found in firewall software, they contain an
intruder
prevention
system, the ability to
connect multiple PCs (as a router or
switch), monitor ability on all traffic in and
out of the network, open secure ports
(VPN) and automatically obtain updates
to firmware.
No matter what virus protection and
firewall you are running, it’s very impor-
tant to keep it current and effective with
regular updates. In addition, it’s important
to regularly check for security updates for
your operating system software.
Wi-Fi Glossary
Access Point (AP) —
A wireless bridg-
ing device that connects IEEE 802.11 sta-
tions to shared resources and a wired
network such as the Internet.
Ad Hoc —
In wireless LAN (WLAN)
networks this is a direct wireless connec-
tion between two laptop computers with-
out the use of an AP.
AP —
Access point.
Carrier Sense Multiple Access / Colli-
sion Avoidance (CSMA/CA)
— The wire-
less method that tries to avoid
simultaneous access or collisions by not
transmitting, if another signal is detected
on the same frequency channel.
Direct-Sequence Spread Spectrum
(DSSS) —
The type of modulation used in
802.11b that is capable of maximum half-
duplex data speeds of 11 Mbps.
Frequency Hopping Spread Spectrum
(FHSP) —
A type of modulation used in
early 802.11 devices that uses a time-var-
ied narrow signal to spread the signal over
a wide band. Maximum half-duplex data
rate is 2 Mbps.
Institute of Electrical and Electronics
Engineers (IEEE) —
The professional
standards setting organization for data
networking devices.
Orthogonal Frequency Division Mul-
tiplexing (OFDM) —
A type of modula-
tion that splits a wide frequency band into
many narrow frequency bands. Both
802.11a and 802.11g use OFDM.
Service Set Identity (SSID) —
The
identification for an AP. It is transmitted
continuously in the form of a beacon.
Wired Equivalent Privacy (WEP)
—
A standard for providing minimal privacy
of wireless LAN communication by en-
crypting individual data frames.
Wireless Fidelity (Wi-Fi) —
The Wire-
less Ethernet Compatibility Alliance cer-
tification program to ensure that
equipment claiming to be in compliance
with IEEE 802.11 standards is truly
interoperable. The term Wi-Fi5 is some-
times applied to 802.11a equipment that
operates on the 5-GHz band.
Wireless Fidelity (Wi-Fi)
COMPUTER CONNECTIONS BY
RADIO
Wireless local area networks (WLAN)
using spread spectrum transmit in the 902-
MHz range (802.11), in the 2.4-GHz fre-
quency range (802.11b and 802.11g), and
in the 5-GHz frequency range (802.11a).
Combining spread spectrum transmis-
sion’s characteristics with a low power
output (30 to 100-mW range) means it is
highly unlikely that one spread spectrum
network user will interfere with another.
Spread spectrum transmissions distribute
or “spread” a radio signal over a broad
frequency range. There are various tech-
niques for doing this spreading.
The older WLAN systems operate in the
902-MHz range based on the IEEE 802.11
standard and use frequency hopping spread
spectrum modulation, or FHSS. This modu-
lation technique uses what is called a prede-
termined pseudo-random sequence to
transmit data. This pseudo-random sequence
is actually a predetermined digital signal pat-
tern that places data on a combination of
frequencies across the entire spread spec-
24.4
Chapter 24
trum channel. The receiving station must
know the specific signal pattern used by the
transmitting station to decode the data.
These early 802.11 systems generally oper-
ated with slightly higher power (250 mW)
but at much slower data rates of typically 2
Mbps.
New-Generation WLAN
The first of the new generation of
WLAN systems is based on the IEEE
802.11b standard and use a modulation
technique known as direct-sequence
spread spectrum, or DSSS. This modula-
tion technique achieves higher data rates
by using a different pseudo-random code
known as a Complimentary Sequence. The
8-bit Complimentary Sequence can en-
code 2 bits of data for the 5.5 Mbps data
rate or 6 bits of data for the 11 Mbps data
rate. This is known as Complimentary
Code Keying (CCK).
The latest generation of WLAN devices
are based the same type of modulation,
Orthogonal Frequency Division Multi-
plexing (OFDM) but operate on different
frequency bands. OFDM provides its
spreading function by transmitting the
data simultaneously on multiple carriers.
802.11g operating in the 2.4-GHz range
and 802.11a operating in the 5-GHz range
both specify 20-MHz wide channels with
52 carriers spaced every 312.5 kHz.
OFDM radios can be used to transmit data
rates of 6, 9, 12, 18, 24, 36, 48 and 54
Mbps.
The WLAN Advantage
The main advantage of WLAN systems
is that the laptop PC users are not tied to an
RJ-45 type of wall outlet. At home they
can roam between the home office and the
patio. At work, they can move with ease
between an office and a conference room,
for example.
There is a significant economic advan-
tage for businesses relocating office ar-
eas. With the use of WLAN technology, it
is not necessary to spend the time and
money to rewire an entire floor or build-
ing. These small radio devices with their
small antennas and low power can readily
transmit through several layers of drywall.
If more than one access point, or AP, is
required to cover the business area, sev-
eral AP devices can all be linked together
by putting them in the same virtual LAN in
the wired network. Consequently, rather
than having to wire each individual office
and conference room, only the various AP
nodes need to be wired together. This can
produce a huge savings in time and ex-
pense.
WLAN Security
Although the majority of WLAN oper-
ate in the open mode allowing anyone in
the area convenient access the network,
often a minimum level of information se-
curity is desirable. This can be provided
by using a WLAN encryption protocol
built into the equipment called Wired
Equivalent Privacy, or WEP.
For those situations requiring a higher
level of security, most commercial firms
simply re-employ their virtual private net-
work (VPN) or tunneling strategy com-
monly used to allow secure network
remote access for mobile workers and
teleworkers. However, in the case of
WLAN use, extra steps need to be taken to
ensure that the VPN user ID and password
are not being wirelessly transmitted in the
clear without some form of encryption. A
new WLAN security standard called IEEE
802.1x attempts to address this need but is
currently plagued with interoperability
issues.
Wi-Fi systems being used in Amateur
Radio applications are typically referred
to as High Speed Multimedia (HSMM),
and these techniques are discussed in de-
tail in the HSMM section of the
Modes and
Systems
chapter of this
Handbook.
Wireless Technology Glossary
AMPS (Advanced Mobile Phone Ser-
vice)
— First standardized cellular service
in the world, released in 1983. Uses the
800-900 MHz frequency band.
Analog
— A signal that can vary con-
tinuously between a maximum and mini-
mum value. For example, the voice
voltage waveform from the output of a mi-
crophone is analog. RF voltage waveforms
(as those from AM, FM and SSB transmit-
ters) are also analog.
Cap Code
— A specific address encoded
into both a data transmission and the in-
tended receiving equipment so the receiv-
ing equipment can discriminate against
unintended or unwanted messages.
CDMA (Code Division Multiple Ac-
cess)
— A digital radio system that sepa-
rates users by digital codes.
Cellular
— Characteristic of or pertain-
ing to a system of wireless communication
made up of many individual cell units. The
term itself is derived from the typical geo-
graphic honeycomb shape of the areas into
which a coverage region is divided.
CELP (Codebook Excited Linear Pre-
dictive coding)
— A type of low-bit-rate
voice coder that emulates a single human
voice tract. Details can be found in Ref. 3
at the end of this chapter.
CSMA/CD (Carrier Sense Multiple Ac-
cess / Collision Detection)
— A set of rules
that determine how network devices re-
spond when two devices attempt to use a
data channel simultaneously (called a
colli-
sion).
After detecting a collision, a device
waits a random delay time and then attempts
to re-transmit the message. If the device de-
tects a collision again, it now waits twice as
long to try to re-transmit the message.
DHCP (Dynamic Host Configuration
Protocol)
— An external assignment
mechanism that provides a “care-of ad-
dress” to a mobile client (see also
Foreign
Agent).
Digital
— A signal that has only dis-
crete values, usually two (logic 1 and logic
0), that changes at predetermined inter-
vals. The value (e.g., voltage) present in a
single time period is called a bit. The num-
ber of bits transferred per second is called
the bit rate that has units of bits per second
(bit/s), or kilobits per second (kbit/s), etc.
E-mail
— Electronic mail sent and re-
ceived via computers with modems.
Transmission media can be existing tele-
phone or other communication lines, wire-
less, or not uncommonly both.
Encode
— The process whereby a trans-
mission contains additional data or code
added to facilitate proper routing of the
transmission to the desired point or points.
Encryption
— Technology used to
form a secure channel between a wireless
client and the server to support user au-
thentication, data integrity, and data pri-
vacy.
ESN (Electronic Serial Number)
— A
manufacturer-assigned identity contained
in a data transmission from a call placed to
verify that the hardware used belongs to a
valid cellular account.
Ethernet
— A local-area network
(LAN) protocol. Ethernet uses a bus or star
topology and supports data transfer rates
of 10 Mbit/s, 100 Mbit/s, 1 Gbit/s and 10
Gbit/s. Ethernet uses the CSMA/CD ac-
cess method to handle simultaneous de-
mands, and is one of the most widely
implemented LAN standards.
FDMA (Frequency Division Multiple
Access)
— A radio system that separates
user channels by frequency. Amateur Ra-
dio equipment presently uses FDMA.
Footprint
— The coverage area of an
individual cell.
Foreign Agent
— A special “node”
which is present on a foreign network and
provides mobility services to visiting mo-
bile nodes.
GPS (Global Positioning System)
— A
Department of Defense-developed, world-
wide, satellite-based radio navigation sys-
tem.
Handoff
— Process whereby a mobile
telephone network automatically transfers
a call from cell to cell — possibly to an-
other channel — as a mobile crosses adja-
cent cells.
Home Agent
— A host on a mobile’s
home network responsible for trapping its
packets, and forwarding them to the
mobile’s present location.
LAN (Local Area Network)
—
A com-
puter network that spans a relatively small
area. Most LANs are confined to a single
building or group of buildings. However,
one LAN can be connected to other LANs
over any distance via telephone lines and
radio waves. A system of LANs con-
nected in this way is called a
wide-area
network (WAN).
Most LANs connect
workstations and personal computers.
Each
node
(individual computer) in a
LAN has its own central processing unit
(CPU) with which it executes programs,
but it is also able to access data and de-
vices anywhere on the LAN. This means
that many users can share expensive de-
vices, such as laser printers, as well as
data. Users can also use the LAN to com-
municate with each other, by sending e-
mail or engaging in chat sessions.
Mobile Host
— Also known as a “mo-
bile node,” this addressed entity in the
Mobile IP protocol roams between its
home network and foreign networks.
Mobile IP
— This mobile industry stan-
dard enhances the IP protocol to remedy
problems associated with using the stan-
dard TCP/IP with a mobile entity. It allows
for transparent routing of IP datagrams to
mobile hosts (nodes) on the Internet.
Modem
— A hardware device, either in-
ternally or externally connected to a com-
puter that provides a connection from the
computer and some of its programs to a
landline (phone or communications line).
Network Independence
— The ability
to roam among networks (e.g., BellSouth
Wireless Data Network, CDPD, Wireless
24.5
Web, Wi-Fi, Wireless and PC Technology

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika:

Zgłoś jeśli naruszono regulamin