Planning the FM Stereo Installation

Broadcast Engineering, December 1963, Vol 5 no 12
Broadcast Engineering, December 1963, Vol 5 no 12

This is a reprint of an article by the same title first published in the December 1963 “Broadcast Engineering” magazine; volume 5, number 12. By George W. Yazell:

In planning a new installation, the broadcast station engineer will be called upon to evaluate the products of various manufacturers before an order is placed for new FM stereo station equipment. In preparing his recommendation, the engineer will review descriptive literature, advertisements, and instruction books. He will seek information and advice from his consultant, other station engineers with stereo experience, and sales representatives of broadcast equipment manufacturers. His thinking may also be influenced by magazine articles and advertisements.

It is unfortunate, but true, that during the engineer’s survey he will encounter many conflicting opinions and claims. Some “advisors” may go so far as to imply that their system of stereo signal generation is the only one worthy of consideration, and all the rest have so many shortcomings as to be impractical or even unworkable.

The simple truth is that any manufacturer offering a transmitter or associated device for sale to broadcast stations must obtain FCC type acceptance. In doing so, complete and authentic test data is submitted for the Commission’s review and approval. Type acceptance by the FCC is your assurance that the equipment will meet certain specifications.

Thus you can either draw straws, or accept the views of the “advisor” with the most forceful opinion and still feel safe that the equipment you recommend will work. A more practical solution would be to prepare a list of equipment and features you require, with careful attention to needs peculiar to your own station; then select the equipment which most nearly matches your requirements.

List What You Have

The first step is to list and evaluate any equipment, facilities, and assets already available for the proposed installation – even if it is only a construction permit, a bank account, and a plan of operations. Some items to consider include:

  1. Ask management for a budget. This is probably the most significant factor in your recommendation. You should set both a practical budget and an absolute top limit. If you find it impossible to do the job within the budget limitations, do not hesitate to say so. Point out that stereo is a two channel system and that in addition to special transmitting equipment, the studio installation will require two of each amplifier, loudspeaker, telephone line, etc. Therefore, a stereo installation will cost considerably more than monophonic facilities.
  2. Review the program plans for the station. The quantity, complexity, and flexibility of the audio equipment selected must adequately meet these needs, with some reserve facilities for future expansion.
  3. You may presently have an FM, AM, or TV station a combination of these. In this case you can probably count on using existing studio facilities, some of the technical equipment, the tower, remote control facilities, and technical manpower.
  4. Consider the abilities of your technical staff. You may be the only engineer, or may have available a large staff of technical personnel. In any event, select equipment having circuits and components your technicians can install and maintain.
  5. Survey the supply situation. Determine the location and stock capabilities of electronic supply houses in your area. Keep in mind that any electronic component must eventually fail; and an inexpensive component can cost hundreds of dollars if you are “off the air” several days while a replacement is being flown in from a distant source of supply. If the supply picture is discouraging, you can best protect yourself by selecting practical equipment employing readily available components – and ordering an adequate supply of spares for parts you cannot obtain locally.

List your needs

Your next step is to prepare as complete a list as possible of the total equipment requirements.

Broadcast Engineering, Typical Stereo diagram
Broadcast Engineering, Typical Stereo Diagram

Sketch a block diagram of your proposed layout (Fig. 3). Then prepare a chart of all the equipment you will need with space provided for prices, data, and notes on each device. As you prepare these charts several things will become evident:

  1. You will probably discover more equipment is needed than you originally anticipated.
  2. In determining what must be purchased, you must carefully integrate your needs with the equipment now on hand.
  3. Your ultimate decision will depend on many interacting factors rather than on one outstanding feature of a particular device.
  4. It will be wise to purchase as many items as possible from a single source to take advantage of: the compatibility of equipment that is designed to work together as a system, coordinated shipments and service, possibly lower cost because of quantity purchase, and -if required- simpler finance arrangements.

Making a Decision

After considering the points outlined above, and making the lists, you are ready to select equipment.

If the budget is limited you may investigate the possibility of some used equipment. However, since today’s FCC Stereo Specifications were only established as recently as 1961, there will be little used equipment available. In the majority of cases, converting old monophonic equipment will be difficult, and costly, and the end result may be less than satisfactory. Old “dual channel” audio consoles have been successfully converted, but the process usually requires almost complete rebuilding. It is necessary to install dual faders, correct phase differences, and balance gain between channels.

Used FM transmitters are frequently advertised, but many are left over from the early days of FM. Some transmitter manufacturers of the late ’40s are no longer in business. Replacement tubes and parts are difficult, if not impossible, to get. Some older transmitters lack stability and some contribute to the degradation of stereo separation because they do not maintain the proper phase relationship between upper and lower sidebands. If such a transmitter is to be used, it probably will be necessary to purchase a new exciter and, of course, a stereo generator.

Since stereo listeners are a discriminating and critical audience, audio equipment should be chosen with care. It will be wise to settle for only the finest professional stereo turntable and tape equipment. It is better to have the minimum requirements of excellent equipment than a control room crowded with “make-do” items.

Stereo consoles are available with a wide range of prices and facilities. Some offer stereo channels only for record and tape inputs, while the more complete models even make provision for stereo networks and remote circuits. Much of today’s programming is on records and tapes, but regional “off-the-air relay” stereo networks are springing up. Stereo microphone facilities are a must if you want your locally produced commercials to sound as impressive as your stereophonic music.

Current models of FM transmitters are highly efficient, trouble-free, and easily remote-controlled. All FM transmitters follow one pattern- a basic exciter and a number of amplifier stages to produce the required power output. The power amplifiers in the various models are somewhat similar, except in high-power transmitters (20 kw and up).

A wide variety of FM exciters and stereo generators is offered, and this is one area in which confusion might occur. (Again, it should be pointed out that all these units are subject to FCC-type acceptance.) A typical exciter and stereo /SCA generating system is shown in Fig. 5. The block diagram explains the signal path and function of the various circuits.

Broadcast Engineering, FM stereo exciter diagram
Broadcast Engineering, FM stereo exciter diagram

Conclusion

The selection, installation, and operation of FM multiplex stereo equipment require the careful attention of a highly skilled technician. Installation, adjustment, and maintenance should be in exact accordance with the manufacturer’s instruction book. Following these instructions, the broadcast engineer can feel confident in planning a stereo installation that will be a pleasure to operate and a source of pride and profit.

Used by permission of the publisher; SAMS Technical Publishing, Inc.

I found a stack of these old Broadcast Engineering magazines from the early sixties when cleaning out the WUPE-FM (formerly WNMB) transmitter site.  I thought it would be interesting to see how Broadcast Engineers some 50+ years ago were planning for FM stereo.  One of the stations I worked for, WRVE (formerly WGFM) was the first station in the country to broadcast with the General Electric stereo system.  This was later adopted as the standard for FM stereo broadcasting in the US.

For more historical broadcasting publications, go to American Radio History.

ATT Long Lines Site, Rock City NY

Another one of those former ATT Long Lines sites has been re-purposed. This site was known as Rock City and as the name suggests, it is a fairly remote location. These locations were chosen by ATT to facilitate microwave relay between cities.  Some of the more remote rural locations are so far off the beaten path that they do not make good wireless carrier sites today.  Such is the case here, there simply are not enough people around to turn this into a profitable cell site.

Former ATT long lines site, Rock City NY
Former ATT long lines site, Rock City, NY

This site is useful in other ways, the local township purchased it and has put it to use for E911 dispatch and other uses such as WKZE translator W290BZ.

Former ATT long lines Western Electric Tower, Rock City NY
Former ATT long lines Western Electric Tower, Rock City, NY

The tower is less than 200 feet tall, therefore it is no longer painted or lit. These old Western Electric towers were really built. Under that peeling paint, the galvanizing is still in near-perfect condition. The tower dates from 1968.

Former ATT tower, Rock CIty NY
Former ATT tower, Rock City, NY

The Western Electric KS-15676 microwave antennas and waveguides have been removed. The top platform is quite large, one could build a house up there. The W290BZ antenna is the cross-polarized LPA attached to the center pole which is barely visible.

Former ATT long lines site, Rock City NY.  The big empty.
Former ATT long lines site, Rock City, NY. The big empty.

This room held the switch gear and TD-3 microwave radios.

Former ATT site, Rock City NY 100 KW generator
Former ATT site, Rock City, NY 100 KW generator

The original General Motors 100 KW diesel generator. The fuel tank was removed before the site was transferred from ATT to the new owners.  If reconnected to a fuel supply and the block heater turned on, I’d bet this unit would start and run.

ATT Rock City NY generator, Detroit Diesel straight six engine
ATT Rock City, NY generator Detroit Diesel straight six engine
ATT Rock City NY fuel tank cathodic projection unit.
ATT Rock City, NY fuel tank cathodic projection unit.

The tank had a Cathodic protection unit installed, which ran a small DC current through the tank to keep it from rusting.

The original visitor’s log book is still there, showing every ATT person who visited the site from 1968 until it was decommissioned in 1994.  This site was unmanned and remotely monitored and controlled from somewhere else.  Maintenance personnel showed up at regular intervals or to fix specific problems.

Like many of its rural counterparts, this site sits mostly empty since the microwave equipment was removed in the early 1990s.  This one seems to be well taken care of, others are in terrible shape.

WMHT’s former analog transmitter

During the digital TV conversion in the US, all broadcast television stations installed new transmitting equipment and antennas.  Most stations ended up on a different frequency than their original analog channel.  In Albany, New York, all of the TV stations moved to a common transmitter site and installed their antennas on a single tower.

home of WRGB, WTEN, WNYT, WXXA, WMHT, and WCWN
Albany DTV tower, home of WRGB, WTEN, WNYT, WXXA, WMHT, and WCWN

For more on the Albany DTV site, check out the NECRAT page: www.necrat.us/albdtv.html

So, what happened to the old Analog TV sites in Albany?

For the most part, after the analog turn-off on June 12, 2009, the sites have sat empty.  Such is the case with the former WMHT site.

Sign outside of former WMHT transmitter building
Sign outside of former WMHT transmitter building

This old sign about sums up the end of analog television.

Former WMHT Comark analog transmitter
Former WMHT Comark analog transmitter
Former WMHT analog transmitter wide shot
Former WMHT analog transmitter wide shot
Former WMHT operator position
Former WMHT operator position

The former transmitter operator desk. The maintenance log is still open. From the looks of things, they opened the circuit breakers and walked away. Everything remains intact from the antenna to the klystrons and exciters. It does appear that the coolant has been drained from the system. Other than that, it seems like the whole thing could be restarted with minimal effort.

Former WMHT Onan DFN 350 backup generator
Former WMHT Onan DFN 350 backup generator

There were two Onan DFN 350 backup generators. With a TV transmitter, running the cooling system after shutdown is vital. The idea here is that both generators in parallel could run the whole station, if one generator failed, then the cooling system would still run and cool the klystrons.

Former WMHT site kitchen
Former WMHT site kitchen
Former WMHT tower, wave guide and WVCR antenna
Former WMHT tower, waveguide and WVCR antenna

The former WMHT tower, which currently holds the WVCR-FM, WXL-34 (NOAA weather radio), and W44CT-D (Three Angles Broadcasting) Low power TV transmitter.

Current site occupants; WVCR-FM and W44CT-D
Current site occupants; WVCR-FM and W44CT-D

These equipment racks and the NOAA weather radio transmitter in the other room are the only active equipment at this site.

WMHT-TV Chanel 17 (488-494 MHz) was signed on 1962 from this site.  The Comark transmitter was installed in 1984.  The station’s analog ERP was 2000 KW visual, 200 KW aural.

It is an interesting site.

Old ATT promotional video

I found this old ATT promotional video from 1967.  It mainly concerns the PSTN wired network reliability.

It’s a mildly hoaky propaganda piece, but we often forget how our modern communications infrastructure is very young.  If ATT seems proud of their system, they had a right to be.  Prior to electronic communications, you wrote a letter and hoped that it arrived.

There is also this video: What is the Bell System?

If you have the time, there are many interesting archive videos on the ATT Tech Channel.  Be careful, one can spend a lot of time watching these videos!