April 2013
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Server isssues

My apologies. As of late, there have been several service disruptions on this site.  In speaking with my web host, they have identified the following issues:

  • On Thursday 4/11 and 4/18 between 6-10 am local time (1000-1400 UTC) the server that hosts engineeringradio.us was subjected to a DDoS (distributed denial of service) attack, where approximately 200,000 login attempts were made per hour from 90,000 different IP addresses.  This was part of a greater attack on WordPress websites.
  • On Wednesday 4/24 there was another DoS attack of a more limited and focused scale around 3-4 pm time frame
  • On Tuesday 4/30 beginning at 5 am, (0900 UTC) there was a server issue which returned an error 404 message to anyone trying access the web site.  The .htaccess file was somehow corrupted, which later caused a error 500 message.  This outage lasted until approximately 2 pm (1800 UTC) when the .htaccess file was reloaded.

I have taken several steps to secure the web server and web site against intrusions and other attacks.  A distributed DoS attack is very hard to track and combat, the best course is to beef up security policies and weather the attacks when they come.  I have contemplated moving this website to my own server, but that is more work than I have time for right now.  Perhaps at some future point, if reliability continues to be an issue, I will do that.

For now, your patience is appreciated.

Friday Funnies: Estimated time


Radio? Not interested

With the pending LPFM filing window in October, I decided that perhaps I could spread the information to some local groups that might want to put a community radio station on the air where I live.  Back over a decade ago, there were a couple of local commercial AM and FM stations in the area, but they moved out of town to a larger city some 24 miles to the east.  If local legend is to be believed, the AM station was very popular, with its studios and offices over the local pharmacy.  That station is now running 24/7 comedy, which given the area, is ironic almost beyond words.  As it stands now, this is one of those rural areas that, on paper, looks well served by several different radio stations.  Truth is, there are radio signals receivable here, but there is no local radio.  The last time anyone from those previously local stations had a meaningful thought about the respective Cities of License was months if not years ago.

With all this in mind, I first approached a local community non-profit group.  They seemed mildly interested, but expressed doubt about finding a studio location.  Their basic take was, we can help, but we want others involved.  Seemed to be a lukewarm, but understandable and not totally unwarranted response.

I then approached the local school board.  The idea was to get the high school involved with the station broadcasting sports events and teaching kids how to do play by play and perhaps other types of radio shows.  They fainted interest at first, then decided that they didn’t have the staff to deal with a broadcast program and there were other excuses like “liability issues.”

I then approached the local governments (two different towns) who were almost openly hostile to the idea.  While they didn’t say as much to my face, they rather implied that it would be a waste of time and the town(s) were not interested.

I have approached other local groups, which don’t seem to be interested at all.

Has radio lost its mojo with the local population?  Are we who still remain in the radio business simply fooling ourselves into thinking that somehow this is important?  I don’t know.

The hazards of rural LPFM; large area, few people, generalized indifference.

WBCN All digital field test results

When I said the WBCN test data may not see the light of day, perhaps I spoke too soon.  For your viewing pleasure, here are the results of the WBCN all digital HD Radio tests:

WBCN All-digital AM IBOC Field Test Project (link has been broken, this may have been released by accident)

Well, that will teach me, won’t it.

I have given it a summary read and my first impressions were correct; from a technical standpoint (antenna, ATU)  this is a very favorable test configuration.  The results look pretty good on the surface, although they appear to have had some night time interference problems, go figure.  I’ll update this post when I have time to fully read the whole paper.

Update: The link I provided earlier has been taken down.  It may be that the information was not supposed to be released to the general public.  Several people have asked me to up load the report to my own server so that they can download it and read it themselves.  This leaves me in a bit of a quandary; the report itself is important information and its implications on the future of broadcasting are huge.  On the other hand, it is the work of a private organization and not public domain, thus if released by accident, then it should not be shared.

This story from Inside Radio is more or less accurate as to what report contains, although it paints a somewhat favorable picture.  There appears to be some issues meeting the NRSC5C mask for the MA3 (all digital) mode.  That seems to be fine, however, as the NRSC5C mask can be modified to meet field conditions.  How convenient is that?  The information about the number of AM HD Radio station seems a bit off, latest I have is 207 AM day time, 66 AM night time stations out of 4,659 transmitting hybrid digital analog HD Radio, or 4% daytime and 1% nighttime respectively.

When I have time, I will do some more analysis and post my own conclusions.


Eventually, the internet WILL be censored

Congress, is yet again contemplating a cyber security bill, this time called CISPA.  This one has some worrisome privacy implications for the general internet user.  I recall, not too long ago, another such measure called SOPA/PIPA which created a huge uproar and was voted down.  For Congress and its corporate sponsors, this development was just a slight inconvenience when applying the “if at first you don’t succeed, try, try again,” legislative method.

Not mentioned in this particular bill is the internet kill switch, which exists now in one form or another, and the unofficial back doors into operating systems and routers.  Those things are in place but their use is not codified.  The internet can be monitored, user data can be stored indefinitely and it can be restricted or switched off at a moments notice.  That is the reality of the world we live in.

This is why a vibrant, independent radio broadcasting medium is important.  After doing some numbers crunching over the weekend, I came upon some pretty interesting data points:

  • Large and medium large (over 30 stations) group owners account for approximately 2,300 AM and FM stations
  • NPR affiliated stations number about 900
  • There are 4,736 AM, 6,603 commercial FM, 3,917 educational FM and 802 low power FM stations licensed as of March 31, 2013.
  • There are 77 AM and 178 FM (not counting translators) stations known to be silent

Therefore, approximately 3,200 of the 15,803 stations on the air are controlled by major corporate interests or media conglomerates, the remaining stations are owned by medium small groups (less than 30 stations) or individuals.  Those figures create an interesting situation when discussing the future of radio.  What does the majority of owners and listeners want?  Ask the market.


The fourth dimension, at least in theory.  We keep track of time in a linear way, each second marking a particular point that will happen only once and never be revisited.  There will never be another 10:42:30.1 on April 17, 2013, for example.

Point in space and time

Point in space and time

Of course there are several ways to record the same time:

  • Coordinated Universal Time (UTC): Which is the time at the prime meridian, 0° Longitude.  From there, time zones span out to +12 or -12 UTC, meeting again at the International Date line.  In military parlance, UTC is known as Zulu because it is in timezone Z.
  • Local Time: In any given location, is determined when the sun is directly overhead (± sidereal correction) at noon.
  • Local Timezone:  One of twenty four arbitrary divisions where the sun may be directly overheard (± sidereal correction) somewhere within the division at noon.
  • Unix Timestamp:  The number of seconds that has transpired since 0000, January 1, 1970.  Unix time stamp 1366209730 equals 10:42:30, April 17, 2013.  In hex looks like 516F0260.  Used by all Unix/Linux variants.
  • GPS Time: UTC – LS (Leap Second) + 19 s.
  • ISO 8601 date/time: 2013-02-17T10:42Z
  • Julian Date: A continuous count of days and fractions of such since noon Universal Time on January 1, 4713 BCE.  April 17, 2013 10:42:30.1 equals 2456399.946193

One thing to note and mark your calendars: Unix (and variants) may have a problem on January 19, 2038 because of a 32 bit integer issue.  This is known as Y2038, and a smart man would start planning now.

Category 7 Cable

As data transfer technology progresses, so do cable types.  Category 6 UTP copper cable is commonly used today in ethernet installations where 1000BaseT (or gigabit ethernet) systems are required. Cat 6 cable has a certified bandwidth of 250 MHz (500 MHz for Cat6a). Category 6 cable is a newer version of Category 5 and 5e cable wherein the wire pairs are bonded together and there is a separator to keep each pair of wires the same distance apart and in the same relationship to each other.  The four twisted pairs in Cat 6 cable are also twisted within the overall cable jacket.

Category 7 cable is much different from its predecessors.  It has an overall shield and individual pairs are shielded:

Category 7, STP ethernet cable

Category 7, STP ethernet cable

Shields on individual pairs are required to reduce cross talk (FEXT, NEXT). It also requires special shielded connectors called GG45 plugs and jacks.  Pinouts and color codes are the same as gigabit ethernet (Category 5e and 6) however, Category 7 (ISO 11801 Class F) jacks and plugs also have to contacts on the corners of the connector or jack.  This allows better shielding.  A small switch in the jack senses when a category 7 type connector is inserted and switches to the corner contacts, thus keeping jacks and patch panels backwards compatible with Category 5/6 cables.

Category 7 GG45 connectors, jack and plug

Category 7 GG45 connectors, jack and plug

Category 7 cable is rated for 600 MHz bandwidth (1000 MHz for 7a) which translates to 10 GB ethernet.  This was previously the domain of fiber cable.  Copper cable has some advantages over fiber; lower propagation delays, requires less complicated equipment, copper is less expensive than fiber and more durable.  It is nice to have the flexibility to use copper cable on 10 GB ethernet for runs of 100 meters or less.  Longer runs still require fiber.

Category 7 and 7a cable looks remarkably similar to the older Belden multipair “computer cable” pressed into service as audio trunk cable seen so often in older studio installations.

Blown up surge suppressor module

This is a picture of a surge module taken from an LEA series type surge suppressor:

LEA MOV module destruction

LEA 600 volt MOV module

Looks like it took a pretty significant power hit, enough to explode several MOV’s.  This site is at the end of a long transmission line that stretches across an entire county.  Over the years, the station has made many complaints to the utility company about the quality of their power and the frequency of interruptions encountered at this transmitter site.  Occasionally, something will happen.  Often times it is the figurative shoulder shrug.

That is why we installed the surge suppressor.

Proper drive levels for a Harris SX serries transmitters

I was working on a Harris SX5 the other day and snapped a picture of the scope while measure RF drive levels.  There are still quite a few of these units out the in the field, judging from my search engine results.  I thought it would be helpful to post something about it.  The RF power amp boards for the Harris Gates solid state AM series transmitters are the same design, I believe.

In order to fully drive the RF MOSFETs in this particular series transmitters (Harris SX1, 2.5 and 5 including A models) at least 26.5 volts peak to peak is required.  Less than that and the device will turn full on and internally short.  To measure RF drive, the transmitter must be in local with control voltage on, with the rear door interlock defeated (this can be safely done if the transmitter is wired with separate AC feeds for control and RF power supply). Make sure the RF power supply is defeated and will not turn on.  Measure across the input of the each of the toriods that feed the gates of the RF devices.

Harris SX series transmitter drive level test

Harris SX series transmitter drive level test, 27.45 volts, 1,110,000 Hz

It should measure between 26.5 and 29.5 volts. This one measures 27.45 volts peak to peak. Each input toroid on every PA board should be measured as the toroids themselves have strange failure modes and may pass resistance and continuity tests, yet still not provide proper drive voltage to the attached devices. This has to do with core permeability.  Each toroid feeds two RF MOSFETs, replace part is IRF-350.

As always when dealing with a SX transmitter, good luck.

We are off the air!

A phone conversation that occurred one Saturday morning:

DJ: (answers hotline) Hello?

Myself:  This is Paul from Radio Engineering Services, you called the answering service and said you are off the air?

DJ: Yes!  The red bat light is flashing and everything!

Myself: Okay, did you try to put the backup transmitter on?

DJ: No.  I didn’t want to mess anything up.

Myself:  You are off the air; I don’t know how things can be more messed up than that

DJ: (laughing) Okay, you’re right.

Myself: Do you have the directions for the backup transmitter?

DJ: Yes, they are right here

Myself: Okay, go ahead an do that, I will call the local engineer and see if I can get him out to the transmitter site, then I will call you back.

DJ: Okay, thanks.

The good news is the backup transmitter came on and they were back on the air.  It is also nice to know that the station has a live DJ on Saturday morning at 7:00 am, many do not.  The main transmitter power outage was likely due to a utility company transient, the area had suffered an ice storm the day before and they were out restoring power that morning.

At least this was a real emergency, I used to get calls at home that the headphone jack on the console was loose.  I took the home phone number down after that.


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

Free counters!