World of Ham Radio 1997/WOHR97_AmSoft_(1997-02-01).iso/swl/docs/ch18tvi.doc

Text File | 1997-02-01 | 32KB | 655 lines

Packet interference to channel 18 on cable-TV systems - Draft
copy

Chuck Manetta  N4YJC     August 5, 1991

To: All interested Amateur Radio operators! Distribution: World-
wide

On June 11, 1991 I sent out a Bulletin through the Packet
Bulletin Board System to "RFI @ ALLUS".  This Bulletin was titled
"ANY ANSWERS TO PACKET / CABLE 18 RFI YET?".  This bulletin was
concerning the interference created by Packet Radio to the Cable
Channel 18, and vice versa Cable Channel 18 to Packet Radio.  The
response to this bulletin was nothing short of incredible!  In
approximately one month, I received in excess of 50 replies from
the United States and Canada!  A number of these replies were
from hams that were very interested in what helpful information I
might have found.

This overwhelming response to this bulletin, showed me that there
was a major adverse interaction between the Cable Industry and
the Amateur community. This caused me to research this problem
with more vigor. The answers apply to all amateur VHF operation,
in all modes.

I would like to give credit to all of the Amateurs and
Professional Consultants who have helped me research this area of
interest:

KY6V WB6KGB KB4FOW KA4OPZ N4LDG KP4OO KB4RLL N4VDM N4KWB N4UTO
KC4BBM WD8KCT KG6XX KC4IEE WD4DPH KN4QH WB6CBJ WB2NGZ WN4ISX
KC4WTX KM4ID KA7CGB KG7FU KA9NME WA2RCB WD4LYV KC2FD WB5BBW N5LDD
K2TNN VE7BLZ AA9AW VO1MQ N2KZH VE7CJT VE7HGN N5HOF K0FPC WA2ZKD
N8AHK N2DS W0BQH NJ8J KB5MGE W1CDM W9IUP N1CB W4NTG WB7NNF N7MWA
KA4JEE WV9J W5NDG N7HFZ K6RAU KB6CYS

Ed Hare KA1CV, Senior Laboratory Engineer for The American Radio
Relay League.

Roger Holbeg,  Supervisory Attorney, Mass Media Bureau,
Enforcement Division of The Federal Communications Commission.
Washington DC.

Michael Lance,  Electronics Engineer, Mass Media Bureau, Cable
Television Branch of The Federal Communications Commission.
Washington DC.

Engineers and Personnel from The Federal Communications
Commission, Field Operations Bureau.  Miami Office.

Thank you all for your help and guidance!
.pa
Interference to cable-TV channels from amateur VHF operation.

The problem exists because the cable-television spectrum covers a
wide frequency range.  It starts down in the low end of the VHF
range and continues on through the UHF range.  This spectrum, as
you know, also includes a number of amateur bands!  In theory,
the cable system is supposed to be a "closed" system.  By
"closed", I mean entirely enclosed in shielded cable.  No cable
leaks out, and no amateur radio leaks in!  But in reality we find
that this is not true.  There are many areas of improper
shielding, loose connectors, substandard coax and even the
possibilities of RFI or EMI (Electro-Magnetic-Interference)
radiating through the cabinets of your TVs or being introduced
into your TVs by the cable coax shielding itself!

As amateurs, before we start any investigation into the causes of
a case of cable TVI, we should first make sure that our shack is
clean.  Make sure your equipment is properly grounded.  Make sure
that your TNC is not over-deviating your radio.  Check that your
transmission lines are in proper condition. If necessary, apply
the needed cures to your own cable-connected television system.
This demonstrates that the cures used do work and that they cause
no harm.

..PART 2

The television channel is 6 Mhz wide!  Any signal transmitted in
this 6 Mhz spectrum will cause noticeable interference to a
television signal! Even a signal that is 40 dB weaker than the
television signal will result in perceptible interference.

There are a number of cable channels that we as amateurs can have
problems with.  These cable channels roughly, if not exactly,
correspond with these Amateur Bands:

Cable  2  [ 2]   (55.55 Mhz)    =     6 Meters
Cable 17  [ D]   (139.25 Mhz)   =     2 Meters
Cable 18  [ E]   (145.25 Mhz)   =     2 Meters
Cable 23  [ J]   (217.25 Mhz)   =  1.25 Meters
Cable 24  [ K]   (223.25 Mhz)   =  1.25 Meters
Cable 64  [UU]   (421.25 Mhz)   =    70 Centimeters
Cable 65  [VV]   (427.25 Mhz)   =    70 Centimeters
Cable 66  [WW]   (433.25 Mhz)   =    70 Centimeters
Cable 67  [XX]   (439.25 Mhz)   =    70 Centimeters
Cable 68  [YY]   (445.25 Mhz)   =    70 Centimeters
Cable 69  [ZZ]   (451.25 Mhz)   =    70 Centimeters

Be advised that there are no stipulated rules as to what channel
number designator has to be on what frequency.  (This is supposed
to be a closed system!)  These channels and frequencies may vary
from one cable area to the next, although most cable systems use
one of three "standard" systems. (The nice thing about standards
is that there are so many to pick from!)

This interference can go both ways!  In the majority of the cases
reported, the interference was caused to the cable by the
amateur.  But there have been instances where there have been
large enough leaks from the cable system to interfere with the
amateur!  From what I have seen, these instances have been
created by either an improperly terminated cable ends
(unconnected!), or by customer-installed "illegal" hookups.
Rarely, the problem can be caused by a bad cable distribution
amplifier or shield break somewhere on the pole cable.

As an example, I was receiving a S9 carrier on 145.250 on my
packet radio.  My radio was an Icom 28H and I had an 11 element
vertical beam at 60 feet.  I reported this to my cable company.
A few days later they sent out their Engineer and DF Vehicle.  I
brought him up in my shack and showed him the interference.  We
used my beam antenna to determine that the interference was
coming from a beam heading of 315 degrees (NW). We went to our
vehicles and found on that heading, the offending equipment 500
yards away!  It was an improperly terminated connector inside
someone's house!  An illegal hook up!  So you can imagine what a
bad distribution amplifier outside your window will do!  Most of
these leaks can be easily located with your HT or a hand held
scanner. These are a few frequencies to listen for:

Cable Channel 17 (D) --- Audio at 143.75 Mhz.
Cable Channel 18 (E) --- Video at 145.25 Mhz.
Cable Channel 18 (E) --- Audio at 149.75 Mhz.
Cable Channel 23 (J) --- Audio at 221.75 Mhz.
Cable Channel 23 (J) --- Video at 223.25 Mhz.

With an FM Handi-Talkie or scanner receiver the audio frequencies
will seem to be distorted and over deviated , but obviously
audio!  On either the FM or AM the video carrier will sound just
like an unmodulated carrier.

If leakage from the cable system caused harmful interference, it
is the responsibility of the cable operator to eliminate the
interference, regardless of the cause. If they determine that the
leakage is coming from a subscriber's home, they must, if
necessary, disconnect that home until the cause of the
interference is found and corrected.

Part 76 of The Federal Communications Commission Rules and
Regulations, which governs the Cable Industry, clearly states:

76.613  Interference from a cable television system.

   (a)  Harmful interference is any emission, radiation
        or induction which endangers the functioning of
        a radionavigation service or of other safety
        services or seriously degrades, obstructs or
        repeatedly interrupts a radio communication service
        operating in accordance with this chapter.

   (b)  The operator of a cable television system that
        causes harmful interference shall promptly take
        appropriate measures to eliminate the harmful
        interference.

There is much more to be read out of this part of the FCC Rules
and Regulations and can be seen at your local Field Operations
Bureau if you are interested.

In these bulletins, I am going to focus mostly on the type of
interference caused to the Cable Channel 18, 24, and 64-68.  The
reason for this is two-fold.  One, is because these are the
channels that most commonly experience fundamental overload
interference from amateur stations, and, two, because any
interference caused by amateur stations to these cable television
channels is clearly not the legal responsibility of the amateur.
Depending on the ultimate cause of the problem, it may be the
responsibility of the cable operator, the TV manufacturer or the
subscriber.

..PART 3

Now if you are causing interference to your or your neighbors
cable system there are many causes, suspected pieces of
equipment, and possible cures that can be found.

But first I would like to address the situation of fielding your
neighbors complaints.  Your average neighbor probably does not
understand the simplest aspects of radio theory. All they know is
that they just spent $1000 on a brand new cable television system
and you are messing it up!  Well, it is hard to make this person
understand that the cable company decided to put their channel
right on top of our amateur frequency!  And quite possibly, he
may never be able to understand.  Well there are many areas of
the country that have local interference committees comprised of
amateurs to help you deal with this situation.  It is a great
advantage if possible to have a neutral third party meet with the
offended neighbor and attempt to assist him in isolating the
problem. This third party is most often your ARRL section
Technical Coordinator (TC). To find your TC, contact your ARRL
Section Manager (SM). A list of SMs appears on page 8 of any
recent QST.

Above all, and this cannot be stressed strongly enough, be
polite, courteous and as civil as possible when you are dealing
with your neighbors! This same cooperative, friendly attitude
should be used when communicating with your local cable company.
There are all kinds of "big" problems that can be caused by
undiplomatically just telling someone "It's your problem!"

And there may be no practical way to cure any specific problem!
It may be that the only possible cure is for the local cable
company move their premium channels to another frequency.  And I
have been told by other amateurs that this is exactly what the
cable company in their areas have done.

Now for a little theory!

There really are only three ways an unwanted signal can interfere
with wanted television signal:

Radiated Interference  -  This type of interference is usually
the fundamental frequency and is usually radiated directly out of
your antenna!  But this method can also include signals radiated
through your shielding, off of your shielding, off of your ground
wire or anything else that could directly radiate your signal.

Conducted Interference  -  This interference is propagated
directly via a conductor such as A/C wiring or a common ground
system.  There are two different types of conducted interference,
differential and common mode.  I will explain these shortly.

And Induced Interference  -  Induced interference starts out as
radiated interference and is picked up or received by some
internal or external part of the affected television or its
associated wiring. This type of interference is usually common
mode.

Now to explain in more detail the distinct differences between
differential mode and common mode interference.  In any
electrical circuit there must be two paths, the forward path and
the return path.

In the differential mode signal, it is conducted via a two wire
pair, such as your A/C power cord or your antenna lead in.  In
this case the circuit is created between the two wires in the
system.  In one wire and out the other!  It is called
differential because under normal circumstances these two wires
are out of phase with each other.  This circuit occurs without
the necessity of an earth ground.

With the common mode signal, the unwanted signal can either
overpower the normal out of phase signal and make the multi-wire
appear to be a single phased long wire antenna with the return
path being through the internal circuitry (IE: Capacitors) of the
television to the earth ground, thus completing the circuit.  Or,
the signal can ride the outer coaxial shield and find the earth
ground through the same internal circuitry to chassis ground.

It is important to make the distinction between the two, because
leakage into or from the cable system, a differential-mode
phenomenon, is clearly a cable company responsibility, but a
common-mode signal conducted only via the coaxial shielding
clearly is not.

Sidebar by Ed Hare, KA1CV, Senior ARRL Laboratory Engineer

Who is to blame?

There is a lot of misunderstanding between the cable subscriber,
the cable-company service personnel and the amateurs. The
subscriber often feels that the amateur is to blame. After all,
if the amateur wasn't operating, there wouldn't be a problem. The
amateur often feels that the problem is always the responsibility
of the cable company, and that it can always be fixed if the
cable system is better shielded. The cable-company repair
personnel are often stuck in the middle. Sometimes they tell the
subscriber that the ham must be transmitting signals outside of
the ham bands, thus causing the problem (he really ought to know
better!), or, just as bad for him, believes that the interference
problem is always due to some defect in the cable system.

In reality, any, or all, of the parties may have some
responsibility. Let's take a close look at what is really going
on!

Although it is not usually related to cable TVI to channel 18 or
channel 24, I must point out that the amateur is, by law,
required to ensure that any spurious emissions from his or her
station do not cause interference to other services. Th ham must,
and will, make any necessary adjustments to the station equipment
to ensure that it is in compliance with FCC regulations.

In the case of channel 18, or channel 24, the cable company makes
use of amateur frequencies for these channels. The problem is
being caused by the amateur's fundamental signal. Any leakage,
anywhere in the system, can allow that signal to get inside the
cable. Once this happens, the interference cannot be filtered
out.

If the leak is in the cable company's wiring, it is their
responsibility to fix it. Keep in mind that they are not legally
bound to fix leakage INTO the cable, only leakage OUT of the
cable, but most operators will take whatever steps are necessary
to ensure that their customers enjoy top-notch service.

If the channel-18 video carrier can be readily heard on the test
2-meter receiver, the cable company will probably need to locate
and repair a leak. If this carrier is nearly inaudible, it may be
best to try some of the following cures first:

There are several other forms of "leaks" that are not the
responsibility of the cable company, although they are usually
willing to help if they can. Some cable ready TVs and VCRs, and
even some set-top converters, can be affected by the strong
amateur signal present on the OUTSIDE of the coaxial shield (this
signal is a common-mode signal). Many a cable operator has spend
days changing perfectly good wiring when the real problem was
common-mode interference. They, the ham or the subscriber can put
a common-mode choke on the incoming cable line. In many cases,
this will now allow for interference-free viewing.

The house AC wiring may also pick up a fair amount of signal. A
common-mode choke, sometimes in conjunction with an AC-line
filter, may help here. In extreme cases, it may be necessary to
install both types of filters in the TV, the VCR and the set-top
converter.

If the cable system doesn't leak (as evidenced by your 2-meter
receiver) and the application of the common-mode filters and ac-
line filters do not effect any improvement, you may be dealing
with a case of direct pickup by the television set circuitry.
There is (almost) nothing the cable company or the amateur can do
in this case. Contact the manufacturer of the TV for assistance.

I say almost, because after the common-mode and ac-line filters
are installed, it may now be possible to get good reception by
using a set-top converter or VCR to tune in the desired channel.
Keep in mind, when you are using an external tuner, the TV will
not be tuned to the amateur frequency, so it may not be
susceptible. Most set-top converters and modern VCRs are pretty
well shielded, so after you solve the common-mode problem, they
may now function just fine. The result is a happy subscriber,
amateur and cable repair person.

In summary, all parties concerned are responsible for conducting
themselves in a courteous and neighborly manner. The amateur is
responsible for the proper operation of the amateur equipment,
the cable operator is responsible for leakage within the cable
wiring, and the manufacturers of the TVs and VCRs are responsible
for ensuring that their equipment will continue to function
properly near strong radio transmitters. Remember, if you have a
hole in your roof, you don't blame the rain when your furniture
gets wet! 73, Ed Hare, KA1CV, Senior ARRL Laboratory Engineer.

..PART 4

In Part 3, I explained in very simple terms the difference
between differential and common mode signals.  I went into this
area because there are different ways to eliminate the two
different types of interference.  Understanding the difference
between the two will assist you in locating the path of the
interference into the television!  The interference may be
entering the system by one method, or by any combination of
different methods.  Finding the pathway of the interference can
sometimes be a very complex, and at times very frustrating piece
of detective work.

There are many areas or pieces of equipment where this
interference can enter your system.  Let me mention a few that I
have heard of: (I am sure that there are many more.) Bad, loose,
corroded or improper size cable connectors; improperly grounded
cable systems; poorly-shielded (cheap) patch cords between cable
boxes, VCRs, TVs and the like; poor 300 - 75 Ohm cable
transformers; any twin lead wire; distribution amplifiers (either
in your house or in the cable company distribution system);
splitters; A/B Switches; video games; TVs; FM broadcast radios.

In fact, anything that is connected to your cable antenna system,
cable ground, or A/C source to any equipment that is connected to
any part of your cable system, or any combination of them all can
be the culprit!!  Well, that kind of narrows it down!  Are we
having fun yet?

But do not despair yet.  With the right amount of perseverance
and a little luck, you might be able to solve the problem.

First of all, let's focus on the simple and most obvious
solutions.  Sometimes, we as amateurs, as soon as we think of
RFI, we think of either low pass filters, high pass filters,
baluns, SWR, proper grounds or the like, when in fact the #1
influencing factor is our fundamental frequency radiating out of
our best radiator, the antenna! Let's use the least amount of
power necessary to accomplish the communication.  Try to avoid
putting our antennas or transmission lines right next to cable
installations.

Maybe you will be lucky and find a leaky connection with your H/T
as described in Part 2!  If this is the fact, then eliminate that
and you are all set!  If not, we have a little detective work to
do using the process of elimination.

In an ideal typical cable installation, the cable will be brought
in from the pole, parallel to the ground with the shortest run
possible, connected to a lightning arrestor which is connected to
a good low resistance earth ground. This ground should be
exclusively for the cable system, although more often than not,
the earth ground is shared with the telephone system.  This in
itself is not really a problem, as long as the cable ground is
connected directly to the ground source and not some kind of
terminal block in the telephone system.  The cable then should
continue downward to ground level and run under the house to the
appropriate rooms.  All runs of coax up the walls and in the
attic or ceilings should be avoided if at all possible.  In many
locations this is not possible.  The people in apartments with
multiple units and distribution systems are really at a
disadvantage because of the amount of cable run all over the
place.  All of this excess cable can act as a long wire antenna
system for both differential and common mode interference.

..PART 5

Now let me tell you some of the ideas for solutions that I have
found:

First of all, if you contact your cable company, have them make
sure that you have a good strong signal at all of your TV
outlets. Then, the most useful piece of "equipment" that I have
seen is the ferrite choke.  They come in a number of shapes and
sizes.  They come in the form of rods, split cores, toroidal
cores, beads and many others.  They also come made in many
different mixes, each having a certain capacity to choke out
different frequency ranges.  Obviously they are not a miracle
cure for all purposes, but they do work great on most types of
common-mode and some of the differential-mode interference.  For
the frequencies that we are working with (VHF), the most
effective material to use is the #43 mix.

These ferrite chokes can be used on just about every wire in your
house. Make certain that you choose a ferrite mix that will
function on the frequency you are trying to suppress. In a cable
coaxial antenna the desired signal is restricted to the center
conductor and a large toroid can be placed over the coaxial
antenna, thus suppressing any common-mode current flowing down
the shield without affecting the desired VHF signal inside the
cable.  Test have shown that 300 ohm twin lead wire can be
protected in the same manner, as long as you run both leads
through the same toroid.  If you put a toroid on each lead, the
primary VHF signal will be attenuated also.  Obviously this would
not be desired.

Since the object is to interrupt the common-mode rf current path,
thus breaking that RFI circuit, sometimes it is much easier to
wind your A/C power cord through the toroid, rather than trying
to wind the stiff coaxial wire through it.

Let's say that you take your A/C power cord and run it through a
toroidal core or wrap it around a ferrite rod. This will
attenuate the given frequency for that ferrite mix (X) amount.
If you wrap it two times it will attenuate it, (X) times 2.
Three times, (X) times 3, and so on.  The usual way to use these
devices is to take your cable coax or A/C power cord that is
leading into your TV and wrap it around a ferrite 14-15 turns, as
close to the set as possible.  Now, if you don't have enough
coax, just make up a section out of new coax, wrap it, put end
connectors and a barrel connector on it and connect it to your
cable connector.  (I like to bring a few of these with me when I
do a troubleshooting "service call".) With the A/C power line,
you can use an extension cord to wind the toroid if you don't
have enough free line.

* I really don't think this is a good idea. It will form a
transformer, of sorts. This could couple unwanted energy from the
AC line to the coaxial line, and vice versa. I recommend separate
cores in all cases - KA1CV. If you have a big enough ferrite, you
can wind your A/C line and Coax through it.  This may quadruple
the effect of the toroid.  But, you must wind the wires in
opposite directions so that the coupling of the rf current from
the common-mode interference is maximized.  If you are not sure
which direction to wind them, try it both ways. The difference
will be fairly obvious.

These toroids can be found in many locations.  There are
advertisements in most amateur magazines, you can find them in
electronic supply stores.

In a pinch, you can even use discarded TV reflection yokes.
After the wiring has been removed from these yokes, just tape the
two ferrite sections together to form a large toroid. This MAY
work, but keep in mind that the ferrite material was designed for
15 kHz. Who knows what it may do at VHF!

There are also other types of cures that we can try, like A/C
line filters and tuned stubs at the television antenna lead.

First let's try to find out how the RFI is getting in.

..PART 6

Let's eliminate all unnecessary components of the cable system,
such as old video games that you never use anymore, and
temporarily eliminate all but one TV (and its converter box, if
necessary). Tighten all connections.  Cable connectors should be
finger tight, plus a quarter of a turn with a wrench.  Check to
see if the cable connectors are properly secured to the cable.
All unused inputs or outputs of the cable system should be
properly terminated with a terminating resistor.  These are
available in most any electronics supply store.  Eliminate any
300 Ohm twin lead antenna wire that for whatever reason may be
around and check to make sure that all cable coax is of the 100%
shielded type.

Now, it would be of some help if you had a fellow ham with a H/T
to help you in this endeavor.  This way you can operate the
packet station and he or she can tell you if the RFI is still
present at the television. If you use the H/T on low power, you
will probably find that it is about the same signal strength as
the packet station. If it causes the same type of interference,
it will let you do a lot of troubleshooting right in the
neighbor's house.

These steps can be approached from many different directions.
Choose which is easiest for you.  But for an example:

Take the antenna leads off of your TV or cable converter if this
is what receives cable channel 18.  Terminate the antenna input
on the equipment with the proper resistor. 300 ohm for a 300 ohm
set and 75 ohm for a 75 ohm set. Keep the leads as short as
possible.  Transmit on 2 meter packet.  If you still have RFI,
there is a good chance that the RFI is entering through the A/C
line, or being directly picked up by the television circuitry.
Wrap the A/C line around the toroid.  Transmit again.  If the RFI
is eliminated or reduced, you have found the path and cured the
problem.  If the RFI is still there, check to see if there are
any other wires or conductors attached to the TV.  Remember, any
thing that can transform itself into an antenna, can be the
source of the RF current.  If this is the case, more
experimenting with more toroids may be necessary.  Now after
these areas have been eliminated and the RFI is still present,
the RFI is either stronger than the toroids and more turns or
toroids are needed or the RFI is being induced through the case
of the TV.

If this is the case, you may need to stop right here. Most state
laws prohibit you from fixing your neighbor's TV without a state
electronic repair license. Besides, if anything goes wrong when
you have the back off the set, you will be assuredly (and
expensively) blamed! Contact the set manufacturer through the
Electronic Industries Association (EIA), 2001 Eye St NW,
Washington, DC 20006. The EIA maintains a database of EMI/RFI
contact persons at each of their member companies.

On the other hand, if after you properly terminate the cable
input with the resistor, and the RFI disappears, then you know
that the RFI is entering via the cable before your TV.  This can
either be via common-mode on the shielding of the cable coax, or
by the RFI penetrating the shield of the coax itself and entering
via the center conductor.  The latter is a more difficult problem
to fix and you may need the help and cooperation of your cable
company, and a lot of perseverance.

A quick check to see if there is leakage into the cable system is
to determine if there is leakage out. Tune your H/T receiver to
145.250 and see if there is a carrier present. If there is not,
or only a very weak one, then the cable system itself is "clean".
You will have to look elsewhere.

This method of locating the path of the RFI current and
eliminating it can be used with most all types of appliances and
radios.  You just have to use the process of elimination.

Now there are a number of factors that we really can't do too
much about.  Some televisions have only a 300-ohm balanced input.
For these TVs, we need a 300 - 75 Ohm transformer in line.  These
pieces of equipment have been known in many instances to be a
major contributor to the problem.  In many other TVs, you have a
coaxial 75 ohm input, but your TV converts it right back to 300
ohm inside the case!  And in the cases where the RFI is induced
through the case of any essential piece of equipment, depending
on what piece of equipment is suspect the only things that you
can do are:

Contact a licensed television repair technician if your
television is suspect and see if the television can be modified
to prevent RFI. Some manufacturers have good information about
these types of modifications.

Contact your cable company if their cable converter box is
suspect.

Reduce the intensity of the Electro-Magnetic Field.

Increase the distance to the Electro-Magnetic Field.

Or, shield the equipment from the Electro-Magnetic Field.

..PART 7

In closing, I would like to point out a few things that may help
you in this endeavor.

Anything in your house that is conductive can be an effective
antenna for RFI.  This includes water pipes and grounds.
Remember if your ground wire is more than a half wave long in
respect to your fundamental frequency, it may be an effective
safety ground, but, it also may be a very effective long wire
antenna for RFI.  How long and where are the water pipes in your
house?  How long is your station ground wire before it gets to
the ground rod?  If your station ground is shared with the cable
ground, or the electrical ground (shame on you!), this could be a
real problem.

Do not modify or fix your neighbors equipment.  If something
should happen coincidentally to his television, they are going to
blame you!

Terminating your Amateur Radio activities is not an acceptable
(permanent) solution to the problem. As long as your station is
in order, and the interference is not caused by spurious
emissions from your station, the FCC will allow you the
privilege to continue operating.

But if you decide to be diplomatic about it, there are other ways
to enter the packet network, such as 440 Mhz or other bands
depending on your location. It also might be a good idea to
refrain from operating if you are in conflict with the Super
Bowl, or a community-access viewing of your neighbor's grand-
daughter's dance recital.

There are many sources where you can find information on the RFI
phenomenon.  I would recommend first contacting The American
Radio Relay League.  They have several free informational
packages, and a new book on interference; "Radio Frequency
Interference - How to Find It and Fix It."  You can also contact
The Federal Communications Local Field Office in your area. They
too have information on the subject.  You can contact your local
cable company or The National Cable TV Association, Director of
Engineering, Science and Technology Department, 1724
Massachusetts Ave., Washington, DC 20036.

Now if you find an unusual solution to any type of RFI (EMI), I
would urge you to fill out an EMI Report Form, which is available
from the ARRL.  Hopefully your discovery and knowledge can be
passed on to other amateurs who may be experiencing the same type
of interference.

I sincerely hope that these bulletins have been
informative and helpful in solving your RFI problems.

Good Luck and Good Hunting!

Sincerely,

Chuck Manetta  N4YJC