Harris GATES M-6576 User manual

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m2ke/13m
HARRIS
INTERTYPE
CORPORATION
M-6576
FM- 7.5H FM TRANSMITTER
GATES
A DIVISION OF HARRIS-INTERTYPE

WARRANTY
Seller warrants new equipment manufactured by Gates Radio Company against defects in material or work-
manship at the time for delivery thereof, that develop under normal use within a period of one year ( 6 months
on moving . parts) from the date of shipment, of which Purchaser gives Seller prompt written notice. Other
manufacturers' equipment, if any, including electron tubes, and towers shall carry only such manufacturers'
standard warranty.
Seller's sole responsbility for any breach of the foregoing provision of this contract, with respect to any
equipment or parts not conforming to the warranty or the description herein contained, is at its option, ( a) to
repair or replace such equipment or parts upon the return thereof f.o.b. Seller's factory within the period
aforesaid, or ( b) to accept the return thereof f.o.b. Purchaser's point of installation, whereupon Seller shall
either ( 1) issue a credit to Purchaser's account hereunder in an amount equal to an equitable portion of the
total contract price, without interest, or ( 2) if the total contract price has been paid, refund to Purchaser an
equitable portion thereof, without interest.
If the Equipment is described as used, it is sold as is and where is. If the contract covers equipment not
owned by Seller at this date it is sold subject to Seller's acquisition of possession and title.
Seller assumes no responsibility for design characteristics of special equipment manutactured to specifications
supplied by or on behalf of Purchaser.
Seller shall not be liable for any expense whether for repairs, replacements, material, service or otherwise,
incurred by Purchaser or modifications made by Purchaser to the Equipment without prior written consent
of Seller.
EXCEPT AS SET FORTH HEREIN, AND EXCEPT AS TO TITLE, THERE ARE NO WARRANTIES, OR
ANY AFFIRMATIONS OF FACT OR PROMISES BY SELLER, WITH REFERENCE TO THE EQUIPMENT,
OR TO MERCHANTABILITY, INFRINGEMENT, OR OTHERWISE, WHICH EXTEND BEYOND THE DE-
SCRIPTION OF THE EQUIPMENT ON THE FACE HEREOF.
RETURNS AND EXCHANGES
Do not return any merchandise without our written approval and Return Authorization. We will provide
special shipping instructions and a code number that will assure proper handling and prompt issuance of
credit. Please furnish complete details as to circumstances and reasons when requesting return of mer-
chandise. Custom built equipment or merchandise specially ordered for you is not returnable. Where return
is at the request of, or for the convenience of the customer, a restocking fee of 15% will be charged. All
returned merchandise must be sent freight prepaid and properly insured by the customer. When writing to
Gates Radio Company about your order, it will be helpful if you specify the Gates Factory Order Number
or Invoice Number.
WARRANTY ADJUSTMENTS
In the event of equipment failure during the warranty period, replacement or repair parts may be provided
in accordance with the provisions of the Gates Warranty. In most cases you will be required to return the
defective merchandise or part to Gates f.o.b. Quincy, Illinois for replacement or repair. Cost of repair
parts or replacement merchandise will be billed to your account at the time of shipment and compensating
credit will be issued to offset the charge when the defective items are returned.
MODIFICATIONS
Gates reserves the right to modify the design and specifications of the equipment shown in this catalog
without notice or to withdraw any item from sale provided, however, that any modifications shall not ad-
versely affect the performance of the equipment so modified.

INSTRUCTIONS FOR INSTALLING OPERATION
OF
FM- 7.5H, 7.5U FM TRANSMITTER
IB-888 0963 031
Gates Radio Company
Quincy, Illinois

FM HARMONICS IN THE TV BAND
The sharp upsurge in FM broadcasting has in some instances developed
unlooked for interference with local TV reception. In every instance this
interference is in so-called fringe areas for TV reception and where the
strength of the TV signal is weak enough that outside highly directional home
TV antennas are necessary. — When this condition develops, the TV viewer
quickly learns from his service man that the local FM station is the offender.
--- The FM broadcaster is immediately deluged with requests to eliminate
the interference. In some instances CATV ( Community Antenna Television)
systems are also offended as they pick up weak distant TV stations. ----
What is the FM broadcaster's responsibility? Answer: To meet FCC rules
and regulations as related to harmonic radiation of his FM equipment but not
to guarantee perfect TV reception.
Below is a chart showing the picture and sound frequencies of TV stations
between Channels 7-13 inclusive. Channels 2-6 are not shown. FM harmonics
do not fall in these Channels. In fact, commercial FM station harmonics will
affect only Channels 8 and above --- look at the chart.
TV Channel Picture Frequency Band --- Mc -- Sound Frequency
7 175.25 to 179.50 197.75
8 181.25 to 185.50 185.75
9 187.25 to 191.50 191.75
C10 193.25 to 197.50 197.75
11 199.25 to 203.50 203.75
12 205.25 to 209.50 209.75
13 211.25 to 215.50 215.75
The frequency range for commercial FM broadcasting is 92.1 Mc to 107.9 Mc:
--- To determine the second harmonic of your FM frequency, just multiply your
frequency by 2. Example: If your frequency is 99.9 Mc, multiplied by 2 would
make a second harmonic of 199.8 Mc. By consulting the above chart, you will
note the second harmonic falls in the picture portion of the TV Channel 11.
Correct FM Harmonic Radiation
The FCC stipulates that transmitters of 3000 watts power and over must have
a harmonic attenuation of 80 db. For 1000 watts, 73 db., and for 250 watts,
66.9 db. All reputable manufacturers design their FM transmitters to meet
or exceed these specifications.
Fringe Area TV Strength Versus FM Harmonics
4 %e
Let's take a typical FM station that radiates 70,000 microvolts per meter at
1 mile. At 80 db. harmonic attenuation ( as called for by FCC), this station will
radiate approximately 7 microvolts per meter at 1 mile on the second harmonic.
In the case of our Channel 11 example, it is estimated that a fringe area TV
station from 60 to 90 miles distance would have a signal strength of from 5 to
25 microvolts per meter. It can then be easily understood that a 7 microvolt
signal, well within FCC specifications, would definitely interfere with the TV
signal, yet with the FM broadcaster's equipment performing normally.

This is sometimes further aggravated by the FM station being located between
the TV station and the TV receivers. In this instance the TV antennas are
focussed not only on the TV station but your FM station as well. The home
TV antennas are beamed at your legal second harmonic as well as the fringe
TV station.
What To Do
When interference occurs, it will develop ragged horizontal lines on the TV
picture varying with the FM program content. If the TV sound portion is
interfered with ( usually not the case), then the FM signal will be heard in
addition to the TV sound.
1. It is not up to the FM broadcaster to go on the defensive. He did not put
the TV station 75 miles away nor did he select the TV Channel. -- In
most instances the condition is a natural phenomena that neither you, the
TV station, nor the FCC can correct.
2. Do not adjust the FM harmonic or " T" notch filters supplied with the
FM transmitter. These are factory adjusted and most FM stations do not
have the expensive equipment necessary for correct adjustment. Tampering
with this calibrated adjustment will probably make the condition worse.
3. Do not rely on TV service men's types of measuring equipment. They are
not built to accurately measure harmonics and invariably give erroneous
readings that invite the CATV or local service men's association to say
"I told you so." Remember it is difficult to radiate harmonics if the
equipment is built to suppress the harmonics and it is.
4. In many instances interference may be caused by overloading on the front
end of the TV receiver. This problem usually occurs when the receiver is
located close to the FM transmitter. This problem can be overcome by
installing a trap tuned to the frequency of the FM carrier. The TV service
man can and must learn how to do this. In most cases it works, while in
some instances, if not properly installed or tuned, it will not completely
eliminate the interference. In one case where interference of this type
existed, a TV station put traps for the fundamental FM frequency on
nearly every TV set in town. Not the FM transmitter.
Summary
The FCC is well acquainted with this nation-wide problem. If TV viewers write
FCC, complaining about your FM station, remember the FCC has received a few
thousand similar letters. — It is not the obligation of the FM broadcaster to
assure fringe area reception of a TV station any more than is the obligation of
the TV station to assure the FM broadcaster perfect reception in his TV city.
Probably your installation will not have problems as outlined above. If they do
exist, don't blame the equipment. Every transmitting device puts out a second
harmonic, even the TV stations. The fact that these harmonics legally fall into
the spectrum of a TV station many miles distant is coincidental, but not your
fault.
o
Gates Radio Company