A Few Questions For Mr. Fry....

[pianoplayer88key]

... The current equipment I'm using...drifts all over the place and is extremely difficult to fine tune... Also while its far field signal is well within the range I want to restrict it to, the close-in signal isn't nearly strong enough.

For a given r-f radiator, the intensities of the E&H far fields are related to the intensities of the E&H near fields close to the radiator.

One set of fields cannot be changed independently of the other set.

I realize that. When I said "its far field signal is well within the range I want to restrict it to", I wasn't saying it's close to the limit with little margin for improvement, I meant its radius is a small fraction of what I would be willing to allow in my case. It's barely getting across a room in the house, yet I'd be willing for it to reach the edge of my half-acre yard if that's what it takes to get a close-in signal as strong as I want it. As it is now, when I have it set on an AM frequency, its fundamental just grazes 98 dBu on my PL-606 a few inches away. (I'm hoping to have it strong enough so that within a few cm or so, it's about as strong on my radio's built-in antenna as the signal it would be getting from a 50kW station 300 feet away, while using a tuned Select-A-Tenna and a several hundred (or maybe couple thousand) foot longwire antenna disguised as utility ground. To give an idea of how much gain that is, I receive a 50kW station 7.3 miles (760 kHz, conductivity 8 mS/m) from my house with that setup at about the same strength I receive a 2.5 kW on 590 with the built-in antenna from about 8 feet from the tower (but still outside the fence of course!)) I also would want to be able to turn down the gain, so I could have something like a 1 to 10 µV/m signal at 6 inches if I wanted to.

 

[rfry]

I realize that. ... etc.

Sorry, but comparisons of the signal strengths in "dBu" shown on a Tecsun PL-380 and/or PL-606 a few inches from your father's grid-dip meter relative to those shown by those receivers 300 feet away from the tower of a 50kW station on 760 kHz, and/or about 8 feet away from a 2.5 kW station on 590 kHz will not be scientifically accurate, or relevant.

 

[druidhillsradio]

Just curious, has anyone ever placed 2 Tecsun's side by side to see if the observed signal strength is close to being the same on the same frequency?

 

[pianoplayer88key]

Just curious, has anyone ever placed 2 Tecsun's side by side to see if the observed signal strength is close to being the same on the same frequency?

Here you go.

I should mention that test was conducted around 4am inside a '99 Astro. That was done to attenuate some local signals, otherwise 760 (depending on where in the house or yard I was) would have indicated about 82 dBµ on the PL-606 (The PL-380 caps at 63 dBµ.) Also that's when it was available. I hope to repeat the experiment some early afternoon with steadier groundwave signals. Also the radios' bottom ends were put together to try to balance minimizing loopstick interaction with keeping them close together for the photoshoot. Both radios were set to ±1 kHz bandwidth.

 

[rfry]

I didn't start this to attack you personally Mr. Fry. I'm just curious about the double standard ... Especially when we see the irony of your stern words on this board - however well intentioned, and the FAR more flagrant and in-your-face actions of flaming pirates happening all around us.

Here is at least one case where the FCC did not ignore a pirate operator, and his fine was reported to be $25,000.

http://www.radioink.com/Article.asp?id=2133204

Here is link to one of the NOUOs issued to that operator, showing that the FCC measured a field intensity of 522,224 µV/m at a distance of 262.1 meters from the transmit antenna.

The radiated power needed to produce that field at that distance over an unobstructed, free-space path is about 625 watts.

http://transition.fcc.gov/eb/FieldNotices/2003/DOC-300932A1.html

 

[druidhillsradio]

I hope to repeat the experiment some early afternoon with steadier groundwave signals.

Thanks that' good info. I woould really like to see the daytime when you get a chance. Regards,

 

[radioman148]

I didn't start this to attack you personally Mr. Fry. I'm just curious about the double standard ... Especially when we see the irony of your stern words on this board - however well intentioned, and the FAR more flagrant and in-your-face actions of flaming pirates happening all around us.

Here is at least one case where the FCC did not ignore a pirate operator, and his fine was reported to be $25,000.

http://www.radioink.com/Article.asp?id=2133204

Here is link to one of the NOUOs issued to that operator, showing that the FCC measured a field intensity of 522,224 µV/m at a distance of 262.1 meters from the transmit antenna.

The radiated power needed to produce that field at that distance over an unobstructed, free-space path is about 625 watts.

http://transition.fcc.gov/eb/FieldNotices/2003/DOC-300932A1.html

One case out of how many thousands that are doing this?

 

[rickradio]

A few questions of my own for Mr. Fry:

Were you in "Revenge of the Nerds" or any of its sequels?

Do you wear horn-rimmed glasses (with tape across the bridge)?

Do you have a collection of pocket protectors (not just one)?

And in those protectors, a complete set of 14 mechanical pencils, along with 6 protractors, 9 compasses, a calculator with cosigns and tangents, a slide rule collection that would make Einstein salivate, all used in equal rotation for every Part 15er's parade upon which you insist on raining?

A closet full of plaid shirts?

Seventeen pairs of high-water pants?

Has anyone ever mistaken you for the "Terry the Toad" character in "American Graffiti," or the Stuart Pankin character in "Hollywood Knights?"

At least now I know I'm not the only one who's tired and annoyed by your hairsplitting posts.

 

[rfry]

One case out of how many thousands that are doing this?

More cases are shown at the links below.

That these FCC actions constitute "hairsplitting" is left for others to decide.

http://transition.fcc.gov/eb/FieldNotices/
http://transition.fcc.gov/eb/rfo/ActAct.html

 

[druidhillsradio]

I may be incorrect, but I don't think there are any cases of Part 15 AM stations being hasseled in Florida. The FCC Office in Tampa and Miami have their hands full with FM pirates. I think Florida leads or may be at the top of enforcement for FM pirate activity.

 

[rfry]

I may be incorrect, but I don't think there are any cases of Part 15 AM stations being hasseled in Florida. (etc)

Didn't research all of the Part 15 AM NOUOs, but...

The link below leads to a fairly recent FCC citation issued to an operator of an unlicensed FM station in Florida, based on measured field intensities of about 7,000 µV/m at a distance of about 770 meters from the transmit antenna.

Of interest here is that the radiated power needed to produce that field at that distance easily could be produced by a transmitter with less than 100 milliwatts of output power using even a simple 1/2-wave dipole antenna.

Some may define or hope that such an operation is compliant with Part 15, or at least will escape detection by the FCC -- but in this case, clearly it did not, even in Florida.

Bottom line: It doesn't take tens/hundreds/thousands of watts of radiated power before the FCC takes notice and reacts.

Of course everyone is free to operate whatever system they wish, hopefully with an accurate understanding of the physical realities of those systems with respect to Part 15, and the risk that applies.

http://transition.fcc.gov/eb/FieldNotices/2003/DOC-305290A1.html

 

[rfry]

Of interest here is that the radiated power needed to produce that field at that distance easily could be produced by a transmitter with less than 100 milliwatts of output power using even a simple 1/2-wave dipole antenna.

Correction... the radiated power needed will be less than 1 watt (about 0.968 watts).

 

[BobOnTheJob]

I absolutely agree. It 's ridiculous! There are so many high powered pirates it the New
York area that are actually interfering with major legitimate stations. Don't you feel that pointing you finger at the nanowattcasters is absurd???? Please get a life!!!!

I haven't seen Mr Fry point any fingers...just supplying solid facts for non-forced consumption by the reader. What I do have a problem following is the radio equivalent of "there are drug dealers on the street...how dare you enforce the stop sign rules" logic.

 

[Bongwater]

I absolutely agree. It 's ridiculous! There are so many high powered pirates it the New
York area that are actually interfering with major legitimate stations. Don't you feel that pointing you finger at the nanowattcasters is absurd???? Please get a life!!!!

I haven't seen Mr Fry point any fingers...just supplying solid facts for non-forced consumption by the reader. What I do have a problem following is the radio equivalent of "there are drug dealers on the street...how dare you enforce the stop sign rules" logic.

Not trying to be snarky, but we're dealing with a government agency with a LOT fewer resources than perceived.

Even cops have to prioritize when confronted with two situations. Sometimes a cop will have to stop a rape or murder if it means dismissing someone openly smoking a joint out in public as long as that person is not causing any harm to anyone else......

 

[WPHA]

Ok, here's just a hypothetical situation, to make us say "Hmmmmm"...

I would think that, let's say an FCC agent was doing some measurements, and noticed an unlicensed FM signal. It had CLEAN audio, was NOT overmodulated, and sounded like it was being operated intelligently, if not professionally. It was also "in the clear" in that there was no other station with an audible signal (on a GOOD radio) on its frequency, or on the two 1'st adjacent freqs. IOW, it was causing NO noticeable interference to ANY station receivable in its area. (The FCC Agent was there on some other business, and "just happened to notice" the signal.)

Upon tracking it down, and ringing the doorbell of a typical middle-class house in a nice subdivision, was greeted by a responsible-looking, intelligent adult. Upon asking this person about the radio station, and showing ID, was invited in to look things over. He discovers that the operator was using a well-made transmitter, and it was running something in the area of 50 milliwatts. (Yes, we KNOW that this exceeds the ridiculous limits of Part 15 for FM, but let's set that aside for a moment.) The operator indicated that it is his desire to keep his signal clean and respectable, to provide a service to his neighbors in the local subdivision. A good attitude being key, and demonstrating a responsible operation.

How inclined would said FCC agent be to see to it that significant penalties were brought against that operator, as opposed to just saying "Shut it down." with no further official FCC action? (Or possibly even just "turning his head"?)

Just wondering... 8)

 

[rfry]

...How inclined would said FCC agent be to see to it that significant penalties were brought against that operator, as opposed to just saying "Shut it down." with no further official FCC action? (Or possibly even just "turning his head"?)

This would depend on whether or not the agent was following the rules and guidelines of his/her employer (the FCC), as set out in the applicable Federal Codes given in 47 C.F.R. Part 15.

Your post suggests that such limits could/should be selectively enforced based on the perceived motives of an unlicensed operator when s/he does not meet the functional limitations required by Part 15.

Would you not agree that this is a slippery slope?

 

[pianoplayer88key]

What about a beginner hobbyist with very limited knowledge, test equipment, etc, who wants to build a part 15 transmitter from scratch, using mostly household parts, and service his few dozen rural/wilderness hundred-acre neighbors? Assume he does know about the 3-meter antenna/groundlead rule, and not to interfere with licensed broadcasters, so he picks what seems to be an open daytime frequency. With the help of a portable radio, he tunes his transmitter (no frequency display/markings of any kind), adjusting the tuning capacitor as necessary or rewiring any coil that may be used. However, he has no way to determine his power output - he just puts parts in there until he finds something that works and services his neighbors.
How would that hobbyist avoid a run-in with the FCC without, for example, taking out a mortgage on a multimeter with which he could measure the transmitter power? Would there be some way to base it on range somewhat? I would assume he's not in compliance if he's, for example, depleting a car battery within an hour (if the TX is battery operated), tripping a hundred-amp breaker (if it's on AC), dominating a graveyard frequency well beyond the horizon, overloading neighbors' radios NOT adjacent to his own property, etc. All he wants to do, though, is service his several dozen local neighbors with a clean, clear signal, like many of you probably would easily be able to do from inside apartment complexes. It just so happens that each of his neighbors has a hundred-acre ranch, instead of a 300-500 square foot apartment. How would he avoid getting a NOUO from the FCC?

 

[radioman148]

What about a beginner hobbyist with very limited knowledge, test equipment, etc, who wants to build a part 15 transmitter from scratch, using mostly household parts, and service his few dozen rural/wilderness hundred-acre neighbors? Assume he does know about the 3-meter antenna/groundlead rule, and not to interfere with licensed broadcasters, so he picks what seems to be an open daytime frequency. With the help of a portable radio, he tunes his transmitter (no frequency display/markings of any kind), adjusting the tuning capacitor as necessary or rewiring any coil that may be used. However, he has no way to determine his power output - he just puts parts in there until he finds something that works and services his neighbors.
How would that hobbyist avoid a run-in with the FCC without, for example, taking out a mortgage on a multimeter with which he could measure the transmitter power? Would there be some way to base it on range somewhat? I would assume he's not in compliance if he's, for example, depleting a car battery within an hour (if the TX is battery operated), tripping a hundred-amp breaker (if it's on AC), dominating a graveyard frequency well beyond the horizon, overloading neighbors' radios NOT adjacent to his own property, etc. All he wants to do, though, is service his several dozen local neighbors with a clean, clear signal, like many of you probably would easily be able to do from inside apartment complexes. It just so happens that each of his neighbors has a hundred-acre ranch, instead of a 300-500 square foot apartment. How would he avoid getting a NOUO from the FCC?

If it's rural enough that nobody, but his neighbors could hear, and none of those neighbors complained then he'd be OK . IMO.

 

[LibertyNT]

I actually know an FM operator who run about 10 watts.
He was contacted by the FCC, and did have Agents inspect.

However,
The Agents let him continue to broadcast stating
"At least someone is serving the Community"

 

[rfry]

How would that hobbyist avoid a run-in with the FCC without, for example, taking out a mortgage on a multimeter with which he could measure the transmitter power?

Unlicensed transmitters legally operating in the AM broadcast band under FCC 15.219 need to limit the d.c. input power applied to the final r-f stage of the transmitter to 100 milliwatts. This value is the product of the d.c. voltage across, and the direct current flowing in the path through the final, active device that supplies r-f power to the output connector.

In a solid-state amplifier this voltage is measured between the emitter and the collector, and the current is that flowing between the emitter and the collector. Both measurements are d.c. values.

For example, if the voltage was measured to be 10 V DC, then the current in that path could not exceed 10 mA DC.

Both of these parameters can be measured by a simple and inexpensive multimeter such as available from Radio Shack, and others.

Would there be some way to base it on range somewhat? ... It just so happens that each of his neighbors has a hundred-acre ranch, instead of a 300-500 square foot apartment.

Range will depend on many factors, including noise/interference and the quality of the receiving equipment.

The link below shows the radiated fields possible from a functionally legal Part 15 AM system, which might represent about the best case for an optimized typical setup, over a perfect ground plane.

Note that a field strength of 0.150 millivolts/meter is about the minimum needed by a typical consumer-grade AM receiver, and that the radius to that field from this system is about 580 meters.

The area of a circle with a radius of 580 meters is about 261 acres, so this system would not well serve "several dozen local neighbors" with adjacent, 100-acre plots.

http://i62.photobucket.com/albums/h85/rfry-100/Part15AM_BestCase.gif