TuneIn Radio

I posted previously about how to listen to radio station streams on an Android phone. In the time between then and now, somebody has come up with a much better way to do it.  TuneIn Radio is both a website for streaming and a mobile application for Android and iPhone users alike.

I have found that every local radio station that has a web stream is listed.  The major overseas broadcasters like the BBC, CBC, Radio Netherlands, and so on as well as all of the non-government US owned shortwave stations are listed.  As their website states:

With over 30,000 FM and AM radio stations from across the globe, TuneIn Radio makes radio local, no matter how far from home you might be.

Far easier than what I posted before. Further, this is exactly the type of service that terrestrial broadcasters needed the most; a concise consolidated listing broken down by genre and locality, to compete with Pandora, Slacker, Last.fm,  et. al.

In order to download TuneIn Radio, point your mobile web browser to http://tunein.com and it will automatically direct you to the proper download source.  Or one could search through the Apple store or Android Market to find the app.

Radiation levels: Compare and Contrast

Not related to radio engineering, however, I’ve been doing daily radiation measurements at my house (upstate NY) since the Fukushima disaster. A few bits of house keeping information first: This is a CD V-700 radiation meter, which is a model 6 manufactured by Anton. It was last calibrated in 1986. When I place the Geiger tube over the operational check source, it goes up to about 2 mr/hr as described in the owner’s manual. It may not be completely accurate, but it is accurate enough for this experiment.

This video was taken on March 17, 2011. It sets a good reference for normal background radiation levels:

This video was taken on March 27, 2011. It shows a significant increase in background radiation. Further, much of this appears to be gamma radiation, as the gamma shield is closed during this video:

Both of these videos were taken on the most sensitive (x1) setting. It shows that the radiation level is about 8 to 10 times above normal. It is a cause for concern, but not alarm. Not yet. If it continues at this level for several days or weeks, then the overall radiation exposure will begin to accumulate. Right now, it is about the same as taking two NY to Los Angles flights per day, according to this chart (0.35 mr/hr = 3.5 uSv per hour x 24 hours = 84 uSv per day):

Radiation chart
Radiation Chart

As of March 28, 2011, the wind has shifted more to the south west and the levels have dropped somewhat. From our beloved press corps, there have been a few reports here or there on this, most with the standard “this is nothing to worry about” disclaimer. I have also noticed a series of stories and reports that radiation is not all that bad, don’t worry about it, living next to a nuclear plant is fun(!), and we don’t know as much about radiation as we thought we did. I don’t know about all that, I’d rather base my opinion on the scientific body of evidence gathered over the last one hundred years or so. The conclusion of that information is that radiation is bad for human physiology and exposure should be limited.

There is also a crowd source website called “Radiation network,” which is showing all the levels across the US are normal. This makes me wonder about their instruments and or candor, you can draw your own conclusions.

Unbalanced to Balanced Audio

There is a large number of things that amazes me on an almost daily basis.  To wit: a local mom and pop radio station called me because they couldn’t get their computer program to work right.  I decided that I’d give them an hour or two, in exchange for my hourly labor rate, and see if I could fix their problem.  The issue at hand was loud hum and other noise on the input source.  I knew before I even looked at it that the likely culprit was a ground loop.

It was worse than I imagined, with several unbalanced and balanced feeds improperly interconnected, line level audio going to a microphone level input and so forth.  I explained to the guy about putting line level into a mic level input, something akin to plugging a 120 volt appliance into a 240 volt outlet.  Improperly terminated balanced audio nullifies all of the common mode noise rejection characteristics of the circuit.

In any case, there are several ways to go from balanced to unbalanced without too much difficulty.  The first way is to wire the shield and Lo together on the unbalanced connector.  This works well with older, transformer input/output gear, so long as the unbalanced cables are kept relatively short.

simple balanced to unbalanced audio connection
simple balanced to unbalanced audio connection

Most modern professional audio equipment has active balanced input/output interfaces, in which case the above circuit will unbalance the audio and decrease the CMRR (Common Mode Rejection Ratio), increasing the chance of noise, buzz and so on getting into the audio. In this case the CMRR is about 30 dB at 60 Hz.  Also, newer equipment with active balanced input/output, particularly some brands of sound cards will not like to have the Lo side grounded. In a few instances, this can actually damage the equipment.

Of course, one can go out and buy an Henry Match Box or something similar and be done with it.  I have found, however, the active components in such devices can sometimes fail, creating hum, distortion, buzz or no audio at all.  Well designed and manufactured passive components (transformers and resistors) will provide excellent performance with little chance of failure.  There several methods of using transformers to go from balanced to unbalanced or vice versa.

Balanced to unbalanced audio using 1:1 transformer
Balanced to unbalanced audio using 1:1 transformer

Using a 600:600 ohm transformer is the most common.  Unbalanced audio impedance of consumer grade electronics can vary anywhere from 270 to 470 ohms or more.  The 10,000 ohm resistor provides constant loading regardless of what the unbalanced impedance.   In this configuration, CMMR (Common-Mode Rejection Ratio) will be 55 dB at 60 Hz, but gradually decreases to about 30 dB for frequencies above 1 KHz.

Balanced to unbalanced audio using a 4:1 transformer
Balanced to unbalanced audio using a 4:1 transformer

A 600:10,000 ohm transformer will give better performance, as the CMMR will be 120 dB at 60 Hz and 80 dB at 3 KHz, remaining high across the entire audio bandwidth.   The line balancing will be far better into the high impedance load.  This circuit will have about 12dB attenuation, so plan accordingly.

For best results, use high quality transformers like Jensen, UTC, or even WE 111C (although they are huge) can be used.  I have found several places where these transformers can be “scrounged,” DATS cards on the old 7300 series Scientific Atlanta satellite receivers, old modules from PRE consoles, etc.  A simple audio “balun” can be constructed for little cost or effort and sound a whole lot better than doing it the wrong way.

A brief list, there are other types/manufactures that will work also:

Ratio Jensen Hammond UTC
1:1 (600:600) JT11E series 804, 560G A20, A21, A43
4:1 (10K:600) JT10K series 560N A35

Keep all unbalanced cable runs as short as possible.  In stereo circuits, phasing is critically important, so pay attention to how the transformer windings are connected.