The technical problems with AM broadcasting can be broken down into three broad categories:
- Interference from other AM stations
- Interference from unintentional radiators (AKA electrical noise)
- Poor receivers
Much of the poor fidelity issues with AM broadcast audio comes from the narrow IF bandwidth of the typical AM receiver. Older AM receivers had much wider IF bandwidths, sometimes as much as 15 KHz +/- carrier. As the AM band was over filled with stations starting in the late 1940′s, this became a big problem. The tube type front ends with great sensitivity but not very much selectivity were unable to cope with adjacent channel interference, leading to what was known as “monkey chatter.” This type of interference can be technically described as the higher audio frequency peaks from an adjacent channel stations being demodulated. Those hearing this type of interference found it very annoying and rightly so. Thus, receiver manufacturers were deluged with complaints about the poor quality of their units. The solution was simple; narrow the bandwidth until the “monkey chatter” disappeared. This new de facto standard IF bandwidth turned out to be +/- 3 KHz carrier.
It does not take a rocket scientist to see that 3 KHz audio is only very slightly better than telephone quality. This was the beginning of the perceived AM low fidelity problem. In the mean time, FM broadcasting, after years of lagging behind in spite of it’s superior audio, made great strides into mainstream acceptance.
NRSC-1 was supposed to reduce this type of interference by limiting AM broadcasting stations audio bandwidth to 10 KHz. The idea was to attempt to keep the modulation index somewhat within the allotted channel. This standard was mandated by the FCC in 1989, after which receiver manufacturers were to change their design to allow for wider IF bandwidths, thus improving AM fidelity. There was even an AMAX standard adopted by some receiver manufacturers. Unfortunately, by this time, the majority of AM stations were transitioning from music to talk radio. The new standards were too little much too late.
A quick scan with a quality AM receiver shows that many stations are transmitting high quality audio, which, with a properly adjusted IF bandwidth can sound remarkably good:
Screen shot – WEOK True Oldies Channel
This is a screen shot from a SDR (Software Defined Radio) showing WEOK, Poughkeepsie, NY broadcasting the True Oldies Channel. The signal strength is slightly low, but this is a rural area and the noise floor is also low. I limited the bandwidth to +/- 7.5 KHz carrier because of the pre-emphasis used on most AM stations makes the high end sound strident. Looking at the spectral display, there is more audio available beyond what I am listening to. Which brings me to this; AM fidelity is not inherently inferior, it can sound quite good. There is no reason why AM receiver manufacturers cannot improve their product to include some advanced features;
- Variable IF bandwidth based on signal strength
- Variable user selected IF bandwidth
- Sharp selectivity – adjacent channel rejection
- Selectable side band demodulation (carrier plus upper or carrier plus lower sideband)
While this will never sound as good as FM stereo, it still can sound pretty good, especially with older music recorded before say 1975 or so.
Manufacturers would have to have some impetus to include these features in their chipsets, such as multiple requests by listeners who are looking for better AM quality, which leads us back to programming…
The other issues with AM electrical noise reception and interference from other radio stations are surmountable, so long as there is a reason to. Which, leads us back to… programming.
I have seen many a Dell LCD computer monitor go south for want of a $0.50 part. Dell must have gotten a hold of a bad batch of capacitors, because almost invariably, the problem is with the power supply capacitors for the back light. The symptoms are; the monitor goes very dim and can only be read when shining a light on it, or the power button flashes green.
A new Dell 19 inch (E1914H) monitors runs about $90.00 – 110.00. I can repair a defective unit in about 20-30 minutes or so, which makes it worth while for the client. When repairing equipment, the cost of labor and parts balanced across the cost of new equipment should be a prime consideration. Sometimes, it is simply not worth the time to repair something. Others, like this instance, it makes sense as long as the repair is simple.
This is a Dell E198FPf LCD monitor. After the initial diagnosis:
Dell E198FPf LCD monitor back lighting problem
First step is to remove the stand and the four screws behind the stand bracket.
LCD monitor stand removed
The hardest thing about this repair is getting the bezel off. Dell uses a bezel around the monitor face that uses little plastic clips to hold it in place. To get the bezel off, one needs to press the clips toward the center of the monitor while lifting up. It requires the careful application of force.
Dell E198FPf monitor bezel
I start on the bottom and use a small screw driver in one of the slots to get it started. I start on the bottom because if the plastic gets a little marred, no one will see it when the repair is finished. Once the first clip is released, then the others and be released by twisting the bezel carefully toward the center of the monitor while lifting.
LCD monitor bezel removal
Once the bezel is removed, the wiring needs to be disconnected. This consists of the back light, the data buss and sometimes the on/off switches, which are mounted on the bezel.
LCD monitor backlight connector
LCD monitor data buss connector
After all the wiring is removed, there are either two or four screws that hold the power supply to the monitor screen.
LCD monitor power supply bracket screws
Finally, the power supply board is exposed. Depending on the model of the monitor, the hex head screws that hold the VGA connector may need to be taken off. Sometimes not.
LCD monitor power supply
Removing the screws on the back of the power supply board exposes the capacitors and other components.
LCD monitor bulging capacitors
And the culprit is discovered. These two bulging capacitors are causing the LCD monitor backlight power supply shut down making the monitor unusable. The larger one is a 1000 uF 25 volt and the smaller is 680 uF 25 volt. I replaced both with in kind 35 volt units. I also took the liberty of replacing the rest of the electrolytics on the power supply board (total of five additional capacitors). While the unit is disassembled, it is far easier to replace all the $0.50 components than to do it one at a time over the next few years as each fail. This monitor should be good for another 5 years of service at least. These values vary somewhat from monitor to monitor. Also, if only repairing one or two monitors, the parts can be obtained at Radio Shack for $1.99 each.
It is a good way to regenerate equipment, even if they are set aside as spares.
I could tell you a joke about UDP,
But you might not get it.
We don’t need no water, let the… oh, wait… The actual roof is actually on fire you say?
YES: Ahh! Time to run around like crazy people!
Carrier HVAC unit damaged by fire
This happened over the weekend at one of our clients in NY. The back story is this; over the last two weeks, the area has received almost three feet of snow. This roof is pitched slightly toward the back of the building. The roofing material is some type of PVC, which is very slippery when wet. Thus, at some point the snow/ice pack shifted towards the back of the building, it broke the natural gas pipe off where it entered the unit:
Broken gas pipe, HVAC unit 1
The next time the HVAC unit cycled on, there was giant torch on the roof with flames reportedly eight feet high. A local fire fighter just happened to be driving down the road and spotted the fire, thus likely saving the building from major damage. The fire department came and cut off the gas and electric. The building was evacuated for about 20 minutes while they overhauled and checked for internal fires.
Carrier HVAC unit damaged by fire
A second unit suffered the same fate, only with less damage:
Carrier HVAC unit damaged by fire
The fire in this unit was contained to the controller area. Same situation with the gas pipe, only it looks like the pipe was not broken all the way off:
HVAC unit broken gas pipe
The other two units are shut off while the gas pipes are dug out of the snow pack and checked for damage. At some point, they will be turned back on so that the heat can be restored to the second floor sales bullpen. Meanwhile, the sales people; they are complaining.
We threw a tarp over the unit with the cover ripped off because more snow is on the way:
Carrier HVAC unit tarped
I have been reading the comments regarding the FCC’s NPRM (13-249). Clearly, many people are interested in keeping the AM broadcasting band both active and relevant. Some of these suggestions have merit, but are unlikely to be adopted by the FCC. Others are viable and could alleviate at least a few of the technical shortcomings of the AM band. The rest fall along expected positions. Here is a brief rundown:
- Clear Channel, iBiquity: Allow stations to transmit in all digital mode. Likelihood: Possible. The hybrid version of AM HD Radio has been a failure on several fronts; added interference to adjacent channels, self interference, poor adoption, wonky CODECs, etc. However, letting stations choose to broadcast in all digital AM HD Radio may decide the issue once and for all. As long as the all digital carriers fall within the current analog channels, this would be fine. Actually, I would add that station transmitting in all digital be allowed to choose DRM as well as HD Radio
- REC Networks, MMTC: Move AM stations to former TV channels 5 and 6. Likelihood: Unlikely. It would be a neat solution, however, there are currently many full and low power TV stations still using those frequencies.
- Clear Channel, SBE, MMTC, Crawford, et al: Allow AM stations a special translator filing window. Likelihood: Almost assured. This has been broached by the FCC itself. I would add that Class D and Class C stations be given priority.
- SBE, du trial, Lundin and Rackely, MMTC et. al: Remove the “ratchet rule,” reduce antenna efficiency requirements and city of license contour requirements. Likelihood: probable. Over the years, the FCC’s rules and regulations designed to help AM broadcasting’s technical product have done the opposite in many cases. This is especially true of the “ratchet rule.”
- SBE, du Trial, Lundin and Rackely, MMTC: MDCL (Modulation Depended Carrier Level) Likelihood: Possible. MDCL does not do much to improve AM signal quality, but it can save the station owner some money on the electricity bill.
- Alabama Broadcaster’s Association, et al: Better FCC enforcement. Likelihood: Not very. This is another area were interference and AM noise problems can be fixed. Given Ajit Pai’s desire for “non-regulatory” relief, stepped up enforcement seems to be a non-starter.
- Hatfield and Dawson: Eliminate substandard AM stations. Likelihood: Not very. Getting rid of substandard stations and let the remaining AM stations enjoy a little breathing room is actually a big step in the right direction. H&D notes that the FCC should petition congress for tax relief for those stations that choose to surrender their licenses. Unfortunately, it does not appear likely that the FCC, congress and the current station owners would go for it.
- du Treil, Lundin and Rackely: Do away with skywave protection for class A stations Likelihood: Possible. The argument goes; skywave listening represents a very small number of mostly hobbyists (AM DXers) as other, better methods for program distribution exist for serious listeners. Sad but true.
- du Treil, Lundin and Rackely: No more new AM stations. Likelihood: Possible. There is a cogent argument to be made regarding the overcrowding of the AM band. Stopping any further crowding is a good idea.
- SBE, Cohen, Dippell and Everist, et al: Tighten regulations on electrical noise emitters. Likelihood: Unlikely. The FCC does not have the mettle to tighten regulations against powerful manufacturing and technology lobbies.
- iBiquity: Do not let anything get in the way of the HD Radio rollout. Likelihood: Is it possible to get in the way of something that is standing still?
Talking amongst engineers and AM broadcasters, many of these ideas have merit. The real question is, will any of this bring more listeners?
Hockey is about the only sport I care about these days. The Olympic hockey rivalry between US and Russia has been epic ever since the Lake Placid games in 1980. Why then, does NBC not broadcast the game live? In order to see the game live, one has to subscribe to NBCsn, which is in the premium tier on my cable system. No, they would rather force people to pay lots of money because they can. Such if life in the land of Monopoly.
Well, for every problem, there is a solution. Mine involved a VPN connection to somebody else’s network. I watched the game, but the commentary was in Russian. I didn’t understand most of it, however, as to the results of the game; I got the general feeling that the Russians were not amused:
Not time (for/to) smile
It seems the referees made a few controversial calls, including denying a Russian goal because the US net was out of place. I wonder how that will be mentioned on the repackaged replay.
There were other streaming options as well, one just needs to hunt around to find things.
In the information age, it seems the establishment’s control of the narrative is slipping away. I view this as a positive development.
I was pleasantly surprised to learn that after a two month sabbatical, Radiodiscussions.com has returned with an updated look and all of it’s archived posts intact.
Radiodiscussions.com screen shot
I am pleased that the current owners had a change of heart. Radiodiscussions.com was not perfect, however, it was a good place to gain insight, take part in conversations, read up on rumours and innuendo, follow the flame wars on various threads, etc. In other words, observe radio people in their natural habitat.
We have been doing work at a particular radio station for a few years now. Every time I go there, I look at this… thing:
Burk DOS Autopilot/CDL running on Windows 98
It is a very old PC running Windows 98 and Burk Autopilot/CDL 4.6 for DOS. The auto pilot program is running from a windows DOS prompt and seems to be working okay; my concern is about the age of the hardware and the potential for failure. The Autopilot is what controls the AM station’s power levels, which vary from 1,000 watts daytime, to 4 watts night time. We have all read about AM stations fined by the FCC for running daytime power levels at night. Failure of the ancient autopilot computer could lead to exactly this scenario.
I attempted to purchase the newer, Windows XP version of Autopilot, only to be told “that item is not in this year’s budget.” Apparently, it was not in the budget for following year, or the one after that. Thus, when the hard drive on the old Windoze 98 machine began making a terrible grinding noise, I knew the end was near. I made an attempt to run the Autopilot from a Windows XP DOS prompt, at which time I was informed: “The program cannot start or run due to incompatibility with 64 bit versions of windows…” GAK! I kind of knew this already.
I began day dreaming about running a DOS virtual machine inside of a Ubuntu or Lubuntu operating system. Then I found a DOS emulator program for Linux called “DOSemu” which looked like exactly what the doctor ordered. Using the carcases of several old HP desktop computers, I came up with one working PC that had two organic serial ports. This is actually not a bad unit, as it has a 1.6 GHz dual core processor and 2 GB RAM. On this machine, I loaded the 32 bit version of Ubuntu 12.04 desktop. Naturally, the original Autopilot/CDL 4.6 disks were nowhere to be found so I had to copy the directory off of the old computer. It was also understood that this project was simply going to suck. Therefore, the superannuated Windoze 98 machine had no network interface nor any USB ports. My only option was to copy the files unto a 3 1/2 inch floppy disk. Fortunately, I have a USB 3 1/2 floppy drive, which I was able to use to copy the files onto the new computer into the /home/ARC16 directory.
Downloading and setting up Dosemu was fairly straight forward. There were a few configuration steps that needed to be completed before the Autopilot software would work and communicate with the ARC-16 remote control:
- In the DOSemu configuration file, the hardware serial port needs to be configure to work with the DOS emulator. This is located at /etc/dosemu/doseum.conf. The default conf file has all of the serial ports commented out. Remove the comment and change the serial port source: $_com1 = “/dev/ttyS0″ or $_com2 = “/dev/ttyS1″ The serial ports available can be determined by the following terminal command: dmesg | grep tty The output should look something like this:
paul@engineeringIII:~$ dmesg | grep tty
[ 0.000000] console [tty0] enabled
[ 37.531286] serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
[ 37.532138] 0000:04:00.3: ttyS1 at I/O 0×1020 (irq = 3) is a 16550A
[16206.667112] usb 2-1.3: pl2303 converter now attached to ttyUSB0
For USB to serial port converters, the serial port source may look something like this: $_com1 = “/dev/ttyUSB0″
- The DOS emulator time can be synced to Linux time by: $_timemode = “linux” This is great because Linux can be synced to a NTP source, meaning Autopilot time will always be correct.
- The logged on user that will be running the DOS emulator needs to be added to the “dialout” group. This can be done by sudo adduser [user name] dialout. This will allow the Autopilot software access to the comm port.
- The DOS autoexec.bat file should be edited so that Burk autopilot loads automatically when DOSemu is started. DOSemu automatically assigns the D drive to the Linux home directory. Thus, simply adding:
to the end of the autoexec.bat file will start the ARC16 program automatically when the DOSemu program is started.
- DOSemu can then be added to the Ubuntu desktop startup.
DOS autopilot running on Linux machine
Burk Autopilot/CDL (DOS version) running on a Linux (Ubuntu 12.04.4) machine. The stupid thing will probably run forever now.
This computer is also used to program the satellite receivers, which are located at the transmitter site. Thus, there are several manuals and program clocks stored in the documents folder. I also installed the x11VNC server program, so that the computer desktop can be logged into remotely from the studio over the LAN link.
I noticed that the DOSemu program hits the processor fairly hard, with one core running about 45% most of the time. That should be fine, as this machine is used very infrequently for other tasks.
We removed this old Harris BC5HA transmitter recently:
Harris BC5HA, WROW Albany, NY
It was installed new in 1974, when the station moved to this site from another one a few miles up the road. It functioned as a main transmitter until the BE AM5E was installed in late 2001. The BE transmitter, other than a power supply issue, has been a solid, reliable unit. Truth be told, the last time the BC5HA ran was in 2006. After that, the unit refused to run, a bad modulation transformer was suspected. It was deemed not worth it to repair, thus, out the door it goes. We ended up giving it to a local contractor who scrapped the metal in lieu of payment for his labor. The only thing he could not take was the aforementioned modulation transformer, which is full of PCB’s. That will have to be hauled away by a licensed disposal company.
Broadcast Electronics AM5E, WROW Albany, NY
We may be getting a second hand Nautel transmitter from another station as a backup transmitter. If that comes to fruition, then a couple of racks can be added to the end of the Phasor/transmitter/transmitter row and the wiring for the remote control and STL can be simplified and neatened up.
I found this old ATT promotional video from 1967. It mainly concerns the PSTN wired network reliability.
It’s a mildly hoaky propaganda piece, but we often forget how our modern communications infrastructure is very young. If ATT seems proud of their system, they had a right to be. Prior to electronic communications, you wrote a letter and hoped that it arrived.
There is also this video: What is the Bell System.
If you have the time, there are many interesting archive videos in the ATT Tech Channel. Be careful, one can spend a lot of time watching these videos!