I am still in awe of iBiquity and I have to hand it to them for stick-to-it-liveness. The newest “fix” for their FM IBOC system, colloquially known as HD Radio™, is in contour on-channel repeaters. According to the article “Performance of FM HD boosters varies,” (Radio World online edition), the reason for such boosters is to “increase or fill in FM Digital footprint so that the digital coverage matches that of analog.”
The idea that IBOC is somehow an improvement over FM analog is becoming (or has become) untenable. In order to make the new system cover the same area with the same reliability as the old analog system, on-channel bandaids boosters are now needed. And what is with this extending coverage? How much more expensive will radio station owners have to deal with to make this scheme work? And I still don’t understand where the improvement over analog-only systems comes from.
As the article points out, however, all is not well in paradise; the IBOC booster signals interfere with analog signals close to the booster transmitter. This becomes problematic if the receiver is an analog-only device. As of this writing, most of the radios in this country do not have HD Radio™ capabilities. Thus, radios that are currently working perfectly well will be cut out and can become useless around these repeaters.
For your reading pleasure, the entire NAB report can be found here.
Try as they may, neither the NAB, iBiquity or Greater Media can supplant the laws of physics. Then there is that insanity definition floating around:
Insanity: doing the same thing over and over again and expecting different results.
We are currently working with one of our clients who need to rebuild an FM transmitter site. The site is an old house that used to function as a studio. The transmitters are wedged into various places and the whole place looks like a fire trap. We are working on moving the transmitters to a new building at the base of the tower and installing all ancillary equipment according to good engineering standards.
The transmitter site design has changed somewhat over the years. What may have been good engineering standards in the past have changed with newer transmitter designs and needs. Up until about 1990 or so, most transmitter sites were cooled with outside air. As such, there was often a “filter room” or “air mixing room” with associated blowers and fans for moving air through the building. Older sites often had these features built-in as part of the transmitter installation. WPTR’s GE BTA-25 was a good example of this.
Modern solid-state transmitters are a little more delicate than their older tube-type brethren. Tubes were designed to run hot and had no trouble with temperatures up to 110 to 120 degrees or so. Continental transmitters were famous for this. As Fred Reilly once told me “We’re Dallas and it gets hot here. The manufacturing floor is not conditioned. It doesn’t matter, 100 degrees, 105 degrees, they just keep on working.” I think he was talking about the assemblers as well as the transmitters.
Solid-state transmitter switching power supplies are also somewhat finicky.
A good transmitter site design will incorporate the following:
Good air conditioning. Calculating the AC load for the transmitter waste heat, other installed equipment, as well as the building solar gain. Waste heat is a function of AC/RF transmitter efficiency, which is found in the owner’s manual. If unknown, 50% is a good design standard, in other words, waste heat equals TPO.
Good grounding. A good grounding system is a must for all transmitter sites. This includes lightning and RF grounds. Low impedance paths to a single point ground is a must.
Good power conditioning. Mountain top transmitter sites are susceptible to all sorts of utility company irregularities. Surge protection is a must. Series types are better than parallel.
Good lighting. Nothing is worst than fumbling around in a half-lit transmitter room trying to make repairs.
Adequate workspaces and clearances. Electric panels require three feet of clearance from the front. Cabinet doors should be able to swing fully open. All-access panels should be, well, accessible.
Adequate electrical system. Pole transformers and service entrances are properly sized for the load. Backup power. Plenty of work outlets around the room.
Some of these may seem like no-brainers, however, one would be surprised at how transmitter sites have grown over the years. An FM site that may have started with one 5 KW transmitter in 1950 will have been greatly upgraded over the years. Today, that same site may not employ a 30 KW transmitter, full air conditioning, several tower tenants, etc.
WHUD transmitter site diagram
This is a transmitter site that we redesigned about four years ago. The original site was built in 1958 and had a Gates FM5B as the main transmitter. The electrical service consisted of two 200 amp panels which had been greatly altered over the years. It had an old Onan 65 KW propane generator inside the building. Grounding, Air Conditioning, lighting, and workspace were all substandard.
The first thing we did was replace the generator with an outdoor unit. That allowed us to remove an interior partition, freeing up a good deal of floor space. The next thing we did was upgrade the electrical service and replace the generator transfer switch. Much of the interior wiring had been altered or added to in non-code-compliant ways. All of those modifications were removed or bought up to the current electrical code.
A safety grounding ring was installed around the outside of the building and all grounding points were bonded together. Nautel has an excellent guide for transmitter sites which includes lightning grounding and protection for AM and FM transmitter sites. Recommendations for Transmitter Site Preparation (.pdf) and Lightning Protection for Radio Transmitter Stations (.pdf) are available for download from their site. All RF cable outer jackets are bonded to the ground at the base of the tower and the entrance to the building. All the interior equipment is bonded together. Ferrite toroids are placed on all cables going into and coming out of the transmitter cabinets.
With the electrical service upgrade, we added the series LEA surge protector.
Inside view of LEA surge suppressor
This site as at the very end of the utility company line and has always suffered from power issues. This unit greatly smooths out the various nasties that get sent our way.
I decided that it was easier to use compact fluorescent lights (CFL) rather than long tubes. This site is as the top of a rough mountain road and it is simply easier to carry several small boxes in the cab of the truck than four foot or eight foot florescent light tubes. There is a total of ten 28-watt fixtures in the main transmitter room which light up every nook and cranny.
WHUD transmitter
All of the transmitters and electrical panels were laid out to give working room around them.
The air conditioners were also greatly upgraded and added to the generator load. Prior to this, when the power went out, which was often. the air conditioners did not run and the transmitter room would overheat unless the door was left open. What we previously the filter room became space for tenant equipment. There are a few two-way and paging companies still at this site.
Of course, all this work was done while keeping the station on the air as much as possible. There were a few instances of having to turn off to move transmission lines and so on.
The result of all this work is greatly improved site reliability.
While I was away, the FCC released a Further Notice of Proposed Rule Making (11-105) regarding LPFM and translators. There are several issues with a backlog of translator applications and the possible LPFM window that looms out in the future somewhere. The current FCC translator rules bear little or no resemblance to the reality of FM translator use today.
The basic translator rules are found in FCC 74.1206 through 74.1290 with the programming and permissible service outlined in FCC 74.1231:
Sec. 74.1231 Purpose and permissible service.
(a) FM translators provide a means whereby the signals of AM or FM broadcast stations may be retransmitted to areas in which direct reception of such AM or FM broadcast stations is unsatisfactory due to distance or intervening terrain barriers, and a means for AM Class D stations to continue operating at night. (b) An FM translator may be used for the purpose of retransmitting the signals of a primary AM or FM radio broadcast station or another translator station the signal of which is received directly through space, converted, and suitably amplified, and originating programming to the extent authorized in paragraphs (f), (g), and (h) of this section. However, an FM translator providing fill-in service may use any terrestrial facilities to receive the signal that is being rebroadcast. An FM booster station or a noncommercial educational FM translator station that is operating on a reserved channel (Channels 201-220) and is owned and operated by the licensee of the primary noncommercial educational station it rebroadcasts may use alternative signal delivery means, including, but not limited to, satellite and terrestrial microwave facilities. Provided, however, that an applicant for a noncommercial educational translator operating on a reserved channel (Channel 201-220) and owned and operated by the licensee of the primary noncommercial educational AM or FM station it rebroadcasts complies with either paragraph (b)(1) or (b)(2) of this section: (1) The applicant demonstrates that: (i) The transmitter site of the proposed FM translator station is within 80 kilometers of the predicted 1 mV/m contour of the primary station to be rebroadcast; or, (ii) The transmitter site of the proposed FM translator station is more than 160 kilometers from the transmitter site of any authorized full service noncommercial educational FM station; or, (iii) The application is mutually exclusive with an application containing the showing as required by paragraph 74.1231(b)(2) (i) or (ii) of this section; or, (iv) The application is filed after October 1, 1992. (2) If the transmitter site of the proposed FM translator station is more than 80 kilometers from the predicted 1 mV/m contour of the primary station to be rebroadcast or is within 160 kilometers of the transmitter site of any authorized full service noncommercial educational FM station, the applicant must show that: (i) An alternative frequency can be used at the same site as the proposed FM translator’s transmitter location and can provide signal coverage to the same area encompassed by the applicant’s proposed 1 mV/m contour; or, (ii) An alternative frequency can be used at a different site and can provide signal coverage to the same area encompassed by the applicant’s proposed 1 mV/m contour. (c) The transmissions of each FM translator or booster station shall be intended only for direct reception by the general public. An FM translator or booster shall not be operated solely for the purpose of relaying signals to one or more fixed received points for retransmission, distribution, or further relaying in order to establish a point-to-point FM radio relay system. (d) The technical characteristics of the retransmitted signals shall not be deliberately altered so as to hinder reception on conventional FM broadcast receivers. (e) An FM translator shall not deliberately retransmit the signals of any station other than the station it is authorized to retransmit. Precautions shall be taken to avoid unintentional retransmission of such other signals. (f) A locally generated radio frequency signal similar to that of an FM broadcast station and modulated with aural information may be connected to the input terminals of an FM translator for the purpose of transmitting voice announcements. The radio frequency signals shall be on the same channel as the normally used off-the-air signal being rebroadcast. Connection of the locally generated signals shall be made by any automatic means when transmitting originations concerning financial support. The connections for emergency transmissions may be made manually. The apparatus used to generate the local signal that is used to modulate the FM translator must be capable of producing an aural signal which will provide acceptable reception on FM receivers designed for the transmission standards employed by FM broadcast stations. (g) The aural material transmitted as permitted in paragraph (f) of this section shall be limited to emergency warnings of imminent danger and to seeking or acknowledging financial support deemed necessary to the continued operation of the translator. Originations concerning financial support are limited to a total of 30 seconds an hour. Within this limitation the length of any particular announcement will be left to the discretion of the translator station licensee. Solicitations of contributions shall be limited to the defrayal of the costs of installation, operation and maintenance of the translator or acknowledgements of financial support for those purposes. Such acknowledgements may include identification of the contributors, the size or nature of the contributions and advertising messages of contributors. Emergency transmissions shall be no longer or more frequent than necessary to protect life and property. (h) An FM translator station that rebroadcasts a Class D AM radio broadcast station as its primary station may originate programming during the hours the primary station is not operating, subject to the provisions of Sec. 74.1263(b) of this part. (i) FM broadcast booster stations provide a means whereby the licensee of an FM broadcast station may provide service to areas in any region within the primary station’s predicted, authorized service contours. An FM broadcast booster station is authorized to retransmit only the signals of its primary station which have been received directly through space and suitably amplified, or received by alternative signal delivery means including, but not limited to, satellite and terrestrial microwave facilities. The FM booster station shall not retransmit the signals of any other station nor make independent transmissions, except that locally generated signals may be used to excite the booster apparatus for the purpose of conducting tests and measurements essential to the proper installation and maintenance of the apparatus.
With a possible exception for use by Class D AM stations, the translator service has gone far away from what it was intended to be and even, in some cases, contradicts the current rules. DIY Media goes more into this in Unholy Alliance.
Consolidators are using translators to get around market ownership caps by using them to re-broadcast HD-2 and HD-3 channels, which would otherwise go unheard. Others are using translators to establish large networks of over-the-air relays to greatly extend their coverage far beyond any natural signal contour. Religious and public radio stations rely extensively on translators to establish radio signals that are several times the size of the original station. In one case, a translator in Harrisburg, PA is broadcasting a satellite feed of the True Oldies Channel that does not appear on any AM, FM or HD sub-channel in the market. The 80/160 KM distances noted above in section B(1)(i) and (ii) seem to be largely ignored.
What the FCC wants to know is this: There are thousands of pending translator applications; what is to be done about them in light of the new LPFM legislation Congress passed last year? Should they be dismissed, approved, or some market-based combination of the two? Keep in mind, the new LPFM stations are on an equal regulatory footing with translators, unlike full-power FM or the previous LPFM licenses granted in 2003.
Whatever the outcome, it would appear that this will be the final chance to get an LPFM license when the filing window opens. After this, there will likely not be a scrap of spectrum left to dole out. The deadline for filing comments with the FCC is August 29th.
As alluded to in the previous post, I spent a fair amount of time at Mt. Mansfield last month. It is the highest point in the state of Vermont, topping out at 4,393 feet (1,339 M). At the top, there is a large transmission facility that is home to WCAX-TV, WPTZ-TV, WVPS, WEZF, several low-power TVs, NOAA weather radio, etc. Next door, Vermont Public TV is housed in a separate building. Here are a few pictures and descriptions. First of all, Mount Mansfield is the home of the Stowe Ski area. They own the access road to the top of the mountain and are quite proud of it. In the summertime, the toll for a carload of people is $26.00.
Mount Mansfield Toll Road gate
The transmitter building is below the actual peak. This is one of the few transmitter sites that is manned 24/7, as such there is a working kitchen, bathroom, bunk rooms, and so on. I’d imagine it gets pretty deary up there in the wintertime, but perhaps not.
Mount Mansfield transmitter building
The transmitters are located along a long hallway. WEZF and WVPS share a room, and WCAX and WPTZ are in open bays as are the low-power TVs. NOAA weather radio and some other government transmitters are located in the garage.
WCAX digital TV transmitter
All of the TV transmitters are new because of the recent conversion from analog to digital transmission. WCAX is noted as channel three, which was their analog channel, they actually transmit on channel 22 with a power of 443 KW ERP.
WPTZ transmitter
Like WCAX, WPTZ was on channel five, it is now transmitting on channel 14 with 650 KW ERP.
The site is backed up by two 1.2 MW diesel generators, which can be paralleled with the commercial power grid, if needed, during peak demand times. These generators also provide backup power for the Stowe Ski area. There is a 50 KW back up back up generator that runs all of the emergency transmitter cooling equipment if the two main backup generators fail.
Mount Mansfield generator
All of this generating equipment requires a lot of fuel.
Transmitter building and fuel storage tanks
The TV and FM broadcast antennas are located just below the peak
Mount Mansfield TV and FM antennas
I don’t recall which TV station belongs to which antenna. The FMs are combined into the four-bay, three-around panel antenna, this includes WVPS’s HD radio signal.
Mount Mansfield from the top looking west
From the very top looking west into the aperture of the TV antennas. I only stood there for as long as it took to get a good picture, then departed. Off to the left of this view is the antenna for Vermont Public TV.
Mount Mansfield Vermont Public TV antenna
The transmission lines go down the hill on a large ice bridge. An absolute necessity as the rime ice can sometimes accumulate several inches.
Mount Mansfield Ice Bridge
Tower base, is the location of the highest RF concentration, according to the TV engineers. I only lingered here to snap a few quick photos.
Mount Mansfield tower base
All of the STL antennas are mounted to the side of the transmitter building next to the living quarters.
Mount Mansfield STL antennas
On top of all that, as if that weren’t enough, there is the view. I would also comment a bit on the weather. In some cases, the site can be completely engulfed in a grey dull fog bank one minute, then the wind changes direction, the sun comes out and you see this:
Mount Mansfield morning
I can think of worse things.
I regret that I didn’t have a better camera with me as several of the pertinent pictures came out blurry. All of these pictures were taken with my cellphone camera, which works well when it works. It is also very convenient because it is almost always with me and I don’t have to remember to bring another gadget. However, it this is going to be a semi-serious endeavor, I will have to take some of my earnings from these scribblings and buy a good camera.
