I'm not a ham but I follow ham with interest, and know that many hams use part 15 devices for all kinds of utility purposes. I would think tying your call sign into the part 15 operation seems cool. "A service of 39GH5," just making it up.
It seems to me that using my ham call sign for part 15 operation would technically be operating out of band which is a violation of the rules for amateur radio.
The best way, in my opinion, to identify a part 15 station is to use a phrase as was suggested earlier and avoid anything which resembles a call sign.
Neil is correct. It would be out of band operation and a violation of the rules. Plus, it will get real old identifying the station every ten minutes or at the end of a message. LOL.
WA4JM, Druid Hills Radio. See you in 10 minutes.
WA4JM, Druid Hills Radio. See you in 10 minutes.
WA4JM, Druid Hills Radio. See you in 10 minutes.
WA4JM, Druid Hills Radio. See you in 10 minutes.
WA4JM, Druid Hills Radio. See you in 10 minutes.
Snore...........
Ken Cartwright reports on his website, www.kencradio.com , that The FCC has rejected the ground lead filter designed by Hamilton, saying that it does not provide conditions equivalent to operating the transmitter with the 3 meter limit in the antenna system.
Part 15 broadcasting R. I. P.
Please notice the letter is from the local FCC inspector and draws a direct correlation between 15.219 and 15.209. The letter infers that if the installation was in fact 3 meters in total length (ground lead, transmitter and antenna), then the transmitter must still jump the additional hurdle of field strength compliance as well. That's a new one. Does this decision scream something at us about our installations and the current state of affairs of the FCC enforcement folks and Part15 "broadcasting"?
I have thought all along we had not heard, nor seen, all of the issues dragged out in the daylight about this situation. And I think this is an indication. I believe there is more to come. Wait for it......
It may be time to be pro-active and come up with a complete operational solution for part15 AM broadcasting (which is not specifically mentioned in the Part 15 rules) with the FCC "certified" Rangemaster transmitters that will pass muster with inspectors. Apparently we have not found the proverbial silver bullet, yet.
My take on the letter is a bit different. What Agent Nguyen is saying was that by seeing no significant difference in measured field strength in the elevated installation, whether with or without the RF filter in place, then he is still counting the entire length of the ground lead from transmitter to earth's surface which would be in excess of the 3 meter limit and therefore in violation of 15.219. If it doesn't fit under 15.219 then the only other way it could be legally operating without a license would be under 15.209 and the measured field strength was too high to comply. I didn't take it as saying that Ken needed to be in compliance with both regulations. The implication seemed more to be that if he didn't comply with 15.219 then he must be in compliance with 15.209 to be legal. Clearly it was Nguyen's assessment that the installation complied with neither.
To me the biggest implication from the letter is that if their decision is ultimately allowed to stand, it would seem that elevated installations are at a much greater risk of a NOUO than a ground-based installation. I would love to know what his definition of "no appreciable difference" means as Agent Nguyen saw fit not to include any of his field strength reading results in the letter.
I agree with deano. The agent mentioned the very low 14.8 uV/m field strength at 30 m limit of 15.209 after stating that the system does not meet 15.219. Once again, some think that the agent is saying that BOTH 15.219 and 15.209 have to be met. The rules clearly give several alternatives to 15.209, including 15.219. I'm sure that the agent never actually thought that both 15.209 and 15.219 have to be met. I do think that he was careless in drafting his letter in such a way that the same confusion occurred again. This time, he should have stated explicitly that 15.209 applies only if 15.219 is not met.
"The field strength meter readings revealed no appreciable difference between operation of your AM transmitter and associated equipment with the filter attached, and without the filter attached. Consequently, it is apparent that the attachment of the filter to the transmitter and associated equipment does not limit the total length of the transmission line, antenna and ground to the three meters required for unlicensed operation pursuant to Section 15.219 of the Commission's rules." - letter from FCC inspector
"Operation in the band 510-1705 kHz. - 15.219 (b) The total length of the transmission line, antenna and ground lead (if used) shall not exceed 3 meters." - from CFR 47
"The FCC's Office of Engineering and Technology ("OET") also tested the devices and OET's results confirm the ineffectiveness of this configuration. The field strength measurements also exceeded the 14.8uV/m at 30 meters limit prescribed by section 15.209 (a) of the rules." - FCC inspector
It appears the FCC inspector began with 15.219 as the standard. The measurement of the effectiveness of the filter is tied to field strength measurements. The statement of the inspector points out that the evaluation is based on field strength comparisons. And incidentally, the field strength exceeds the allowable signal from 15.209. The entire determination is wrapped around the effectiveness of the filter to limit the "effective length" of the transmitter components in 15.219 b. Using comparative field strength readings in a lab (not tested on a transmitter/antenna range) is not definitive proof of the ineffectiveness of the device or that the installation still cannot be changed in such a way as to be considered compliant; the 40 foot tower at CKENC not withstanding. According to Keith Hamilton, this device was tested prior to its implementation. Just a side note, Part 15 transmitters are not certified in the OET lab. They are tested in independent labs and the data submitted to the FCC for acceptance.
I would suggest, if the transmitter DC and audio signals are sent to the transmitter by shielded cable (available from Hamilton), wouldn't the shield radiate causing the filter on the ground lug lead to be ineffective? The audio ground and the transmitter ground are common and the same potential inside the transmitter. I doped out the circuit board my own Rangemaster and found zero resistance between the external ground lug and the audio ground terminal. There are apparently no internal choking devices to keep RF from traveling down the audio shield.
Without the OET report, can we make a definitive judgment as to the configuration used in testing the filter? And as has already been brought to the discussion, what constitutes an "appreciable difference"?
Apparently, the other nearby transmitter(s) were on at the time of the test and could have skewed the results of the filed agents tests by adding signal to the mix in the field strength meter; signal areas of all the transmitters overlapping. I would consider this testing regime flawed at best without further explanation.
I would suggest it ain't over 'til the fat lady sings. We need all the facts in order to make statements that Part 15 broadcasting is R.I.P., dead. There are thousands of Rangemaster 1000's that have been operating everyday for years with no problems. Should we also consider the possibility that local community politics are in play here? Could it be that Ken is making the local licensed AM look bad and getting into their pockets? I know what I think. I used to work in broadcasting in the very same town. You can draw your own conclusions.
Marshall posted: It appears the FCC inspector began with 15.219 as the standard. The measurement of the effectiveness of the filter is tied to field strength measurements. The statement of the inspector points out that the evaluation is based on field strength comparisons.
This is a well know technique in scientific investigation, namely, if something is changed and there is no "appreciable" outcome effect then the changed parameter is not affecting the outcome. Had there been an "appreciable" difference with the filter then the next step would be to determine how much difference. Once the determination has been made that the effect of the filter is not significant then there is no need to pursue it further. Since the physical limits of 15.219 were exceeded in this case then it makes sense to check if 15.209 compliance applies and if compliant then operation can continue. This was done.
The problem with evaluating 15.219 in terms of field strength is that it brings into play many factors such as antenna system efficiency, ground system, transmission line effects, etc., and we lose the advantage of 15.219 which is a simple way to achieve compliance which is within the capability of almost any hobbyist. Had the filter significantly reduced the field strength then the question would be was the reduction enough and upon what is this based. I would hope that the required field strength reduction would not be to the limits of 15.209 but fortunately this is moot.
I believe the FCC examiner went out of his way to be open minded in considering the filter alternative and it would have been difficult to proceed had the filter produced a significant change.
Neil
The way the rules are written, Section 15.209 is the fundamental rule. It gives the allowed emission limits for the entire radio spectrum from 9 kHz to "above 960 MHz." Section 15.209(a), which contains the table of emission limits, begins with the phrase, "Except as provided elsewhere in this Subppart..." Section 15.215(a) says, "The regulations in Sections 15.217 - 15.255 provide alternatives to the general radiated emission limits [in 15.209(a)--my added note] for intentional radiators in specified frequency bands." So, 15.219 is an alternative to 15.209, and 15.209 applies only if 15.219 does not.
The additional field strength measurements, as well as the OET evaluation, were no doubt done because Ken Cartwright had Senator Wyden looking after Ken's interests. The FCC very likely expended numerous man-hours on this case. The field agent did a lot additional work, and the OET laboratory personnel did a lot of evaluation, and took several months to make the final decision. This case was certainly not routine. The Government was very responsive to a citizen's concerns, although said citizen did not get his way this time. This did not turn out like the "Reid Exemption" in Goldfield.
I know lots of you pooh-pooh the Talking House transmitter but maybe KenC should invest in one along with the ATU that is certified to be Part 15 accepted as a system.
ISS, a company that supplies TIS and other broadcast transmitters, markets their InfOspot system as Part 15 certified. It consists of the Talking House transmitter with ATU along with a remote interface and fancy enclosures (read high-priced.)
The point is that using the Talking House transmitter with its ATU is advertised as using up to 300 feet of coax antenna cable as a Part 15 certified system.
There would definitely be some litigation if that was turned down by the field agent.
But then again, all the agent has to show is interference rather than non-compliance to shut him down.
It does not surprise me that the FCC did not approve the Hamilton ground lead filter. Such an approval would not have been in their best interests. It would have greatly complicated their enforcement of the rules. What surprised me is that they responded at all. It was probably the pressure applied by Senator Wyden that forced them to make an official decision. Please note that the decision that they had to make had a definite negative effect on the range possible with Part 15 AM. The policy of the FCC is to limit the range possible with Part 15, not to increase it. Let's hope that they do not have to make any more decisions about Part 15 AM.
The decision that was made was, perhaps intentionally, not perfectly clear. No data was presented. The FCC simply said that compliance with the three-meter rule was not demonstrated. I looked at how much attenuation is required to get Ken Cartwright's elevated antenna to work as if the antenna were at ground level.
The field strength recorded in the original NOUO was 4000 uV/m at 137 m. This is equivalent to 18,300 uV/m at 30 m. The radiation resistance of the elevated antenna is about 8.3 ohms. At ground level, the radiation resistance is about .11 ohms. The power gain of the elevated antenna is a factor of 8.3/.11 = 75.5 = 18.8 dB above the power gain of the antenna at ground level. Hence, to make the elevated antenna equivalent to a 3 m antenna at ground level, the filter should produce an attenuation of -18.8 dB. We don't know what attenuation was produced by the actual ground lead filter tested by the FCC. On another website, Hamilton reported that the attenuation produced by his old ground lead filter design, that has the ferrite toroid, was - 6 dB. He did not release any attenuation data for his new filter design that was installed at Ken Cartwright's site. If the new filter had anything similar to the attenuation reported for the old filter, the attenuation was clearly not enough.
Sufficient attenuation (-18.8 dB) would have reduced Ken Cartwright's signal from 18,300 uV/m at 30 m to 2100 uV/m at 30 m. This is actually fairly representative of a good Part 15 installation at ground level. It can give a range of about a quarter mile. The field strength is much higher than the 15.209 limit of 14.8 uV/m at 30 m.
Even if the filter had provided enough attenuation at Ken Cartwright's installation, it would not have been appropriate for other installations. If the elevation had been 20 feet instead of 40 feet, the radiation resistance of the elevated antenna would have been about 2.5 ohms. The antenna gain increase due to elevation would have been 2.5/.11 = 22.7 = 13.6 dB. The appropriate filter attenuation would be only -13.6 dB.
About the only way to prove that a filter has enough attenuation for an elevated installation not to exceed the 3-meter rule is for the Part 15 operator to supply extensive engineering data, which he will not be capable of providing. Very likely, the FCC would also not be interested in evaluating such data.
Ermi.
The explanation of your views on the government agency's evaluation of the ground filter from Hamilton is interesting and appropriately factual.
However, this expose' is exactly what I mentioned on my blog (node 2339) concerning the current assault on Part 15 micro-broadcasting.
Most folks interested in Part 15 low power AM broadcasting, whether public/community service oriented or hobbyist, read highly technical information and outcomes from computer modeling only to go, "Huh?" Highly technical explanations have been offered for years, yet not making much headway in a change in the actual practice. Well intended operators wanting to operate as a low power unlicensed broadcasters, continue to find themselves with compliance issues. We lack consistent standards and accepted operating practices.
And as you pointed out, even with the evolution of the FCC Part 15 rules, the government has been completely silent as far as AM micro-broadcasting is concerned. They have no intention of encouraging the AM micro-broadcasting service at all. Many of us labor under the illusion that community micro-broadcasting is an accepted practice and necessary. The FCC doesn't see it that way.
It would seem more helpful to provide a design schematic or simple concept we can all use to bring these transmitters into compliance. Maybe these suggestions could be based on actual field testing, instead of computer modeling. It is just my opinion that highly technical explanations in some cases add to the confusion and drama instead of moving us toward a solution.
I learned years ago communication takes a transmitter and a receiver. If the message is sent and not understood, the transmission it not useful in communicating. Message sent, message not received. I would suggest you consider your reading audience.
I support your opportunity to tell us what we should know. I'm just not so sure some of us get what you're saying sometimes.
And as a final note, those of us who carry an amateur radio license (KK7CW, Amateur Extra Class, licensed for over 25 years) and operate with power outputs exceeding a kilowatt, please don't call Part 15 amateur radio. Some of us have worked our hind sides off to get our licenses and work very hard to maintain them. I prefer the term hobby radio for Part 15.