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Pirate Radio FAQ


From: (Rick Harrison)


Subject: Low Power Broadcasting FAQ

Date: 3 Feb 1995 06:53:34 -0500

Organization: CyberGate, Inc.  Florida

Lines: 401

Message-ID: <3gt5fu$>


Archive-name: radio/broadcasting/low-power-faq

Posting-frequency: sporadic

Last-modified: 1995.02.02

Low Power Broadcasting FAQ (Frequently Asked Questions)


[1] What equipment do I need to start a station?

[2] Is low power broadcasting legal?

[3] How much power do I need?

[4] Where can I get a transmitter?

[5] What kind of antenna should I use?

[6] How do I select a frequency?

[7] Where can I get more information?


[1] What equipment do I need to start a station?

You will need audio sources (tape players, CD players, microphones, etc.),

an audio mixer, a transmitter, a coaxial cable (usually RG-8 or RG-58/U) to 

carry the signal from your transmitter to your antenna, and an antenna.

When you are selecting audio equipment, try to get items that have metal

cases (not plastic or wood) and three-prong grounded electrical plugs.

This will reduce your chances of having problems with radio energy from

your transmitter getting into your audio gear and causing interference.

The most important item for a low power broadcaster is the _raison_d'etre_,

the reason for existing.  You won't have a high power signal, and you won't

have billboards and TV commercials announcing the existence of your station,

so listeners will have to put some effort into finding and receiving your

signal.  They probably won't make the effort unless you are offering

something unique and interesting.


[2] Is low power broadcasting legal?

This depends on what country you are in.  Here in the United States, legal 

unlicensed broadcasting is limited to microscopic power levels (see the 

Part 15 Rules FAQ in for details).  For example, the limit 

for unlicensed FM transmissionss is 250 microvolts per meter, measured at a 

distance of 3 meters from the transmitting antenna; at this power level,

stereo reception with a good signal to noise ratio is only possible within

a 100 foot radius, and an average car radio can barely detect the signal

at a distance of 200 meters.  Violators who get caught are usually given a 

monetary fine, and sometimes their equipment is confiscated.


[3] How much power do I need?

There is no simple answer to this question.  For starters, it depends

on whether you are broadcasting on the AM (medium wave) band, the FM

band, the international shortwave bands, or TV.  In order to reduce

interference to other radio services, it is always a good idea to use the

lowest amount of power that will serve your target audience.

On FM and TV frequencies, raising your antenna height and improving the 

gain of your antenna system is generally a better way to increase your range

than using a more powerful transmitter.  If an FM or TV broadcast antenna 

is only 12 feet (4 meters) above the ground, for example if it's in the 

attic of a one-story building, then its range will always be limited to 

a few kilometers and the signal will always be plagued by multipath 

interference, even if you pump a million watts into it.


[4] Where can I get a transmitter?

Below is a brief list of companies selling low power transmitter kits.

Please send me information about any companies not listed, so that I can

include them in future versions of this list.  


Note to newcomers: to assemble these kits, you must be able to solder

components onto a circuit board, and it helps if you know the difference

between a resistor and a capacitor.  If you haven't reached this stage

of electronic know-how yet, consider buying some of the educational kits

available from C&S Sales, 1245 Rosewood, Deerfield IL 60015, telephone

800-292-7711.  Their electronic components course (item #ECK-10, $14.95)

might be especially helpful to newbies.

When assembling radio circuit kits, I prefer to use narrow-diameter

silver-bearing solder (Radio Shack #64-013) and a 15 watt soldering iron

(64-2051).  You will need a more powerful soldering tool for making

antennas out of large-diameter wire, soldering really large connectors

to a printed circuit board, etc., but the 15 watt iron works fine for 

assembling most kits and reduces the chances of over-heating transistors 

and other heat-sensitive components.


DC Electronics

P O Box 3203

Scottsdale AZ 85271

phone 800-423-0070

The Improved Stereocaster is an FM stereo transmitter based on the

BA1404 chip with a few milliwatts of output power ($29.95 plus $3.50 S&H).

It has a smooth fine-tuning control which makes it easy to get on the exact

frequency you want, and a voltage regulator for the BA1404 which improves

stability.  Documentation is not quite as lucid as Ramsey's.


Free Radio Berkeley

1442 A Walnut St., #406

Berkeley, CA 94709

phone 510-464-3041 / 800-549-0732

Items listed in their advertisements include a 5 watt mono FM transmitter 

kit ($55 plus shipping), a 1/2 to 1 watt stereo FM transmitter kit ($50), 

an FM transmitter with phase locked loop (PLL) frequency control ($95),

plus kits for output filters, dummy loads, RF amplifiers, and antennas.

FRB is spear-heading an organized challenge to the FCC's regulations and

is trying to foster a low power broadcasting movement.  Contact them for 

more info.  (Internet:



North Country Radio

PO Box 53, Wykagyl Station

New Rochelle NY 10804-0053

phone 914-235-6611

(send $1 for catalog)

Many TV-related items: a 50 milliwatt UHF transmitter with crystal

controlled frequency ($78); a "video pallete" to create special effects;

a switcher that does cross-fades and wipes; and upconverters that will

take channel 3 video from a VCR and shift its frequency up to any UHF

channel 25 thru 70.  For licensed radio amateurs, they have a line of

more powerful UHF TV transmitters.


With a 100-foot range and a price tag of $62.50, their FM stereo

transmitter is not exactly competitive, but it is interesting from a

technical point of view.  Their stereo infrared transmitter and receiver

could be used to build a difficult-to-trace studio-to-transmitter link.



Panaxis Productions

P O Box 130

Paradise CA 95967-0130

(send $1 for catalog, or $2 if you're in a hurry)

This company offers many interesting books and kits.  The REB-1 kit is a

100 milliwatt transmitter for the upper end of the AM band ($34.95 plus

shipping).  The FMO kit ($75) is a high fidelity stereo FM transmitter

kit with 2 to 20 milliwatts of output power.  The FME-500, a half-watt mono 

FM transmitter with excellent technical characteristics, can be combined 

with their stereo generator to build a high-quality low power station 

(> $200 for the two kits).  Panaxis kits might not be suitable for absolute

beginners; you should have some experience in circuit assembly before you 

tackle these.


Progressive Concepts

1434 N. Mills Ave.

Claremont CA 91711

RF amplifiers, FM transmitters and stereo generators, components for RF 

circuits and more.



Ramsey Electronics

793 Canning Pkwy

Victor NY 14564

phone 716-924-4560

The FM-10A is an FM stereo transmitter kit ($34.95 plus shipping) with 

a few milliwatts of output power; it is based on the BA1404 integrated


Ramsey kits have well-written instruction manuals, and most of the circuit

boards have lots of wide-open space which makes modifications easy.  The

company also has a good reputation for service.  These factors make Ramsey

kits a good choice for beginners, in my opinion.  

Their AM transmitter kit (item #AM-1, $29.95) and their TV transmitter kit

(item #TV-6, $27.95) might also be of interest; however, there is much

room for improvement in the design of these two circuits.  (Robert Myers

of Ramsey Electronics tells me they do intend to release an improved

version of the AM-1 kit at some point in the future.)



13552 Research Blvd

Austin TX 78750

This company sells a low-power TV transmitter for channels 3 thru 6 which

appears to be of high quality ($49.95 plus $4.50 S & H).  For licensed

radio amateurs, they also sell some ham TV transmitter kits with 1 to 2 

watts peak output power that can be adapted for use on UHF channels 14 

thru 19, and a linear amp for boosting the output of these transmitters.



3605 Broken Arrow

Coeur d'Alene ID 83814

phone 208-664-2312

Another BA1404-based FM stereo transmitter kit ($24).



Xandi Electronics

Box 25647

Tempe AZ 85285

phone 800-336-7389 / 602-894-0992

The XFS108 kit ($41.95) is an FM stereo transmitter, probably based on

the BA1404.  Their advertisements give no specifics.


In a message dated Nov 08 06:01:55 EST 1994, wrote:


>There is a company called "Spectrum Communications" in Dochester England

>that sells fm transmitters and associated gear.  A transmitter tunable from

>88-108Mhz (part CTX100V) with output of 0.5Watt is available for 135 pounds.

>This unit is synthesised. ... The phone number is 0305-262250.



[5] What kind of antenna should I use?

Antenna theory, design and construction is a very complex topic.  If you

really want to understand antennas, I recommend that you buy a copy of 

_The_ARRL_Antenna_Book_ (published by ARRL, 225 Main St., Newington CT 

06111 USA).  It is a large book and you might have to spend several weeks

studying it before it all begins to make sense.  

Assuming you want to get on the air in a hurry, and then build a better

antenna system later on, I will describe the quickest and simplest options 

available.  The systems described here are all less than optimum, but they 

will get you on the air pronto.

WARNING: There are several ways you can get killed or injured while putting 

up an antenna.  Never get within 10 feet of a power line, and never mount an

antenna where it could possibly fall onto a power line, or where a power 

line could fall onto the antenna.  Avoid falling off of roofs and ladders. 

Permanent outdoor antennas must be provided with a ground rod so that 

lightning, if it happens to strike, will go into the ground instead of into 

your equipment and your body.

For FM broadcasting, try Radio Shack's omni-directional FM antenna (catalog 

#15-2164, price $12.99).  Don't forget the 75-to-300 ohm impedance matching

transformer (#15-1140 or 15-1143).  (A 50-to-300 ohm transformer would be

better, but you won't find those at Radio Shack.)  This antenna can be 

mounted on a typical TV antenna mast, or a chimney, or hidden in the 

attic.  Best results will be obtained when it's outdoors, away from trees 

and other objects, and mounted several feet higher than the rooftops in 

your neighborhood.

In AM broadcasting, a vertical section of TV antenna mast, 10 or 20 feet

long/high, makes a decent antenna.  The center conductor of the coaxial cable

from your transmitter is connected to the bottom of this vertical mast; the 

base of the mast sits on an insulator which sits on the ground.  If the 

vertical radiator is made of several sections of antenna mast, make sure the 

sections are electrically connected -- try screwing some self-tapping sheet 

metal screws into the joints.  The outer conductor (shield) of the coaxial 

cable is connected to a set of "ground radials," which are pieces of copper 

wire radiating out from the base of the antenna like spokes from the hub of 

a wheel.  (The radials are not connected to the vertical radiator.)  The 

radials can be buried a few inches below the surface for a permanent 

installation.  "Beware the lawnmower."  

For shortwave broadcasting, a horizontal dipole works well enough.  Cut two 

pieces of un-insulated copper wire; the length of each piece will be 234 

feet divided by your frequency in MHz.  Example: for 7385 kHz, each element

will be (234/7.385 =) 31.7 feet long, and you will need two trees or other 

support structures about 63 feet apart.  Solder one element to the center 

conductor of your coaxial feedline, and solder the other element to the 

outer conductor (shield) of the co-ax.  (Note: the solder joints cannot bear

the weight of the cable; loop the cable once over an insulator and provide 

some "strain relief".)  Make a little loop at the free end of one element, 

and tie a long piece of string to that loop.  Tie a small, heavy object 

(such as a lead fishing weight) to the other end of the string.  Throw the 

weight up into the branches of a tree so that it goes over a branch and 

comes back down to earth; then hoist up that half of your antenna.  Repeat 

the process for the other element.


[6] How do I select a frequency?

Receivers with digital tuning will only lock onto signals that are on

standard broadcast frequencies.  In the US, AM stations are at 10 kHz

intervals, ranging from 540, 550, 560 ... to 1600.  (Some Travellers

Information Stations are licensed on 530, 1610, and 1620.  The channels

1610 through 1700 may soon be allocated to broadcast stations.)  In some

other countries, AM stations are spaced at 9 kHz intervals.  FM stations 

are spaced at 0.2 MHz intervals, ranging from 88.1, 88.3 ... to 107.9 MHz.

Do not use an out-of-band frequency; they are allocated to other services.

(For example, the frequencies just below 88 MHz are used for TV broadcasts,

and the frequencies just above 108 MHz are used for aircraft communication.)

Make a survey of the band you are planning to use.  Get some graph paper

or notebook paper and make a list of all the channels.  Listen during the

day and at night, making a note of what station(s) you can hear on each

channel.  Use a good receiver with digital tuning and a decent antenna, 

not some cheap piece of junk clock-radio or dime-store pocket radio.

Repeat this band-scanning process several times during the course of a

couple of weeks.  (If you really want to be thorough, get a list of all

the licensed stations in a 150-mile radius.  You can extract this data from

the _Broadcasting_Yearbook_ [a trade publication] or the FCC database

[available on computer disks from several vendors]).  If you know any DXers

(people who make a hobby of listening to distant and unusual signals), ask

them for a copy of their "log."

Now, sit down with your data and search for an appropriate channel.  Don't 

start with any prejudices or pre-conceived notions: don't plunk your signal

onto 99.9 MHz just because you think it's cute ("666" upside down) or onto 

1000 kHz because you think it's an easy number to remember.  Don't try to 

wedge your signal into the non-commercial part of the FM band (88 to 92 MHz)

if there isn't an appropriate opening there.

An appropriate channel for low power broadcasting is one that is not

occupied by a local station, or by an often-audible* distant station.  The 

adjacent channels -- the next channel above and the next channel below

the one you're considering -- also must not be occupied by local stations,

because they will "splatter" onto your signal (and they will claim that

you are splattering onto them).

There are a couple of other things you must keep in mind when selecting

an FM broadcast frequency.  First, if there is a TV station broadcasting

on channel 6 in your area, it is unwise to operate on 88.1, 88.3, or 88.5

MHz.  TV receivers have broadband tuning circuits (a TV channel is 6 MHz

wide, enough spectrum to hold 30 FM stations), so broadcasts at the "low

edge" of the FM band can easily interfere with reception of channel 6.  In

some areas where the authorities have foolishly licensed both a channel 6

and a low-edge FM station, the stations often have to go to great lengths

to deal with interference complaints.

Another thing for FMers to consider is the mixing of signals that can occur

in a listener's receiver.  Most FM radios use an intermediate frequency

of 10.7 MHz; in other words, whatever frequency you're tuned to is converted

down to 10.7 MHz before the sound waves are extracted from the radio waves.

As a result, a strong signal can interfere with reception of stations that 

are on a frequency 10.6 or 10.8 MHz above or below it.  For example, if you

transmit on 92.3 MHz, some listeners who are located near your transmitter 

will have trouble hearing a station on 102.9 or 103.1 MHz (92.3 + 10.7 = 

103.0).  The interference might take the form of an "image" of your signal 

being heard on the other frequency, or vice versa; or a mixture of the two 

signals might be heard on blank spots and on top of weak signals all over 

the band.  Any other transmitter in your immediate neighborhood, whether 

it's a cellular telephone system, an AM or FM broadcaster, or any other 

service, might interact with your transmitter in unexpected, interference-

causing ways.  So, do some testing with a variety of receivers (including 

cheap junk) before you make a final decision on your frequency.  In many 

major cities where the FM band is quite crowded, you will find a few 

conspicuous empty channels; in some cases, these channels have been kept 

unused (or had to be evacuated) because of interference problems caused by 

signals mixing together at the transmitters or in people's receivers.

  *How to define "often audible" is a matter of debate; opponents of

   radio freedom say that _every_ channel is occupied by a distant station 

   that some DXer might be able to hear with his 50-foot antenna tower

   and $1,000 radio.


[7] Where can I get more information?

Introductory electronics textbooks are available at most bookstores and

libraries.  Magazines such as Electronics Now, Popular Electronics, 73,

QST, Communications Quarterly, and Nuts & Volts sometimes have articles

and advertisements of interest to low power broadcasters.  Monitoring

Times and Popular Communications carry relevant news items from time

to time.  The ACE, a monthly newsletter, covers shortwave pirates well

and occasionally contains data useful to AM and FM broadcasters (send

$2 for a sample copy to Box 11201, Shawnee Mission KS 66207).

Keep an eye on these Usenet newsgroups:

Files of some relevance are available for ftp from these sites:

site            directory                       filename

====            =========                       ========         /users/ro/frbspd                (several)   /fm10                           FM10-FAQ (& others)


This text is copyright 1994-95 by Rick Harrison.  Permission is hereby

granted for unlimited distribution of this text via Usenet newsgroups,

Internet file servers, and computer bulletin boards.  Any publication

of this text in semi-permanent form (such as hardcopy or CD-ROM)

requires the author's prior permission.

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