I have added a link to Free Radio Berkeley‘s website on the side bar. Their website contains a great deal of information about low power broadcasting. Free Radio Berkeley started out as a pirate (unlicensed) FM station. Like many unlicensed stations the Federal Communications Commission attempted to shut them down.

However, instead of playing dead, they fought the FCC in court on first amendment grounds and so far have met with legal success forcing the FCC to recognize and legitimate low power broadcasters.

Their website contains information about the history of Free Radio Berkeley, legal information, technical information regarding how to build radio and television transmitters, and pointers to other groups active in the field.

The mass communications media of this country have fallen into the hands of a very few large corporate interest. It is extremely important that the public have access to broadcast media and that’s what makes this micro-broadcasting movement so very important.

Radio used to refer to signals broadcast through free space using electromagnetic radiation in the spectrum that we refer to as radio waves, consisting of everything from very long wave (high audio frequencies) which are used communicate with submarines under water to millimeter wavelengths just now starting to be used for short distance high speed data transmission.

In broad terms radio can transmit audio, video, data, facsimile, remote instrument data, and more. IN more common terms people are used to thinking of radio as bringing voice and music into their homes without wires.

Radio in the past has been a broadcast medium. That means that a signal is sent out that will be broadly received, received by many. It was such an expensive medium that a large audience was necessary to justify the expense.

In modern times it is now possible to originate a signal on the Internet that a number of people can listen to simultaneously from anywhere in the world that has internet connectivity. Because it is much less expensive to broadcast over the internet (netcast) verses broadcasting over the air, it makes it practical to target programming to much smaller audiences and thus many program subjects that would not have been able to garner a large enough audience to be commercially viable in the past, can exist on the internet.

For those of you that have an interest in the paranormal, one source of broadcasts on various paranormal subjects ranging from spiritual to UFOs to cryptozoology, is Paranormal Radio at http://www.paranormalradio.net/. You will need Quicktime to listen.

On Paranormal Radio you can listen to live broadcasts (there is a schedule at the website) or listen to various programs that they have archived.

If you know of other interesting radio on or off the net, write me at nanook@eskimo.com, put “RADIO” in the subject so I’ll spot it amongst the spam, and I’ll get it up here for everyone.

(Updated 7/11/2014): Today, 7-1/2 years later I finally learned that this was in fact a hoax, that Larry is still alive.  This was made known to me by another fellow KNHCer that indicated to me that he preferred not to have his name published. At the time I made every attempt to contact Larry but was unsuccessful.  I am happy to hear the same of the Tumwater radio station was just a retirement.  It’s still difficult for me to fathom that someone would want to put forth such a hoax and that more than seven years went by before someone contacted me to let me know otherwise.  There are some cruel bastards in this world.

(Updated 3/22/2007): I based the following post from a communications I received from someone who claimed to be from KNHC, unfortunately I did not save their information, frankly I was in a bit of a state of shock at the time.

I have not been able to confirm this death from any 3rd party, nor have I been able to determine if Larry is still alive. If this was a hoax on someone’s part it is a terrible cruel hoax. If anybody knows the status with certainty, please contact me.

I learned over the weekend that Larry Adams passed away.

Larry Adams was the original founder of KNHC 89.5 FM radio at Nathan Hale high school. He was one of two instructors of the radio and electronics class and he is a man who has influenced my life greatly.

I’ll admit that I didn’t like him at first, he seemed terribly serious and stern. Only towards the end of my time at Nathan Hale did I come to realize what he had done for me and so many others.

He is a very good man and the world will miss him.

Digital Radio Mondaile is a new technology for broadcasting on medium wave (AM broadcast band) and short wave frequencies that looks interesting. It uses a form of modulation called Coded Orthogonal Frequency Division Multiplex which is claimed to be resilient to common forms of interference.

Click on the link above to read the details. The description of this modulation scheme sounds to me very much like the modulation scheme used by the old Telebit Worldblazer and Trailblazer modems except at RF rather than audio frequencies.

I wonder how this will work in practice with distant stations at night where you usually have several stations coming in at once and interfering with each other.

I’m not excited about the encoding scheme used for the audio, AAC compression followed by Spectral Band Replication.

I know a lot of people have good things to say about AAC, but I’ve compared to AAC to OGG and MP3, and of the three usually OGG is better even at substantially lower bit rates. There are rare instances where AAC does a better job, particularly things like picked acoustic guitar. For some reason OGG seems to suppress the fundamental relative to the harmonics leaving the instrument sounding hollow. But this only happens if there aren’t other simultaneous sounds. The beginning of the Beatles Here Comes the Sun is a good example of something OGG chokes on. On the whole though OGG does better than the other two even at much lower data rates.

Then the other part of that is pretty ugly too. Spectral Band Replication, that’s a buzz word for not transmitting the high frequencies and then trying to guess where they should have existed based upon the lower frequencies present. The idea is that most higher frequencies are harmonically related.

I have an audio processing program that is useful for trying to make really bad or mangled recordings more tolerable, things like scratch removal, hiss removal, and subtractive noise removal. It also has this spectral band replication capability; and if you take a really old recording where everything over 7 Khz or so is rolled off, it does make it sound “better”, but it doesn’t necessarily sound like it is supposed to.

In real music, while it is true that most high frequencies are harmonics of lower frequencies in the source, the relative intensity of the harmonics is not fixed, nor is the envelope of the harmonics necessarily the same (and more often than not it is not) as the fundamentals.

Think of a gong. You first hear the lower frequency fundamental tones prominently. Harmonics are present but as time progresses the fundamentals fall off at a higher rate than the harmonics and they seem to peak a second or two after the gong is struck. This is the sort of thing that spectral band replication is not good with.

I would have rather seen them go with OGG, and if they had they might have been able to transmit the high frequencies and still stay within the target bit rate.

Still, if it resurrects AM and makes it usable for the transmission of music again, then that’s a positive thing.

Dan Thorn brought to my attention this article by Tim Shook regarding KNHC which details the equipment that was in use at the time and some of the interesting problems we had with it. There is also a black and white photograph of Larry Adams and Gene Arnold.

Tim neglects to mention in his on-air position at the station. I’d be lying if I said I wasn’t a bit envious of his golden voice that resonates speakers with deep smooth bass.

Time mentions a range of about 20 miles when KNHC was running 1500 watts. Prior to running 1500 watts, KNHC operated with 320 watts, and at that power on one drive to Spokane, I listed to it all the way across the past, lost it when I went down into the Canyon at Vantage, but once up on the other side received it again and continued to receive it about half-way to Spokane and that was with a portable Sony Earth Orbiter radio sitting in the front seat of the car.

Over the years KNHC has received numerous power increased, at one point to 30,000 watts. Around 2001 they moved the transmitter operations to Cougar Mountain and are now broadcasting with an effective radiated power of 8500 watts from that location. Even though the power is lower, the increased elevation makes up for it resulting in fewer dead spots.

Another data point worth mentioning is that Seattle Public Schools is considering selling the station believing it will bring up to eight million dollars. It would be a tragic loss if it were sold because it has launched the careers of many students. The F.C.C. 1st class license I received while attending Nathan Hale was the ticket to the first job I held for 17 years. The value of KNHC to the students is incalculable.

In all probability, if they did sell, they will not be able to get anything near the projected their estimated 8.5 million dollar price because the operating frequency of 89.5 m Hz is within the educational band of 88-92 MHz and I do not believe there are available frequencies in the commercial portion of the band.

This is a type of antenna known as a box loop that is very useful for AM broadcast DXing. It is a highly directional highly selective antenna. The directionality in particular has a very sharp strong deep null that is useful for rejecting interfering stations, and the selectivity minimizes receiver overload by strong local stations on other frequencies.

The antenna I built used 1×6 wood planks about 30 inches long, notched half-way through in the center with a notch as wide as the plank was thick to allow them to be fitted together in this “X” pattern. The rigidity of this structure is very important. Use a hard wood like walnut or oak, not a soft wood like pine. Make the notches fit is very tight and then glue them together with wood glue.

The variable capacitor mounted near the “X” is a type used in old tube radios, something on the order of 50pf-365pf. With these dimensions eight turns of #16 copper enameled wire was just right to allow the antenna to cover 530-1600 kHz. If you build it larger then fewer turns may be required, and conversely if you make it smaller, more turns will be required.

The wire used is a trade-off between “Q” (how selective the antenna is) and ability to actually wind the wire tight on the form. For example, #12 wire would result in an even more selective antenna but you’d break the form trying to wind it tight enough to be rigid. In my experience #16 is a good compromise.

The type used in most transistor radios with the plastic spacers provide neither adequate range nor the ability to easily fine tune, The best type is the type out of the old radios that has a built in planetary drive so that it takes three or four revolutions to open or close the capacitor completely.

The turns should be spaced about 1/2 inch apart. Make notches in the end of the planks to accommodate each turn so that the spacing remains fixed.

Connect one end of the loop to the “ground” (chassis) side of the capacitor. Connect the other side of the loop to the terminal on the capacitor that is the non-ground side.

On the first loop from the ground end of the winding, make a tap consisting of a wire leading back to the center of the “X”. Attach the ground shield of your coax to the ground side of the capacitor and the “tap” at the first loop to the center of the coax.

The idea of having the coax feed off a tap of just one turn is that it allows very little loading of the antenna and thus the “Q” remains high providing good selectivity and sensitivity at the resonant frequency.

A large wooden or plastic (something non-conductive) table is a good place to work with this antenna and your receiver. Connect the other end of the coax to your receivers antenna and ground connector. Having a physical ground on the receiver will improve the systems overall stability by making the receiver end of the arrangement insensitive to body capacitance and other stray effects.

Set your receiver to a weak station around the center of the dial and tune the variable capacitor on the antenna. You will encounter a point where the signal is enormously stronger and if you build the antenna to the specifications given here that point will be very sharp. The selectivity, if built as described here, will be sufficient that it will actually attenuate the sidebands of the station you are tuned to. This can be helpful in situations where you have adjacent channel interference and your receiver is not sufficiently selective.

As described, this should cover pretty much the entirety of the old AM band, it may not cover much above 1600 kHz because the old style capacitors had too great a minimum capacitance.

Most of the old broadcast radio capacitors had at least two sections, one that tuned the local oscillator and one that tuned the input to the mixer. On better receivers with one or more RF stages, there would be additional sections for each RF amplifier stage.

The section for the oscillator is smaller than the others. One thing you might try to extend the antenna to cover the 1600 – 1710 kHz section is to take one turn off the antenna which will raise the overall frequency range of the antenna, and then add a switch to cut in another capacitor section to cover the lower range.

By adding more turns and additional capacitance, this type of antenna can also be made to work efficiently down into the long wave portion of the radio spectrum. This is a good option for a long-wave antenna when you don’t have room for larger alternatives.

Back when I was using this antenna, I was in Seattle WA, and at the time there was nothing on either 1200 kHz or 1210 kHz locally. At night, the only station on 1200 kHz was WOAI from San Antonio TX. With just the built in ferrite rod antenna I would get maybe 1-2 on my S-meter, but with this antenna I could peg the S-meter with the same signal.

Being the somewhat insane type that I am I also tried a modification of this basic design where I took another tap at 1/2 turn from the ground end, and wired a one transistor amplifier as an oscillator using the ground, 1/2 turn tape, and 1 turn tap in a Hartley oscillator except the only capacitor was the variable across the entire coil. I put a potentiometer between the 1-turn tap and the base of the transistor to allow me to adjust the “gain” so that I could adjust it to be just on the verge of oscillation so instead of being an oscillator it became a regenerative amplifier.

I included a link to a site describing Hartley oscillators in case the reader is not familiar with them. The bottom turn of the coil with the half turn tap was used as the entire coil for the oscillator which wasn’t allowed to have quite enough gain to oscillate. I used a bipolar transistor with bias, but you might have better performance with an FET as shown on the site I linked to. Whichever method you use, you will want to insure that the transistor operates at very low power so that if it does break into an oscillation you do not damage your receivers front end.

This antenna didn’t need more gain, but the regenerative amplifier allowed me to narrow the bandwidth still more (to several hundred hertz if I got it right on the edge of oscillating) and I could adjust how narrow the bandwidth was by the adjusting the pot.

The reason I added this is that I was trying to receive some foreign stations that operated on frequencies other than the 10 kHz allotments used in the United States, things like 654 kHz, and the additional selectivity was desired. I was never successful though at receiving any of these, too much power line noise and other noise sources to receive very weak signals where I was.

Without the regenerative amplifier, I also tried using this antenna for transmission but because the impedance was so high across the full coil of antenna, the voltages across the capacitor exceeded the value required to arc it over at very low power levels so this is not useful for anything more than a few hundred milliwatts unless you got capacitors with a huge plate spacing.

Radio and television DXing has been a long time hobby of mine.

My first interest was DXing AM radio. Initially, the stations I received were not real technically challenging given that at the time clear channel allocations existed, so there were frequencies such as 1200 Khz where WOAI in San Antonio, TX, was the only station at night.

I received a Sony Earth Orbiter receiver as a gift from a close family friend and that receiver had greater sensitivity, selectivity, and an external antenna terminals.

At first I tried a long-wire antenna but found that the receiver severely overloaded resulting in spurious signals all over the band. Living in Seattle, WA, there was a plethora of high power (5-50 KW) AM stations nearby.

Then I learned of a type of antenna called a box-loop. I’ve given instructions on how to build one like I had built. I highly recommend this type of antenna, the performance exceeds that of just about everything else I tried. The selectivity of the antenna eliminated the problem of overload by strong local stations, and the directivity allowed another way to reject unwanted signals.

At the time the environment was just too noisy to receive the really weak signals of interest and my reception was limited to stations in the US, Canada, and Mexico.

Another area of interest for me is television DXing. At one time I had a reasonable setup consisting of a Wineguard deep fringe yagi antenna, Wineguard mast mounted pre-amp, and twinax (shielded twinlead) downlead.

A yagi antenna in which the elements come out 90 degrees from the mast, most modern TV antennas have gone to the log periodic design which has the elements swept back.

For DXing I prefer Yagi antennas to log periodic. I found the directivity of the yagi to be superior to log periodic.

One thing I have subsequently read that others have done, but I did not think of, is to orient the antenna so the elements are vertical rather than horizontal. Some VHF stations have gone to circular polarization because it provides rejection of reflections which causes ghosting if the receiver is equipped with a similar circular polarized antenna. But for those still using horizontal polarization, mounting a Yagi with the elements vertical provides rejection of ground based signals. This was frequently an issue for me as E-skip happens most frequently on channels 2 and 3 and we had a powerful local station on channel 4 that tended to bleed onto channel 3 and to a lesser degree 2.

Most of the E-skip I received came from the mid-west region, only rarely from the south. The local station was to the south, but I was near the top of a ridge, the station was on Queen Anne hill, and it was 100 Kw line of sight so even with the Antenna aimed away the signal was considerable and if I was trying to receive something from the south then it was really bad. Multi-hop E-skip when it occurs often results in a change to the polarization, so a vertical polarized antenna might be helpful both in rejection of local stations and double-hop E skip reception.

I found some interesting resources on the Internet.

• EMT, SETI, Radio Astronomy, DSP, and Amateur Radio
• Radio Line of Sight Plot Server
• Real Time Propagation Information
• A really cool TV DX site. This guy has taken it to the extreme.
• W9WI.com – TV technical information for DXers
• An interesting article on TV signal propagation.+
• An article on DX history mostly dealing with TV/FM.

I was curious what the longest DX record was in terms of distance covered verses power used, and I ran across this article, “Extraterrestrial DX“. This article was put out by the SETI league and details attempts to listen for Martian transmissions in 1924.

I have previously related to a limited degree my participation in and experience with pirate radio stations I and other friends operated during my junior high and high school years.

I also actually had some legal experiences. There are things both have in common and I’d like to relate some of those things and what it is about radio that I find so intriguing.

I obtained my First Class Radiotelephone Operators License in my junior year of high school. How I came to obtain it at that time, or at least what the big motivator was, is kind of funny. In retrospect, I owe a lot to the instructors in my radio class, both helped me in their own very different ways.

We had a radio station (KNHC) at my high school (Nathan Hale), and I was actually allowed to come over and attend radio and electronics classes there while I was still in junior high school. This was possible because my junior high school (Jane Addams) was directly across the street from the high school, so it was physically workable.

I graduated from Nathan Hale in 1977, and I am happy to say that KNHC is still on the air almost thirty years later, however, I am not sure where it’s future lies as I have learned that the Seattle School District plans to shut down Nathan Hale in the near future.

There were two instructors that taught the radio and electronics class at Nathan Hale, one of them was the station licensee. I owe a lot to both because they both helped me very much but in their own very different ways.

One of the instructors was Gene Arnold, formerly in the navy, a lot of his electronics background was acquired in the navy and so his teaching methods reflected that to some degree, for example, we learned the resistor color code which is:

black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, gray 8, white 9

A tool Mr. Arnold related to us to learn this color code was one used in the navy and one that probably would not have been approved by the school district but which was none the less effective was the line, “Bad boys rape our young girls but violet gives willingly.”

If you notice the first letter of each word in that sentence corresponds with the first letter of each color in the color code.

Mr. Arnold did not exemplify what I think of as military, he had a very kind gentle relaxed manner. He drove a blue 1955 T-bird that he had bought from the factory new and it was immaculate. He taught mostly through lecture and made the math and concepts involved very easy to understand.

Then there was Larry Adams, the licensee of the KNHC. The story as I heard it was that they had put together a small 1-watt or so AM transmitter at the school and operated it as a radio station. They were visited by the F.C.C. who encouraged him to pursue a legal station and thus KNHC FM came into existence, originally as a ten watt educational class FM station.

My impression of Larry Adams was that he was in many ways the complete opposite of Mr. Arnold, not at all relaxed, very wired and uptight. To be honest, at the time I thought he was a complete asshole, only after my junior year of high school did I realize what a genuinely caring person he was and how much he did for me without my realizing it.

And this brings me to the story. With Mr. Arnold, we students could get away with quite a lot without any serious repercussions. Larry, by contrast, was very much into safety, doing things the right way, and generally demanded responsible behavior. My behavior at that point in my life was anything but responsible so this did make for considerable friction between us (and many other students as well).

The school had work benches that were originally supplied with low voltage DC power via a large rectifier and battery bank network. Even though this power was fused, it was deemed unsafe because the huge fault current available had a strong potential for causing fires, etc, and so the fuses were all pulled on this power source and instead we had portable power supplies that we used.

We also got a lot of surplus junk there, including some telephone company cable which had a few thousand pair of about #24 gauge wire with a plastic insulation.

One day during lunch we were bored, so myself and a number of my friends took about three foot long pieces of this wire, wound little coils out of it, stuck it in the power plug in the benches, then stuck foil in the fuse holders to complete the circuit. This would have the effect of pretty much instantly vaporizing the wire and its insulation creating large quantities of smoke.

We all found this highly entertaining and so continued to do so until from the ceiling of the entire class room to about two feet down was solid smoke, you could not see the ceiling. There were no smoke alarms at that time.

Back at that time smoking was also popular, I didn’t smoke but most of my friends did, and it was not allowed inside the school, but it was allowed in smoking areas outside of the entrances. Many students however would not want to go outside so they would light up in the rest rooms or class rooms when no teachers were present.

Mr. Adams returned from lunch, walked into the class but did not look up at the ceiling, took a couple of sniffs of the air, and asked if someone had been smoking. Of coarse everyone denied it. Only then did he look up and realize the ceiling was not visible. At that point myself and a number of my friends were ejected from radio class, at the time we were told permanently, but we were let back in the following day.

At the time, I had only my Third Class Radiotelephone Operators License. This license gave sufficient privileges to act as an on-air personality, though I never did have a radio show there being more interested in the engineering aspects, but it did not allow actually doing engineering work. However, prior to this incident, Mr. Adams did allow me to work on equipment.

After the incident, he wouldn’t allow me to touch anything and would tell me I could not because I didn’t have my First Class Radiotelephone Operators license that was legally required to do so. Determined not to allow him to use that as an excuse to keep me away from things I picked up a copy of the First Class Radio Telephone license study manual, studied the material, and in a couple of months time went down to the F.C.C. office, took the test, and passed. Went straight from a third class to first class license bypassing the second class altogether (there was no requirement to get a second class license as an intermediary, it was just the normal path most people took).

I expected Mr. Adams would be irritated by my receiving my license, instead it was very well received, and it was only then that I realized he knew I needed some motivation and supplied it. He wasn’t being an asshole at all, he was motivating me to do what was in my best interest.

Obtaining the license though also represented a problem, it made the operation of a bootleg radio station much more dangerous for two reasons. First, I could no longer claim ignorance of the law since knowledge of the laws was a requirement for passing the test. Second, if I had been caught, there was a strong potential for my license to be revoked.

Never the less, I continued to operate my pirate station for about another year, I was just a lot more paranoid. My operation of the station as a pirate station did terminate shortly after this when my antenna broke and the transmitter final played frequency multiplier and caused interference with the 80 meter amateur radio band. This resulted in a letter from the F.C.C. field office chief engineer at the time, R.C. Dietch, informing me they had received complaints and to cease the cause of the interference immediately. Strangely, it said nothing of the illegal operation of a station without a license though there is absolutely no way they couldn’t have been aware of it. Not wanting to lose my license I stopped operating the station as a pirate station.

I did however experiment with carrier current radio, this is where an RF signal is injected in the power lines and radios plugged into the line or near it can pick up the signal. Normally, carrier current propagation does not extend past the first power transformer, however, City Light has a practice of wiring the secondaries of the transformers together allowing the signals to propagate a considerable distance.

Overall though we found this mode of operation to be unacceptable because it actually caused much more interference than open air radiation of the signal did. There were many non-linear devices on the power line such as light dimmers, off-the-line power supplies, etc, that would mix the RF signal with the 60 Hz AC power causing severe buzz in the signal at many locations. Also, these same non-linear devices would create harmonics of the fundamental frequency resulting in out of band interference.

Then I experimented with trying to get the absolute maximum range out of a part 15 legal transmitter. I did this by building a home brew transmitter with 100 mw input to the RF final stage, a very large modulation capability, and this fed into a 10 foot British joystick antenna, the transmitter being located immediately between the ground and the base of the antenna so that ground lead length did not detract from the maximum permissible antenna length. Because this type of antenna is resonant, it is much more efficient than a ten foot piece of wire would be. With this arrangement, my signal was actually receivable on a sensitive receiver up to about two miles away.

I was not satisfied with this range and so pretty much gave up at broadcasting my own signal at that point.

I did participate in a radio show at KCMU (the student station at the UW) prior to them changing formats, and then later at KBCS (the Bellevue Community College student station), which was also ended in part by a format stage but also by a wacko blind DJ there that told management that we were overmodulating the transmitter. KBCS at that point did not have limiters, the output of the board fed directly into the transmitter. There was a big red light on the board that came on if the modulation was over 100%. That and the VU meter were used to manually keep the modulation within limits. It was, however, impossible to predict spikes in music, etc, that would occasionally drive modulation over that value.

Anyway, both of these were a lot of fun. Both had a feeling of being very alive and organic. We made it a point to involve the audience heavily and this did seem to be popular with the audience but at times we’d go a bit over the edge and get management upset.

Later, a friend of mine who I shared those shows with, landed a job as general manager of a small AM station and hired me to do engineering and program director work, an odd combination. We put together a format that was very much like the “New Wave” stations that came later on FM, but with very heavy audience participation. When he was hired, the station was losing money, within two months we had turned it around and made it profitable, but in spite of now being able to make payments the bank foreclosed and the station was sold and our involvement in it ended.

Never the less, it was enough of a run to find that this very organic approach of heavily involving the audience and having a strong human element in the programming was very workable. Another element of the format is that we went to great lengths to never have dead air, always have music, and to have a very high audio density. If it could be made to work on a 500 watt AM station, it could have worked much better on a larger station. Unfortunately, we never got the opportunity to do that.

This is something I would like to do. It’s my feeling that this would work even better today because so many stations have gone to automation or corporate faceless networks that such a station would really stand out and be welcomed by the audience. Back then we had to do things very much by hand, interviews were edited by cutting and splicing tape, etc. Todays technology would make this much easier.

I would like to relate a couple of subjective experiences. Having had experience with both AM and FM, AM at that last station and my pirate stations, FM at KNHC, KCMU, and KBCS, I have to say there is something different about AM. I can’t say exactly what it is but even though the audio quality is inferior to FM, it seems more alive.

I think in part this might be due to the fact that AM can propagate great distances at night, and that the signal gradually got weaker but seemed to keep going where FM could never propagate great distances and it was very much different in terms of signal propagation. FM you could get a good strong signal, move ten feet and get nothing.

But there was also something different about how FM affected music in most cases. FM signals sounded very “flat” to me, even though the frequency response and signal to noise ratio was much better than AM, music on FM just sounded unnatural on most commercial stations.

One thing I came to learn later on is that this did not seem to be a problem with monophonic FM transmission. I wonder if it might have had something to do with the sharp filters required to rapidly roll off frequencies above 15 Khz on stereo transmissions. Whatever it was, music to me never sounded right on FM with the exception of those stations that were not transmitting in stereo.

I suspect though that the explanation might not be as simple as that. This is a wild thought but I’ve had the feeling that AM signals are in some sense interdimensional and that the signal, once radiated, continues on forever. Technically, both AM and FM signals are absorbed by various mechanisms and limited in range, but AM feels to me like it actually is not, it just goes on and on and becomes ever more nebulous.

If I had the opportunity to do it again there is another element that I’d like to add and that is live music and events. Financially, we did not have the opportunity to do that. Back then, remote broadcasts were difficult and expensive because you’d have to have special broadcast lines installed, or an expensive microwave link.

With the advent of digital audio it is now possible to transmit broadcast quality audio over an ISDN line or moderate speed digital link and with the Internet being so ubiquitous the connectivity is easy to obtain cheaply.

I hope you’ll forgive my ramblings, thinking of long delay echo got me to thinking about my pirate experience and then by extension everything else related to radio. I miss my involvement in radio, it was a lot of fun.

I ran across this research article that describes the possibility of plasma waves as being the source of long delayed echoes. This is a PDF file so you will need a display postscript reader such as Adobe Acrobat to read it.

In this article they actually calculate the delay and it agrees well with observed delay times. They also show how microwave frequency transmissions could have delays generated in this manner, however, I am somewhat skeptical of the latter explanation.

The way that frequencies higher than about 28 Mhz can generate long delayed echoes via plasma waves is via non-linear mixing (heterodyning) in the ionosphere.

The idea goes something like this, an amateur radio operator is working moon bounce on 1296 Mhz. At the same time, another signal the operator is completely unaware of has a frequency of 1303 Mhz. They mix in the ionosphere in a non-linear manner producing a difference frequency of 7 Mhz and this 7 Mhz signal can be propagated via a plasma wave and later mix with a 1303 Mhz signal again and reconstitute the original 1296 Mhz signal.

Signals propagate in plasma waves at approximately 1/100th the speed of light so an around the world propagation of a plasma wave would take around 13 seconds. The actual velocity of plasma waves depends on variable factors though, how dense the ionosphere is, the percentage of atoms that are ionized, etc, so for this figure to vary considerably is not unreasonable.

On the surface this sounds like a good potential explanation. However, here is the problem. Most of these long delayed echoes are recognized audibly by human operators. Any modulation of the mixing signal, in this case the 1303 Mhz signal, would be reflected in the difference signal generated and propagated via plasma wave around the earth, and then when that signal is reconstituted by again mixing with the 1303 Mhz signal, those modulation products would be present in the 1296 Mhz signal.

None of the reports of long delayed echoes that I have run across involve any additional modulation of the original signal. I’m not aware of any good reason an unmodulated carrier would be transmitted continuously at 1303 Mhz, but if this mechanism were responsible for long delayed echoes of frequencies higher than 28 Mhz, at least some of them should have resulted from modulated signals and thus carry the modulation of the mixing signal.

Another aspect that I find troubling is that these long delayed echoes often are offset from the original transmission frequencies by a small amount and this theory does not explain that offset. The resulting signals often are at a slightly lower frequency than the original suggesting a reflecting surface or mechanism moving away from the source of transmission and reception.

One aspect that does suggest that long delayed echoes have something to do with the earth’s ionosphere or magnetic field, or possibly the interaction of the earth’s magnetic field with the solar wind is that some observations suggest a correlation with auroral activity.