This transmitter was new in 1987.  It had a bad day yesterday, deciding to throw a temper tantrum and trip the HV power supply breaker.  Fortunately, the station has a back up transmitter.  When we arrived, we found the HV power supply feed through insulator at E1 arced over and broken.  Again, fortunately this station’s management believes in stocking spare parts and a replacement was on hand.

This is part of the RF filter for the HV power supply. This happened once before, about two months ago. The replacement insulator then was used, so that might be a factor. Two months ago, both capacitors in the Pi filter and the HV power supply cable (RG-8 coax) was replaced all the way back to the rectifier stacks.

The FM25-K can produce spontaneous high frequency oscillations if not tuned properly.  We looked at transmitter output with a Rode Schwartz spectrum analyzer and found it to be clean.  Exactly why it blew out another feed through insulator is a bit of a mystery.  Since the first replacement was a used part, we surmise that it may have been cracked.  If this replacement insulator arcs, there needs to be a full investigation.

As I said in the beginning, I have found these transmitters to be okay, not the best, not the worst.  Most of the problems I have encountered with the K series FM transmitters had to do with the controller cards.  There are two, one analog and one digital.  That’s what Harris calls them anyway.  Like the SX transmitter, and the MW transmitter to a certain extent, the control circuits are way over complicated and full of +/- 5 volt CMOS logic.   Having that type of control logic connected to a radio tower (e.g. lightning rod) is asking for trouble.

First, I attempted to down load a few apps, but they either crashed or didn’t do what I wanted or weren’t in the right language, or something.

Clear Channel has something called iHeartRadio, which is a clearing house for mobile users that want to listen to Clear Channel radio streams on their iPhones.  I don’t know, once you have heard one Kiss-FM station, you’ve heard them all as far as I am concerned.  Most other Clear Channel programming is boring and uninspired.

What I finally ended up doing was going to Moodio and reading up on a few things.  Here is a good step by step way to use Moodio to listen to radio station web streams on any mobile device.

1. Be aware that not all data plans are the same.  ATT, Sprint, and others now cap data transfer and charge extra if a subscriber goes over.  Know your plan.
2. On a regular computer, go to Moodio (http://www.yourmuze.fm/)
3. Set up a user account
4. Select from there list, the stations you want to listen to.  They have many US stations as well as many from Europe.  If the station you are looking for is not there, you can request that it be added.
5. Select the default data rate.  Since I have unlimited data, I chose the highest rate for the best sounding audio.  Others may want lower data rates so as not to exceed data caps.
6. Point your mobile device web browser to www.m.yourmuze.fm
7. Log into your account
8. The stations on your listen list will be displayed.

That is a lot of steps to take.  Somebody has to be very into radio or a radio station to do something like that.  A forward thinking radio station or group will be writing or paying somebody to write mobile streaming apps for their stream(s).  A forward thinking radio station or group would then feature links to these apps prominently on their web pages.  Very prominently if they are in a PPM market.  Ahem, very prominently if they are in a PPM market.

That is what a forward thinking radio station would be doing…

I have noticed that the newer generation satellite receivers are not as good as the older Starguide III and II units.  The Starguide receivers were pretty light duty when compared to the Scientific Atlanta 7300 or 2300 series units.  Those things were build like tanks, took up a lot of rack space, and so long as one replaced the power supply capacitors every so often, never failed.  The newer satellite receivers are very intolerant of phase shifts or any carrier disruptions.  Many times, the signal strength might look to be above the drop out threshold (usually 4.5 to 5 dB), but the audio still occasionally cuts out.  That symptom is almost always bees in the feed horn.

3.2 meter COMTECH satellite dish

This dish is mounted up high above the roof of the building on 6 inch well casing.  In order to service the feed horn, one has to either rent a cherry picker or loosen the azimuth bolts and spin the entire dish around so the feed horn is over the roof area.  Then an eight foot step ladder is need to get to the feed horn.  Luckily, it is a flat roof.  Needless to say, I made sure the feed horn had the proper cover over it so that no bees could get in.

Satellite dish feed horn with insect cover installed

Bee fade is best cured with a can of Raid hornet and wasp spray.  The culprits are almost always paper wasps, which, I can tell you from experience, have a nasty sting.  Once the nest is cleaned out of the antenna aperture, a proper cover must be installed.  If one finds that they don’t have a proper cover, I have found that a top from a spray paint can will work as a temporary cover until a proper one can be installed.  I would not call a spray paint can cap a permanent solution because the sun will eventually degrade the plastic and it will fall apart.

The FCC is still in the comment/response process (FCC Docket 04-296) which can get long and drawn out.  I would not expect to see any NPRM until late fall 2010 with any changes taking effect in early 2011 or so.

Basically, CAP looks like this:

An EAS to CAP converter monitors a CAP source (think e-mail server) and when a CAP message is received, it converters it to EAS protocol and sends it to a input source of a  EAS encoder/decoder.  The EAS encoder/decoder then passes that information through and broadcasts it.   Of course, the EAS encoder/decoder can still be programmed to pass through specific types of messages for specific area and ignore all others.

Thus far, several manufactures have designed CAP converters for use with existing EAS units:

• TFT, Inc model 2008 CAP to EAS converter
• SAGE Alerting Systems ENDEC
• Gorman Redlich CAP to EAS decoder system
• Digital Alert Systems DASDEC-II
• Trilithic systems EAS plus

Implementation would look something like this:

For a TFT-2008 system.  Others such as SAGE and Trilithic are integrated into the EAS encoder/decoder units.  Basically, the CAP part of the EAS system needs an ethernet port with access to an IP gateway to receive messages from the CAP server located off site.  That is the weak link in the system, as far as I am concerned.

It is not like some of our so call trading partners have been trying to tinker with the inner tubes or anything.  It is also not like that same trading partner makes most of the cheap ethernet switches and routers found in many radio stations, hardware that can be easily configured remotely.  Configured to redirect certain IP addresses to new, exciting, and exotic locations such as Iran or Pakistan.

Perhaps I am paranoid, or not.  It falls back to my time in the military when somebody said “It’s good to be a little paranoid if everyone is out to get you.”

There are lots of video on how to configure a NV transmitter, which, as I have said before, fancy GUIs are all well and good, I am more concerned with the MOSFETS generating the RF.  I would forgo the GUI in favor of more more reliability, but that’s just me.

I would put the DRM+ video up on the blog, but the embed function is disabled.  Anyway, I enjoyed watching many of these, you might too.

The article goes on about CCD (Colony Collapse Disorder) where entire bee colonies die off for unknown reasons.  Some speculate that increased use of pesticides might be to blame (makes perfect sense to me).  Still others think that cell phone towers are the culprits.  Noting:

“Animals, including insects, use cryptochrome for navigation,” Goldsworthy told CNN.

“They use it to sense the direction of the earth’s magnetic field and their ability to do this is compromised by radiation from [cell] phones and their base stations. So basically bees do not find their way back to the hive.”

One study in India involved attaching a cell phone to the side of a bee hive and powering it on for two fifteen minute periods each day. These researchers found that the honey production in the hive dropped off and the hive queen’s egg laying was cut in half.

All of that is indeed interesting, but somehow I think that a lot of information is lacking.  First of all, any first year physics student can tell you, the RF field around a cellphone antenna decreases logarithmically as a function of distance.  In other words,  for each unit of distance away from the antenna, the power density decreases by 10 times.  Therefore, placing even a mobile phone directly on a bee hive will likely generate much higher RF fields than would otherwise be encountered, unless there was a bee hive in one of the cell tower antennas.

Secondly, there is no mention of power levels, although the frequency appears to be in the 900 MHz range, if this is the study (.pdf) being referred to in the article.

Finally, the compound referred to, cryptochrome, is also interesting.  Breaking the word down, one finds “Crypto” which means hidden, and “Chrome” which means color.  According to the Wikipedia article, which most often can be believed when it comes to such subjects, it is indeed used by some animals to detect magnetic fields.  However, RF used by cell phones has long been in use by other technologies such as two way radio, pagers, cordless phones, baby monitors, TV, early radar and other high power emitters.  It would be most unusual that RF induced CCD would just now be showing up.

In short, there is very very thin evidence that cell phone are causing CCD and it is a shame on CNN for propagating such non-sense without doing research.

The FCC data base gives antenna height in electrical degrees when what you really want to know is how tall is that tower.  Never fear, to figure all this out, requires math.  Pretty simple math at that, too.  I prefer to do these calculations in metric, it is easier and the final product can be converted to feet, if that is desired.

First of all, radio waves travel at the speed of light, known as “c” in many scientific circles.  Therefore, a quick lookup shows the speed of light is 299,792,458 meters per second (m/s).  That is in a vacuum, in a steel tower, there is a velocity factor, most often calculated as 95%, so we have to reduce speed of light in a vacuum to the speed of RF in a steel tower.

299,792,458 m/s × .95 = 284,802,835 m/s (speed of a radio wave in a steel tower)

Frequencies for AM radio are often given in KHz, which is 1000 cycles per second.  For example, 1,370 KHz × 1000 = 1,370,000 Hz (or c/s)

Therefore:

284,802,835 m/s ÷ 1,370,000 c/s = 207 meters per cycle.  Therefore the wavelength is 207 meters.

There are 360 degrees per cycle, therefore:

207 meters ÷ 360° = 0.575 meters per degree

If the height of the tower is 90°, then 90° × 0.575 m/° = 51.57 meters.  Add to that the height of the base insulator (if there is one) and the concrete tower base and that is the total tower height.

To convert meters to feet, multiply by 3.2808399.

In the United States, that tower would be 169.78 feet tall.

Click on picture for original memo (.pdf)

I was digging through some old manuals at the shop today and I found this June 1987 memo from Orban to AM stations titled “AM radio CAN sound almost like FM.”

The main purpose of the memo was to get AM radio stations to implement the NRSC standard for pre-emphasis and high frequency roll off to improve the sound of AM broadcasts on ordinary radios.

I am not sure why the receiver manufactures never designed an IF filter that would be compatible with NRSC, it seems like a fairly simple design.  Instead, what we have is “digital” AM radio (IBOC) which does not work well, creates many more problems with interference that of pre NRSC broadcasting.

If one were to look at the entirety of AM broadcasting history, one would find some striking parallels with what is happening with IBOC today on both AM and FM.

To start, the NAB began petitioning the FCC to allow more AM broadcasting stations, even as it was known that these stations would create interference with existing stations, especially at night.  Still, the NAB persisted and the FCC relented and through the fifties, sixties, seventies, and eighties many more class II and III stations were established on what used to be clear channels (classes I and IA).

Once the AM band was chock full of stuff, they began going to work on the FM band with 80-90 drop ins.

You see, for the NAB, more radio stations means more dues money, greater lobbying power because of the larger size of the industry.   Then came deregulation of ownership limits.  By this time, Big Group Radio was calling the shots and they wanted more.  This led to the great consolidation rush of the late 1990’s from which the radio industry is still reeling.  The consolidation rush led to highly overpriced radio stations being leveraged to the absolute maximum, leading to the recent bankruptcies.

Finally, the NAB’s great push toward adopting IBOC digital radio in the early years of the 00’s.  IBOC was supposed to save the day, greatly improving quality of both AM and FM and bring radio into the 21st century.  Except that the promised technical advances never materialized.  IBOC remains a great expensive boondoggle and I am beginning to think that perhaps we should stop listening to the NAB.

The memo itself is a fascinating thing, which were one could substitute AM with RADIO and come to some of the very same conclusions today regarding analog and IBOC digital radio.  For example, this paragraph on AM stereo:

AM stereo was thought to be an answer (to improve AM), but AM stereo was embraced with the false assumption that having ’stereo’ automatically meant having ‘high fidelity’.  While AM stereo did provide somewhat better fidelity, it was not comprehensively engineered to get the best fidelity from AM.  It was hoped that the gimmick of having two channels would be enough to save AM.

AM stereo could have been an improvement, had it been properly implemented.  Unfortunately, the underlying problem of bad sounding receivers was never addressed.  About which, the same memo notes:

Receiver manufactures did what they could to reduce listener complaints – - they narrowed the bandwidth (thereby reducing audio fidelity) until the complaints about interference stopped.  Listeners clearly indicated, through their buying habits, a clear preference for lower fidelity over continuous irritating static, buzzes, whistles, and “monkey chatter’ from adjacent stations.  People accepted this situation for a long time – - until the simultaneous advent of improved receiver technology and the FCC’s anti-simulcasting rules created the FM boom of the late 1970’s. (ed note: I remember listening to FM because there were fewer commercials, not better sounding audio)

Then the memo goes on to stress the importance of implementing NRSC standard for AM broadcasting that included the sharp frequency roll off at 10 kHz, noting that receiver manufactures would design “fine new receivers” that would take full advantage of the new standard, but only if broadcasters first showed good faith by widely and promptly implementing it.

As I recall, NRSC-1 was adopted as rule of law by the FCC in 1989, about two years after this memo was written.  One could reasonably expect that receiver manufactures then started producing radios that took advantage of the NRSC pre-emphasis curve with IF filters that did not cut off audio frequencies above 3.5 kHz, but rather rolled them off in a gentle slope until about 7 kHz, more aggressively after that until 10 kHz, where they cut off.

Except they didn’t.

Instead, twenty years later, AM radios universally sound bad, with audio bandwidth of about 3 kHz or so.

I believe that AM receivers could be made with three IF bandwidths, automatically selected based on signal strength.  Within the 5 mv contour, full (10 kHz) audio can be reproduced using a high frequency roll off described above.  In the 1 – 5 mv contour, a 6 kHz bandwidth and less than 1 mv a 3 kHz bandwidth.  The automatic selection could be defeated with a “wide/narrow” IF bandwidth selection switch like the GE superradios have.  Of course, if one where listening to stations transmitting AM IBOC, the “narrow” setting would be the best.

Half of me thinks that the ship has already sailed on AM broadcasting.  The stations on the air will continue to decline until they are no longer able to broadcast due to expensive repairs or replacement, at which time they will be turned off.  The other half thinks that AM radio, as evidenced by the huge public response to WEOK and WALL broadcasting the true oldies channel, can be revived.  With the impending inevitable FM IBOC power increases, translator shoe ins, LPFM, etc; the FM band may become worse than the AM band.  At which point the public will have to decide whether free radio is important to them, or 3G/4G services will become the new method of broadcasting.

Time was when a remote required ordering an equalized phone line from Ma Bell.  This usually required 2-4 weeks, depending on the local branch.  Spontaneous remotes were but a pipe dream.  Then came Marti with inexpensive RPU transmitters and receivers, this greatly reduced the lead time required for establishing remote broadcasts.  The downside to Marti equipment is it takes at least some technical know how to set up because of all the antennas and coax and such.

Comrex came on the market with Telephone Line frequency extenders then with 3 line comrex units (3XP/3XR).  A three line unit split the incoming audio into three different sections, reducing each to 300 to 3,400 Hz telco line base band.  At the other end, the answering unit changed the sections back to their original frequency range, then recombined them into pretty good sounding audio from 50 to 10,000 Hz or so.  I have used these units on several occasions.  I believe that one of the stations I work for still has one of these in their storage unit, along with several EFTs.

Latter, Comrex came out with POTS line codecs like the Hotline, Matrix and Blue box.  Now only one phone line was needed to do a remote. This greatly simplified remote availability and set up.  The downside to these is it had to be straight dial tone, no PBX’s or any thing like that.  A noisy line can create problems with audio quality and dropouts.

The Matrix can be used with ISDN and they used to have a GSM module to use with certain cellular networks.

The latest Comrex products include IP and VOIP capabilities.  These systems are great when a broadband WIFI networks is available to be used.  Unfortunately, an open WIFI with good signal strength is not always at hand.  So the 3G/4G option is a natural.

One commonly held belief is that when lightning strikes an object, the ground immediately absorbs all of the charge.  That is not true in most cases due to ground resistances.  Eventually, the ground will absorb the charge but it can take several seconds to do this, especially with a big strike.  Equipment is damaged by current flow, therefore, every effort must be made to keep all of the equipment at the same potential, even if that potential is 10KV.  That is where a single point ground buss comes in.  Bonding every piece of equipment to a common ground buss ensures that no one device is at a lower potential while the charge dissipation is occurring.

The second misunderstanding about lightning is that it is DC voltage.  That is true, however, a lightning strike has an extremely fast rise time, on the order of 30 microseconds.  That makes it behave more like AC voltage around 10 KHz.  Therefore, ground buss wires need to have a minimum inductance.  Solid #2 wire is best, keeping it as straight as possible and using long sweeping turns where needed.  All bonds should be exothermically welded (CAD weld).

Ground system installed at WKZY, WHHZ and WDVH-FM transmitter site in Trenton, Florida.  Central Florida is the lightning capital of the US.  Prior to doing this work, the Harris FM25K transmitter was knocked off the air at least once a month.  Since this was installed in 2005, they have had zero lightning related damage.  The ground rods are 20 feet long, driven down into the water table, spaced 20-30 feet apart.

All coax shields and metal conduits that come into the building should be bonded to the ground system where they leave the tower and where they enter the building.  At most tower sites, I install a ground ring around the outside of the building with rods every 20 feet or so.  From that ring, 5 to 6 radials outward 40 feet with ground rods every twenty feet works well.  I also install 5 to 6 radial out from the tower base with the same configuration.  The tower and building grounds are bonded together.  This is important because when the tower gets hit, the ground will quickly become electrically saturated.  If the building and the equipment is inside is at a different potential, current will begin to flow toward the lower potential, thus damaging gear.

All Coax, control and AC cables in and out of sensitive equipment should have ferrite toriods on them.  Transmitter manufactures normally supply these with new solid state transmitters, as MOSFETS are particularly sensitive to lightning damage.

This is a Potomac Instruments AM-19 directional antenna monitor.  It was damaged by a lightning strike two weeks ago on the WBNR tower in Beacon, NY.  The case arced to the rack it was mounted in.  This was a large strike, as several components in the phasor control circuit were also damaged.  The fact that this arced means that somehow the sample lines are not attached to the single point ground for this site, which needs to be corrected.

Insulated AM towers present special design problems when it comes to lightning protection.  Generally speaking, tower arc gaps should be set so there are side by side and there is no arcing on positive modulation peaks.  Depending on power levels, this can be anywhere from 1/2 inch to 2 inches.  Tower impedance also plays a roll in setting arc gaps.  The final link between the ATU and tower should have several turns in it.  The idea is to make that path a higher impedance path for the lightning, causing it to dissipate through the arc gaps.  Incoming transmission lines from the towers should be bonded to a copper buss bar at the entrance to the building.  All of this grounding needs to be tied to the RF ground at the base of the tower.

Arial phone cables can act like large lightning antennas for strokes several miles away.  It is very important that the cable shield and the cable termination device is bonded to the building ground buss.  I have seen installations where the TELCO tech pounds in a separate ground rod outside and connects the TELCO equipment to that.  That defeats the concept of single point grounds and should be fixed ASAP.

Electrical services entrances also can act like big lightning antennas.  Normally, pole mounted transformers will filter some of this energy out.  Internal electrical distribution systems can also add impedance, thus act as inadvertent filters for lightning.  In most mountain top transmitter sites, however, some type of power line surge protection is needed.

Inside view of LEA surge suppressor

There are two types, series and parallel.  Parallel types are the least expensive and least intensive to install.  They are usually found mounted next to or on the service panel and fed with their own breakers.  They usually have some type of MOV or similar device that acts as a crowbar across the AC mains, conducting spikes to ground.  Series types go in between the service entrance and the main panel.  They include a large inductor designed to force spikes off into shunts.  A series type protector offers more complete protection than a parallel.