Recently the FCC issued an AM NOUO citing violations both of 15.209 and 15.219.
Some may think that this system must have used a transmitter with unusually high power output to produce the 8,400 µV/m field measured by the FCC at 89 meters.
However the NEC4.2 analysis linked below shows that commonly-available transmitters operating at 100 mW d-c input power and providing 47 mW r-f output power at the input of a 20-ohm loading coil can produce that measured field, for the other conditions shown. Numerous other conditions could produce that same measured field at that distance on that frequency, while maintaining 100 mW d-c input power for the transmitter.
As to the accuracy of NEC4.2, it should be noted that an accurate NEC model of a 1/4-wave monopole base-driven against 120 x 1/4-wave buried radials calculates the same groundwave field at 1 km for 1 kW of applied power as shown for that system by the FCC (about 306 mV/m).
If I read rich's post accurately, we are being told that perfectly compliant Part 15.219 sytems can be ordered off the air by the FCC?
Can you elaborate on the seriousness of this situation?
Compliance requires more than just using a compliant/FCC-certified transmitter. It also depends on its installation.
Here is a "clickable" link to that NOUO. Readers can reach their own conclusions.
http://transition.fcc.gov/eb/FieldNotices/2003/DOC-321497A1.html
According to the NOUO the total length of the transmission line and antenna exceeded 3-meters, which would explain the violation against 15.219.
I cannot figure out what point you tried to make with the opening post.
I cannot figure out what point you tried to make with the opening post.
The point leads from the second paragraph of my opening post stating that some might expect that a high power transmitter must have been necessary for this NOUO.
As shown by the NEC analysis, that isn't a requirement. It is possible for users of AM transmitters limited to 100 mW d-c input power to come to the attention of the FCC.
This case definitely came to the attention of the FCC, but the NOUO doesn't specify what power level the transmitter was producing, yet you seem to know that it was a stock and standard 100mW type. What brand was it?
Moreover, everyone knows that the reason for the size limitation on antenna et al is precisely to confine the radiation produced by a compliant transmitter.
You have brought attention to this NOUO. Was that your objective?
This case definitely came to the attention of the FCC, but the NOUO doesn't specify what power level the transmitter was producing, yet you seem to know that it was a stock and standard 100mW type.
Sorry, but the quote above is not a logical conclusion from my posts here.
My objective in this thread is to show that an AM transmitter limited to 100 mW d-c input power can produce an NOUO, depending on how it is installed.
To be logical your post here would need to relate in some way to the NOUO, since they were both included in your presentation.
As I read the NOUO the violation was having the transmitter atop a 50 foot tower which made the ground lead length plus the antenna length exceed the 3 meter limit.
The 100 mW DC input limit is a necessary but not sufficient condition for compliance with 15.219.
The lesson might be that use of a certified (or not) AM transmitter which is presumably set to 100 mW power input does not guarantee compliant operation (15.219)if the ground lead is too long.
Neil
Oswego, Illinois is nearly in your backyard. Were you able to hear this station on 1600kHz?
Somebody sure did-
"The Chicago Office received information that an unlicensed radio station was alledgedly operating in Oswego, Illinois."
It would take somebody familiar with licenses and allocations to pick this station out.
Do we know the identity of the informer?
The conclusion I take away from Rich's post is that, based on the NEC analysis, it is possible for a perfectly legal transmitter, also installed legally, to produce the field strength reported by the FCC.
However, in THIS particular case, the violation appears not to be the field strength, but the length of the ground lead. I suspect that the field strength led to the investigation, which led to the discovery of the illegal installation, which led to the FCC citation.
The moral of the story - ensure that your feedline+antenna+ground wire length meets FCC Part 15 rules, use a certified transmitter and you'll be OK.
The conclusion I take away from Rich's post is that, based on the NEC analysis, it is possible for a perfectly legal transmitter, also installed legally, to produce the field strength reported by the FCC.
Actually - the radiating conductors of the antenna system described in the FCC NOUO, and as modeled in my NEC analysis to emulate those conditions are both non-compliant with FCC §15.219(b).
An AM transmitter with a d-c input power of 100 mW or less used with radiating conductors whose total length was limited to 3 meters could not produce the field measured by the FCC (and shown by the NEC model) at a horizontal distance of 89 meters.
The NOUO is dated June 4, 2013.
The NEC4.2 Analysis is dated June 2013. Was it generated before or after June 4?
Anyone downloading that graphic and viewing it with a suitable viewer can access its image creation details, which are embedded in that jpg file.
For those unable to do this, here is link to what they would see (using Irfanview).
The date and time of creating that graphic page was today, June 15, 2013 at about 7 AM -- following my first reading/knowledge of this NOUO.
For confirmation of this date/time, see the second line from the bottom at the link below.
Oswego, Illinois is nearly in your backyard. Were you able to hear this station on 1600kHz?
Oswego, IL is about 209 miles from me, and about 242 miles from you. Did you hear it?
No, I could not hear that station, and knew nothing of its existence until this NOUO appeared.
In the daytime it is difficult to receive the Chicago 50 kW AM stations using 195-deg towers, from that far away.
Carl, are you hinting that I was the FCC's "informer?" If so, that is a serious charge to make -- especially as there is no basis for it.