RF Column 41 - March 1995
Copyright (c) 1995 H. Douglas Lung ALL RIGHTS RESERVED

TOPICS:   Building a path Calculation spreadsheet
              (Download the files from ftp.gate.net/pub/users/dlung)
          Shopping for a transmitter at NAB 95 - Tips for buyers
          More transmitter tube life survey results
          How to get connected to the Internet - easiest & cheapest

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This month I'll continue my series on RF path analysis. No new
formulas this time, but I'll incorporate the Fresnel zone formula I
discussed last month into my spreadsheet model. This is TV
Technology's NAB preview issue and I thought I'd add some of my
suggestions on how to shop for TV transmitters at NAB. UHF
transmitting tube service life numbers continue to trickle in. Tom
Stevenson at Varian sent me what data they had on klystrode tube life.
After comparing the tube life numbers I'm seeing in this survey with
"conventional wisdom" five years ago I found some positive trends you
might find interesting. Finally, to help push more readers onto the
Internet or other on-line services I'll survey the offerings from
three nationwide Internet service providers. The FCC's files are now
available by using the Internet options available from America On-Line
(AOL) and Compuserve Information Service (CIS). I'll tell you where to
find them. If it seems like this month's column is large, it is --
more than double the size of my usual column! Take it with you to read
on the plane to NAB.

The microwave path analysis spreadsheet I presented in my November
column continues to generate a lot of interest. If I've already
e-mailed you a copy of the original spreadsheet, send me another
message and I'll e-mail the new improved version to you. Specify
Excel, Lotus, Quattro or Quattro Pro format. If you are not using the
latest version let me know which version you want. Figure 1 shows a
spreadsheet graph created in Quattro Pro for an actual path in San
Antonio, Texas. As you can see, in this version I've added real
terrain information and incorporated the Fresnel zone clearance
formula I explained last month. The black and white figure really
doesn't do it justice - you should see it on a color monitor. The
bottom line (brown) on the graph is the flat earth terrain plot, the
line above it (green) is the terrain plot after adding the K-factor
corrected earth curvature, the line above that is the allowance for
obstructions (red). The straight line on the top (blue) is the direct
path between the transmit and receive antennas and the curved line
below it (dark yellow) is the first Fresnel zone clearance required.
Note that on this model I use the full Fresnel zone clearance, not the
six tenths value often shown on graphs. The sixth tenths fudge factor
commonly used to adjust the clearance for a standard K- factor. Since
I have already adjusted the terrain for K-factor, doing it again for
the Fresnel zone clearance would make the model understate clearance
requirements.

Figure 2 shows the layout of the spreadsheet. If it looks different
than the one in the December column its because I realized putting the
distance line in a row instead of a column made it difficult to handle
a large number of terrain points. Using the vertical format it's easy
to adjust the spreadsheet as needed to accommodate as many terrain
points as desired, up to the memory limits of your computer and
spreadsheet. Most spreadsheets include a "Parse" function that allows
you to import text data into the spreadsheet and separate out the
numerical data. That's how I got the terrain database report from
Dataworld into the spreadsheet without retyping all the numbers. I
couldn't fit the entire spreadsheet onto the page, so I've shown the
first few lines, a section around 3.8 miles from the transmitter where
the Fresnel clearance is the smallest and the end of the path at the
receive dish.

A few comments on the columns. You can use any increment for the path
length steps in column A. While a smaller increment will make a more
detailed plot, you can also vary the increment along the path without
affecting the accuracy at the points plotted. Depending on how your
spreadsheet graph is set up, be warned it may look strange if you do
this. Column B contains actual height above mean sea level (AMSL) from
the USGS 30 second database for each plotted point on the path. Column
C adds the K factor adjusted earth bulge I showed you how to calculate
a few months ago to the terrain height AMSL in Column B. I used a
constant 30 foot height for the obstruction heights in Column D,
corresponding to a medium size tree or small commercial structure. You
can put in actual values for questionable clearances if you have them.
Column E is the total height, which is simply the sum of the terrain
with K factor adjusted earth bulge and obstruction height added
together. Path height in Column F is calculated as a straight line
from the transmit to receive dish. If you need a refresher on any of
these formulas see my earlier column and study the formulas in figure
3.

Last month I presented the how and why of Fresnel zone calculations.
Using the formula I described I calculated the clearance and
subtracted it from the path height. The result is in Column G. The
path clearance in Column H is obtained by subtracting the total
adjusted terrain and obstruction height from the Path Height in Column
F. Fresnel clearance is calculated by subtracting total adjusted
terrain height from the lower Fresnel height in Column G.

Figure 3 shows the formulas used in spreadsheet. I described most of
them in my November and February articles so I won't go into details
here. The "$" signs in the formulas around the variables stored in
column F, rows 3 through 8, force the formula to keep the reference to
those cells absolute (the same) even if the formulas are copied into
another row. That makes it easy to use the spreadsheet copy command to
fill in the formulas in columns C, E, F, G, H, and I in rows 16 and
beyond until you reach the end of the path. These formulas were
written using Quattro Pro and should work on all versions of Quattro
and Lotus spreadsheets. If you use Microsoft Excel you will have to
modify them slightly. The Excel help screens and manual describes the
differences between Lotus and Excel spreadsheets. Note that figure 3
shows only the first two lines of the path calculation. You should
copy the formulas in C17, E17, F17. G17, H17 and I17 into succeeding
rows as described above. If you use a standard obstruction height like
I did, you can also copy the reference in D17. You can type over the
copied value if you want to enter a different obstruction.

Next month I'll add path loss calculations to the model and look at
some of the ways to compute distances between two points on the earth.
It turns out there are three ways to do it -- the F.C.C. way,
spherical geometry and a complicated formula which takes into account
the fact the earth is really a bit egg shaped!

Wandering the floors at NAB its easy to get mesmerized by a nice
looking transmitter surrounded by smooth salesmen. How do you know if
this is the transmitter you should buy? Here are some tips from my
experience selecting transmitters, both full power and low power.
While I haven't always followed the rules, the times I haven't added
significantly to amount of work I had to do to make the installation
work to my satisfaction.

Rule Number One. Make sure the transmitter is capable of delivering
the performance you expect. Verify actual performance by looking at
the data taken as part of the FCC Type Acceptance procedure and during
station proof of performance testing. Did the unit easily meet the FCC
specs or was it close to the edge? Make sure the transmitter was not
adjusted between tests. It is much more difficult to make a
transmitter meet all specifications at the same time than it is to
adjust it to optimize a specific parameter before making each
measurement.

Rule Number Two. Ask how many units have been shipped. While you
certainly will get the latest technology by purchasing the first of a
series, you will also be the one to find all the problems. If the new
design offers so many advantages over the more tested traditional
transmitters that you feel you must have it, make sure that your unit
will be upgraded at no extra cost for all design changes made over the
next five units or so. This should include on site engineering time.
You take a risk buying the first of a series. The manufacturer has a
lot at stake too, so they should be willing to help you make it work
as promised. You might also want to check into the financial stability
of the company. Make sure they can handle the losses if the new design
has major problems.

Rule Number Three. Obtain a list of current users of the transmitter.
The number of transmitters purchased by these users should match the
number of units shipped you obtained from the previous question. If it
doesn't, it may mean there are some unhappy customers the manufacturer
doesn't want you to know about. Be sure to ask about the number of
units shipped first. The manufacturer will want that to be as large as
possible. Call at least some of the users before committing to a
purchase. Find out what their problems were and how good the service
was. If a particular problem keeps showing up you can word the
purchase contract such that it forces the manufacturer to address the
problem. This helps you and the other owners.

Rule Number Four. Look behind the front panels. How difficult will it
be for you to maintain the transmitter? Is redundancy built in or are
there opportunities for single point failures? How difficult will it
be to keep some signal on the air if some parts fail? Are common
failure items like blowers and power supplies easy to get to and easy
to replace? I've seen some transmitters that used bolts and loose nuts
instead of pressed in nuts to mount equipment. If a large panel
divided the bolt and nut, this could mean one person alone couldn't
replace some components in the transmitter. Ask to look at the service
manual. Does it cover all adjustments and do you understand it? If you
have to maintain the transmitter, you must be able to follow the
manual.

Rule Number Five. Make sure factory support is available when you need
it. Most transmitter manufacturers offer 24 hour service. Often this
is done using an answering service that pages a designated engineer on
duty. You probably wear a pager. You also know there are times when
the pager can't reach you -- certain locations or perhaps you are
swimming with the pager somewhere else. Ask the manufacturer how many
people are available during non-business hours on pager. Ideally a
supervisor can be paged if the designated engineer on duty can't be
contacted. Talking to an engineer won't solve all problems. A part may
be needed. Ask the manufacturer if it is possible to have parts
air-freighted to you counter to counter during non-business hours. Use
this as a worst case scenario. The transmitter fails at 10 PM the
night before Thanksgiving (always a Thursday). To get it back on the
air a part available only from the manufacturer is required. How long
will it take you to contact someone from the manufacturer and receive
the part? In some cases it might take you until Tuesday the following
week! You'd be off the air for five days!

Rule Number Six. If the response to rule two was that several units
had been shipped, ask what problems were discovered with the early
units and how these problems were corrected. I've found most
manufacturers are honest about first run product problems. If you get
an answer like "we had no problems", make sure the other users you
obtain in Rule Number Three can verify that. Otherwise, you have to
suspect the manufacturer's credibility and you'll probably have
trouble in the future.

Rule Number Seven. If you've gotten this far and have decided this is
the transmitter you want, see how much money you can hold back on the
payment until the transmitter meets the agreed upon specifications. Be
sure to specify the transmitter cannot be readjusted during the
testing to make it meet a specific parameter. If readjustment is
demanded, then all readings done before the adjustment should be
repeated to be sure they still are in spec. If you have rigorous
specifications I'd advise using having a mutually agreed upon outside
consulting engineer perform the measurements. On a large purchase, you
should be able to withhold ten percent or more of the total purchase
price until performance specifications are met. You may even want to
have the contract worded to force the manufacturer to take the
transmitter back and refund any prior payments if it cannot meet the
agreed upon specifications. If the transmitter is a new model with
little or no track record it isn't unreasonable to ask for a much
larger amount contingent on satisfactory performance. Happy hunting!

My UHF transmitter tube survey is turning into more of a long running
feature than a simple, statistical report. I suppose I shouldn't be
surprised, because several factors affect a tube's life. One thing
I've noticed from the hours reported is that the longer a tube's been
on the market, the longer it lasts. I remember when the first wideband
EEV external four cavity klystrons came out the average life was
around 20,000 hours. Now, five years later, I've seen the same type of
tube last over 40,000 hours. What's the difference? I believe it comes
from both users and manufacturers gaining experience with the tube.
When the first generation of tubes fails, station engineers and
transmitter and tube manufacturer engineers take steps to prevent the
same sort of failure. Sometimes these steps, like decreasing filament
voltage, can be applied to tubes still in service. An analysis of
failed tubes alerts manufacturers to weak points in tube and system
design. Now that we've gone through a generation or so of Varian
klystrodes and EEV I.O.T.s it's not unrealistic to expect to see
longer lifetimes from these tubes.

Dave White at WQOW-TV in Eau Claire Wisconsin pointed out the perfect
example of this. The broadcast klystron tube that's been manufactured
the longest (at least in the U.S.) is the Varian 30 KW integral four
cavity tube. Dave send me an e-mail to say he felt my estimate of
30,000 to 40,000 hours average life for the integral cavity tubes was
way off the mark. I based that on my past experience with Varian's 55
KW tubes in visual service and on the comments I received from other
stations using the same tubes. Based on more recent information, I
could probably extend it to 50,000 hours. The 30 KW tubes are another
story. Dave's experience includes three UHF stations using RCA TTU-30
and TTU-60 transmitters. He wrote that the three tubes he had fail
last year had ages between 65,000 to 110,000 hours. He also noted that
in aural service he had two tubes in service with well over 100,000
hours on them and two visual tubes with over 70,000 hours life! He
said "We have not experienced ANY tube failures with less than 50,000
hours...".

Tom Stephenson at Varian sent me a detailed e-mail outlining the tube
life of Varian klystrodes at Georgia Public TV, one of the first sites
to use klystrodes. All of the tubes were used in separate visual /
aural service. As with the klystron, tubes in aural service seem to
last longer, with the greatest lifetime reported at 42,032 hours. In
visual service, the greatest lifetime so far was 24,389 hours. These
tubes were still in service as of December 31, 1994, so the numbers
may be higher now. Tom didn't provide data on when tubes failed but by
comparing aural life and visual life I was able to make some best case
estimates. If I assume the aural tube had never been replaced, and if
the visual hours were significantly less that meant the visual tube
had been replaced once, I get a minimum life before failure numbers
around 5,000 hours and maximum life before failure numbers over 20,000
hours for these earlier tubes. These numbers tend to support my
current estimated life of 20,000 hours for visual and combined service
and also my hypothesis that tubes in service today will last longer
than those they replaced. I've noticed that some transmitter
manufacturers are recommending purchasing 60 KW tubes and operating
them at 30 KW in combined service. It will be interesting to see if
that technique extends tube life out to 30,000 hours or more, close to
that obtainable with klystrons.

If you've been reading my columns the last few months, you know I've
come to believe that an e-mail connection via the Internet or other
on-line service will become as essential as a fax machine or phone
line in the near future. If you don't have access to on-line
information and e-mail you and your company will be at a disadvantage
to those that do. As I mentioned in my Buyers' Guide column, I think
the future of digital TV lies somewhere beyond HDTV and crude
interactive cable games. The closest analog to my vision of future TV
is the World Wide Web. It's easy to use and appears to offer an almost
infinite selection of choices. Companies like MCI, BellSouth, Nynex,
Microsoft and more are talking about releasing services that will use
the Web. Eventually they will figure out that most people actually use
a small percentage of the total offering and that re-transmitting the
same thing over and over to many different locations is a huge waste
of bandwidth. That's where broadcasting can come in -- "broad"-casting
the most requested information over the air along with local services
and advertisements.

To explore the World Wide Web using a graphic interface you need a
direct connection to the Internet. While America On Line and
Compuserve are both promising Web browsers in the future, neither was
available as this column was written. Obtaining a direct connection to
the Internet isn't difficult. It is possible to use a dial up modem
for Internet connections with software that supports PPP (Point to
Point Protocol) or SLIP (Serial Line Interface Protocol). Software is
available for both the PC and Mac. Check your local computer store.
Until recently, this software took quite a bit of effort to get
working, since there are many parameters that have to be set correctly
to work with a given Internet provider. The settings that work for one
provider probably won't work for another.

Two nationwide Internet providers have now started bundling software
with their services. I tried out one, Netcom's Netcruiser, and was
very impressed with how easy it was to set up and how well it worked.
I noticed a "Netcruiser" disk at the checkout stand at the CompUSA in
Miami. For under $10, it seemed worth a try. Installation on my 486
notebook went without difficulty. The software can be updated almost
automatically (just click on a few buttons) over the Internet. The
cost is reasonable. There is a $25 setup charge, however, the first
month's usage is free, so the real cost is less. The monthly charge is
$19.95 per month for up to 40 hours of "prime time" access (most hours
on weekdays) and unlimited hours non-prime (weekends and very late at
night during the week). If you need more prime time hours than this
the cost is $2.00/hour. They have access numbers in most larger cities
and 800 number access is available for an extra $4.90 per hour. You
probably can't make a long distance call for less than that. The
software includes a decent World Wide Web browser (one complaint is
that you can't scroll horizontally with it) plus Gopher, FTP, Telnet,
e-mail and USENET news software. While you can find better software
than what's included with Netcruiser, it is good enough, given the
ease of installation. Call 1-800-353-6600 for more information. Even
though I've read several criticisms of it on Compuserve and in the
Netcom newsgroups, from my experience Netcruiser is the easiest and
for many the cheapest way to get on the Internet. The criticisms
usually come from new users (or old users of organized services like
Compuserve) that don't understand the anarchy of the Internet or from
power users that find the Netcruiser software too limiting.

Netcom's Netcruiser's biggest disadvantage is that it won't work with
other Internet software like Netscape's excellent Web browser. That
may have changed by the time you read this. I've also found their
download times to be much slower than that of other providers I've
used. The transfer rate often drops well below 1 Kilobyte per second
or even stops for a minute or more on file transfers using a 14.4K
modem.

PSI is one of the companies that offers a bundle of software along
with an Internet connection that will work with software from other
vendors. Their "InterRamp" package sells for $99 and includes software
tested with their service. Other software will work, but the package
makes sure all users start from a common point. This reduces PSI's
support costs. The PSI "InterRamp" service costs $29 per month for 29
hours of use, with each additional hour costing $2.00. While
"InterRamp" costs more than "Netcruiser", it offers more flexibility
in software and perhaps more important, offers high speed ISDN access
in many major cities. They have attractive packages to help you get
connected with ISDN, especially if you live in an area serviced by one
of the Baby Bell's they are working with. For multimedia Web browsing
a 14.4KB modem can seem awfully slow. While I don't have any
experience with them, PSI's "InterRamp" inexpensive ISDN option is
worth checking out for high speed access using the latest software.

If you live in a large city, check out local Internet providers. Many
of these offer unlimited access for around $20 per month. They may
also be in a better position to provide technical support than the big
national companies. My main account is with Cybergate in South
Florida. While the monthly fee is higher than Netcom, most of the time
the network speed is much higher, so I spend less time on line. Many
local providers are fairly small operations with limited backup. That
means there will be times when the service goes down or when the lines
are constantly busy. This even happens to the big nationwide providers
every now and then. For those times, I recommend having a backup
Internet provider that has no monthly fee.

I use Prometheus Information Network Group (PING) as my main backup.
If you've gotten an e-mail message from me while I'm on the road
you've noticed the message comes from dlung@ping.ping.com instead of
dlung@gate.net. With a full service provider it is fairly easy to have
e-mail forwarded to another address. PING does not charge a monthly
fee for their 800 number access. I pay $5.40 per hour of connect time.
There is a one time setup charge. Contact PING at 1-800-PING-TEL for
details. I've found PING to be very reliable and fast. They were among
the first providers to install 28.8K modems. If you live in an area
without a local Internet supplier or a local access number to a
nationwide supplier PING may be your best option. Its tough to find a
long distance carrier that can match PING's $0.09 per minute cost
anywhere (48 states) / anytime, not counting the Internet access.
You'll need your own software to work with PING. It doesn't have to be
expensive -- many of the books on the Internet include all the
software you need to get started. After you get on you can download
free or shareware versions of all the applications you'll need. I've
found PING's support to be excellent. I'd recommend PING for a backup
provider or for users who don't want to commit to a monthly fee from
another provider.

Many of my readers use America On-line (AOL). AOL now has limited
Internet access. You can obtain files from the FCC's server using
either the Gopher or FTP tools available by clicking on the "Internet"
box on the main menu screen. To use Gopher, select Gopher, then select
Government for a list of government Gophers, scroll to the end to
select "More" government gophers and scroll down that list until you
find "Federal Communications Commission". A much faster way is to use
FTP. Click on the "FTP" button on the "Internet" screen. Click on "Go
to FTP" on the next screen. At the next screen click on "Other sites"
to get a box where you can type in the address of the site. Type in
"fcc.gov/pub" exactly as I typed it here -- same case, no spaces,
forward slash and don't type the ""s. Press [ENTER] or [RETURN] on the
keyboard and after a while you should see the FCC's server directory.
Select "Daily Business" to get a listing of dates in year-month-day
format. Note that leading zeroes are dropped from the days, causing
the list to appear out of sequence. Select the appropriate day to see
the FCC Daily Digest released that day along with new orders, news
releases, notices, speeches and such released that day. You can
download them to your computer to read later.

AOL, by the way, charges $9.95 per month for up to five hours of
access, after which the rate increases to $2.95 per hour. If you
primarily want Internet access, after eight hours you'll be paying
more than you would with Netcom's "Netcruiser" account. Perhaps its my
imagination, but it seems like AOL is organized to keep you on line
with the meter running as long as possible. AOL also has the USENET
news groups available, so you can check out rec.video.satellite.tvro,
rec.video.satellite.misc, rec.video.satellite.dbs or
sci.engr.advanced-tv for satellite and HDTV related topics. Call
800-827-6364. They always seem to have specials running so ask about
free trials, connect time and software.

I haven't forgotten Compuserve, my first on line service (I started
over ten years ago!). Compuserve remains the only service I'm aware of
that has a forum for broadcast engineers -- the Broadcast
Professionals' Forum (GO BPFORUM). I've searched USENET news groups
for something similar with no success. Perhaps there is a mailing
list, but I haven't heard of it. There was a discussion recently on
the sci.engr.advanced-tv group about starting a sci.engr.broadcast-tv
group. Maybe it will happen, but right now BPFORUM is all there is.
Many RF related manufacturers or their engineers are on BPFORUM --
Tektronix, Harris Corporation, TTC, Modulation Sciences and more.

I've found most RF discussions end up in the BPFORUM's B.ENG. -
CONTRACT section. You'll also find copies of the programs I've written
on BPFORUM. By the time you read this the path calculation spreadsheet
should be there, along with the Basic program for my Cheap Remote
control, calorimetric RF power calculator and peak to average
calculator. Compuserve now offers limited Internet service -- USENET
news groups and FTP file transfers. Using Compuserve's Wincim 1.31
software I found it easy to FTP fcc.gov and browse the files available
there. Some of the off-line readers (like OzCIS) allow you to select,
read and reply to USENET news groups off-line. Use these programs to
significantly reduce on-line time and costs.

Compuserve (CIS) lowered its hourly rates in February. Their standard
plan costs $9.95 per month and $4.80 per hour for extended services
like the Internet and BPFORUM. Call 800-848-8199 for more information
and again, ask about special deals and free software. Is AOL a better
deal at $2.95 an hour (or even less if you use under nine hours per
month) with the same monthly rate? That depends. AOL has nothing like
the BPFORUM. Using an off-line reader like NavCIS, TAPCIS or OzCIS
allows you to download interesting messages from CIS forums and news
groups or e- mail messages in a few minutes and then spend as much
time as you like reading and replying to them off-line, without the
meter running. I'm not aware of off-line readers for AOL's forums or
mail, so any reading or writing you do is on-line with the meter
running. If you like to check on weather forecasts, news, stock
quotes, or airline flights and reservations these services are "free"
on Compuserve while on AOL the hour meter keeps ticking. Money aside,
AOL does have a nice graphic user interface and, while it may take a
while, it is easier to navigate through the various offerings on AOL
than it is on Compuserve, even using Compuserve's Wincim program.

If you are comfortable with the command line, don't mind a text based
interface for most items and want to communicate with other TV
broadcast engineers, I'd recommend using one of the off line navigator
programs and Compuserve. If you can afford an extra $9.95 a mont, then
add AOL for the nifty interface and extended Internet offerings. AOL's
user interface is another option for the broadcast digital "air-way" I
described in the 1995 Buyers' Guide issue. If all you need is e-mail,
then AOL is probably the cheapest option, provided you keep the usage
below eight or nine hours a month, otherwise an Internet account like
"Netcruiser" or a local provider's shell account will be cheaper.

Shell accounts permit you to connect as a terminal to a computer
connected to the Internet. You can't directly download files from the
Internet to your computer, nor can you use a graphic interface for
browsing the World Wide Web. You can still get text information from
the FCC, browse the Web using a text browser like Lynx and send and
receive e-mail. Shell accounts are very low cost and in some
communities are available for free through a library or school or for
a small donation from other non-profit organizations.

I hope I've given you enough information to convince you to get
connected. I've personally tried Netcom's Netcruiser, America On Line,
Compuserve (including Wincim and OzCIS) and PING's Internet services.
I haven't tried PSI's "InterRamp" but I included it because of their
pioneering efforts to get consumers connected with ISDN. There are
many other on-line services out there which I haven't tried but which
you might want to look into. Delphi offers inexpensive text based
Internet connections, although I've heard some reports they are slow.
I haven't gotten any free offers lately from Prodigy, but I just saw
an ad where they now offer access to the World Wide Web on the
Internet. If it is working, they are the first of the "big three"
on-line companies to offer Web access.

There are several Internet providers that advertise "free" Internet
access in the back of computer magazines. These make their money by
collecting a portion of the cost of the long distance call required to
access their computers. While I haven't tried them, they might be a
no-risk way to test the waters on the Internet for only the cost of a
long distance call. Many local bulletin boards (BBS) now offer some
Internet access at low rates. Most do not offer the SLIP or PPP
connection you would need for direct Internet connections and
graphical user interfaces. Local Internet providers can offer support
and low rates, although often with reduced reliability. Check local
computer magazines and the business section of the newspaper for
information on them.

TV distribution is moving towards digital, HDTV or not. All direct
broadcast satellite services operating in the DBS band are digital.
Cable TV is moving slowly towards digital to get more channels and
services to customers. Broadcasters will have to keep up. This change
offers a unique opportunity to redefine television, to make it more
responsive to what people want, to provide more opportunities for
"value added" services. The growth of the World Wide Web to include
commercial information "for fee" services and shopping malls gives a
glimpse of where digital broadcasting could be in the next century.
Learning your way around the Internet is the best way I know to
witness the much hyped "convergence" of computers, video and
broadcasting. It's also the way to keep up with the latest news from
industry and the F.C.C. Don't get left behind.

Next month I'll finish the path calculation spreadsheet by adding
distance and coordinate calculations along with path loss and link
budget analysis. I found an excellent, easy to follow and inexpensive
book on UHF and microwave engineering. If you want to dig deeper into
the various microwave propagation modes or need a refresher on
waveguide theory, don't miss my review of this book. Your comments and
experience could be part of that column as well -- e-mail, fax or
phone your comments to me.

E-mail is the best and fastest way to reach me and to get copies of
the various programs I've written for this column. I can also e-mail
text copies of back columns to you, minus graphics. I can now send
binary files to accounts on Compuserve, America On Line and the
Internet (provided your Internet software supports either attached
files or UUENCODED files). If you are on Compuserve, please use my
Compuserve number -- 70255,460. If you are on America On Line, the
Internet, MCI Mail or any other service, address messages to me at
dlung@gate.net. I will be checking my e-mail during NAB. If you see
something interesting in the RF field, send me a note. If you are
showing something interesting in the RF field, let me know before NAB
so I won't miss it!

If you must use more archaic ways of communication, you can fax me at
305-884- 9661, though faxes will sit while I'm traveling. You can also
call me at 305-884-9664, but please avoid peak business hours. After 6
PM eastern time is best. Mail should go to Doug Lung, 2265 Westwood
Blvd., Suite 553, Los Angeles, CA 90064. It is forwarded to me on a
regular basis, about once a month if I'm not in L.A. Expect a six to
eight week delay for replies, more if I'm busy.



Copyright (c) 1995 H. Douglas Lung ALL RIGHTS RESERVED