Archive

July 2017
M T W T F S S
« Jun    
 12
3456789
10111213141516
17181920212223
24252627282930
31  

Categories

До свидания!

Isn’t this where…

If you are reading this, one of two things has happened; either I pulled the plug on the blog, or that great guy up in the sky has pulled the plug on me.  It occurred to me, whilst driving all those many miles year in and year out doing contract engineering, that insurance actuary tables exist for a reason.  Sooner or later, something catastrophic was bound to happen.  Thus I created this post which will automatically publish itself every Monday morning unless I intervene.

It was eight plus years ago that, on a whim, I started this blog.  When I started I knew that all paths cross themselves eventually. We all end were we begin, and so it is with this. Over the last eight years, I tried and sometimes succeeded in describing what it is like to be a broadcast engineer.  Occasionally, I have strayed off topic.  I have written about and struggled with the engineering aspects of the radio business.  Sometimes, I would like to think, my readers were at least entertained, perhaps informed, enlightened, or felt empathy.

The truth is this; at some point I ran out of ways to express myself without turning this into a rant-feast.  Radio is the ultimate legacy consumer technology.  Independent radio stations have the ability to, even today, be a wonderful entertainment medium.  Radio can still serve the community in times of disaster or distress.  However, the absolute soul crushing mediocrity of automated programming is killing the entire industry.  Of course, the cause of this is the equally crushing debt load being carried by the majority of radio station owners.   That reality, intersecting with declining advertising revenue and segmentation of market share, spell the end of the commercial radio business model.  I look upon the sale of tower assets as another sign that the death spiral is deepening.  This is not going to change; debt loads will remain and the business will mediocre itself to death.  People in the business will be forced to accept ever increasing work loads coupled with decreasing salaries.  All of this being supervised by the Sauron like, all seeing corporate eye, thousands of miles away.

In the end, the only thing that could kill radio is radio itself.

I will also take the opportunity to thank everyone that participated, commented, sent me off line e-mails and what not over the years.  Without your input, I would have ended this long ago.

So, this is it.  The blog will stay up and running for as long as the domain and/or hosting remains active.

The GatesAir FLX-40 transmitter

The GatesAir FLX-40 transmitter is my first liquid cooled transmitter installation.  Previously, I have installed an air cooled Nautel NV-40, a V-40 and a couple of BE FM-35T/20T units.  The WEBE transmitter site in Bridgeport, Connecticut is an interesting facility.

Smoke Stack, Bridgeport Energy, Bridgeport, CT

Smoke Stack, Bridgeport Energy, Bridgeport, CT

This coal fired power plant smoke stack which currently holds up the six bay, half wave spaced Shively antenna.  The old BE FM35A transmitters are getting little bit long in the tooth.  Thus, we picked one to scrap, the other will be kept for backup service.

Scraping 34 year old BE FM30A transmitter

We saved a whole bunch of parts to keep the other FM35A on the air in backup service.

BE FM30A power supply cabinet

The power supply cabinet with that 500 pound plate transformer was the last to go.

On second thought, that plate supply transformer is a good spare to have

On second thought, that plate supply transformer is a good spare to have

The FLX-40 came on a large truck.  Fortunately, we were able to open the side gate at the power plant and get the truck to the front door of the transmitter building easily.  The transmitter consists of two large cabinets, each with two 10 kilowatt power blocks.  There is also a pump station and an outdoor heat exchanger.

FLX-40 cabinet two off the truck

FLX-40 cabinet two off the truck

FLX-40 cabinet one

FLX-40 cabinet one

FLX-40 in place, cabinets bolted together

FLX-40 in place, cabinets bolted together

This transmitter design is based on the Harris digital TV transmitters.

FLX-40 pump station

FLX-40 pump station

The pump station and heat exchanger are the same systems used for TV transmitters.  Liquid cooled units require a bit more planning on the installation end.  The coolant piping should have a high spot from which everything else slopes down hill.

Send and return coolant lines

Send and return coolant lines

I put a 1/4 to 12 inch pitch on everything.  Of course, there are several low points, the heat exchanger, pump station and bottom power blocks.

Holding steady at 18 PSI for 24 hours

Holding steady at 16 PSI for 24 hours

After assembling the cooling system, we pressure tested it for 24 hours.

Installation debris in the coolant line strainer

Installation debris in the coolant line strainer

Following that, we flushed the system with distilled water for several hours before we filled it with 40/60 glycol/water mix. Record low temperature in Bridgeport is -7 F (-22 C), thus a 40/60 mix will give protection down to -15 F (-26 C). The more water in the coolant, the better heat transfer capacity it has.

At the highest point in the system, there is a sight glass and an air purge valve

At the highest point in the system, there is a sight glass and an air purge valve

The pump station is controlled by the transmitter, which speeds up the pumps according to how much heat needs to be moved. In turn, the pump station control the fan speed on the heat exchanger outside.

FLX-40 pump station on line

FLX-40 pump station on line

The pump station runs with one motor most of the time. The other pump motor will run in the event of failure or if there is not enough flow through the power blocks. Each of the four power blocks has a flow rate meter on the return line.

Heat Exchanger Fan motor controllers, Variable Frequency Drive modules

Heat Exchanger Fan motor controllers, Variable Frequency Drive modules

Variable Frequency Drive (VFD) fan motor controllers show them running at half speed.

50 KW heat exhanger

50 KW heat exhanger

GatesAir 50 KW heat exchanger mounted on concrete pad behind the building. Air flows out from the motor side.

One of several shipping containers with modules and other parts for the FLX-40

One of several shipping containers with modules and other parts for the FLX-40

As with most things, some assembly required.  The RF modules needed to be placed in the power blocks according to their serial numbers on the test data sheet.  This insures that the information on the test data sheet matches the installed transmitter configuration.  The power combiner between the two cabinets as well as the reject load and directional coupler all need to be installed.

RF modules with large aluminium heat spreaders.   Coolant flows through each module.

FLX-40 power amp module

FLX-40 power amp module

WEBE, Bridgeport, CT GatesAir FLX-40 on the air for the first time

WEBE, Bridgeport, CT GatesAir FLX-40 on the air for the first time

On the air!

FLX-40 into the antenna

FLX-40 into the antenna

We ran the transmitter for several hours into the antenna yesterday afternoon. The coolant system is still purging air, so we periodically needed to add water/antifreeze to the pump station to keep the pressure between 12-18 PSI. Eventually, the TPO will be 34 KW with the HD carrier(s).

All in all, I would say that this was a fun project. The liquid cooled transmitter had a few extra steps during the installation process, but not too difficult.

Engineering Radio; the satellite reaiming tour 2017!

As previously discussed, the migration from AMC-8 to AMC-18 is in full swing. There is less than two weeks left to complete the re-aiming process.  All totalled, we have 24 of these things to re-point and all but two of them  are done.  Toward that end, I have this down to an art:

  • Go inside and make a note of the signal strength on the satellite receivers on AMC-8
  • Look up the elevation angle on dish align app for AMC-8 then compare that to what the inclinometer reads, note the difference between the calculated and actual readings
  • Look up the elevation angle on the dish align app for AMC-18, apply the difference noted above to the final value
  • Connect the XR-3 satellite aiming tool to the LNB, make sure LNB power is on and the unit is set to AMC-18, C-band
  • Elevate the dish to the AMC-18 final elevation angle calculated above
  • Note the azimuth on the dish align app, look at the satellite picture and pick out a land mark.  Swing the dish towards the land mark
  • As you start to see signal from various satellites, swing more slowly.  If the elevation angle is set correctly, when the dish passes AMC-18 at 105 degrees W, the XR-3 will lock on
  • Peak the signal (azimuth and elevation)
  • Rotate the LNB feed horn for maximum signal to noise ratio
  • Go inside, check satellite receivers, reprogram carrier frequencies as necessary

It is pretty easy. I can do the whole thing in about thirty minutes if there are no rusted bolts, etc. I wonder how many small station owners will wake up on July 1st with no satellite programming?

Comtech Satellite dishes, WABC transmitter site, Lodi, NJ

The Applied Instruments XR-3 (XR-S2ACM-01) VSAT-ACM  satellite signal meter with AMC-18 locked.  This hand held tool is great and makes aiming any dish a snap.  As the sky around AMC-18 is a wee bit crowded, it is easy to mistakenly find the wrong satellite.  With the Identify function, the satellite the dish is aimed to will be displayed, then the dish can be adjusted accordingly to the correct bird.

Applied Instruments XR-3 satellite signal meter

There are many different flavors of dishes; Comtech, Patriot, Prodelin, etc.

Prodelin 3.7 Meter satellite dish

These are all about the same to work with, the only difference is the degree of rust and deterioration on the mounting hardware, the age of the LNB and number of bees nests that need to be removed.

Studio Buildout, Part III

I have been so busy that I forgot to post the pictures of the completed studio build out.  Overall, I would say that I am pretty pleased with the end result.  Of course, this is not Manhattan but rather an unrated market in central New York, and the budget reflected that.  Overall, the radio stations are in much better technical condition than before.  They are now located in the center of their community within walking distance of the town hall, other civic locations and activities.

There are five radio stations broadcasting from this new studio space.  Two stations are simulcast using the Westwood One Classic hits format from the satellite.  The only AM station is a Fox Sports Radio affiliate from the satellite with a local morning show.  Another one is a “we play anything” computer juke box and final station has a country format with quite a bit of local content.  Any station can go on the air from either studio.  In addition, all stations can simulcast the mother ship from Oneonta, which comes down via a Barix Exstreamer 1000.

Walton TOC

The Technical Operation Center consists of four racks containing the Ethernet routers, switches, a patch panel, automation systems, audio routing switchers, air monitor receivers, audio distribution amps, Barix units, Wheatstone Blade IP 88A STL, etc.  The equipment racks came from a disused site in New Jersey.

The satellite dish and receivers are located at the transmitter site, audio and closures come back via the Wheatstone Blade IP 88A.

Everything in this room is backed up by a STACO 2.5 KVA UPS.

TOC wire terminations

The wire termination from the studio are mounted to Krone LSA-PLUS blocks.  Studio trunk wiring consists of connectorized 25 pair CAT 5 cable.  There are also six runs of shielded CAT 5e cable for Ethernet and extended KVM from the TOC.

There is a manual transfer switch with a NEMA L14-30 input receptacle on the bottom.  A twenty for 10/4 SOJ cable will reach the ground from the window in the left hand side of the picture.  This is the standard NEMA plug/receptacle set for a moderate sized portable generator.  That feeds a 100 Amp sub panel which in turn feeds the racks and studio equipment.  Thus the entire facility can be run on a 5000 watt (good quality) portable generator in the event of a prolonged power outage.

The ground buss bar is connected to the main building ground at the service entrance.  All racks and studio consoles are grounded to this main ground point.

The air monitor receivers feed both studios.  There is also a provision to connect audio silence sensors up to each air monitor DA to notify the station staff in the event of an off air situation.  Believe it or not, this type of system has never been installed for these stations.

Studio A is the main studio.  The AudioArts Air4 console is a good fit for this type of operation.  These consoles have USB outputs, so the console can act as a sound card for the digital editing computer.  Each studio is equipped with an air monitor switch that can select any station to feed the external monitor input on the Air 4 console.  This allows the guy on duty to keep an eye on all the signals coming from the facility.

Studio A

The counter tops were custom made at a local kitchen place on trade. The microphone are Heil PR-22 with shock mounts, which are better than the Realistic mics in the old studio.  This is the first time that the main studio has had more than one microphone. The morning show guy has already pressed those guest mics into service with a few on air interviews.

The monitor speakers are JBL LSR305 mounted on home made speaker stands consisting of 18 inch black iron pipe and floor flanges.

Studio A

The small equipment rack is on casters and can roll out from under the studio furniture to get at the back of the equipment.  A used Gentner DH3 TELCO hybrid is used to get phone callers on the air.  Adobe Audition is used for editing and production on the left hand computer monitor.  That CPU is in the bottom of the roll around rack.

Studio A

The office chair and other furniture was also acquired on trade.

Studio A

What the operator sees. STORQ computer on the left for music, Scotts SS32 on the right for automation. Both are extended from the TOC. Unless the morning show guy is live on the air, the console is bypassed and the audio stays in the TOC.

It all works pretty well.

Studio B

Studio B is the same as Studio A except fewer microphones.

Studio B

Studio B operator view.  This studio can be used for one of the other stations or production.

Again, this is not a Fancy Nancy installation, but it does get the job done.

VOA Site B, Greenville, NC

I took a brief vacation last week along the coast of North Carolina. It was relaxing and fun to be sure. I was also aware of and slightly curious about the Voice Of America shortwave site, a slight distance inland in Grimesland, NC.  Thus, I made arrangements visit the facility on my way home.  Chief Engineer, Macon Dail, was gracious enough to give us the guided tour.  The facility is an engineering marvel.  The scale and complexity is enormous.  The entire facility is scrupulously maintained.  Many of the transmitters and other equipment have been upgraded to make them more functional.   I tried to take meaningful pictures, but in many cases, they simply do not to justice.

Edward R Murrow Transmitting Facility, (VOA Greenville Site B) Grimesland, North Carolina

Officially known as the Edward R Murrow Transmitting Station of the International Broadcasting Bureau, VOA Site B was constructed in 1961.  Six of the eight shortwave transmitters are original to the construction of the building.  The other two (BBC SK55 and AEG S4005) were added in 1986.  All of the dipole curtain arrays, rhombics, transmission line and the antenna switching matrix are also original.  A few brief statistics about this site:

  • Land area is 2,715 acres (1099 hectare).
  • Over twenty six miles (forty two kilometers) of 300 ohm open transmission line rated at 500 KW.
  • Sixteen dipole curtain arrays, average antenna gain 17 dBi.
  • Twenty rhombic antennas, antenna gain 15 dBi.
  • Two of the dipole curtain arrays can slew azimuth and take off angle.
  • Three Continental Electronics 420A 500 KW Doherty modulated transmitters.
  • Three General Electric 4BT250A1 250 KW high level plate modulated transmitters.
  • One Brown Boveri Company (BBC) SK55C3 500 KW PSM transmitter.
  • One AEG Telefunken S4005 500 KW PDM transmitter.
  • Antenna switch matrix connects any of the eight transmitters to any of the thirty six antennas

While we were there, both of the newer transmitters were on the air, running at 250 KW.  The GE transmitters are used as needed and the Continentals are rarely used due to age, difficulty to tune, change frequencies and gross power inefficiency.

The station staff has, out of necessity, fabricated some very cool upgrades to the transmitters and facility.  The first of which is the alarm annunciator, which is based on a Star Trek (Original Series) sound scheme.  Once or twice I heard the bridge general alarm go off, followed by a female voice stating the problem: “GB8, OFF AIR.”

Chief Engineer’s office.  NCC-1701; no bloody A, no bloody B, no bloody C, and no bloody D

The GE 250 KW transmitters have been retrofitted with a computer controlled auto tune system for frequency changes.  The antenna switch matrix controller has been replaced by a PLC based system.  As the transmitters are so old, many of the transmitter specific parts need to be machined or fabricated locally.  The rest of the transmitter parts are stocked in a large parts storage room, all of which is meticulously labeled and tracked.  The floors are waxed and spotless, there is no dust on the horizontal surfaces, the work shop is clean, tools are put away, grass and weeds are cut, etc.  All of these little details did not go unnoticed and indicate great pride by the staff in the facility itself.

The heart of the facility is the control room which consists of four rows of equipment racks and a central operating position elevated above floor level.  Arranged around that are the eight shortwave transmitters in two long transmitter galleries.

VOA Site B control room

From this point, the operator can view all of the transmitters in the two transmitter galleries.

Operating position

Around the control operator are arranged a series of computer monitors showing various station function status.

Transmitter modulation and status indicators

Antenna Matrix status and control

VOA transmitter control and status (center)

Audio monitoring router

The equipment is installed into the equipment racks by type; one rack contains the frequency generators for each transmitter, the next contains first stage power amplifiers, the next contains audio processors and modulation monitors, etc.

Equipment racks and Shift Supervisor’s  office

Transmitter frequency generators

Audio processors, modulation monitors and patch panels

Backup audio feeds

The audio comes from the VOA studios in Washington DC via satellite. There are Comrex Access links as a backup and the Gentner EFT-1000s are used as a backup to the backup.  Prior to 1995, an eight hop microwave system covering the 300 mile (483 KM) distance was used.

GE 4BT250A transmitter with computer controlled tuning system installed

The station staff has created a computer controlled tuning system for the GE transmitters. Each transmitter can change frequency several times a day, during each frequency change, all of the transmitter stages need to be retuned. When done by hand, this can take several minutes to accomplish. The computer system uses follow pots and micro controllers to set the tuning elements to specific values. They can be touched up by hand if needed. A frequency change can usually be done in less than one minute.

GE 4BT250A transmitter

Your humble author and CE Macon Dail discussing the auto tune system

GE 4BT250A auto tune modification

GE 4BT250A IPA tube and input tuning.

The 2nd IPA and PA input tuning work the same way. The copper sleeve slides up and down over the coil to change resonant frequency. The vapor cooled tube sits inside the tub at the top, anode facing down. These tuning sections are a mechanical nightmare according to Macon. One of the reasons why VOA site A was closed down was due to the frequent frequency changes at that site causing excessive wear and tear on the old GE transmitters. This particular transmitter was being repaired; the staff was rebuilding a tuning network bypass capacitor assembly

GE 4BT250A transformer vault

The GE transmitter transformers still contain PCB’s. The plate transformers are in the back, basically pole transformers, one for each phase. Primary voltages is 4,180 volts, secondary rectified voltages are 12 KVDC (PA plate supply)  and 15 KVDC (modulator plate supply).

Hallway and maintenance access to back of GE transmitters

AEG Telefunken S4005 500 KW transmitter on the air

While we were there, the newer transmitters were in operation transmitting Spanish language programming to the Cuba on 13,605 KHz and 11,930 KHz.  Currently, the Greenville site is broadcasting mostly Spanish language programming with some English, French and Bambara language programming for Africa.

A fact that does not escape the notice of the staff.

VOA transmitter gallery, showing transmitters GB8 through GB4

Continental Electronics 420A 500 KW Shortwave transmitter control and metering panel

The three Continental 420A transmitters (GB-1, GB-2 and GB-3) are essentially a pair of 250 KW amplifiers combined. As these are Doherty power amplifiers, frequency changes are very difficult to effect. These transmitters spend most of their time in backup service.

Electrical distribution panel

The antenna matrix building is very impressive. Routing eight 250 or 500 KW transmitters to 36 different antennas takes a bit of doing. Mechanizing that set up is no mean feat. The pictures I took of the antenna matrix building do not show the size and complexity of the system.

Transmission line between transmitter building and antenna matrix building

For that, we need a satellite photo:

VOA Site B antenna matrix building

Basically, the transmitter building is in the lower left hand side of the picture. The transmission line go over to the antenna matrix building (looks like rectangular duct work), then run all the way to the back of the building. Each antenna transmission line come into the building and runs to the other side. Pneumatic arms then couple the transmitter line to the antenna line. This is all controlled by a custom made PLC and controlled by the operator from the main operating desk.

Custom made antenna matrix control system

300 ohm open transmission lines

300 ohm open transmission lines

Some of these lines are very long but have low loss due to the air dielectric. The most used antennas are the dipole curtain arrays.

Dipole curtain arrays

These consist of a series of broadband dipole antennas arranged side by side and stacked three or four high. behind those antennas is a reflector screen. There are two curtain arrays that are slewable. The dipole antennas phase relationship to each other can be changed to adjust the take off angle and azimuth, thus giving optimum coverage to the targeted area.

Close up curtain array

In this picture, the dipole antennas are to the right. Behind them is the reflector screen, behind that is the antenna feed system. Each antenna feed goes through the reflector screen to the center of the dipole antenna.

Each array requires four towers to support it.

Curtain dipole array supporting towers

Curtain dipole array supporting towers

Remote Antenna Switch.  Allows two antennas to use one transmission line.

The entire antenna field is viewable from an observation platform on the main building

Observation room

Entrance gate and slewable curtains in background

Curtain arrays

The entire facility is very impressive. The truth is, I could have spent several more hours there, but I know that people have jobs to do and I felt that I had taken up enough time. We often forget in this country that not everyone in the world has access to the internet. Shortwave broadcasting has a long reach and is not subject to government controlled firewalls or other forms of electronic censorship. Currently, the Greenville site is broadcasting mostly Spanish language programming with some English language programming for Africa. There are many areas in the world that are in political tension right now, some startlingly close to home. Places like Brazil, Argentina and Venezuela have been in the news lately. I do not see a time when these long reach broadcasting services will not be needed. Becoming a welcome source of good information for those affected people is good for brand USA. It would be money well spent to invest in a couple of new Continental 419H (still made in the USA) DRM capable transmitters for this facility. While the old GE and Continental units are great, the time may come when they are really needed but unavailable due to being down for repair.

Special thanks to Macon Dail for his time, knowledge and patience.

Fake News

The newest (or not so new) buzz word; Fake News. It is really hard to tell these days where the truth begins and the lies end. It seems that every major player see fit to adjust the facts to fit their narrative.  Most major news sources have been caught reporting less than factual stories about almost everything.  Edward Bernays would blush.  According to the latest Wikileaks dumps (Vault 7, sonic screwdriver, secret strap, SWIFT network hacks, HIVE and God only knows what else), certain parts of the government seem incapable of telling the truth or following the constitutionally guaranteed protections against intrusion upon its own law abiding citizens.

It is difficult to understand what the current president is talking about sometimes, but it seems business as usual; more missile strikes, bombings, and continuation of the Bush-Cheney/Obama initiatives from our post 9/11 era.

But fear not, to the rescue is Facebook and Google.  Those paragons of truth and justice will tell you, the mere simpleton, what is real and what is fake.

We are in such good hands!

Oh dear God.

Speaking of Radio…

I was talking to a friend from Russia about history, my job and various other things that are going on in my life. I received this reply, which I thought was interesting on a number of levels:

I’m glad we are on the same page about the era of the ‘cold war’. We were interested in your life even more than you in ours. We had almost no sources of information except for ‘The morning star’ which is a newspaper of the Communist party of Great Britain. The Voice of America and the Liberty (or Freedom, I have no clue because for us it was ‘RADIO SVOBODA’) were extremely hard to tune on. All foreign broadcasts were jammed. So to listen to the station you should maximize the volume up to the limit which was dangerous. Soviet houses are not at all soundproof and your neighbors could easily rat on you. Since that time I’d been dreaming of a small radio with could receive a clear signal from abroad. Of course we have the Internet broadcasting now but they often use old recording instead of live air and the signal depends on your data carrier. You should be online, you should have an app and unlimited data on your contract, your phone should be charged all the time. Too many conditions. Unfortunately a lot of foreign sites are banned here and the trend is to make this number bigger and bigger.

I find that perspective interesting.  We take for granted our ability to listen to information and listen to different points of view, even those we don’t agree with.  There are still trouble spots in the world and some people are not as fortunate.  It is very easy to block internet traffic and there are several countries that currently block access to some or all of the internet, for the safety of their citizens, no doubt.  Ideas are dangerous.

VOA/RFE transmitter site, Biblis Germany

VOA/RFE transmitter site, Biblis Germany. Photographer: Armin Kübelbeck, CC-BY-SA, Wikimedia Commons

In the last ten to fifteen years, many large government shortwave broadcasters have reduced or eliminated their programming favoring an internet distribution model.  This is a mistake.  It is very difficult to successfully jam terrestrial radio broadcasts.  Shortwave Facilities are expensive to develop and maintain, there is no doubt about that.  However, as the Chief Engineer from Radio Australia (ABC) once told me “HF will get through when nothing else will.”  Ironically, ABC has eliminated its HF service on January 31, 2017.

It seems to me that a sort of “Shortwave Lite” version of broadcasting might be the answer.  Use more efficient transmitters with lower power levels closer in to the target areas.  Such transmitters could be coupled to rotatable log periodic antennas to target several listening areas with one system, thus greatly reducing the number of towers and land required.  Solid state transmitters with a power of 10-50 KW are much, much more efficient than their tube type brethren.

DRM30 (Digital Radio Mondiale) has not gained wide spread use in the MF and HF bands.  Like it’s HD Radio counterpart, lack of receivers seems to be one of the adoption issues.  As of 2017, there are only four DRM30 capable receivers for sale not counting software plug ins for various SDRs.  That is a shame because my experience with DRM30 reception has been pretty good.  I have used a WinRadio G303i with DRM plug in, which set me back $40.00 for the license key (hint for those nice folks at the DRM consortium; licensing fees tend quash widespread interest and adoption).

CFRX, Toronto coverage map, average HF propagation conditions

CFRX, Toronto coverage map, average HF propagation conditions

Finally, I have advocated before and still advocate for some type of domestic shortwave service.  Right now, I am listening to CFRX Toronto on 6070 KHz.  That station has a transmitter power output of 1 KW into a 117 degree tower (approximately 50 feet tall) using a modified Armstrong X1000B AM transmitter netting  a 15-32 µV received signal strength some 300 miles away.  That is a listenable signal, especially if there is no other source of information available.  The average approximate coverage area for that station is 280,000 square miles (725,000 square kilometers). That is a fairly low overhead operation for a fairly large coverage area.  Perhaps existing licensed shortwave broadcasters should be allowed to operate such facilities in a domestic service.

The point is, before we pull the plug on the last shortwave transmitter, we should carefully consider what we are giving up.

Part 101, Private Fixed Microwave Service

I have been tasked with installing one of these systems for a sixteen channel bi-directional STL.  This system was first mentioned here: The 16 channel bi-directional STL system.  As some of you pointed out, the unlicensed 5.8 GHz IP WLAN extension was the weak link in this system.  It was not an interference issue, however, which was creating the problems.  The problem was with layer two transparency in the TCP/IP stack.  Something about those Cambium PTP-250s that the Wheatstone Blade hardware did not like and that created all sorts of noise issues in the audio.   We installed the Wheatstone Edge Routers, which took care of the noise issue at the cost of latency.  It was decided to go ahead and install a licensed link instead of the license free stuff as a permanent solution.

Thus, a Cambium PTP-820S point-to-point microwave system was purchased and licensed.  The coordination and licensing took about three months to complete.  We also had to make several changes to our network architecture to accommodate the new system.  The PTP-820 series has a mast mounted radio head, which is the same as the PTP-250 gear.  However, for the new system, we used three different ports on the radio to interface with our other equipment instead of the single port PTP-250 system.  The first is the power port, which takes 48 VDC via a separate power cable instead of POE.  Then there is the traffic port, which which uses Multi-Mode fiber.  Finally, there is the management port, which is 1GB Ethernet and the only way to get into the web interface.  The traffic port creates a completely transparent Ethernet bridge, thus eliminating all of the layer two problems previously encountered.  We needed to install fiber tranceivers in the Cisco 2900 series switches and get those turned up by the IT wizards in the corporate IT department.

Andrew VLHP-2-11W 11 GHz microwave antenna

Andrew VHLP-2-11W 11 GHz microwave antenna

The radios mount directly to the back of the 24 inch 11 GHz Andrew antenna (VHLP2-11) with a UBR100 interface.  The wave guide from the radios is a little bit deceptive looking, but I tried not to over think this too much.  I was careful to use the O ring grease and conductive paste exactly where and when specified.  In the end, it all seemed to be right.

Cambium PTP-820S mounted on antenna

Cambium PTP-820S mounted on Andrew antenna

Not wanting to waste time and money, I decided to do a back to back test in the conference room to make sure everything worked right and I had adequately familiarized myself with the ins and outs of the web interface on the Cambium PTP-820 radios.  Once that was done, it was time to call the tower company.

Cambium PTP-820S on studio roof

Cambium PTP-820S on studio roof

One side of these are mounted on the studio building roof, which is a leased space.  I posted RF warning signs around the antennas because the system ERP is 57.7 dBm, which translates to 590 watts at 11 GHz.  I don’t want to fry anybody’s insides, that would be bad.  The roof top installation involved pulling the MM fiber and power cable through a 1 1/4 inch EMT conduit to the roof.  Some running back and forth, but not terrible work.  I used the existing Ethernet cable for the management port.  This will be left disconnected from the switch most of the time.

Cambium PTP-280S 11 GHz licensed microwave mounted on a skirted AM tower

Cambium PTP-280S 11 GHz licensed microwave mounted on a skirted AM tower

The other side is mounted at about 85 feet AGL on a hot AM tower.  I like the use of fiber here, even though the tower is skirted, the AM station runs 5,000 watts during the daytime.  We made sure the power cables and Ethernet cables had lighting protectors at the top of the run near the dish and at the bottom of the tower as well as in the transmitter room rack.  I know this tower gets struck by lightning often as it is the highest point around for miles.

PTP-820S RSL during aiming process

PTP-820S RSL during aiming process

Aligning the two dishes was a degree of difficulty greater than the 5.8 GHz units.  The path tolerances are very tight, so the dishes on each end needed to be adjusted in small increments until the best signal level was achieved.  The tower crew was experienced with this and they started by panning the dish to the side until the first side lobe was found.  This ensured that the dish was on the main lobe and we were not chasing our tails.  In the end we achieved a -38 dBm RSL, the path predicted RSL was -36 dBm so close enough.  This means the system has a 25 dB fade margin, which should be more than adequate.  While were were aligning the transmitter site dish, a brief snow squall blew through causing a white out and the signal to drop by about 2 dB.  It was kind of cool seeing this happen in real time, however, strangely enough, the tower crew was not impressed by this at all.  Odd fellows, those are.

Currently brushing up on FCC part 101 rules, part C and H.  It is always good to know the regulatory requirements of any system I am responsible for.  As AOIP equipment becomes more main stream, I see many of these type installations happening for various clients.

The Gates Air FAX-10, Numero Dos

This is the second Gates Air FAX-10 that I have installed. This one is in the shipping container transmitter site from the previous post of the same name.  In this case, we dispensed with the equipment rack that came with the transmitter and installed it in a standard Middle Atlantic rack.   The Harris rack configuration wastes a lot of space and since space is at a premium, we decided to do it our own way.

Gates Air FAX-10 in Middle Atlantic rack

Gates Air FAX-10 in Middle Atlantic rack

The bottom of the rack has the transmission line dehydrator. The top of the rack has the Dielectric A60000 series 1 5/8 inch coax switch, a Tunwall TRC-1 switch controller and the Burk ARC-16 remote control.  I cut the rack panel top to accommodate the coax switch.  The racks were removed from an old studio site several years ago and were in storage since that time.

Gates Air FAX-10

Gates Air FAX-10

The Gates Air FAX-10 transmitter on the air, running a sports-talk format.

Dummy load and Broadcast Electronics FM10B transmitter

Dummy load and Broadcast Electronics FM10B transmitter

View from the other side showing the test load and BE FM10-B transmitter.  This transmitter had a problem that I have run into before with BE FM transmitters.  The jumper between the exciter and IPA had the wrong phase rotation causing reflected power.  I added a foot to it’s length and that problem disappeared.

Hoth

Alternate title: Winter in the Northeast

For all you southerners and west coast people, we have been having an average winter here in the Northeast. While many of our transmitter sites are drive ups, we have several located at ski area mountain peaks.  Technically, those mountain top transmitter sites are a fantastic way to get the Height Above Average Terrain (HAAT) way up there.  Logistically, they are much more difficult to deal with.  Installing a new transmitter or even refueling a generator takes major effort.  Working in the cold and wind is much more fatiguing and requires paying special attention protective clothing, hydration, exposure, etc.

Here are a few pictures from Killington and Pico mountain ski areas in Vermont

Your ride is here.

Your ride is here.

The snow grooming machine is the only way to bring anything up to the top of the mountain during the winter time. In this case, I needed to replace a BW Broadcast TX 1500 watt transmitter.

Trail from ski lift to tower

Trail from ski lift to tower

Even with the snow grooming machine, the last few hundred yards needs to be walked. Fortunately, the snow is packed and not too deep here.

Tower on Pico Mountain

Tower on Pico Mountain

Tower is encrusted with ice. I can tell the tower climber is having a great day:

Tower climber working on ice encrusted towe

Tower climber working on ice encrusted tower

Riding the chair lift back down the mountain gets plenty of strange looks from those skiers coming up:

Pico chair lift

Pico chair lift

Over on Killington Peak, conditions are actually worse.

Killington Peak tower

Killington Peak tower

The ERI antenna heaters cannot keep up with the ice buildup.

ERI two bay antenna with ice.

ERI two bay antenna with ice.

The general manager insists that this winter is not too bad and everything should be working right. My statement to her: Based on my 27 years experience, your shit is fucked up. But if you know how to fix this, come on up and show me.  She deferred.

FM transmitter building and antenna

FM transmitter building and antenna

What the fire tower looked like last winter.

Killington peak fire tower

Killington peak fire tower

Train from the Gondola to the tower

Train from the Gondola to the tower