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Page history last edited by PBworks 16 years, 3 months ago

Low Powered AM Broadcasting

This site is going to take on a new direction. More towards looking at the needs of those who use Part 15.219 for unlicensed 100 milliwatt community broadcasting. As well as Part 15.221 Carrier Current methods of broadcasting.

As we look at the ideas of LPAM, we will notice that, at this time in the interest groups pondering the ideas for a new low powered AM broadcasting service. There are yet very many unsettled individuals in the cause. Who though interested and many are well meaning. They can not contribute to the work required to aid the cause. Being there are many technical issues to be worked out. And, there are many fine details of the technical nature to be recalled and researched up by the electronic techs and engineers. And well, they fight and disagree and fail to aid the other by giving the other a useful reference or educational lecture on the needed points for compiling what we need for the technical applications.

"Ask a simple but good question, you will not get an answer in forums and user groups. Instead post an errant equation. You will get all the answers you need as everyone corrects you!"

And another issue at hand is the lack of understanding by some of the advocates that the service needs to have certain electronic specifications defined. And the users of a new LPAM Service on Medium Wave need to understand the criticalle aspects of Medium Wave antennas and the ground losses that short height antennas suffer. Since the antenna will be of short height.

Well since the LPAM advocates lack these views, and do not fathom the issues. It will be a long while yet before they settle down. And it will be a long while before they get focused upon what they need to define some useful rules for rule making.

To get going on the technical issues, it is productive to look at the issues of antennas used by Part 15.219 unlicensed stations. And learn from those issue about antenna feed point resistances and losses due to ground resistances. And if you need help from an engineer, just post an errant postulation and you might get back some details that answer your questions. Or else comments that make points you can research. Some seem not to want to be helpful unless you give them an opportunity to look good and show off their brilliance.

Here at this site we will deal with the issues of antennas for use with some suggested new Part 15.219(b) rules we are working on. And try to help out Part 15 stations, while the LPAM groups and forums take their time and maybe grow up a little. Learn to become more useful and helpful with one another.

To help right off, this site was found where you can download the an entire Antenna Handbook: Click here

Let's Be Realistic:

Folk have made suggestions such as that the service should be designed for wide band AM for high fidelity? Yea, ok that will fly....when you own the airwaves and the FCC. Till then be realistic. That idea wouldn't work since when you wide band the radio receiver to hear such a station the noise increases with the increased frequency. And you would have to get the receiver manufacturers to conform. And the radio station is now operating in extended side bands and creating adjacent channel bleed over. So this is a technical in~feasibility.

The owner of this site owns a software defined radio receiver with a band spectrum analyzer. If the bandpass audio filter is widened past +/- 5 kHz (10 kHz wide channel) the fidelity suffers for the increase in high frequency noise.

Another group of suggestions made, came in the form of a Rule Making Petition. It might have came to be as it is by being compiled in a democratic way? Who knows. However it created several different power class station levels from 1 watt up to 250 watts. And attempted to divide the 1600 to 1700 kHz spectrum up in 5 kHz wide channels instead of 10 kHz wide. Again all of this is infeasible.

As seen in the previous spectrum graphic the typical AM channel is 10 kHz wide. And so a 5 kHz wide channel would destroy the spectrum fidelity if the audio is limited to a band pass of +/- 2.5 kHz. Or if the bandpass was left at +/- 5 kHz, the station would be operating in the adjacent 5 kHz channel when you make all the channels 5 kHz wide.

audio modulation bandwidth and curve

Here we see the same receiver's bandwidth filter set for a bandpass of 5kHz which is the audio modulation bandwidth. Notice how that the modulation level drops off at 5 kHz. This is a deliberate filtering curve of the transmitter to keep the signal down a few dBs on the 5kHz edges and out of the adjacent channels. So think first before you make a suggestion in a democratic process of making comments.

In addition, although the International convention calls for shortwave radio spacing of 5 kHz, which is not something the FCC here in the USA practices in assigning shortwave frequencies to USA stations. Anyways, as you can see above, the WWCR station frequency of 5890 kHz for example also has the channel width of +/- 5 kHz. Hence no matter what, there is still a requirement for channels spacings of 10kHz wide. This just happens to be the technology and you have to go with it. If the technical suggestion does not look good on the spectrum analyzer, or on the oscilloscope, or is known through experience to not work well on the band, on the airwaves. Well such suggestions are immediately tossed out.

In the above graph, you can see that WWCR's signal is strong and that the channel edges have high amplitude near the +/- 5 kHz channel limits. Knowing then that stations can achieve such signal strengths under certain conditions, it is not advised to make changes in channel spacings. Beside on the Medium Wave Band, modern digital receivers for Medium Wave use, mostly tune in 10 kHz steps and could not tune in between the channels. So it is good to go with convention rather than not; and make waves out of everything. To create something new in radio we want to minimize the impact the service has upon other services. And we all have to share the bandwidth also. So bandwidth conservation is of importance. And defining a useful and reasonable power level that economizes the bandwidth is key also.

Given the right power level there would be plenty enough bandwidth for all the stations possible. And with little interference to each other. And so the band would not have to be chopped up. Hence there are simple ways to resolve channel sharing issues as well as potential interference issues. However we are not seeing the camp of technically enlightened folk speak up much here. We can not get off without experienced views. You can not envision a radio service without an engineering view. And engineers have to also engineer up the economy of the product. It is not just technical applications only. It has to include the bottom line which is the required service revenue generation.

Democracy should play a part in the design of such a service. Yet when the ideas offered go against acceptable practices of the FCC and the regulations that stations have to follow in the various broadcast bands. Well those things do not fly.

When the suggestions offered for a radio service go against the current type acceptance standards, no electronics tech or engineer will go along with using those suggestions. Some do, and so you might have to wonder about them?

You know it takes a few hours of research sometimes just to look up and study one term, maybe a policy term, or a new program term at the FCC. So please think before you make your suggestions. And do a little study before you offer up a really good idea. And please read the topics and views here so that you are fully informed and armed with the right sort of information.

This site is devoted to the development of a feasible plan to submit for the FCC's consumption. For the purposes of launching a Low Powered AM Broadcasting Service for We The People.

This should not take 10 years or a life time to achieve:

The innovator of this site is not here to ever create a 501 (c) 3 tax exempt corporation supposedly on the band wagon of LPAM. The reason this is so, is because many institutions pick up a good cause to ride the band wagon of and then become a tax exempt corporation. And then they never help to bring into existence the goal they are suppose to be about. You see, if they do bring it into existence then the money contribution cause is over with. Their income is over with. They can not kill their cash cow. And well you should be advised that such things exist.

If we need help in the form of contributions. We will not be doing so in a tax exempt manner. And we will do so only as long as it takes to get a new LPAM Rule Making Proposal submitted to the FCC and the processing and handling of the matter completed.

If you would like to make a financial contribution and the donation button is not working. Sometimes it doesn't work? PayPal needs to fix things! Please contact the site owner about sending us a money order. Contact Owner Here Please Title Email Subject As "LPAM Contribution"