Another way to go about it

[audioguy]

Many of you are probably aware that the FCC has just opened up the TV bands for unlicensed operation. This is mainly for wireless broadband and similar computer communications devices. If you read the new rules, you will see that they don't provide any opportunity for unlicensed "broadcasting" per se-- either TV or FM. For one thing, there are extensive requirements for spectrum sensing and database connectivity.

However, the concept of unlicensed operation, or what the Commission sometimes prefers to call "licensing by rule", has gained considerable support at the FCC over the years, mainly due to the success of Wi-Fi and similar services that operate in what was formerly thought to be "junk spectrum". And now, this concept has been extended to the TV broadcast bands.

How could we leverage the new climate at the FCC to legitimize and further advance the cause of unlicensed operation in the AM and FM bands? It is obvious that there is a need for this kind of service. It is in the public "interest, convenience, and necessity".

I believe that if we formed an industry association to advance the cause of unlicensed radio broadcast band operation, we would get more traction than individual petitions, which the FCC can choose to ignore.

I would propose restraint in terms of the technical goals. Asking the FCC to approve unlicensed operation of transmitters at the 5 or 10 watt level would go nowhere fast. Instead, I would suggest asking for some relaxation of the existing Part 15 rules, e.g.--

For AM, allow operation of a certified transmitter at 100 mW using a 3m antenna and any kind of ground system. This will accommodate the various installation situations that are problematic today, and would also provide more useful range, given the very high noise levels present in the AM band today in most locations.

For FM, allow operation of a certified transmitter at 10 mW using a permanently attached dipole antenna (either horizontal or vertical polarization).

The intent would be to provide a useful coverage range of 1-2 miles under typical urban reception conditions. Additionally, this would only be allowed on the condition that no interference is caused to any licensed station (as is the case today).

What do you think of that?

 

[XRQKFM]

I fully support everything you just wrote; and it's my ultimate goal and direction I'm headed towards. The only minor change I would make on FM; would be to make it 100 milliwatts and a dipole or non gain ground plane city and maybe 500 milliwatts for rural service with a small population spread out several miles. Perhaps the same conditions for AM with a slightly higher power in remote areas with no other radio service.

The proof of micro broadcasters being responsible in their operations is clear by the lack of complaints from non broadcasters. It has worked well in New Zealand as a test country with 400 milliwatt power limits proving it viable.

It would save the Feds money, by focusing their enforcement efforts on the foulmouth 100 watt pirates that pop by the hundreds on the east coast.

Audioguy, thanks for an outstanding post. I could have not said it better; believe me I have tried!


Steve
www.radiobrandy.com

 

[radioman148]

>>For AM, allow operation of a certified transmitter at 100 mW using a 3m antenna and any kind of ground system>>

I thought this was already allowable. Is the difference "any" kind of ground system?

 

[audioguy]

radioman148;

Yes, on the AM side I am proposing to remove the restrictions on the grounding system, because this is problematic for people in many different situations. It would also end the constant wrangling over what constitutes a legal ground system. Under my proposal, as long as the transmitter is certified, the power input is 100 mW or less, and the antenna is no more than 3m, you would be permitted to use whatever ground system you wanted, including mounting the transmitter on top of a tower. End of story.

The FM proposal represents a very significant increase over the current limits. A power of 10 mW would be enough to cover several miles. I am proposing that the transmitter and antenna be an integrated unit, so that the field strength should be very predictable. They would be tested and certified in the manufacturer's configuration. As it is now, based on the permitted field strength, the usable coverage is about from one end of your house to the other (if you're lucky).

 

[radiopilot]

I like this proposal with only one difference why only certified transmitters? Part 15 allows the use of home built transmitters and one can build/use up to five transmitters per the rules, what about these hobbyists?

One of the first introductions to AM radio for Boy Scouts is building radios/transmitters... should they be not allowed?

I suggest any AM transmitter with 100mw and any ground system appropriate for the area would be allowed under the new Part 15 rules.

On the FM side I agree a 100mw transmitter w/ no-gain antenna as Steve suggests and forget the 250uv/3 meter rule... it's ridiculus a notion at the whim of the NAB.

Radiopilot

 

[radioman148]

radioman148;

Yes, on the AM side I am proposing to remove the restrictions on the grounding system, because this is problematic for people in many different situations. It would also end the constant wrangling over what constitutes a legal ground system. Under my proposal, as long as the transmitter is certified, the power input is 100 mW or less, and the antenna is no more than 3m, you would be permitted to use whatever ground system you wanted, including mounting the transmitter on top of a tower. End of story.

The FM proposal represents a very significant increase over the current limits. A power of 10 mW would be enough to cover several miles. I am proposing that the transmitter and antenna be an integrated unit, so that the field strength should be very predictable. They would be tested and certified in the manufacturer's configuration. As it is now, based on the permitted field strength, the usable coverage is about from one end of your house to the other (if you're lucky).

Thanks for spelling it out audioguy. I agree with you.

 

[rfry]

Under my proposal, as long as the transmitter is certified, the power input is 100 mW or less, and the antenna is no more than 3m, you would be permitted to use whatever ground system you wanted, including mounting the transmitter on top of a tower.

There are two components of the "ground system" for a Part 15 AM transmitter.

One is the r-f ground itself, which by definition cannot directly produce far-field radiation. Common examples of an r-f ground are one or more buried ground rods, buried wire radials, a buried metal water pipe, or buried wire mesh.

Other examples are two or more horizontal wires in a symmetric arrangement elevated 10 or 20 feet above the earth, and a flat metal roof with no conducting path to a buried r-f ground -- all of which more properly are called a "counterpoise."

The second part of the Part 15 AM ground system as popularly defined is the conducting path leading from the ground terminal on the transmitter to the r-f ground. This includes the short wire from the transmitter to a "massive" ground wire, a metal mast, flagpole, or billboard steel, as well as the length of those additional conductors themselves.

However the fact that same r-f current is flowing with little loss along the entire length of that conducting path until the point where it attaches to the buried r-f ground (or counterpoise) means that it will radiate very strongly. If the length of that conducting path is more than about 1 meter it will radiate more than the 3-meter conductor attached to the antenna output connector of the transmitter!

So the conducting path from the transmitter to the r-f ground or counterpoise really is part of the Part 15 AM antenna, not the ground, or part of the ground.

This would be good to recognize in any suggested proposal to change the rules for Part 15 AM, perhaps by limiting the conductor at the tx r-f output connector and its feedline to a length of ~ 3 meters, and the length of the conducting path from the transmitter to the r-f ground or counterpoise to whatever length people hope for. That would have a minimal affect on the output circuit and loading coil parameters used by current Part 15 AM transmitters.

If the length of that conducting path to r-f ground can be whatever length anybody wants to use, probably that will raise some attention at the FCC, because it will mean that Part 15 AMs can have much greater coverage areas then presently allowed by a functionally compliant Part 15 AM setup.

And nothing at all wrong with that, if that is the FCC's decision.

//

 

[audioguy]

Thanks for all of your good comments. Keep them coming!

Regarding home built AM band transmitters, I agree that they should continue to be permitted for operation by home experimenters under some set of technical requirements. Whether or not it would be viable to request that they be included in this new proposal to allow more flexible installation is up for discussion. That would probalby be the simplest thing for users to understand, and for the FCC to enforce. I do not think that setting a field strength limit is a viable way to regulate "home experimenter" operation, since no one except the FCC has access to the necessary field strength measuring equipment (nor do they have the experience required to take the measurements properly). One could describe a complicated set of grounding requirements, but again that brings us back into the world of interpretation, which would be desirable to get away from.

Without getting into a complicated discussion of what constitutes the antenna system and what constitutes the ground system, and how much each part radiates, my proposal is to simplify the entire matter by simply removing the restrictions on whatever is connected to the ground side of the circuit. The only operational aspects that would be restricted would be the input power to the final amplifier stage and the length of the "antenna" element. This would address a lot of the issues that part 15 AM operators have to deal with-- lightning grounds, elevated mounting, operation indoors on an upper floor where there is no real "rf ground", power supply and audio cables, etc. It would also greatly simplify things on the enforcement side, which would appear to be a worthwhile goal for both the FCC and Part 15 operators.

Those who want to "broadcast" to their home radios would not need to attach much of a ground system, other than the ad hoc ground that is created by plugging the transmitter into the ac line. Those who would like to serve a small community or neighborhood would have the flexibility to increase their range by means of elevated mounting. They should be able to achieve 1-2 miles in the daytime under typical conditions by doing so.

Let's face it, you can only squeeze so much blood out of a turnip-- if you limit the power to 100 mW, the signal is not going to provide useful service over a large distance, even if it were to be fed into a full sized antenna. The (licensed) local station that serves my area in Michigan is allowed to operate with 8 watts at night, and their signal only goes a couple of miles using a full sized antenna. And that's eighty times as much power as a 100 mW part 15 transmitter, assuming (incorrectly) that all 100 mW were delivered to the antenna.

 

[radioman148]

I like your approach.

 

[XRQKFM]

The reason for the 100 milliwatts is that while 10 milliwatts will provide good car radio coverage for about a mile, it would barely provide in home coverage on the average radios sold at K-Mart & Wal-Mart; a 1/2 mile is more like it. By the time the signal reaches the antenna, you may have only 80 milliwatts hitting the antenna.

I prefer the transmitter to be housed separately inside a XMTR shack and have a cable feed the elevated antenna for several reasons:
1. Redundancies: You want to be able to stay on the air in an emergency, being able to switch to an auxiliary transmitter would be critical for justifying our service and need to serve areas that currently lack local radio service.
2. With the XMTR inside, only an RF cable needs to run to the antenna; as opposed to having a left-right cable for audio and a power cable.
3. For safety reasons, I prefer being able to set the audio levels and other settings on the ground; It's allot safer than hanging from a bucket 30 feet in the air or strapped to the side of a tower.
4 In some situations, you might want to use a direction antenna; like when you are on the edge of a town or mountainside.

At our 40 acre, Arizona, research facility; we have done extensive testing on the subject. Sensitivity on some radios leave allot to be desired; We have a Panasonic (80's vintage) portable radio with its antenna snapped off at the base, at a 1/2 mile in a residents we can hear our station with a little noise, while newer radios with their antennas fully extended get nothing. You have to take the end users inside radios into account when considering the coverage area.

The same is true for AM, only it's worse for the AM broadcasters; Not only do you have to take in account the end users radio and how it is positioned, but the structure too. AM signals have a hard time penetrating module homes and trailers. If you live an area filled mostly with prefabs and trailers; you would be lucky to effectively cover inside a home a 1/4 mile away; assuming the radio is properly positioned and of reasonable quality. I was visiting one location, where I could not pick up a 5,000 watt radio station on the bottom of the dial, only 27 miles away inside the prefab home; even with a very sensitive Panasonic RF2200, I could barely pull it out of the mud; yet it was full scale outside the home with the RF gain at 0. The 1-2 mile range for Procaster and Rangemaster is for car radio coverage, not indoor coverage.

Now if you are in an RV park, it is not a problem because most RV's use external antennas for both the in dash radio and the living quarters radio. That is why we target areas with allot of RV's, for our fixed part 15 AM broadcasting. Check out the www.xrqkfm.com homepage, you will see thousands of RV's gathered, and that is in only one direction.

Perhaps a GMRS, type of license would be one way to go, if this service was accepted. We all know the NAB is going to put up one hell of a fight like they always do; this time the ball may be in our court. The last thing the NAB wants; is to have the requirement that broadcasters maintain a local manned 24/7 studio and office in the COL become law. It would be in their best interest to see it our way this time, as opposed to the other option; which could be very expensive. Besides these broadcasters have no interest in serving the local smaller communities they took the license from anyway. The FCC is starting to acknowledge a need for local radio, and is already considering mandates; this time the congress and white house may be more agreeable than in the past. To bad Adelstein, is leaving the commission; he was really pushing for local radio!


Steve
www.radiobrandy.com

 

[radioman148]

I will vouch for the fact that in my experiments if you're using anything other than a good car radio, part 15 AM reception after a few blocks is almost non-existant.

 

[audioguy]

Yes, I agree that very low power operation-- on AM or FM-- is challenging unless people are using good receivers. And even then, there are reception problems due to electrical noise, building attenuation, and the like. The power levels needed to completely overcome all of these obstacles are likely to be far in excess of anything the FCC would allow on an unlicensed basis. In Canada, AM stations are going off the air every week and moving to the FM band. And here in the U.S., AM programming is increasingly being aired on FM translators and HD channels or being streamed on the Internet, because even with kilowatts of power, stations are not satisfied with their penetration.

There already is a LPFM service, and there have been proposals for a similar LPAM service (although they haven't gone very far). The problem with any sort of licensed service is that there are very few opportunities to get a license, and if you do, you have to adhere to a lot of regulations. Unlicensed Part 15 operation has limited range, but offers a great deal of freedom. And, as many people on this board can attest, there are useful applications for this kind of short range radio "broadcasting" service.

In the context of unlicensed operation, I do not think the FCC would be willing to expand the permitted power levels too far beyond the present limits, although I would hope for some improvement, especially on the FM side. But for those that need stronger signals, probably the only way to go is to try to get a low power FM license. Or perhaps, if you're in the right place, you might be able to buy the license of a station that has gone off the air. Due to the current economic downturn, there are a number of AM's that have gone dark.

So, to sum it up, what I am proposing is not about licensed operation. It is about modernizing the Part 15 rules to make unlicensed operation more useful and easier to implement (and enforce).

One other thing I forgot to mention: most Part 15 devices are required to have permanently attached antennas. I think the FCC would be very reluctant to certify Part 15 FM transmitters with external antennas. It is so easy (and tempting) for people to connect external power amplifiers or high gain antennas to these devices-- you basically lose control over the field strength that the device will produce. It should not be difficult to design the transmitter to bring out whatever control circuitry might be needed so that it can be controlled from inside, with the RF circuitry and antenna mounted outside on a pole or tower.

I agree that a ground plane type of antenna would be just as easy to implement as a dipole. The reason I initially suggested a dipole is that the user could orient it for either vertical or horizontal polarization as needed. In both cases I would still recommend that the transmitter be directly connected to the antenna, for the reasons stated.

 

[radioman148]

>>So, to sum it up, what I am proposing is not about licensed operation. It is about modernizing the Part 15 rules to make unlicensed operation more useful and easier to implement (and enforce).>>

I'm all for that, but I have my doubts that it will ever happen.

 

[audioguy]

radioman148,

It is possible, but it will not be easy. I have some ideas about how to go about it. Remember, nothing ever changes unless people work to make it happen!

In a future post, I will discuss the next steps. Meanwhile I would like to hear from others on this board who think this is something they would be willing to work on and support. And of course, keep your ideas and suggestions coming!

Let's do something positive to make things better, instead of arguing about the same things over and over!

Everyone that wants to get involved is welcome!