Same Old Same Old About FCC Regs.

[Carmine5]

It's a simple matter to just thank R. Fry for the information and choose to either use it, ignore it or weigh it in the balance of other, equally credible information such as found on Keith Hamilton's Rangemaster website or the Procaster site.

Thanks to the economy I was forced to sell an AM CP I had acquired a year and a half ago. I couldn't get a small business loan, couldn't toll the CP and was tired of spending thousands of dollars of my own money in engineering and legal fees plus fighting a less than enthusiastic city council over a possible tower site near a town I had planned moving to (and I had yet to make a formal environmental impact study of the site). What a headache! I threw in the towel.

But the need for true community radio has never been greater so I'm glad that we at least have this limited provision which, with some clever engineering on the part of a few companies, allows any who desire to set up a small station.

When I recover financially, Part 15 AM with a type accepted transmitter(s) will be my next endeavor.

C5

 

[Tom Wells]

As with anything, if it seems too good to be real, it's probably not.

Ye'd think if I could figure out how to better "load in" or tune mine to get better than half a mile I with 100mw I would have.
I've had 15 years in this location, lots of experientation, and have limited space, and high density, so I get what I get.
I really think 1 mile in open areas is doable with good practice. Even more if salt water figures in anywhere.

Mr Fry is not being negative, he's making sure very important issues are properly understood in an area which can't be seen,
and is difficult (somewhat) to comprehend without the underlying theory.
He is doing free consulting work here, really, probably because he is still vitally interested in the best outcome for community radio.
To keep part 15 operators aware of the physics and behavior of RF in transmission lines, ground leads, and radiators is worth
real money. Most people can't interpret the info even if they could read it.
Don't bite the professor. I'm in awe because I can't remember how to work a Smith chart anymore.
Guess I could pick it up again....

ANYhow, Mr R Fry speaks with the conviction of the instructors I had at Valpo Tech, who were the very best.
I take his words as facts not to be questioned, because of his faith and experience in the laws of physics.
If you can find any text written by F E Terman ( great radio engineer) or the RCA tube manuals, you will meet the same sort
of great engineering writing which, like patent language, must leave no untold detail or issue to define successful implementation
of the technology.

It looked to me like the chart for pt 15 AM radiators showed a best result from the vertical dipole with 1 leg grounded!
Is that grounded at the common point at the TX, end of feedline, at the end of the 1.5m segment of dipole? Or what?
What if I drove that 1.5m into the ground, disclaimed it, then put 3 meters in the air above that?

I haven't tried any of this, I'm suggesting there's still a lot of experimentation that can be useful and effective.
Knowing the rules keeps your expectations realistic.
After looking at the chart, I'm thinking about a tranmitter move and trying that dipole just outside the window.

As regarding field strength measurements, it depends on the selectivity of the meter, to accurately measure
whether the "field" is the subject intended. To do so properly requires a receive circuit equal to a R-390A and a calibrated loop antenna.
I don't think the meters being used are designed for such a low range, but someone who knows more can tell us.

 

[rfry]

And what place does Fry have claiming he's an expert on the subject of Part 15 AM when he has NO practical hands on experience with these transmitters? Believe it or not he is dead wrong about his claim that a FSM can accurately read even the smallest amounts of power from a Part 15 AM transmitter. They cannot.

Note that field strength meters measure voltage, not power. Even a very low-power transmitter can create rather high field intensities close to its antenna. If it couldn't, then it would not provide a useful signal to a radio receiver.

Mr Walker's inputs and conclusion may be based on meters like the MFJ-801. But such meters are untuned, and very insensitive because they use no active circuits. They also are uncalibrated, and can produce only a relative reading (if the field strength is high enough).

An example of a professional grade field intensity meter commonly used by licensed broadcast stations is the Potomac Instruments FIM-41 (link below). It can measure fields as low as 10 microvolts/meter, is highly selective, and is calibrated to within a few percent of a known field intensity that is traceable to the US National Institute of Standards and Technology.

This is the meter I used to measure the 2 millivolt/meter contour of WJR. It would be equally useful to measure the 2 millivolt/meter contour of a Part 15 AM setup -- which for a "Part 15" system mounted on a 10-meter, grounded metal mast occurs about 400 meters (1,312 feet) away.

http://www.pi-usa.com/fim2241/fim2241g.htm

//

 

[WCWalker]

And what place does Fry have claiming he's an expert on the subject of Part 15 AM when he has NO practical hands on experience with these transmitters?  Believe it or not he is dead wrong about his claim that a FSM can accurately read even the smallest amounts of power from a Part 15 AM transmitter.  They cannot.

Note that field strength meters measure voltage, not power.  Even a very low-power transmitter can create rather high field intensities close to its antenna.  If it couldn't, then it would not provide a useful signal to a radio receiver.

Mr Walker's inputs and conclusion may be based on meters like the MFJ-801.  But such meters are untuned, and very insensitive because they use no active circuits.  They also are uncalibrated, and can produce only a relative reading (if the field strength is high enough).

An example of a professional grade field intensity meter commonly used by licensed broadcast stations is the Potomac Instruments FIM-41 (link below).  It can measure fields as low as 10 microvolts/meter, is highly selective, and is calibrated to within a few percent of a known field intensity that is traceable to the US National Institute of Standards and Technology.

This is the meter I used to measure the 2 millivolt/meter contour of WJR.  It would be equally useful to measure the 2 millivolt/meter contour of a Part 15 AM setup -- which for a "Part 15" system mounted on a 10-meter, grounded metal mast occurs about 400 meters (1,312 feet) away.

http://www.pi-usa.com/fim2241/fim2241g.htm

//

Another supposition on your part.  My input and conclusion is not based upon the MFJ.  I don't know any broadcast engineers that use that unit and while I don't know which model the FCC used when they visited my station a decade ago,  I suspect that it was not a cheap FSM.

There are ONLY two plausible explanations that result from the experience I had that day.  a) The FCC engineer with the FSM was lying about the alleged field strength of my transmitter or:  b)  The unit was not capable of accurately reading a very low power AM signal.  The only other option that could even be considered is not likely and that is the guy didn't know how to use his own equipment.

Your arrogance and suppositions on this subject is appalling. Do you honestly expect anyone that possesses even the smallest amount of common sense to buy into your theories when you don't have any experience with these transmitters?

 

[rfry]

It looked to me like the chart for pt 15 AM radiators showed a best result from the vertical dipole with 1 leg grounded! Is that grounded at the common point at the TX, end of feedline, at the end of the 1.5m segment of dipole? Or what? What if I drove that 1.5m into the ground, disclaimed it, then put 3 meters in the air above that?

From a technical viewpoint you could bury any length of the lower arm of the dipole that left about 1.5 meters of it above ground. Mounting the transmitter on top of that, then the loading coil, supporting another < 1.5 meter conductor for the upper arm of the dipole, and getting power and program lines to the transmitter would be a challenge. And what would the FCC think of it? Don't know.

Also note the very high reactance of this setup, which would take a large and lossy loading coil to resonate. And the r-f ground provided by burying the bottom of the lower arm would not be as good as I used in my study, so the field strength from this setup won't be as high as shown.

//

PS: Thanks for your good comments about my posts.

 

[rfry]

Your arrogance and suppositions on this subject is appalling. Do you honestly expect anyone that possesses even the smallest amount of common sense to buy into your theories when you don't have any experience with these transmitters?

With all due respect, Mr Walker, your statements/beliefs on this subject are patently wrong.

You are misleading readers of this thread who choose to believe you.

The truth of what I posted on this subject cannot be denied by anyone with a logical mind -- even those having no experience with the equipment and techniques needed for the accurate measurement of MW field intensities.

You or anyone else wanting to confirm or reject what I wrote here need only to buy, rent, or borrow an FIM-41 (or equivalent), learn how to use it properly, and make the measurement.

//

 

[WCWalker]

Your arrogance and suppositions on this subject is appalling. Do you honestly expect anyone that possesses even the smallest amount of common sense to buy into your theories when you don't have any experience with these transmitters?

With all due respect, Mr Walker, your statements/beliefs on this subject are patently wrong.

You are misleading readers of this thread who choose to believe you.

The truth of what I posted on this subject cannot be denied by anyone with a logical mind -- even those having no experience with the equipment and techniques needed for the accurate measurement of MW field intensities.

You or anyone else wanting to confirm or reject what I wrote here need only to buy, rent, or borrow an FIM-41 (or equivalent), learn how to use it properly, and make the measurement.

//

And with all due respect Mr. Fry, your statements are suspect because they coming from someone that has absolutely NO experience either working with or broadcasting with a Rangemaster, Trans AM 100, Infomax or Talking House transmitter.

And I have some exciting news to pass along to you. HR 1388 aka Generations Invigorating Volunteerism and Education Act has just passed the House and Senate this week! Retirees that are over the age of 55 like yourself along with many of the youth in this country that have too much free time on their hands are going to have the rare opportunity to go to work for the government in a service role. Have fun.

 

[radiopilot]

And I have some exciting news to pass along to you. HR 1388 aka Generations Invigorating Volunteerism and Education Act has just passed the House and Senate this week! Retirees that are over the age of 55 like yourself along with many of the youth in this country that have too much free time on their hands are going to have the rare opportunity to go to work for the government in a service role. Have fun.

Careful William... Rattan might go on the attack again in defense of Mr. Fry... we all know how tight that bond is from the previous responses.

Mr. Fry PLEASE... who is going to go to the trouble of buying/renting/stealing a Potomic FIM meter worth upwards of 6-10K just to measure a 100 mw (that's 0.100 of a watt or 1/10th of a watt, etc.) transmitter that costs anywhere from $25-$800 depending on make and model? Are you really serious... if the FCC agents are having a tough time accurately using this FIM, why do you think the average backyard hobby broadcaster is going to do any better...

Might I suggest your broad knowledge in radio transmitters/radio stations engineering to help the IBOC disaster that is clogging the AM dial (FM too) with countless interference and jamming from running it's defective digital IBOC equipment?

Radiopilot

 

[Rattan]

I do have to say that I found the notion of buying a Potomac FIM-41 more than a bit unlikely for most part 15 stations. I would assume that renting them is also a bit expensive and that so far as borrowing them, well.. Engineers up for lending an expensive and probably delicate piece of equipment to even an enthusiastic hobbyist are probably very rare in the engineering community.

And I may be overestimating the complexity of the device and procedure, but I'd assume that it'd take some time and work to learn to use it with enough proficiency to get the same results as a trained FCC field agent would get.

All in all, the suggestion seems perhaps a trifle unrealistic. It might be an ideal solution for settling that point of the ongoing debate, but I think it'd be beyond the means of many part 15 station operators even if it was within their abilities.

radiopilot, so far as my "going on the attack", no point in it after already trying to remind people that it is possible to debate without resorting to disrespect or attempts at ridicule. If I felt that you were being treated unfairly in an argument, I'd be likely to chime in there as well. Yeah, I know.. It's a useless attempt at being a do-gooder. Just the way my mama brought me up I guess, so haunt me. <shrugs>

Daniel

 

[rfry]

... who is going to go to the trouble of buying/renting/stealing a Potomic FIM meter worth upwards of 6-10K just to measure a 100 mw (that's 0.100 of a watt or 1/10th of a watt, etc.) transmitter that costs anywhere from $25-$800 depending on make and model?

I don't expect anyone to do that. But anyone who did would find that it accurately measures the fields from a Part 15 AM setup -- which was the point of contention.

As another example, an FCC certified Part 15 FM transmitter with its non-detachable antenna had to pass a test showing that it radiates a measured field of no more than 250 µV/m in any direction three meters away from its antenna. This value of field strength is much less than a Part 15 AM setup can produce even hundreds of feet away, yet with the proper test equipment it can be measured accurately.

//

 

[WCWalker]

... who is going to go to the trouble of buying/renting/stealing a Potomic FIM meter worth upwards of 6-10K just to measure a 100 mw (that's 0.100 of a watt or 1/10th of a watt, etc.) transmitter that costs anywhere from $25-$800 depending on make and model?

I don't expect anyone to do that. But anyone who did would find that it accurately measures the fields from a Part 15 AM setup -- which was the point of contention.

As another example, an FCC certified Part 15 FM transmitter with its non-detachable antenna had to pass a test showing that it radiates a measured field of no more than 250 µV/m in any direction three meters away from its antenna. This value of field strength is much less than a Part 15 AM setup can produce even hundreds of feet away, yet with the proper test equipment it can be measured accurately.

//

Wrong again. I've got more than one Broadcast Engineer, an FCC Field Supervisor and others telling me that a FIM CANNOT accurately read the voltage or power level of a Part 15 AM transmitter. I saw it FIRST HAND with my own eyes, ALL FOUR of the THEM. Just what is this perverse fixation that you have with making this claim without ANY prior experience in this area?

Fry. You remind me of a guy that burst upon the LPFM scene in 1998 and tried to dictate to the rest of us how the proposed LPFM service should be set up and run. He, like you, had no experience in this field yet he claimed to be an expert and talked down at the rest of us. In his case he didn't have ANY prior experience with radio yet he made absurd claims that all we needed was a one or two watt power level and a small antenna etc. Later on when the proposed licensed LPAM service came around he and a couple of his friends started at it again by claiming we needed certain power levels, horizontal antennas and certain spacing requirements and so on. Laughably many of their proposals contradicted the laws of known physics and were not technically feasible. After I consulted with a couple of my Broadcast Engineers I was able to set them straight.

Granted you are not without radio experience and I would NEVER question your judgment concerning a licensed station's technical side. But when it comes to Part 15 AM you really don't understand what is going on with some issues, either technically OR from a legal standpoint and how American law is written and operates and applies to Part 15 AM broadcasting. Unfortunately YOUR arrogance is getting in the way of common sense.

 

[rfry]

Just what is this perverse fixation that you have with making this claim without ANY prior experience in this area?

As I wrote, I have used the FIM-41 to measure the fields of medium wave broadcast stations. THAT is all the experience needed to write what I did, as a Part 15 AM setup can produce the same field intensity close to its antenna as I measured ~100 miles from the broadcast station.

If you believe that a professional FIM cannot measure a Part 15 AM field, how do you suppose the FCC was able to do so in the Flagstaff case, and others?

//

 

[WCWalker]

Just because it obtained a reading does not mean it was accurate. Understand?

You could not offer an explanation as to why my station reading was red lining on the FIM used by the FCC agent here in KC despite the fact the power level was set to ZERO. NO power output whatsoever. And there were no other part 15 devices operating at that home at that time. So in other words, the initial reading on the FIM that day was off the scale at 100 mw of power. As I turned down the power it still showed as being over power even when the power level of the transmitter was set to ZERO.

Here's what happened. I made a couple of phone calls after the FCC left. That afternoon I got a call back from their Supervisor telling me to go back on the air. He said they were unaware that what I was doing was legal and that their readings were inaccurate.

Again, there are only two logical explanations for this, both of which you choose to ignore. 1) The FCC agent using the equipment was lying about the reading. But to be honest I don't believe that was the case because I was still redlining as I gradually turned the power down from 100 mw to ZERO. 2) They could not get an accurate reading on the AM signal because of the nature of AM signals is very different than FM. It's like comparing apples to potatoes. The last option I don't buy because it is hardly rational and that is the guy did not know how to use his own FIM.

 

[rfry]

Just because it obtained a reading does not mean it was accurate.

Note that the FIM read about 2 mV/m at the distance where that field occurs for the radiated power on that frequency and for the ground conductivity of the path.

Did you look at the Radio-Locator coverage map for this station at http://www.pi-usa.com/fim2241/fim2241g.htm ? I was measuring it in the vicinity of Saginaw, MI, which is about 100 miles north of the transmitter site. The red trace on the coverage map is the 2-1/2 mV/m contour, and Saginaw is located a bit beyond it.

A Part 15 AM setup can produce a 2 mV/m field close to the radiator, so why do you think a suitable FIM could not measure it?

You could not offer an explanation as to why my station reading was red lining on the FIM used by the FCC agent here in KC despite the fact the power level was set to ZERO. etc

Not enough information is available to diagnose your situation. But it certainly is not because a professional FIM can't measure the fields close to a Part 15 AM antenna.

I'll ask you again: If you believe that a professional FIM cannot measure a Part 15 AM field, how do you suppose the FCC was able to do so in the Flagstaff case, and others?

//

 

[WCWalker]

You're making a fool of yourself on this subject. Your myopic view of these cases and your inflexibility when rationalizing each case proves it.

AGAIN, how can you prove the reading in Flagsaff was accurate? I doubt it was.

More importantly, 15.209 applies to Carrier Current stations and NOT Intentional Radiators. If both applied then you'd have rules that contradict one another assuming that you can even get an accurate reading of Field Strength for such a low power signal. There are too many environmental conditions that exist that can change the Field Strength of a low power AM signal thus 15.219 applies.

 

[rfry]

More importantly, 15.209 applies to Carrier Current stations and NOT Intentional Radiators.

Not so. Here is a quote from FCC 15.209:

Sec. 15.209 Radiated emission limits; general requirements.

(a) Except as provided elsewhere in this subpart, the emissions from an
intentional radiator shall not exceed the field strength levels specified in
the following table:


------------------------------------------------------------------------
Measurement
Frequency (MHz) Field strength distance
(microvolts/meter) (meters)
------------------------------------------------------------------------
0.009-0.490...................... 2400/F(kHz) 300
0.490-1.705...................... 24000/F(kHz) 30
1.705-30.0....................... 30 30
30-88............................ 100 ** 3
88-216........................... 150 ** 3
216-960.......................... 200 ** 3
Above 960........................ 500 3
------------------------------------------------------------------------

The entire text is linked here http://frwebgate.access.gpo.gov/cgi-bin/get-cfr.cgi?TITLE=47&PART=15&SECTION=209&YEAR=2001&TYPE=TEXT

//

 

[WCWalker]

That contradicts the 100 mw output power level rule. It can't work both ways.

I might add that the FCC Field Office in Boston told the owner of a station in Rhode Island that his station could operate under either rule. And I was also told that by more than one source and this was confirmed after my issue here in Kansas City.

A station has the option to either use 100 mw or meet the Field Strength rules. However, since it is IMPOSSIBLE for a FIM to accurately read these low level AM signals, everyone chooses to operate at 100 mw.

 

[rfry]

That contradicts the 100 mw output power level rule. It can't work both ways.

Firstly, Part 15.219 specifies 100 mW input power, not output power. Part 15.209 specifies field strength at a given distance with no power or antenna limits.

These two rules don't necessarily conflict, because using an inefficient "100 mW" transmitter with an inefficient antenna conceivably could produce a field that meets 15.209.

In some cases the FCC has cited both 15.209 and 15.219 in issuing an NOUO based on excess field strength and excess transmitter power -- see http://www.fcc.gov/eb/FieldNotices/2003/DOC-278979A1.html

If you believe that the FCC can't have it both ways, perhaps you should take up your case with them.

//

 

[radiopilot]

Just so Mr. Fry is up on the regulations I have outlined what the requirements are for the emissions of the transmission... Part 15 Section 15.219 is the true section governing the requirements for 100mw AM transmitters and it's all that's required.

As a contracts requirements engineer working on rocket propulsion for NASA and the government... I believe this is correct to to the best of my knowledge which to some is nada at best!

Radiopilot


[Code of Federal Regulations]
[Title 47, Volume 1]
[Revised as of October 1, 2008]
From the U.S. Government Printing Office via GPO Access
[CITE: 47CFR15.209]

[Page 805-806]

TITLE 47--TELECOMMUNICATION

CHAPTER I--FEDERAL COMMUNICATIONS COMMISSION

PART 15_RADIO FREQUENCY DEVICES--Table of Contents

Subpart C_Intentional Radiators

Sec. 15.209 Radiated emission limits; general requirements.

(a) Except as provided elsewhere in this subpart, the emissions from
an intentional radiator shall not exceed the field strength levels
specified in the following table:

------------------------------------------------------------------------
Measurement
Frequency (MHz) Field strength distance
(microvolts/meter) (meters)
------------------------------------------------------------------------
0.009-0.490...................... 2400/F(kHz) 300
0.490-1.705...................... 24000/F(kHz) 30
1.705-30.0....................... 30 30
30-88............................ 100 ** 3
88-216........................... 150 ** 3
216-960.......................... 200 ** 3
Above 960........................ 500 3
------------------------------------------------------------------------
** Except as provided in paragraph (g), fundamental emissions from
intentional radiators operating under this section shall not be
located in the frequency bands 54-72 MHz, 76-88 MHz, 174-216 MHz or
470-806 MHz. However, operation within these frequency bands is
permItted under other sections of this part, e.g., Sec. Sec. 15.231
and 15.241.

(b) In the emission table above, the tighter limit applies at the
band edges.
(c) The level of any unwanted emissions from an intentional radiator
operating under these general provisions shall not exceed the level of
the fundamental emission. For intentional radiators which operate under
the provisions of other sections within this part (SECTION 15.219)and which are required
to reduce their unwanted emissions to the limits specified in this
table, the limits in this table are based on the frequency of the
unwanted emission and not the fundamental frequency. However, the level
of any unwanted emissions shall not exceed the level of the fundamental
frequency.
(d) The emission limits shown in the above table are based on
measurements employing a CISPR quasi-peak detector except for the
frequency bands 9-90 kHz, 110-490 kHz and above 1000 MHz. Radiated
emission limits in these three bands are based on measurements employing
an average detector.
(e) The provisions in Sec. Sec. 15.31, 15.33, and 15.35 for
measuring emissions at distances other than the distances specified in
the above table, determining the frequency range over which radiated
emissions are to be measured, and limiting peak emissions apply to all
devices operated under this part.
(f) In accordance with Sec. 15.33(a), in some cases the emissions
from an intentional radiator must be measured to beyond the tenth
harmonic of the highest fundamental frequency designed to be emitted by
the intentional radiator because of the incorporation of a digital
device. If measurements above the tenth harmonic are so required, the
radiated emissions above the tenth harmonic shall comply with the
general radiated emission limits applicable to the incorporated digital
device, as shown in Sec. 15.109 and as based on the frequency of the
emission being measured, or, except for emissions contained in the
restricted frequency bands shown in Sec. 15.205, the limit on spurious
emissions specified for the intentional radiator, whichever is the
higher limit. Emissions which must be measured above the tenth harmonic
of the highest fundamental frequency designed to be emitted by the
intentional radiator and which fall within the restricted bands shall
comply with the general radiated emission limits in Sec. 15.109 that
are applicable to the incorporated digital device.
(g) Perimeter protection systems may operate in the 54-72 MHz and
76-88

[[Page 806]]

MHz bands under the provisions of this section. The use of such
perimeter protection systems is limited to industrial, business and
commercial applications.

[54 FR 17714, Apr. 25, 1989; 54 FR 32339, Aug. 7, 1989; 55 FR 18340, May
2, 1990; 62 FR 58658, Oct. 30, 1997]

 

[WCWalker]

That contradicts the 100 mw output power level rule. It can't work both ways.

Firstly, Part 15.219 specifies 100 mW input power, not output power. Part 15.209 specifies field strength at a given distance with no power or antenna limits.

These two rules don't necessarily conflict, because using an inefficient "100 mW" transmitter with an inefficient antenna conceivably could produce a field that meets 15.209.

In some cases the FCC has cited both 15.209 and 15.219 in issuing an NOUO based on excess field strength and excess transmitter power -- see http://www.fcc.gov/eb/FieldNotices/2003/DOC-278979A1.html

If you believe that the FCC can't have it both ways, perhaps you should take up your case with them.

//

This proves my point. 1200 mw? That's not even close to 100 mw and there is not one single Part 15 AM transmitter that can be modified to operate at that power level. It would require a whole new design and circuitry as well as different components with different values to handle that kind of power.

I don't need to take it up with the FCC because my station was given a clean bill of health by the people in DC.