I have been spending my days in Brookfield, Connecticut, dragging transmitters around and reconnecting them in various ways. The WRKI-FM WINE-AM transmitter site is finally moving into the “new” transmitter building at the base of the tower. Today, we moved WINE.
WINE was first signed on in 1963 on 940 KHz from a 170 degree non-directional tower on top of a pretty high hill. That same tower serves as the antenna support for WRKI, which signed on in 1957. The station runs 680 watts daytime, however since it is non-directional, it has some pretty serious power reductions at night. The post sun set power drops in two steps, 450 watts for the first hour, then 189 watts for the second hour, followed by 4 watts night time.
The 4 watt night time signal goes about 2-4 miles before it becomes unlistenable. The Post Sun Set Authority (PSSA) allows the station to stay on the air with at least some coverage up to about 6:46 pm in the winter time and 10 pm in the summer, which is better than nothing.
The problem is, the Harris MW-1A transmitter goes down to 250 watts and no lower. In order to make the night time power, the station switches to a dissipation network to burn off 246 watts of RF, at 50% percent AC-RF efficiency, which just ends up being a waste of power. Further, the station engineers have been ignoring the PSSA because there are too many steps and it was easier to just switch to night power at sunset.
What we decided to do instead, was install a small low power night time transmitter, a Radio Systems TR-6000. The MW1A can then be set to use the low power level for the first step of the PSSA, then switch the dissipation network in for the second step of the PSSA, finally switching in the night transmitter at the proper time.
Harris MW1A AM transmitter, WINE 940 KHz, Brookfield, Ct
This is the Harris transmitter, new Circa 1981, was cleaned up and moved into the new transmitter building.
WINE Parallel dissipation network and dummy load
The dissipation network. This will have to be reconfigured for the proper power levels, once the night transmitter is installed. The dissipation network is on the right, a dummy load is on the left. The two large RF contactors switch the dissipation network in and out, or select which transmitter is feeding the antenna/dummy load. This is the really, really old school way of doing it. Most transmitters manufactured after 1990 or so can run at any power level, making a dissipation network unnecessary.
Before re-installing the dissipation network/dummy load, we lined the enclosure with copper mesh. I don’t want that thing interfering with any of the other equipment nearby, which would be the STL receivers, satellite receivers or Town of Brookfield police dispatch radios.
Schematically, it looks like this:
WINE 940 KHz Brookfield, CT night time dissipation network
This is the picture behind the transmitters, shows the coaxial cable feed through ports and the dissipation network on the wall.
WINE WRKI transmitter room, behind the transmitters
Still in use as the main transmitter after 42 years at WCKL 560 KHz, Catskill, NY.
CCA AM1000D transmitter, WCKL Catskill, NY
The last seven years or so, it has not had much use, the station being caught in some strange LMA with Clear Channel, then sold to the Black United Fund of NY something or another. They basically had it dark, turning it on for a few days each year to as not to loose their license. Finally, they LMA’d it to Family Broadcasting (not to be confused with Family Radio). There are rumors of a sale, but it remains to be seen.
They have been broadcasting an eclectic, free form programming style which appears to be the work of mostly volunteers.
The station was first licensed in 1970, thus this is the original transmitter:
CCA AM 1000D name plate, WCKL Catskill, NY
Towers are 446 feet tall, which works out to 90 degrees at 560 KHz.
WCKL 560 KHz antenna array
The station is licensed to Catskill, but the transmitter site is located in Hudson, across the river. With the current ownership situation in flux, I would characterize the operation as “tenuous.”
The transmitter itself is a pretty simple high level modulation tube type transmitter. It uses 4-400 tubes, like the RCA-BT1AR transmitters and is build around a similar design, which makes sense as they were designed and built by former RCA engineers. One of the CCA principles, Bernie Wise, still makes Energy Onix transmitters about 10 miles away in Valatie, NY.
Parts are fairly generic and still available. Things like the modulation transformer may be harder to come by, however, Goodrich Electronics, Harbach Electronics, Energy Onix and others will be able to steer one in the right direction. I’d put up a schematic if I could find one.
I find these older tube type transmitters often sing with modulation, especially the higher frequencies. That sound and the soft sound of the blower moving air is the sound of radio, at least to me.
This is a situation that is and will be playing out over and over throughout the country as the decay advances. W*** signed on the air in March 1963. I believe this is the original tower:
W*** tower
As you can clearly see from this picture, this tower has several problems. Aside from the loose guy wires, the rust and general structural decay, it is bent in several places. Currently, the forces are in equilibrium, but for how long, no one knows. It is certainly not safe to climb. At 144 feet, it is no longer required to be marked or lit, thus, over the years, the paint peeled, the weep holes filed up, the guy wires rusted and loosened, which leaves us with the situation today.
At the transmitter building, there are other issues with the basement flooding, mold, etc. Truth be told, this station makes no money on it’s own. It would cost several tens of thousands of dollars to fix all these issues, and for what; a high end of the broadcast band class D AM station which has not shown up in the ratings for fifteen years. Once upon a time, it was a surviving, perhaps not thriving, local radio station. Those times have long since past.
The question is; what to do with it. Sign it off and surrender the license? Fix all the problems and continue to broadcast? Donate it? If so, who would take it? Or, more likely, wait until the tower collapses and deal with it then.
I’d imagine that there are many others just like it dotting the country. On the whole, the AM broadcasters that are viable would be better off if this dead wood was cut away and discarded.
Since the FCC waved some of its rules regarding carrier power and carrier shift on the AM broadcast band, AM stations are now able to implement MCDL or DCC (Dynamic Carrier Control) technology to save money on their electric bills. This technology has the potential to save tens of thousands of dollars for higher powered AM stations (high power=greater than 10 KW carrier level).
On a standard AM broadcasting station, the carrier represents two thirds of the energy being transmitted, with the modulation index containing the other one third. The carrier contains no information; it is simply there on the center frequency at the power level authorized by the station’s license. Thus, if the carrier can be reduced without effecting the quality of the broadcast reception, it will reduce to overall power consumption of the transmitter. In areas where electric costs are high, the savings can be substantial.
There are various ways to accomplish this. The first is called Dynamic Carrier Control (DCC), where the carrier voltage is reduced during moderate modulation levels (between 20-50%) and restored during peaks. This reduces the output power during average modulation, restoring most of it during quite periods and peaks. The next is Dynamic Amplitude Modulation (DAM), which is similar to DCC. The most savings will noted with less heavily processed programming such as talk radio because the higher the average modulation density is, the less the MDCL circuit reduces the carrier voltage level. The little graph in the diagram shows the reduction in the carrier voltage vs. modulation levels.
Nautel DAM block diagram, courtesy of Nautel, Ltd.
Finally, Amplitude Modulation Companding (AMC) reduces the voltage in both the carrier and modulation product during peaks. This results in better savings for higher density modulation indexes. It is also the most transparent of the three schemes, as the carrier is restored to full power during periods of low or no modulation levels. During peak modulation, the reduction does not drop the power level below the un-modulated carrier level. The little graph in the diagram shows the reduction in the carrier voltage vs. modulation levels.
Nautel AMC block diagram, courtesy of Nautel, Ltd
Nautel has done extensive work on MDCL and includes several algorithms in their NX series transmitters. For older Nautel transmitter models such as ND, XL, XR and the J-1000, there is an outboard exciter, which is in a one rack unit chassis. Older transmitters may need a simple field modification to create a DC coupled audio input. The cost for the upgrade is approximately $5,000 USD, however check with the regional Nautel sales rep.
Once the system has been installed, there are several things to be aware of:
Modulation monitors may not work properly, especially older units, which will show significant carrier shift and have carrier alarms. Belar AMMA-2 modulation monitor is specifically built to work with MDCL transmitters.
When making field strength readings, the MDCL circuitry must be turned off to get accurate readings.
For stations running IBOC, the amount of carrier power reduction may need to be experimented with, as the effect of the carrier reduction may cause the transmitter to exceed the NRSC mask.
Currently, only Nautel and Harris are selling MDCL transmitters. I spent several minutes poking around the Harris website and looking through their product brochures for the DX series transmitters and no mention of DCC o MDCL was found. I’d be happy to include any information from Harris if it were made available.
Once a bastion of the AM dial, News and or News/Talk format radio stations seem to be springing up on the FM band more and more often. The original premise for creating talk radio on the AM band was the lower bandwidth and reduced (or perception of reduced) fidelity when compared to the FM band lent itself to non-music programming. The reality is that receiver manufactures never carried through on the NRSC-2 technical improvements, and AM receivers reproduced thin, low quality audio. I digress, the story goes, the FM band was great for music and the AM band did well with information and talk.
Of course, there were always a few exceptions to those general rules, but for the most part, that pattern held true until about 2009 or 10. That is when AM station’s programming began to be simulcast again (everything old is new again) on FM stations and HD-2 subchannels. It would be interesting to examine why this is so and what it means to the radio business as a whole.
The general trend in the music industry has also been down. This is important because record labels and the radio business used to go hand in hand. Record labels had the job of separating the wheat from the chaff. Those groups or artist that had the talent would be given recording contracts and airplay. With exposure, they would become more known, sell more recordings, record more songs, etc until they peaked and began to decline. Radio stations prospered under this arrangement because they took on none of the risk while getting huge vast quantities of program material to playback, and charge advertising fees for spaces within that programming.
So far so good.
Then, two things happened:
The communications act of 1996
The internet
The communications act of 1996 forever changed the way the radio business was run in this country. No longer were there several thousand individual stations, the most influential of which resided in markets #1 and #2. Instead there were conglomerations of stations run out of Atlanta, Fort Worth and a dozen or so other medium sized cities. No longer were stations competing head to head and trying to be the best and serve their respective audiences; rather, station A was positioned against station B to erode some of it’s audience so that station C could get better national buys from big ad agencies. No longer would possible controversial artists like the Indigo Girls get airplay on some groups. Songs were sanitized against possible FCC indecency sanctions, morning shows became bland and safe, and radio on the whole became a lot less edgy as big corporate attorneys put the clamps on anything that would invite unwanted exposure.
The last great musical genre was the Grunge/Seattle Sound of the early 1990′s. Those bands somehow mixed heavy metal, obscure mumbled lyrics, flannel shirts and ripped jeans into something that the dissatisfied Gen Xers could understand and appreciate. By 1996, this had morphed into “Modern Rock,” and carried on for several years after that, to fade out in the early 00′s. Since that time, there has been no great musical innovations, at least on the creative side, other than the ubiquitous Apple computer and Pro Sound Tools software.
The internet greatly changed the way recording labels did business, mainly by eating into their bottom line. This had the effect of circling the wagons and throwing up a protective barrier against almost all innovation. The net result was fewer and fewer talented artists being able to record, which pushed those people into smaller, sometimes home based recording studios. While those studios can put out good or sometimes even excellent material, often the recordings lack the professional touches that a highly trained recording engineer can add. Add to this the mass input of the internet and no longer are bands or artists pre-screened. Some may point to that as a good development with more variety available for the average person. Perhaps, but the average person does not have time to go through and find good music to download from the iTunes store. Thus, a break developed in the method of getting good, talented artists needed exposure. Youtube has become one of the places to find new music, but it is still a chore to wade through all the selections.
Thus, when FM HD-2 channels came into being, there was little new programming to be put into play. HD radio was left to broadcast existing material with reduced coverage and quality than that of analog FM. That trend continues today where now analog FM channels are being used to broadcast the news/talk programming that used to reign on AM.
What will happen next? If Tim Westergren has any say, the internet (namely Pandora) will take over and terrestrial radio will cease to exist. Current trends point solidly in that direction, although I think Tim is a little ahead himself in his prediction.
News/Talk on the FM dial point not to an attempt to shift the wheezing, white, (C)onservative/(R)epublican programming to a younger demographic, who will, if I am any judge of history, remain unimpressed. No, rather, they are running out of other source material, simulcasting syndicated talk radio is cheap, lean and a good way to make money without having to pay actual salaries.
Occasional reader Jeffery asks a good question, which I will attempt to answer here in simple terms. Phasing, when used with antennas, refers to the relationship that two or more radiating elements share with the waveform being transmitted. It is used to create an RF radiation pattern by adding energy to the wave front in one direction by taking energy away from the wave front in another direction.
Phasing is often described as +/- X number of degrees from a reference point. Graphically, it would look like this:
One wavelength with +/- 180 degrees notated
The reference point can be changed to any point on the wave form, in radio applications it is usually oriented around +/- 180 degrees. If the reference point is a single tower or element then this would be the end of the story. Add a second tower to this system and it would look something like this:
Double wave form
In this picture we have two waves being radiated from two separate elements. These elements are spaced 100 degrees apart and tower #2 is phased to +90 degrees. RF generator is coupled to both towers via a power divider, the reference tower is feed with 57% of the power that tower #2 is being feed. The towers are on a north/south line with the reference tower bearing 180° from tower #2. In the area of subtraction, the wave forms cancel each other out to some degree; in the area of addition, the wave forms sum to create a greater waveform.
This is a typical two tower array, however, there are two slight differences; the reference tower is 215 degrees tall, tower two is 90 degrees tall. This is yet another use of “degrees” to relate electrical length or separations. The second, more notable distinction is that this array is Directional daytime, non-directional night time, which is the opposite of most AM stations in this country.
Electrical height can also be described as a function of wave length, e.g. 1/4 wave, 1/2 wave, etc. Most AM towers in this country are 1/4 wave length, which equates to 90 degrees. Often, higher powered stations, and some low powered stations put up towers near 1/2 wave length due to the better ground wave performance of those towers. At lower dial positions, a 1/2 wave tower becomes an expensive proposition due to the height required.
In theory, an unlimited number of towers can be used to create a pattern by introducing nulls (areas of subtraction) and lobes (areas of addition). In practice, the highest number of towers I’ve ever heard being used in an AM directional array is twelve; KFXR 1190, Dallas, TX. There may be others, too.
An excellent resource for AM directional antenna technical information is Jack Layton’sDirectional Antennas Made Simple, which is out of print but available from various sources.
This is a youtube video of a Police song from the 1980′s received via skywave and recorded off air on an AM radio.
Video Description:
The classic 1983 #1 smash hit, as received in analog C-Quam AM Stereo… in Japan… via nighttime skywave in the Tokyo area, roughly 500 miles away from Sapporo (ed: where the station is located). The audio quality is among the best I’ve ever heard from analog AM radio, thanks in large part to an excellent wideband receiver, very quiet band conditions, and the Orban Optimod-AM 9100 audio processor being used by HBC Radio to its maximum extent: 12.5 kHz audio bandwidth with stereo enhancement added (above and beyond the amount naturally provided by the matrix processing used by AM Stereo).
Absolute trash, I tell you. Just awful.
Of course, I know several FM stations around here that wished they sounded as good. Naturally, in Japan, they have sought to minimize night time interference problems by limiting the number of stations on air and enforcing the rules and regulations in place to protect those stations on the air. They also seem to allow greater bandwidth, out to 12.5 KHz in spite of the narrower channel allocations (9 KHz in ITU regions I and III, vs 10 KHz here in the US, ITU region II). One other thing to note, there is no digital buzz saw occupying several channels of broadcast spectrum. Keep in mind, this was received in Tokyo, likely a very high noise environment.
I was trying to find out the power level of the transmitter, the call sign is JOHR in Sapporo Japan, frequency is 1287 KHz. HBC is the Hokkaido Broadcasting Company, a privately held company. The state run radio outlets in Japan are NHK, which have several radio and TV stations throughout the islands.
Anyway, AM is dead. Killed by the very owners of the broadcasting companies themselves with help from the NAB. They are the ones that petitioned the FCC to loosen up the allocations and allow more and more stations to be crammed into the band. That is old news. The new news is same forces that killed AM radio are diligently working their magic on the FM band as well. More stations, translators, digital IBOC nonsense that doesn’t work, more of everything. After all, more is better. Until it is not. Then it’s too late.
Eventually, disaster will strike. It can range from a fire at the transmitter site to a tornado at the studio. Someday, every station on the air will be knocked off at the worst possible moment. It is the law of nature. Perhaps the most difficult disaster to recover from is the loss of a tower at a transmitter site. An FM tower holds the antenna, therefore, finding a tower or building nearby and placing a temporary antenna there will get the station back on the air in a reasonable fashion.
An AM tower is the antenna, which is much harder to replicate. One possible solution is to use a temporary wire antenna while the tower is being rebuilt. This is allowed in FCC 73.1680 emergency antennas, provided the commission is notified of the situation by informal letter. Directional stations must operate at 25% or less of the station’s licensed power, or demonstrate that radiation limits are are not being exceeded in any direction. That usually can be accomplished by taking a set of monitor points.
A wire antenna can come in several configurations:
Fastest to deploy is the random length end fed wire. This can normally be attached to the existing ATU and tuned up with components on hand. It requires having an OIB, generator and receiver to tune, which not every station has. In addition to that, extra components may be needed in the ATU for tuning purposes.
Next easiest is a tower length wire ready to deploy. This is a length of wire equal to the height of the tower, with insulators and supports. Wire should be supported as high above ground as possible using trees, wooden poles, etc. Still requires having an OIB, generator and receiver to tune. Likely to be within the tuning limits of the ATU components on hand.
A 1/2 wave dipole tuned for 50 ohms. This can be connected directly to the transmitter output, thus is the best solution if the ATU’s were damaged or otherwise not serviceable. In this situation, two 1/4 wavelengths of wire are coupled at the center using a 1:1 balun. Again, this antenna should be supported as high above ground as possible using trees, poles and other non-conductive supports. Can be installed in a V, inverted V, or L shape as required.
All three of these choices would likely limit transmitter power output to 1-2 KW. Choice 3 likely represents the most efficient radiator and can be fabricated ahead of time and stored at the transmitter site.
1/2 wave dipole with 1:1 balun
To make a 1/2 wave dipole, cut two lengths of wire using the formula L(feet)=246/F(MHz). This formula does not account for a velocity factor of 90%, which is typical for stranded wire. The reason being, since a MF dipole antenna is necessarily going to be lower than 1/2 wave length, it is better to start the antenna a little long and trim it to size for a 50 ohm impedance. If commercially made insulators are not available, insulators can be made from non-conductive materials like PVC conduit, PEX, plexi-glass, etc. The insulators on the ends of the wire need to account for the voltage peak that will occur there. If small “dogbone” type porcelain insulators are used, string thee or four of them together using nylon or poly rope. The insulator needs to be able to withstand 8-10 KW of power under full modulation.
A 1:1 balun will distribute the RF currents evenly on both wires, which will help improve efficiency and coverage. Most Ham Radio Baluns are not designed to work below 1.8 MHz and therefore, will not work for this purpose. A balun can be made with a ferrite torroid made from 68, 73, 77 or type F material. A good choice would be Amidon FT-290-77 or FT-290-F. The type F material has a higher AL value, thus fewer turns are needed. In addition to that, high voltage insulated wire should be used to wind the balun.
1/2 wave dipole antenna current voltage distribution
Since, in a 1/2 wave dipole configuration, the voltage is at a minimum at the center of the antenna, and current is at a maximum, some attention needs to be paid to wire size as well.
Amidon ferrite torroid core
To give a good idea of wire sizes required, some basic information is needed. For a 1 KW station, it is assumed that the carrier will be modulated to 100 percent, therefore the peak envelope power will be 4 KW. If the station is asymmetrically modulated, add another kilowatt. Therefore, the maximum current formula is I=√(P/R). P is the power in watts, or 5,000 and R is the radiation resistance or 50 ohms, thus I=√(5000/50) or 10 amps. The maximum voltage is E=√(P x R) or E=√ (5000 x 50) or 500 volts. For a safety factor, multiplying these values by 1.5 is recommended. That will likely account for any impedance differences due to ground proximity and so forth. Therefore for a 1 KW station, the dipole antenna should be designed for 15 amps and 750 volts.
For a 2 KW station the peak envelope power for an asymmetrically modulated transmitter is 10 KW, thus it follows that 30 amps and 1500 volts are safe working figures.
With the proper torroid core, a turns count of 7-10 turns bifilar will suffice. Since it is a 1:1 balun, the turns count on both sides of the transformer will be the same. The balun then should be placed in a suitable water proof housing designed to be attached to the center of the dipole antenna. This is a good example of a commercially available 5 KW 1:1 balun for amateur radio use:
1:1 balun designed for center of 1/2 wave dipole antenna
The antenna can be fed with RG-8, RG-8X, RG-8A, RG-214 or any other coax this is capable of handling the peak envelope power of the radio station. The connector can be UHF, N, LC, etc. In some cases, the may be easier to simply omit the connector and connect the coax to the balun using some type of strain relief on the cable coming out of the box.
Once this antenna is made, a bit of tuning may be required to bring it to 50 ohms. This can be done with a bridge and generator, or with the transmitter on low power. Either way, the measurements must be taken with the antenna at operating height as the distance to ground will effect the termination point impedance. It may require some trial and error.
In all, a good backup antenna can be made for about $50-60 or so. A little bit more if fancy transmission line is used. Well worth the expense and effort to have something ready to go in a moment’s notice.
Update: I’ve been fooling around with this on EZNEC, it may not be that easy to do, especially with the lower frequencies in the AM band. The antenna needs to be at least 0.06 wave length above ground to perform correctly. Somewhat lower over better ground conductivity, e.g. ground radials. Even at this height, it needs to be lengthened significantly to get the feed point impedance close to 50 ohms.
There is a propensity among radio engineers to save old equipment. Sometimes I look at something and think, “Man, that cost a lot of money ten or twenty years ago.” Truth be told, much of what is saved will never be used again. This equipment should be scraped or donated to someone who might find it useful. One thing that is most appreciated by Amateur Radio (AKA Ham) operators are old 1 KW tube type AM transmitters. Ham operators love these things, and with good reason.
A fair amount of repair work, some cleaning and a bit of reworking will turn what might have been a useless dust collector into a 160 or 80 meter AM rig and with a good story to boot.
Personally, I’d rather see a Gates BC1T or RCA BTA1R off to a new home than off to the scrap yard. To that end, today we unloaded the BC1T at WLNA to a willing ham. This particular transmitter had last run in 2001 or so and was used as a spare parts supply for other BC1T transmitters owned by the same company. There was no way it would ever work again and truth be told, it really wasn’t needed any longer anyway. Since the Harris MW5B was replaced as the main transmitter by a BE AM6A, the backup transmitter was never used.
Gates BC1T transmitter
John Aegerter, a frequent commenter on this blog, drove all the way from Madison, Wisconsin to pick it up. Prior to pick up, I removed all of the tubes, transformers, crystals and glass envelope time delay relays. I packed up the glass objects in a box.
Gates BC1T tubes, transformers and spares
There were several spare tubes and parts which are no longer needed. These went with the rig, along with what ever manuals I could find.
Gates BC1T loaded into pickup truck
The transmitter was then loaded into the back of a Dodge Ram 2500 pickup truck and tarped for it’s trip back to Wisconsin.
I received this link in the comments of a previous post and found it interesting. The BBC will be closing down 648 KHz, Ordfordness England at the end of March, no doubt due to budget cuts. The site has been in use since 1972. Prior to this, site was formerly an OTH array, COBRA MIST, which was then adopted for MW broadcasting. The video is 17 minutes long, but, if you are interested in radio history, technical aspects of AM broadcasting and the like, it is interesting.
These are 600 KW transmitters. As Andy Matheson, transmitter engineer, explains, with a wry smile “I find them (transmitters) very satisfying, I enjoy either day work or shift work, just really working with transmitters has always been very satisfying…” I couldn’t have said it better myself.
Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.
~1st amendment to the United States Constitution
Any society that would give up a little liberty to gain a little security will deserve neither and lose both.
~Benjamin Franklin
...radio was discovered, and not invented, and that these frequencies and principles were always in existence long before man was aware of them. Therefore, no one owns them. They are there as free as sunlight, which is a higher frequency form of the same energy.
~Alan Weiner
Everyone has the right to freedom of opinion and expression; this right includes the freedom to hold opinions without interference and to seek, receive and impart information and ideas through any media and regardless of frontiers
~Universal Declaration Of Human Rights, Article 19
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