October 2010
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On this, the 72 anniversary of War of the Worlds

It was early evening when most people were sitting down to enjoy the latest edition of Mercury Theater on the Air on CBS.  After a brief narration by Orson Wells, which is set a year ahead of the actual date, there was a flash forward and brief weather forecast.  It then seemed that the show was not going to be on as Ramon Raquello and is orchestra were performing dance music when the music faded down and the announcer came on the air slightly out of breath:

Ladies and Gentlemen, we interrupt our program of dance music to bring you this special bulletin from the intercontinental radio news…

It was a great piece of theater, too realistic for many, others tuned in late and panic ensued.  People raced out of their houses, went to confession and didn’t pay for gas.  There were reports of long alien ships landing in New Jersey and incinerating crowds with heat rays. Then the black poison gas, oh, the black poison gas.

The day after, New York Times reported that up to 1.2 million people felt they were in grave danger and the world was ending.  It is hard to imagine how they came to that number, especially overnight for printing the next day.

Naturally, those commie federal regulators were having none of it, and the FCC proclaimed that broadcast hoaxes would not be tolerated, even promoligating a rule, 73.1217, stating, in part:

No licensee or permittee of any broadcast station shall broadcast false information concerning a crime or a catastrophe if: (a) The licensee knows this information is false; (b) It is forseeable that broadcast of the information will cause substantial public harm, and (c) Broadcast of the information does in fact directly cause substantial public harm.

There are some radio stations that still broadcast this show every Halloween, with the appropriate disclaimers, of course.  For those that want to hear the War of the Worlds, go to Radio Heard Here.  It is really a great show.

Happy Halloween!

Update:  Occasional reader Sandy sends along this link to the WKBW 1968 version, which was purported to be every bit as real as the 1938 version.  The station was deluged with phone calls.  In fact, legend has it that when the broadcast ended a little after midnight, show producer Jeff Kayne slipped his resignation letter under the General Manager’s door.

WOWO EBS activation

An oldie, but a goodie, February 20, 1971, WOWO gets a EAN via AP teletype and follows procedure:

Back in the days of EBS, there were weekly closed circuit tests via AP and UPI teletype. In the event of a real Emergency Action Notification (EAN) there was a red envelope that contained a set of code words for each month. The test code words were on the outside of the envelope. If a EAN was received, the envelope would be torn open and the actual code words would be matched against the code words in the message. If it were authenticated, then the station would do just what WOWO did right then, send the two tone EBS alert for 25 seconds  and break into programming.

It is amazing that this did not happen more often, especially on a Saturday morning with some a sleepy Airman in Colorado pulling the wrong message tape off the rack at the message center responsible for the whole system.

It has happened more recently when an EAS message was sent to evacuate the entire state of Connecticut.  A EAN was sent in Chicago warning of a national attack when state officials were testing their new system.  I am sure that others have been sent as well.

I suppose the emergency notification has always left something to be desired.

HD Radio equipment, on trade

It has been about a month now, has anyone taken them up on this:

iBiquity Digital and Citadel Media announced a partnership which will enable stations to upgrade to digital while avoiding cash expenditure. Stations will have the opportunity to provide on-air inventory to Citadel Media in exchange for the HD Radio license fee and equipment supplied by Broadcast Electronics, Continental, Harris and Nautel.

I was sure that my former employer, now that I have left the company, would at least look into this.  I know there are many other frugal like minded companies out there that look at trade as being “free.”  Anytime I had a building project, like paving the parking lot or replacing the roof membrane, the first question asked was “Can we trade it?”  I hated dealing with trade.  Often, it would end up as a half paved parking lot and the general manager asking “Gee, what happened?”

I would be surprised if this iBiquity scheme didn’t generate at least some interest in the HD radio holdouts. Has anybody heard anything else on this?

The Pacific Records and Engineering BMXII console

I snapped these pictures at WICC in Bridgeport, CT. It is an older PR&E BMXII console, 26 channels, I believe.

Pacific Recorders BMXII 26

Pacific Recorders and Engineering BMXII 26

These were manufactured starting in 1985, I installed one in 1990. It is a testament to their durability that this one has lasted 23 years.  They were expensive when purchased, and all of them were purchased directly from PR&E, Carlsbad, California.  The beauty of these things is their modularity.  All of the major components are replacable, including the module face inlays.

Penny Giles conductive plastic fader

Penny Giles conductive plastic fader, PRE BMXII console

The faders, Penny and Giles 4000 series, are fully rebuildable.  The part that wears out the most is the nylon bushings that slide along the metal rails.  The contact fingers sometimes also need to be replaced.  These are 10 Kohm conductive plastic linear faders.  P&G does not make these anymore, they have been replaced by the 8000 series, which has a edge connector instead of a wiring harness.  Since the top of the fader is open, it also tends to accumulate dust, dirt and other debris.  The fader board itself should be cleaned off with warm water, light soap may be used if needed.  Do not use alcohol on these because it eats into the conductive plastic and ruins the fader.

PRE BNXII line input module

PR&E BMXII line input module

One of the great things about this console is the fact that all the modules are hot pluggable.  If one needs to be serviced, it can be pulled out of the main frame while the console is on the air and a new module plugged into it’s place.  Only the line output module replacement necessitated taking the station off the air, and then only for a few seconds.  It was a great concept which is now standard in almost every broadcast console.

There were several basic module configurations.  On the input side, line level, mic level and telco were standard console inputs.  There was also a passive remote line select button set.  Out put modules consisted of line level output, control room monitor, and studio monitor modules.

PR&E consoles were top of the line gear, but expensive.  Most radio stations could not afford them and went with less expensive models like Wheatstone, BE, LPB, Autogram, Radio Systems, etc.  The fact that some of these BMXII consoles are approaching 30 years of age and still in service is a testament to their construction.

In the early 1990’s, PR&E began branching out into the lower priced market with their product line.  They produced the Radiomixer and Productionmixer consoles, however, mid market sized radio stations were slow in adopting them because PR&E had the reputation of being expensive.  After all, if you can only afford a Chevrolet, why bother looking at the Mercedes?

WQXR control room

WQXR control room

This is a grainy promotions photo from the early 1990’s showing what I think is the WQXR master control room, nick named “The Bridge.”  I took a tour there around 1993 or so and it was a fantastic facility, of course the New York Times spared no expense.  I really felt like Willie Wonka in the Chocolate factory.

Later in that decade, they changed the name to Pacific Research and Engineering, and the went public.  I think going public was the death knell, soon thereafter they sold the entire product line to Harris Broadcast.  The final non-Harris console was the Airwave, which is a good medium duty modular console, incorporating some of the traditional PR&E designs.  The later consoles stopped routing audio directly through the faders, using voltage controlled amplifiers instead.  This solved some of the channel drop out problems which sometimes occurred in earlier consoles.  The Airwave consoles are much less durable than the BMX series, however, with the advent of voice tracking, perhaps 24/7 durability is not that necessary anymore.

Harris has dropped support of much of the early PR&E line, but there are those that soldier on, buying up parts and rebuilding these things.  Mooretronix has a good selection of BMX and ABX parts.

The WICC/WEBE  installation is about to be refurbed, which means these consoles will be headed out the door.  There are three of them in fair condition.

Digital Radio: A solution without a problem

Or, it could also be phrased “A solution that causes more problems.”  Radio World, once again, has a good article on the consequences of increasing IBOC power of the FM hybrid system.  Especially telling is figure 24, a fuzzy 400 Hz sine wave showing how much distortion is added to the analog signal by a mere 4% HD  signal.  I’d be especially interested to see the results of the full 10% now allowed.

Naturally, HD proponents will cry “But this is only temporary!  Wait until the transition to all digital!”


If HD radios were indeed flying off the shelves as iBiquity claims, and if the public expressed interest, okay, maybe.  Clearly, that is not the case.  The only thing that HD radio is doing is creating more interference. Period.  More interference to the parent station and more interference to the adjacent channels all for an audience that does not exist.   Another way to put it: NOBODY IS LISTENING.  One of the station that I service had a Harris Deathstar go off line for four days.  NOT ONE PHONE CALL, NOBODY CARES!

The public did not perceive a technical problem with analog FM broadcasting.   Of course, that can always change as the band gets filled with interference.

Lets see where FM IBOC stands:

  • Rolled out with 1% digital power vs analog carrier, the system was found to lack building penetration and generally performed poorly in mobile listening environments (NPR labs study, Nov 24, 2009)
  • FCC allows up to 10% digital power vs analog carrier to overcome these problems, a few stations implement some type of power increase
  • The  shows that self interference is the largest problem IBOC needs to fix, one that is un-fixable due to the laws of physics
  • The public yawns, turns on their iPod

IBOC is a failure, both in AM and FM bands.

We are watching the self destruction of radio broadcasting in the US.

WSPK antenna replacement, part I

WSPK is located on North Mt. Beacon, which is the highest point for miles around. It has a fantastic signal. The site is a little difficult to get to, however, especially in the winter.  In previous years, the road has been impassable four months out of the year.  Some engineers have hired a helicopter to get up there when the snow is deep.  For that reason, it is important to keep the equipment in good shape.

WSPK Shively 6810 antenna with damaged top radome

WSPK Shively 6810 antenna with damaged top radome

After last February’s snow/rain/ice storm, it was noted that the top antenna radome was missing it’s top.  A tower climber was sent up to look at it and it was also discovered that the top bay was bent down and the element was almost cracked in half.  A result of falling ice, likely from the big periscope microwave reflector (passive reflector) mounted above it.

WSPK tower

WSPK tower

The periscope reflectors went out of service in 2007, but the tower owner did not want to pay to take them down, thus a problem was not being solved.   It was decided to replace the 25 year old Shively 6810 antenna with a new one, during which work, the radio station would pay to remove the reflectors from the tower.  In exchange for that work, the radio station would then be able to repair and remount the old Shively antenna below the new one, thus having a backup antenna.  Problem solved, except for, you know:  The actual work.

The tower and the periscope microwave system was installed in 1966, operated on 12 GHz and was used by the Archdiocese of New York to relay their educational television programming from their Yonkers headquarters to the various schools in the Hudson Valley.  Sometime around 1975 or so, the FCC mandated that periscope microwave systems could no longer be used due to all the side lobes and interference issues they caused.  They were to be taken out of service as soon as possible.  The Catholic Church, being a multi millennial organization figured “as soon as possible” meant within the next fifty years or so.  Anyway, somebody else needed that frequency, therefore in 2007, they bought the Archdiocese a new digital microwave system.

The problem with the reflectors; they are big.  They are also heavy, and present a huge wind area.  They are also 300 feet up in the air.

WSPK tower periscope reflectors seen from ground level

WSPK tower periscope reflectors seen from ground level

Finding a day with lite winds on top of Mount Beacon can be a problem.  Luckily, the weather was with us.  Still, it took a while to get this work moving along.  The other consideration is RFR and tower climber’s safety.  There are two digital TV stations, WSPK, several cell carriers, something called “Media Flow,” and a bunch of two way radio repeaters.  The main concern was WSPK, the DTV’s and Media Flow since the top of this tower is right in the aperture of those antennas.  All either went way down in power or off the air while this work was on going.

Rigging a gin pole and getting it to the top of the tower was a chore.  The gin pole needed to be threaded through those torque arms like a needle.

Gin Pole

Gin pole

The tower riggers truck had two winches, one a basic 120 volt capstan, the other a hydraulic winch in the bed of the truck with 1/2 inch steel cable.

Tower rigger's truck

Tower rigger's truck

The bolts holding the reflectors in place had to be cut with a saw, you can see the tower climber working on the left hand reflector, gives you an idea of size.  If this reflector were to fall off the tower, chances are good the major damage and or injuries would result on the ground.  Proceed with extreme caution.

Cutting bracket mounting bolt on periscope reflector

Cutting bracket mounting bolt on periscope reflector

Carefully lowering reflector past Shively 6810 FM antenna and Scala PR-950U microwave antenna.  During this phase, the tower climbers had to push the reflector out away from those obstacles with their legs.  You can see the gin pole at the top of the tower.

lowering periscope reflector

Lowering Periscope reflector

Another view:

Lowering reflector

Lowering reflector

Another view:

Lowering reflector

Lowering reflector

Almost down to the ground.  This measured 15 by 10 feet and ended up weighing 830 pounds.

Reflector almost to the ground

Reflector almost to the ground

One down, one to go.  I can’t believe those gigantic things were at the top of this tower, on the top of this mountain for 43 years and the tower is still standing.  This is going to change the appearance of the mountain top from down below.  For years, it looked like a pair of mickey mouse ears, now it will only look like a tower.  I wonder what the environmentalists will think.

I will make a second post with the antenna pictures as this one is getting a little long.

Care and feeding of Propane Fueled Generators

Broadcasters historically have tried to remain on the air during emergency events like major storms, earthquakes and other forces of nature.  Often times, commercial power is interrupted, and thus, the backup power generator is installed.  Propane powered generators for medium duty (powers up to 45 KW) are popular because of the decreased environmental hazards, availability and expense of fuel, ease of maintenance and repair.  This sized generator can run the critical loads of a studio facility or a transmitter site with TPO’s between 5 and 10 KW.

Katolight 45 KW generator w/outside housing

Katolight 45 KW generator w/outside housing

Most propane generators use a gasoline engine modified to use propane.  These generators can also use natural gas, however, because natural gas has slightly less energy, the generator’s service rating is reduced by about 10 percent.

Ford inline 6 cylinder engine

Ford inline 6 cylinder engine

The biggest error I consistently see with propane generators is improper fuel tank sizing.  It might seem just fine to plop a 500 gallon tank down next to a 45 KW generator and expect everything to be just fine.  500 Gallons may sound like a lot of fuel, but the more important consideration is tank vaporization, that is to say, how fast can the liquid propane can be removed from the tank for use.  Propane fuel companies should be able to sizing these things correctly, most of them have books and charts that tell what capacities and sizes are needed.  However, as a general trouble shoot guide, the following information is provided:

Generator manufactures will specify how many BTU per hour a generator will require under full load. If not, these are some conservative rules of thumb:

  • For every 1 KW of electrical generation, 2 horsepower of engine is needed*
  • Under full load, each horsepower will consume 10,000 BTU per hour*
  • Propane has 92,000 BTU per gallon
  • Propane weighs 4.2 pounds per gallon

*Note: These are not the figures you will find in your engineering handbooks, they are adjusted for generator winding and engine efficiency.

Propane Tank Vaporization Rates (Continuous BTU/hr vs volume at tank temperature):

Size propane in a tank (assumes 1/3 full) Maximum continuous BTU/hr at degrees F
20° 40° 60° 70°
120 129,600 188,640 247,680 308,160 338,400
150 146,880 213,790 280,700 349,200 383,520
250 253,800 369,400 485,000 603,480 662,700
325 321,300 467,670 614,000 763,900 838,900
500 396,270 567,700 757,300 942,240 1,034,700
1000 708,480 1,031,230 1,353,980 1,684,600 1,849,900
1450 816,120 1,253,400 1,645,690 2,047,550 2,248,480

Note: Tank vaporization depends on fuel level, tank temperature and withdrawal rate.  The above chart is a conservative generalization and represents a safe median value.

If a propane tank cannot vaporize fuel fast enough, the generator will begin to run lean, eventually overheat and shutdown. The vaporization rate depends on the tank temperature, which drops as fuel is withdrawn.  For the above cited 45 KW generator called to duty after a sever winter storm, the tank would need to vaporize: 45KW x 2 HP = 90 HP.  90 HP x 10,000 BTU/hr = 900,000 btu/hr.  A 500 gallon tank is too small for that size generator.

As the tank temperature drops a propane tank can develop frost on the outside of the tank, even on a hot summer day, which compounds the problem.

The correct size tank for a 45 KW generator is a 1000 gallons.  This can also be two five hundred gallon tanks connected in parallel via a high pressure line.

45 KW propane generator with two 500 gallon tanks

45 KW propane generator with two 500 gallon tanks

Also note, the generator’s radiator is facing the tanks so that when the unit is running, hot air is blowing on the tanks, warming them up.  This particular generator is about 25 years old, which is why it looks a little worn.  It still carries the load and mechanically is in sound condition.

Most propane fuel systems have two regulators; one high pressure regulator on the tank, which takes the variable tank pressure and steps it down to about 10 PSI, and the vaporizor which steps the pressure down to a few ounces per square inch (or inches water column) and adds air creating propane gas for the generator to burn.

High pressure propane tank regulator

High pressure propane tank regulator

It is important that the vaporizer be mounted above the snow line and that there is a little screen on the air intake, otherwise mud wasps will build a nest in the air intake and the next time the generator is required to run, it won’t start.

Low pressure propane regulator/vaporizer

Low pressure propane regulator/vaporizer

Fuel piping is also a concern, if the low pressure lines are not large enough to handle the required BTU, the generator will run lean, creating the same problems of an improperly sized tank.  Different piping has different capacities, see the following charts:

Propane steel pipe sizing diagram

Propane Schedule 40 steel pipe sizing diagram

Propane copper pipe sizing diagram

Propane copper-K pipe sizing diagram

Assumes pressure less than 1.5 PSI, one MBTU is equal to 1,000 BTU per hour.

Once the generator is installed, maintenance is required.  As a minimum:

  • Exercise engine bi weekly for 15 minutes. Propane generators do not need to run under load.
  • Check fuel, oil, and antifreeze levels monthly, more often if heavy use.
  • Change the oil, oil filter, air filter, check antifreeze freeze point, battery electrolyte specific gravity yearly
  • Change out belts and hoses as needed, pay close attention to the block heater hose, this is where leaks often develop
  • Clean out mice nests and droppings as needed

Mice love generators.

WE2XRH and the NVIS antenna

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

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

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.

Copper prices on the increase

It is a concern for radio and TV stations, that someone will notice all that greenish brown piping coming out of the buildings and attempt to liberate it, for the cash that is in it.  Of course, such things can lead to some pretty spectacular failures and possible harm to the thieves.  AM ground systems are often a target because they can be pulled up without anyone noticing right away.

In the last twelve months, copper has gone from to about $2.90 to $3.82 per pound:

Copper prices through 10/10

Copper prices through 10/10 per 100 lbs

This is approaching the all time high price of $4.34 per pound in early 2008.

Copper TELCO cables, wiring, piping, gutters, downspouts, roofing are all targets for thieves.  On the other side of the Atlantic, British Telecom (BT) has been hit so hard, they are striking back.  Employing something called “Smart Water Bombs,” they can mark any unauthorized person that attempts to open BT equipment. According to PC pro magazine:

The SmartWater liquid carries a DNA fingerprint that links a criminal to the scene of the crime and police units carrying ultra-violet light detectors can use the incriminating stains to make an arrest after the trap has been sprung.

That is a novel approach, but it  may be a little extreme for the average radio station.  There are a few steps that one can take to minimize theft at the transmitter site:

  1. Keep things buttoned up, mow the field, trim the weeds around the building and make regular site checks.  Keep the building in good repair.  If the site looks cared for, drive by thieves may think twice about visiting.
  2. Make sure that all of the buried copper ground system is indeed buried.  Any wires or screen showing is an invitation for a tug.
  3. Copper strap is especially vulnerable.  Get a metal stamp and stamp the station’s call sign into it every twenty feet or so.  Take pictures of this and keep them on hand to show police.
  4. Report any thefts right away.  In NY, scrap yards must keep records of all transactions over $50.00.  At today’s prices, that is about 14 pounds of bare copper wire or strap, which is not much.
  5. Have a neighbor keep and eye on the place.  Once, I traded about 10 CD’s and 5 T-shirts to the next door neighbor and from that day forward, nothing ever happened at that site without me knowing of it.
  6. Put up “Danger, High Voltage,” and/or RFR warning signs.
  7. Keep fences in good condition and locked.
  8. If possible, work with the local police department to up site patrols.  Sometimes they will, sometimes they won’t but it never hurts to ask.
  9. If the site warrants it, buy some dual light cameras and a motion triggered DVR.  This is more of a revenge device, but it nets an arrest, it will be effective in stopping repeat occurrences.

If you notice any unusual activity at the transmitter site, especially during a late night visit, have the police come and check it out before you confront a possible thief.

How the Cold War was won

This is not really apropos radio broadcasting, but it is about radio and it has a lot to do with engineering.  Back in the day, as a young man out to do whatever it was, I ended up being stationed on Guam, working at the Coast Guard radio station there.  That was interesting work, to be sure, but every morning and evening, either on my way to or from work, I would drive by this, which looked very interesting:



I had to lift the photo from a Navy Radio history site.  Back in my day, aiming or even possessing a camera around this area or building would likely inflict the extreme ire of the Marines, who attentively observed the area and were ready to call down a painful lesson to all not obeying the “NO PHOTOGRAPHY ALLOWED” signs.

Nick named “The Elephant Cage” it is a Wullenweber antenna used for high frequency direction finding (HFDF) and was part of a system called “Classic Bullseye.”  There were several of these systems across the Pacific Ocean, and they all worked together using a teletype network.  The Army-Air Force version was called a AN  FLR-9, which was slightly larger.

AN/FRD-10 antenna layout

AN/FRD-10 antenna layout

There were two concentric rings of antennas, the tallest being the closest to the center building and used for the lowest frequencies.  It covered from about 1.5 to 30 MHz.  The rings consisted of several individual antennas, all coupled to a Goniometer with coaxial cables cut to identical lengths.  The outer ring had 120 vertical sleeved dipole antennas, the inner ring consisted of 40 sleeved dipole antennas.  The inner ring of towers also contained a shielding screen to prevent the antennas on the other side of the array from picking up signals from the back of the antenna.  A radio wave traveling over the array was evaluated and the Goniometer determined the first antenna that received the signal by comparing phase relationships.   The ground system was extensive.  Immediately under the antennas was a mesh copper ground screen.  From the edge of the copper mesh, buried copper radials and extended out 1,440 feet from the building.

The effective range for accurate DF bearings was about 3,200 nautical miles, which equates to about two ionospheric hops with the angle theta between 30 to 60 degrees referenced to ground.

It was quite effective, it only took a couple of seconds to get a good bearing.  If the other stations on the network were attentive, a position could be worked out in less than 10-15 seconds.

AN FRD-10 transmission line diagram

AN FRD-10 ground diagram

It is a little hard to read, but this is the ground layout of the AN FRD-10 CDAA.  The transmission lines to each antenna are shown, along with the ground screen and building in the center of the array.

We Coast Guard types used this mainly for Search and Rescue (SAR) and the occasional Law Enforcement (LE) function.  I believe we actually saved a few lives with this thing.  I found the Navy operators to be very helpful, I think some of them enjoyed the change of targets from their normal net tripping.

The navy operated AN FRD-10s at the following locations:

  • Imperial Beach, CA (south of San Diego)
  • Skaggs Island, CA (north east of San Francisco)
  • Hanza (Okinawa) Japan
  • Waihawa, HI
  • Finegayan, Guam
  • Adak, AK
  • Marietta, WA

The Air Force/Army installed AN FLR-9’s in the following Pacific Locations:

  • Missawa AB, Japan
  • Clark AB, Philippines
  • Elmandorf AFB, AK

Basically, there was no corner of the Pacific Ocean that could not be listened to and DF’d.  Some people look back nostagically at the cold war, when we “knew who the enemy was,” so to speak.  I am not one of those.  They either didn’t really know the enemy, or have conveniently forgotten some of the less endearing qualities of the Soviet Union.

I believe all of these systems have been decommissioned and most have been taken down and scrapped.  The National Park Service studied the Waihawa, HI system as a part of their Historical American Building Survey (HABS HI-552-B2) (large .pdf file) before it was torn down.  Good technical description and building pictures.  Near the end of the report, it is cryptically noted that:

Beginning in the mid-1990s the NSG (ed: Naval Security Group), noting the absence of Soviet targets and wanting to cut costs and change the focus of its SIGINT collection, began closing FRD-10 sites… Undoubtedly, since the September 11, 2001 terrorist attack on the World Trade Center and the Pentagon, listening posts have gained importance and most likely increased in number and sophistication. The FRD-10 CDAA at NCTAMS Wahiawa ceased listening in August 2004; it can only be assumed the closure occurred because there was a better way to do it.


The Guam site has been striped out and abandoned, the latest photo I can find is from 2008:

Abandoned AN FRD-10, Finegayan, Guam

Abandoned AN FRD-10, Finegayan, Guam

And people think AM broadcasting is expensive…


A pessimist sees the glass as half empty. An optimist sees the glass as half full. The engineer sees the glass as twice the size it needs to be.

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...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

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