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This one’s not about ground leads, however.
The field strength tells the story:
“Your operation on frequency 1620 kHz was measured at 900 microvolts per meter (uV/m) at 1132 meters.”
This one’s not about ground leads, however.
The field strength tells the story:
“Your operation on frequency 1620 kHz was measured at 900 microvolts per meter (uV/m) at 1132 meters.”
There are some interesting references to field strength only regs:
“This exceeds the allowable unlicensed limit of 100 uV/m at 30 meters established in Section 15.223(a) for operation on 1620 kHz, 47 C.F.R. S: 15.223(a), as well as the general unlicensed limit of 30 uV/m at 30 meters established in Section 15.209(a) for operation on 1620 kHz. 47 C.F.R. S: 15.209(a).”
Is somebody selling high power AMs on ebay or was this a modified ham xmtr, I wonder?
Read it all here
Total posts : 45366This is an interesting one to speculate about.
What is the true capability of a part 15 transmitter with very long antenna and good grounding?
There are carrier current transmitters floating around with from 3-Watts up to 50-Watts.
Schematic diagrams exist for 5-Watt, 10-Watt, 20-Watt transmitters.
And, yes, SCWIS knows that modified HAM equipment can get the job done.
Other ideas?
Total posts : 45366seems a hamilton with long ground lead could achieve these field strengths but i refer to this reply here http://part15.us/node/2937 that even at excessive field strengths a hamilton turned all the way up with a full size tower just will not be able to do much damage to even the lowest power licensed facility. ask those with night time authorizations running 20 watts or so how far that signal gets. a hamilton turned all the way up is capable of 800mW with no asymetry and it runs class C? meaning you actually apply maybe a 3rd of that to the antenna/tuning system? ninus system losses? so lets face it, a hamilton, procaster, sstran or other 100mW input am tx even into a full 1/4 wave over 120 radials is just not going to offer any interference potential to even the lowest power licensed broadcaster. there are dimmers, computers, stop lights, etc that put out more RF hash then even 100mW to a full 1/4 wave. so i logic that the ground lead rules are outdated and should either be eliminated officially or just un officially by non enforcement. i agree 100mW is generous but they should go back to the original interpretation that “ground lead” meant from tx chassis to whatever structure the system is mounted to and not to earth ground. it worked out nice everyone was happy. was a nice compromise. we should go back to that.
Total posts : 45366The FCC field strength reading in the NOUO corresponds to a radiated power of approximately 11.5 mW. This might be possible with a Ragemaster connected to a very efficient antanna system, giving an overall system efficiency of 11.5%. The KENC system efficiency calculated from the reading in with the Rangemaster is on a 40 foot tower was just over 3%. In the particular case of this new NOUO, the ground lead length would have to be very long indeed to get the measured field strength.
A Rangemaster can be misadjusted above 100 mW input limit, but not by much, since the modulation percentage would be low for high input power settings.
Total posts : 45366just an opinion based on my observations over the years.
Moderators note: Sorry, scwis
Total posts : 45366I am sure we have all seen the stuff sold there.
Examples:
http://www.ebay.com/itm/AM-TRANSMITTER-EXCITER-0-20w-Carrier-80w-P-E-P-/250701510303?pt=LH_DefaultDomain_0&hash=item3a5ef9769f#ht_1568wt_1059I also suspect some of these are just as rf dirty as FM HLLY transmitters.
Total posts : 45366the cquam is built by that guy who makes the greek cquam lpam transmitters. he gears those higher power ones toward carrier current and licensed markets. i have no doubt they are as spectrally clean as any other modern part 73 am transmitter on the market. the black faced one i have no idea who makes that one or have any clue about how clean an output it has.
Total posts : 45366I definitely agree that it is sad that the FCC seems to fail to see that people are yearning to experiment with wireless communications.
I also think it’s sad that the pendulum has swung so far from “promote the use of technology” to “protect failing business models”
Allowing the public to experiment with communications in a band with such a huge installed base of affordable receivers seems like a real win-win.
Instead it’s protect IBOC and HDRadio and conglomerate ownership and let the development of the utilization of the technology lie fallow.
A true technological tragedy
Total posts : 45366Ermi,
You didn’t say what parameters you used for your results. I ran some NEC simulations to see what would predict a signal strength of 900uV/m at 1132m.
Parameters:
Perfect Ground
CB whip antenna (102″, .2″ diameter)
Transmitter coil resistance: 20 ohms
Ground resistance: 20 ohms
RF input power to coil: .075W (corresponds to 75% eff. into coil)Elevation, FS at 1130m
0ft, 179 uV/m
20ft, 769 uV/m
30ft, 1040 uV/mSo, a transmitter operating at 100mW input power could produce the measured FS with a CB whip elevated somewhere between 20 and 30 ft. with the parameters I used. I believe the parameters are realistic for a good antenna installation.
This is indeed bad news for Part 15 AM enforcement. This seems to be the first NOUO that could have faulted an elevated 100mW transmitter on field strength measurement alone, rather than the typical simple observations that the antenna exceeded the 3 meter rule.
Total posts : 45366Correct me if I’m wrong, but don’t the rules state that must must meet ONE of the 2 Part 15 output requirements – EITHER 100mw input to the final, or the stated field strength measurements?
Total posts : 45366ArtisanRadio is right, Rule 15.209 begins with the words,”Except as provided elsewhere in this subpart, the emissions shall not exceed….”
That rule, 15.209, then specifies the radiation field strength limitations.The all important “EXCEPTION” is found in Part 15.219 which gives the 100mW to the final and 3-meter antenna limitations.
Therefore, 15.219 is an EXCEPTION to 15.209, an ALTERNATE. It is a classic EITHER/OR situation.
Actually the NOUO does a dis-service to interested parties by containing incomplete information. It would be better if the public servants did a more detailed report of everything that is taking place.
We have not been told anything about the transmission system, whether it complied with the 3-meter or 100mW exception, or about the programming….
Which brings us to the reason for the inspection… was it complaint driven? What is the motivation of the complainer? It could have been offensive language, or disturbing political speech, or a format that annoyed a licensee…
The Part 15 community deserves better service from its public servants, so as to maintain our own security of knowing we are operating in proper compliance.
Total posts : 45366Part 15.223(a) actually applies to 1.705 – 10 MHz:
15.223 Operation in the band 1.705–10 MHz.
top(a) The field strength of any emission within the band 1.705–10.0 MHz shall not exceed 100 microvolts/meter at a distance of 30 meters.
Total posts : 45366That’s a good find, radiomonkey, and what else can we think but that the inspector quoted a non-applicable rule in the NOUO, which still doesn’t get the operator off the hook because he was over power anyway.
Total posts : 45366I don’t know if it’s boilerplate boo-boos, carelessness or lack of familiarity with that end of the book. It’s possible that spending most of the time using part 73 might make heading over to 15 a bit odd for the EAs.
Interestingly semi-related, it’s possible that asking simulation software to make sense of extreme outlier data and to then extrapolate that to real world scenarios might have similar effects.
Total posts : 45366Actually the station isn’t over power.
Either he was running at 11 MW or 73 MW,
both completely legal under Part 15.219.Maybe he had a high efficiency transmitter?
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