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By Paul Thurst, on October 20th, 2011
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.
By Paul Thurst, on September 15th, 2011
Series excited AM towers require some way to get standard AC across the base insulator to the tower lights, if tower lights are required. While many new AM towers do not have base insulators, through the use of a folded unipole, it is still a very popular design and has several technical advantages.
There are two methods for getting 60 Hz AC from zero RF potential to an excited tower:
- Tower lighting choke
- Austin Ring transformer
 LBA Group TC-300 tower lighting choke courtesy LBA Group, Inc When to use which depends on the tower and the RF potential on the base of the tower. For towers that are under 140 electrical degrees (RF) and carrier power levels up to 100 KW, a lighting choke works well. They are simple and less expensive than an isolation transformer. They can be installed inside the ATU cabinet or placed in their own weather proof enclosure as required. Tower lighting chokes will add series impedance to the base of the tower and needs to be compensated for by adding capacitance to the circuit. This will become more pronounced at the lower end of the band, where, if one is not careful, RF from the tower can be coupled to the transmitter building’s AC mains, which is very undesirable.
Tower lighting chokes generally consist of three separate windings, one for the beacon, one for the side lights and one for neutral. Their inductance is typically in the 800-1000 µH at 1 MHz region. They can be stacked to increase their peak voltage handling capacity:
 LBA Group tower strobe light choke courtesy LBA Group, Inc Peak voltage is determined by the base impedance and carrier power + modulation. On any AM station these days, a 150% peak modulation figure should be used (125% modulation allowed by FCC rules plus a 25% safety factor). For example, station B has a base impedance of 50Ω (typical 90° guyed tower) and a carrier power of 50 KW. The peak modulation power will be 600 KW. Thus, the peak voltage will be Epeak = √Ppeak x R, or Epeak = √600,000 watts x 50 ohms or 5,477 volts. With higher base impedances, the base current goes down but the base voltage goes up. A typical 140° tower will have a base impedance of 760Ω. Thus the peak base voltage for a 50KW carrier power modulating at 150% will be 21,354 volts. This is the worst case scenario, as few installations are designed that way and every tower impedance is different than the theoretical self impedances given.
For towers over 140 electrical degrees, it is better to use an isolation transformer because of the RF peak voltage/peak current conditions at the base of towers that are electrically tall. The ring transformer design minimizes stray inductance or capacitance at the base of such towers. Austin Insulators (previously Austin Decca) makes a variety of tower base ring isolation transformers. These having varying input and output voltages.
 Diagram of typical Austin Ring transformer courtesy Austin Insulators, Inc I have seen these at many locations over the years. They are rugged and add only a small bit of capacitive reactance to the base of a typical tower. They also completely isolate the building AC mains from the tower. For very high power installations, Austin has the A-9600, which was designed for the Navy VLF transmitter towers where base peak RF voltages can run 200,000 volts or more:
 Austin A-9600 oil filled isolation transformer courtesy Austin Insulator, Inc Voltage drop is another consideration in tower lighting design. Long runs from the transmitter building to the tower should be on heavy gauge wire and at 230 volts if possible. FAA Circular AC 150/5345-43F “Specification for obstruction lighting equipment” advises that the input voltages for incandescent lighting systems vary by not more than ±3%. Additional tower lighting and painting information can be found in FAA Circular AC 70-7460-1K.
By Paul Thurst, on July 12th, 2011
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.
Resulting pattern (WKIP, Poughkeepsie, NY):
 WKIP 1450 Poughkeepsie, NY pattern plot 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’s Directional Antennas Made Simple, which is out of print but available from various sources.
By Paul Thurst, on April 26th, 2011
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.
By Paul Thurst, on March 11th, 2011
We have received somewhere between 5-6 inches of rain in the last four days. That, coupled with the deep snow pack and the still frozen ground has lead to some flooding. The WLNA antenna array is located along the Peekskill Hollow Creek in northern Westchester County, NY. Back in 1980, it might have seemed like a good idea to locate an AM station in a tidal swamp along the Hudson river. I am sure the land was not that expensive and from an engineering standpoint, having a continually wet, partially brackish ground system may have seemed like a slam dunk.
Unfortunately, the idea never really panned out in application. First of all, the neighbors had other ideas, fighting the radio station owners all the way to the NY State Supreme court. Secondly, technically, it never lived up to expectations. The original non-directional antenna on 1430 was a 1/2 wave tower which by all accounts, worked very well. It did not, however, allow for night time service, which is why the new sight and array was sought. By the time the system was built, AM was already in steep decline and I doubt the owners ever recouped their investment.
Fast forward to today. All five base insulators are under water and the transmitter is off the air. These are pictures from last Wednesday after the first flood waters receded from the Monday/Tuesday storm. I imagine it looks worse this morning, although I don’t own a boat and won’t be wading out there to look.
 Base insulator, tower 2 WLNA array, Peekskill, NY This is tower two of the daytime antenna array. Clearly, it spent some time underwater. We cleaned off all the debris from all the tower bases. A far worse prospect are the ATU’s:
 WLNA tower 1 ATU, Peekskill, NY This is the Antenna Tuning Unit for tower 1, which is the reference tower for both the day and night arrays. The E.F. Johnson contactor in the bottom of the cabinet was fully submerged for an undetermined amount of time. The bottom of the unit is covered in fine silt. The high water mark is visible on the right side of the aluminum cabinet.
The contactor is going to need to be replaced, or at least rebuilt. The ATU cabinet will need to be washed out. There are two other ATUs that suffered the same fate.
 WLNA antenna array, towers 3 and 5 This is the end of the catwalk next to the Peekskill Hollow Creek looking west towards the Hudson River. The water level reached the bottom of the catwalks and had receded about 4 feet when this picture was taken.
 WLNA antenna array, tower 5, Peekskill, NY Lookup east, upstream at tower 5.
 WLNA antenna array looking north, Peekskill, NY This is the antenna array looking north, with my back facing the creek. Tower one is the center tower, tower two is on the right and tower four is on the left. The daytime array consists of towers 1, 2, and 3 bearing 300 degrees. The night time array consists of towers 1, 4, and 5 bearing 335 degrees, so the array makes a big X in the swamp. More from the FCC database.
It is going to take a lot of work to clean out all these ATUs and repair the damage. Clean water is at least 1000 feet away. My question is; why bother? Once upon a time, this station was viable, well thought of in the community, etc. Now, I doubt anyone knows it is off the air. The current ownership over the last thirteen years did, what I’d like to call, a controlled flight into the ground. Axing staff, cutting maintenance and generally neglecting the station. Why not take it dark for a while and figure out what to do with it. Likely somebody would buy it, even if for the land it sits on. Anyway, the grind continues…
By Paul Thurst, on March 7th, 2011
This is a set of burned contactor fingers on a Harris HS-4P 30 amp RF contactor:
 Harris HS-4P RF contactor with burned finger stock The back story is this:
The contactor in question is at the base of Tower #3 of the WBNR (1260 KHz, Beacon, NY) antenna array. This is the tallest of all the towers, at 405 feet. As such, it gets struck by lightning often. There was at least one occasion where one of the inductors in the ATU got “sucked in” due to the huge magnetic field of a high current strike. It is not at all surprising to me to find other component issues in this ATU. Because of the burned contacts, I’d suspect that the station was switching modes under power, but I didn’t see that happening today.
The problem manifested itself in very high SWR after changing over from day pattern to night pattern. This did not occur every time, in fact, it only occurred once in a great while at first. Then, over the last couple of months it began occurring more and more often. Since the snow drifts are now down to a manageable six to eight inches, it was a good day to go out and do some exploring.
First of all, I put the station into night time mode just to confirm that there is still an issue. The transmitter, a Broadcast Electronics AM1A showed very high SWR and carrier fold back. Left it in night pattern, but turned it off and took a walk, not a drive, to Tower #4 which is all the way at the bottom of a hill, near the old City of Beacon landfill. I figured that I would check that one first, then look at Tower #3 on the way back. When I got to Tower #3, I found the issue right away.
Fortunately, I was able to salvage a set of contact and contactor bar from another relay in the same ATU that was not using them.
 Burned RF contactor bar The night pattern is only 400 watts, but these are tall towers, 225 degrees, therefore current and voltage are high at the base. In fact, the slightest change at the base of the night time towers will greatly upset things.
 Burned RF contactor fingers  Harris HS-4P contactor repaired This is the repaired contactor. I will say, the EF Johnson RF contactors are easier to work on. Those are the ones with the big rocker bar across the top and two solenoids on either side. All of the wiring, status switches and contacts are exposed and easy to get to. This one, not so much. This is the BE AM1A transmitter
 Broadcast Electronics AM1A transmitter It is not a bad unit, compact, sounds good, reliable, etc. In order to work on the power supply or anything in that top cabinet, the whole thing needs to be removed from the rack and taken down. I suppose that is my only gripe about the thing.
By Paul Thurst, on February 23rd, 2011
WISN 1130 AM has been on the air since 1922, although not always with those call letters. In an interesting twist, the license was granted to the local newspaper, the Wisconsin News and the Milwaukee School of Engineering. Initially, both entities were programming the station, however, by about 1925, the newspaper was responsible for programming and the engineering school was responsible for technical operations.
In 1941, the station increased power from 1,000 watts to 5,000 watts and added night time service. This is a series of pictures from that time period.
 WISN night time allocation study Back in 1941, night time interference was taken seriously. The night time allocation study (on 1150 KHz, WISN’s former frequency) includes co-channel stations in the US, Canada, Cuba and Mexico.
 WISN night time allocation ma The array consisted of four Blaw-Knox self supporting towers in a rectangle. Notice the lack of fencing, warning signs and the like around the towers.
 WISN antenna array From the front of the transmitter building
 WISN transmitter site, 1941 The site looks well designed, no doubt manned during operation, which at the time would likely be 6 am to midnight except under special circumstances. Most of these old transmitter sites had full kitchens, bathrooms, and occasionally a bunk room. The transmitter operators where required to have 1st telephone licenses from the FCC. There is only one manned transmitter site in the US that I know about; Mount Mansfield, VT. There, WCAX, WPTZ, WETK, and VPR have their transmitters.
 WISN RCA BT-5E transmitter, 1941 The WISN RCA BT5E transmitter looks huge for that power level. Back in the day when AM was king, these units were designed to stay on the air, no matter what. I don’t know too much about this model transmitter, but if it is like other RCA/GE models from the same era, it has redundant everything.
 RCA AM antenna monitor Old school antenna monitor. I have never seen one of these in operation, however, as I understand it, the scope was used to compare the phase relationship of each tower against the reference tower.
These pictures are of the WISN 1150 array was it was in 1941. Since then, the station has changed frequencies to 1130 KHz and increased power to 50,000 watts daytime/10,000 watts night time. The daytime array consists of six towers and the night time array has nine towers, all of which are 90 degrees.
Special thanks to John A. for sending these pictures along.
By Paul Thurst, on January 15th, 2011
This is a Hughey Phillips mechanical tower light flasher that has been in service since 1960. Basically it is a motor connected to a cam that rocks a mercury relay back and forth. These were standard technology for tower lights from the 1930′s through about 1970 or a little later. They were very reliable, we still have some with a “pancake motor” in use on some of our towers. They were very robust and immune to lightning damage, RF interference and other problems. The only maintenance that I can think of is lubricating the motor bearings. Eventually, however, they do wear out. Cold weather seems to take its toll, often causing the motor to stop.
 Hughey and Phillips mechanical tower light flashe This particular unit is mounted inside the tuning house for the far tower (north tower) at the WGHQ antenna array. It has finally reached the end of it’s existence; the motor bearings are shot and it has gotten stuck in both the on and off position this year causing the FAA to be notified of the malfunction.
 WGHQ 920 Khz Kingston, NY antenna array Today, I am replacing it with a solid state flasher (SSAC B-KON FS155-30RF). Solid state flasher units have been known to malfunction in high RF fields, such as AM towers. To cure that, the manufacture has built in 0.01 uf bypass capacitors, hence the “RF” suffix. Older units did not have the built in bypass caps, so external 0.1 uf bypass capacitors were normally installed on units mounted to AM towers. While I was working on this, I turned the transmitter down to 500 watts, no need getting any RF burns.
Naturally, this has to happen after there is two feet of snow on the ground. Also, it should be noted that this is the furthest tower away from the transmitter building. Now where did I put those snow shoes? Never mind, it has been very cold and the ground is frozen solid, I’ll take the truck… This is good because I will have all the tools, drills, nuts and bolts without having to walk back and forth several times in the snow.
 Hughey Phillips mechanical beacon flasher I removed the motor and mercury filled relay. I’ll have to figure out how to dispose of the relay. I then drilled a mounting hole through the base of the old flasher housing and bolted the solid state relay to it. This is required because the solid state relay needs a pretty good heat sink.
 SSAC B-KON tower light flasher Turn everything back on and: Ta-da! All works normally, tower beacon is flashing away up there. Time to leave.
 Truck stuck in swamp Pull forward about 2 feet to turn around and CRUNCH! The truck goes through the ice of a hidden stream. Any attempt to move only makes it worse:
 Truck rear burried to axle Put in a phone call to the one guy I know that can get me out. About an hour later he shows up with chains, a shovel and a come-a-long. We attach the come-a-long to the fence support post and pull the truck out backwards 1/2 inch at a time. It took us about an hour and a half to get it all the way out so I could drive it back across the field. I’d have taken some pictures, but my guy; he was a little grumpy.
I won’t do that again.
Still, I did the job I came to do, so it was a good day after all.
By Paul Thurst, on October 18th, 2010
WE2XRH looks like an Amateur radio call sign but it is actually the call sign of an experimental short wave station in Alaska. Transmitting DRM on 4.85 MHz, 7.505 MHz and 9.295 MHz with a Near Vertical Incident Skywave antenna system, they hope to cover all of Alaska and almost nowhere else with shortwave broadcast.
 WE2XRH DART coverage with NVIS antenna system This license was granted for two years in August of 2008 and renewed again this September until July 2012. According to the website Nextgov.com:
The company told FCC that its initial tests would be funded by and conducted for the Defense’s Joint Electromagnetic Technologies program, a classified operation whose mission is to develop technologies for use by special forces and intelligence units.
Defense also will supply surplus transmitters from the closed, Cold War-era Over the Horizon Radar, located in Delta Junction. The radar system bounced shortwave signals off the ionosphere to detect aerial targets, such as Soviet bombers, at ranges up to 1,800 miles.
The transmitters are 100 KW Continental HF units, which for this applications are running about 20 KW. According to this Yahoo Groups posting, several Japanese shortwave DXers have received the station in late 2009, but nothing recently. I shot an e-mail off to their information address, but did not receive a reply.
On High Frequency (HF) NVIS has been used for several years where line of sight VHF communications are not possible. Soldiers during the Vietnam war noticed that if a vertical whip was bent over so that it was horizontal to the ground, the signal strength was slightly less but the signals were much less prone to fading.
 Near Vertical Incident Skywave antenna angle vs. distance In this case, WE2XRH is using a crossed dipole antenna which generates a circularly polarized field. With traditional HF skywave, polarization is not a factor since the ionosphere usually causes some field rotation anyway. It is interesting that the system had this design consideration.
The NVIS is a novel approach and it may work on Medium Frequency (MF) during the night time, but daytime coverage would still have to rely on ground wave signal. The FCC has historically approached MF skywave as a secondary and unreliable transmission method. The idea being to reduce the antenna take off angle to as low as possible, hence the popularity of taller than 90 degree towers. There is good validity to that practice as mixing the ground wave and skywave components at a receive antenna will cause multipath fading.
Setting aside a new broadcasting frequency segment, say 1.6 – 1.8 Mhz, a system could be designed to transmit DRM by using groundwave during the day with a traditional 90 degree tower, and NVIS at night with a horizontal dipole antenna. Then never the two should meet. The night time NVIS system would have a small ground wave component, out to a couple of miles. In addition to that, the night time NVIS system can run on an adaptive power system, when propagation conditions are poor, more power can be applied to the antenna input and in better conditions, power reduced in accordance with a remote receive monitor that reports the Bit Error Rate (BER) back to the transmitter controller.
The best NVIS antenna is the 1/2 wave dipole positioned between 0.1 and 0.2 wave lengths above ground. In the 1.6 to 1.8 MHz band, that equates a half wave dipole antenna 260 to 292 feet long mounted between 66 to 90 feet above ground level.
This would have many advantages over the current directional antenna based MF broadcasting system currently deployed. The current system is based on pushing potential harmful signals away from a station that was licensed to the same frequency (or an adjacent frequency) earlier. This puts the onus for proper operation on the broadcast license holder. Most don’t have the know how or resources to insure that a n AM directional is operating properly. I would estimate at least half of the directional AM antennas in this country are out of tolerance. With a NVIS based night time antenna system, coverage areas would be assigned much like an FM allotment.
The BBC conducted medium wave DRM tests in 2007 with satisfactory results during the daytime, but poor reception at night time due to co channel interference. That is why DRM will not work on the current AM broadcast band and if digital radio is to be broadcast on MF, a new frequency band would be needed.
By Paul Thurst, on October 12th, 2010
Sometimes it is the seemly small insignificant detail that will take a station off the air. To expound on that a bit, I have my own story which happened yesterday. The back story is this: About three years ago, some unauthorized tower climbers climbed the WICC south tower all the way to the top. The station remained on the air at full power while this was going on. Once at the top of the three hundred foot tower, the climber, we can call him “Crack Head,” manged to loosen, then remove the beacon and throw it to the ground. Mind you, this guy had no safely climbing equipment whatsoever and he had to stand on the top plate, which is all of 20″ x 20″ square, of which the beacon takes up 16 inches. A two inch purchase between himself and eternity demonstrates that God does indeed smile on fools and drunks.
 WICC South tower with Long Island sound in background Fortunately, his friend on the ground had a video camera and filmed the entire episode. Even better, they then posted it on Youtube. The police took interest in this video and it’s owners because the damage to the radio station was significant, and with the tower being about a mile away from the end of the Stratford Airport runway 17, presented a real hazard to air navigation. Needless to say, the video was used by the prosecution and both crack heads are now in prison, God having limits after all.
A spare beacon was hoisted to the top of the tower an placed in service. This beacon was quite old and leaky and continually failed, burning out the tower light flasher. Thus, it was time to replace it. We took advantage of the outstanding weather and the crew from Northeast Towers made quick work of it. Removing and lower the old beacon to the ground, then hoisting the new beacon up and installing it. I goobered it by not taking pictures of the beacon fixtures flying up and down the tower. I took the station off the air for about five minutes to check the condition of the wiring going up the tower, making sure there were no shorts up the tower or back toward the transmitter building. While I was doing this, I overheard the two way radio conversation between the tower climber and the ground crew on wiring. It seems the old beacon had only two wires, hot and neutral. The new beacon had three wires, hot, neutral and ground. Tie the neutral and ground wires together, instructed the tower boss.
Nothing more was though of that, it sounded okay to me. Unfortunately, the tower had other ideas. About an hour after we secured from the job and drove away, the station went off the air. It seems the neutral wire was not referenced to the tower previously. Because now the neutral wire was tied to the top of the tower, the RF found a path to ground via the tower lighting choke at the base of the tower. It started arcing to it’s access door causing the transmitter to go off around 4 PM. Equally unfortunate was the fact that the construction gate was closed and I had to get a boat ride with the harbor master, which took about an hour to arrange. The entire situation was further complicated by darkness, which comes predictably around 6:30 PM this time of year.
When I arrived back out at the base of the tower, I took the metal access door off of the tower light choke cabinet. I could see the fresh track marks all across the bottom of the door. With the door off, I turned the transmitter on. Worked just fine. I tried cleaning it off with a Scotch Bright, but to no avail, the transmitter would not run at any power level with the door in place.
Finally, the harbor master becoming impatient and darkness quickly falling, I taped a garbage bag over the tower light choke box with the door off and turned the transmitter back on. The tower crew will have to come back and remove the ground wire on the beacon.
The first rule of trouble shooting: Check the last thing that was worked on first.
Update: And look, here is the original story in Radio World: Tough times a Pleasure Beach.
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Axiom
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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Open Mic