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RCA BTF-20E

Does any one need any parts for one? Long time reader and commenter John has one that looks to be in good shape that he is willing to part with or part out.  I had three of these units in Harrisburg and my recollection is they were pretty solid units.  When tuned properly, they were low noise and sounded good on the air.

The one issue I had was with the small 100 pf pass through/by pass capacitors in the IPA.  Several went bad and were no longer functioning as bypass caps.  The result was the transmitter would self oscillate.  I think there were seven or eight of them and I replaced them all at once.  The exact model of that particular transmitter was a BTF-20ES1, which was one of the last FM transmitters off of the factory floor before the broadcast division went under.

RCA BTF-20E FM transmitter

Late model RCA BTF-20E FM transmitter

John says:

If anyone needs parts out there, I will probably cannibalize this unit as I have just too many. The separate power supply is inside the garage along with the latest version of the harmonic filter entirely made of copper.

I don’t know if the entire unit actually runs or if it is parts only.  It certainly looks like a clean unit.  As I recall, Comark bought out all the RCA broadcast parts and service. Comark was then sold to Thomcast, which was sold to Thales which I think spun off it’s transmitter division to Grass Valley Group.  Grass Valley started by making TV master control switchers, routers and other video equipment.

Anyway, if you are looking for RCA parts for FM transmitters, contact me, I’ll put you in touch with John.

Downgrading AM stations

One of the AM station around here that I am familiar with is considering a downgrade, which is to say reduce power and get rid of a directional antenna system in favor of a non-DA antenna.  In this particular case, it makes sense, as the station can co-locate with another AM that is closer to the COL by a good distance.  The coverage from the new site at reduced power looks to be a good fit.  If this can be arraigned, the AM station in question would loose a multi tower AM antenna system that is 50 years old and all the attendant headaches, expenses and labor that goes with it.

five tower directional AM tower array in a tidal swamp

Many AM stations that are DA-2 or even DA should consider downgrading to a lower power level and getting rid of their DA system.  Directional antenna systems on AM stations are maintenance nightmares.  Unfortunately, in the 50’s, 60’s and 70’s, it was often thought that adding power, extra towers to an AM station would give them great swaths of extra coverage.  Sometimes it worked out, sometimes it did not.  Often what happened was some area was added, but in areas that where nulls toward protected stations, signal strengths went down.  What the station ended up with was more towers, more maintenance, monitor points, a sample system, and more expense.

Taking an AM station in the other direction might actually make more sense.  Go back to one tower non-directional 1 KW or whatever power can be used in the daytime.  Time was when the FCC would only allow certain power levels; .5, 1, 5, 10 and 50 KW.  Those were what a new station had to work with.  No longer is that the case, any power level can be used so long as it meets interference contours and the city of license contour coverage requirements.

Presunrise authority is normally 500 watts and is available at 6 am, post sunset authority varies but often a PSA extends the on air time to 9 pm in the winter time.  For a local radio station, which is what all but the class A AM stations are destined to become, this will be adequate.   For a loosing station, it may be that, or turn in the license and sell the land to a developer.

Diplexing on another AM stations tower closer to town is also a good way to get out of maintaining an expensive antenna array with diminishing income.

Something to think about.

Fireworks sychronized to music played over the radio!

In previous years, I have had the very pleasurable experience of setting up a fire works show remote with music synchronized to our FM radio station.  Ordinarily I don’t go near a remote broadcast, however, this is one of the more intricate broadcasts requiring coordination between the studio, the remote site and the fire works barge anchored 300 yards off shore, out in the Hudson River.  The fireworks company, Garden State Fireworks, are consummate professionals and produce a very well choreographed show.

Giving them the synchronizing track on site is not very hard, however, I was surprised to hear that not every radio station does that.  In fact, one of our, ah, ehm, Clear Channel competitors from The big Metropolitan Center Nearby could not be bothered to do it for the 4th of July fireworks this summer and last summer too.

The synchronizing track is on the left channel of a CD that Garden State Fireworks created, it is 1200 baud FSK data, 8,N,1, so it is pretty robust.

I thought I would post on how I do it and why. First of all, for the how part, there are two options:

  1. Play the music CD at the remote site and relay broadcast quality music back to the studio without any time delay.  Hard to do even with an ISDN line.
  2. Play the music CD at the studio and relay telephone quality audio for the firing track to the remote site from the studio.  Have the remote site play the air signal over the local PA system.

Option number 2 is technically far easier than option number 1, although it takes a fair bit of coordination.  Also, the sound reinforcement guy didn’t like the air signal idea because the quality of the audio.   That is a little nit picky, especially given the fact that much of the music at the fireworks show will be drowned out by the fireworks explosions.    In the end, he saw it my way.

Here is a list of equipment needed:

  1. Telco auto answer coupler, such as the Indy Audio
  2. Telco Hybrid, such as the Telos
  3. If the announcer is at the fireworks site, a POTS CODEC such as a Comrex Matrix or blue box
  4. Wireless microphone
  5. Telephone set and cord with RJ-11 connector
  6. Miscellaneous mic cables, power cords, etc
  7. At the remote site, two pots lines from the local phone company, long distance  service as required.

Here is the block diagram:

Note, this assumes no delay in the telco network, which under ordinary circumstances using wired, not cellular network, there should not be any.  The touchiest part of the whole thing is getting the stage coordinated with the studio during the transition to the remote broadcast.  Once that is done, everything else just falls into place.

The firing computer is located on shore next to our broadcast booth.  They send the signal out to the barge on a wireless LAN link.

That is the how part.  Here is the why (soundtrack is a little low):

That is from three years ago, but you get idea.

Even though I don’t work for these people anymore, I asked if they needed help with the broadcast this year.  “Nope, we got it, thanks.”  I will be paying close attention.

Harris FM25-K

Old blue, I like to call them, the Harris 1980’s model transmitters with black faces, white cabinets and blue trim. I have yet to find one that I really like, the FM 25-K is, well okay. Sort of like that 200,000 mile jeep that works, most of the time, and it’s paid for.
This particular FM-25K transmitter is located at WIZN in Charlotte, VT.

Harris FM25-K transmitter

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.

Harris FM25K HV power supply feed through insulator

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.

How do you listen to streaming audio on an Android smart phone?

Update:There is a better way: www.engineeringradio.us/blog/2011/03/tunein-radio/

Ahh, since I posted about my android, a few readers have emailed me and would like to know. If you have tried to stream audio using a smartphone web browser, you have found out that it simply doesn’t work.  The web browser is unable to decode the radio station stream because most of them are in AAC, AAC+, HeAACv1 or some other codec.  At this point, most people give up on the idea and move on. I, on the other hand, determined that it should be doable.

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…

Satellite dish wasp fade

More bee related RF stories. This happens often this time of year, the paper wasps have worked hard all spring to build their nests up in size and during July, they become large enough to block the aperture of the antenna mounted on a satellite dish. As the nest fills up with eggs and larva, it becomes denser and blocks more RF from the antenna. Soon, the signal on the satellite receiver drops and audio dropouts occur.

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 dish

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 feed horn with insect cover

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 sad story of WCVR

I have been the road warrior lately, if you haven’t noticed a certain decline in the blog posts… One place that seems to keep pulling me back is Randolph, VT, which is about as close to the geographical center of Vermont as one can get and still be on a roadway.   There resides the silent FM station formerly known as WCVR, to be returned to the air as WXVR by Vermont Public Radio.

WCVR sometime in the early 1980's

WCVR went on the air in 1982 and was a community oriented country station for 17 years.  Then in 1999 it was sold to Clear Channel and things began to go down hill.  Over the next decade the station transfered ownership four times.  Finally ending up with absentee landlord Vox radio.  By the time the station was sold to Vermont Public Radio last May, the years of neglect were compounded and the main transmitter was no longer running.  The transmitter site was raided before the transfer and things like spare parts, a backup transmitter and dummy load were removed.  As one engineer from VPR noted, the only thing of any value is the Shively antenna.

This story probably repeats itself a thousand times over throughout the country as small market, formerly community radio stations are left to die on the vine by big time corporate radio gurus in Atlanta, San Antonio, and Las Vegas.

Said station has a McMartin BF5-K transmitter that is not currently running and by the accumulations of dirt, debris and other evidence, has not run in quite some time.

The beauty of a McMartin FM transmitter is it is grounded grid.  Can’t get much simpler than that when it comes to FM transmitters.  The downside is, of course, McMartin has been out of business for almost thirty years.  Thankfully, Goodrich Enterprises is still around and still supports them.

The first order of business was cleaning out the filthy, and I mean absolutely filthy building.  Several hours with a broom, dustpan and shop vac got rid of most of the dirt and made my skin less likely to crawl.  Then came the fateful attempt to run the transmitter.  Loud arcs, power supply hum and dimming lights revealed that all was not well.  All of the fluorescent lights were out, new bulbs did not fix the problem.  So, to the Grainger to pick up new fixtures and install them.  Now, at least, we could see what were were doing.

Next, step by step trouble shooting of the High Voltage power supply.  Step one, resistance checks on the HV transformer and filter chokes to ground.  Next forward and reverse resistance checks on the rectifier stacks.  All of those looked good.  Next, we isolated the HV transformer and the rectifiers and turned the transmitter on; no problems.  Next we added the metering and filtering capacitors and turned the transmitter on; no problem.  Finally we found the problem on the HV power supply RF filter up on the side of the PA enclosure.  In a McMartin FM transmitter there is a little box mounted on the outside of the PA enclosure that holds half the parts in this circuit.  Taking that box off revealed a bad 200 pf 7.5 KV doorknob capacitor that was shorting to ground.  Lots of arc marks, soot, debris and other stuff makes me think that this problem had been going on for a long time.   I can kick myself for not taking a picture.

Hopefully this thing will run for a few month while a replacement is sought.

Compounding that issue is the leaking transmission line connector at the bottom of the antenna, which was fixed, but there appears to be another leak somewhere else as the line still does not hold pressure for very long.

VPR is going to broadcast their Classical Music format on this station, starting as soon as we can make the transmitter run.

UPDATE: Pictures:

300 foot WCVR tower, Randolph Center, VT

300 foot WCVR tower, Randolph Center, VT

Transmitter building:

WCVR Mc Martin BF-5K transmitter:

Arcing power supply filter section, the bad door knob capacitor has been replaced, still evident are the arc marks on the PA cavity:

Mc Martin BF-5K transmitter on the air:

We’ll see how long that lasts.

Radio World Redux

I was reading the July 14th radio world, on line because I still haven’t subscribed, and found this blog quoted by the editor.  More specifically, on page 4, the editor writes about this post where I debate keeping my radio world subscription.  Without actually naming the blog, asks how well he (the editor) is doing his job.

One of my aims in writing this thing is to provoke thought.  The fact that the editor of Radio World is asking his readers about the direction the publication is heading is a sign that, at least in one case, I have been successful.

My other aims are:

  • pass along useful information
  • tell my story
  • write stuff (I am compelled to write things)

Regarding Radio World itself, I still read the digital version of the magazine found on the Radio World website.  The importance of impartial reporting of radio broadcasting’s technical issues cannot be overstated.  These days there are many pressures being applied to Radio in general from things like the FCC, Big Group Radio, MMTC, Ibiquity, NPR, the recording industry and others.  Some of these groups do not have the radio industries best interests in mind, but rather are looking to improve their take.  Indeed, some of the schemes proposed are technically flawed or down right destructive.  Biased reporting degrades the integrity of any publication and diminishes it’s value and when it comes to the most read technical trade magazine, that is alarming.

I applaud Radio World for it’s recent publication of articles that bring to light HD-Radio’s technical issues.  That is a welcome development and such things should continue.   Technical writers need to be technically minded people, not someone that retypes press releases.  When it comes to new technology, hard question need to be asked and answered, that is a reporter’s job after all.

Pandora and me

I finally broke down and purchased a smart phone.  Instead of the ubiquitous iPhone however, I opted for a HTC Incredible Android phone.  Not that I have any distaste for Apple, Inc.  Rather, it is more because of the lack of ATT coverage in areas where I travel and the new data plans from ATT.

The phone is great, I enjoy the functions, the GPS navigation tool, gmail, news, and all the other apps.  It fills many roles while I am out gallivanting around earning a living.

HTC incredible Android phone with Pandora App

I have tried Pandora in the past on my computer.  I found it to be okay, not great.  I guess my main issue was it seemed a little boring just listening to music.  It was good music, and when I interacted with the programming, voting a song up or down, the music selections got better.  But it was distracting to interact while I was trying work on the computer and in the end, I turned the volume down an it became background noise.

In the car, I figured, things would be different.  I could listen to Pandora the same way I listened to my car radio.  Lots of music would be great and not distracting at all.

Except…  I found it to be… boring.  The music was great but the whole thing lacks personality.  I suppose we are blessed around here with several radio stations that play new music.  With Pandora there was almost no new music, even if I created a new music radio station.  Further, it seemed like something was missing:  human interaction.  I enjoy hearing the deeeejay talking about some band factoid or some such.  Just listening to music endlessly left me wanting something more.  Perhaps that is just me.

Whilst on the road to various places, I like to listen to WEQX in Manchester, VT; WDST, Woodstock, NY; WKZE, Salisbury, CT; WXPK, White Plains, NY.  All of those stations have personality and play great music.  They also stream audio, which means I can listen to them on my phone.

So Pandora gets a meh, the phone gets a thumbs up.

Ready for CAP? (AKA Common Alert Protocol)

Like any good government agency, the FCC in conjunction with FEMA are working on upgrading the acronym heavy EAS system with CAP, which stands for Common Alert Protocol. CAP includes something that  FEMA has been working on something called IPAWS, which stands for Integrated Public Alert Warning System.

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:

Implementation would look something like this:

EAS CAP converter diagram

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 called 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.”

Axiom


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.

Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.
~1st amendment to the United States Constitution

Any society that would give up a little liberty to gain a little security will deserve neither and lose both.
~Benjamin Franklin

The individual has always had to struggle to keep from being overwhelmed by the tribe. To be your own man is hard business. If you try it, you will be lonely often, and sometimes frightened. But no price is too high to pay for the privilege of owning yourself.
~Rudyard Kipling

Everyone has the right to freedom of opinion and expression; this right includes the freedom to hold opinions without interference and to seek, receive and impart information and ideas through any media and regardless of frontiers
~Universal Declaration Of Human Rights, Article 19

...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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