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Willful vs. Unintentional Non-compliance with FCC §15.219

If you can't say, Bill, you can't say. It is not as important to know precisely what happened to Jerry, as to know what the FCC's enforcement rationale is. Thanks to pascoradio posting on another site, we know that the structure was a two-story wood-framed building. Such a construction would not hinder RF at 1700 kHz much, and perhaps an AC ground wire might have actually increased the antenna gain. It would be interesting if a test were made to study this, perhaps comparing a second floor iAM installation field strength to that of a similar installation on the first floor.
 
I'm planning on a comparison of four Talking House transmitters: the original issue with cassette player (given to me by one of my forum's members), two Talking House 4.x units I got from a retiring real estate agent as well as the updated i.AM.Radio version provided by Radio Systems.

I need to speak to a friend who has a two story wood frame home to plan on doing such a test. The homes are clustered together pretty close within each block so I wonder if any possible chance of re-radiation might have been what the agent measured.
 
... I wonder if any possible chance of re-radiation might have been what the agent measured.

If J. Gaule's system allegedly installed in a 2nd floor apartment of a 2-story wood-frame structure was found by the FCC to be completely compliant with their ¶15.219, then the field intensity 175 meters away from it would be unimportant -- regardless of re-radiation from the conductors in nearby structures and/or from other re-radiators.

FCC ¶15.219 has no limit on the fields produced by unlicensed systems fully complying with ¶15.219.
 
rfry said:
... I wonder if any possible chance of re-radiation might have been what the agent measured.

If J. Gaule's system allegedly installed in a 2nd floor apartment of a 2-story wood-frame structure was found by the FCC to be completely compliant with their ¶15.219, then the field intensity 175 meters away from it would be unimportant -- regardless of re-radiation from the conductors in nearby structures and/or from other re-radiators.

FCC ¶15.219 has no limit on the fields produced by unlicensed systems fully complying with ¶15.219.
Click to expand...

An experienced field agent would know that something is up if an unexpectedly high field strength is encountered. Assuming 100% efficiency of a Part 15 AM system, the highest theoretical field strength of a Part 15 AM system is about 17,000 uV/m at 175 meters. Suppose a field agent saw an impossibly high field strength like this, and he saw no obvious 15.219 violation, would he pass it because 15.219 has no field strength limit? Very likely he would investigate further.
 
In my previous post, I illustrated a hypothetical field strength reading that should indicate to a field agent that a 15.219 violation had taken place, even if 15.219 does not specify a field strength limit. There is, however, a real-life example that should have indicated to the field agent that there was not only a violation of 15.219(b), for which the operator was actually cited (because of a 20-foot ground lead), but there was also a violation of 15.219(a), because more than 100 mW would have been required to be applied to the antenna and ground system in order to obtain the recorded field strength. This was the much-discussed Liberty 1640 NOUO issued April 9, 2010, in which the measured field strength was 73,800 uV/m at 30 meters. This field strength corresponds to a radiated power of 54.5 mW, which would have left only 45.5 mW to be dissipated as ground loss even if the transmitter were 100% efficient, which is not possible. The input DC power to the final stage had to be considerably greater than 100 mW. Even with the 20-foot ground lead, the antenna was still very definitely electically short, which suggests a high ground loss compared to radiation resistance. The NOUO did not mention the 15.219(a) violation, maybe because the more obvious 15.219(b) violation was sufficient for justifying the NOUO.
 
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The details given in the Liberty 1640 NOUO show that a 73,800 µV/m field was measured by the FCC at a horizontal distance of 30 meters from the transmit antenna, when Liberty 1640 was using a 20-foot ground lead.

NEC4.2 shows a radiation resistance of about 2.65 ohms for a ~30-foot monopole driven 3 meters below the top, against a perfect ground plane.

If the r-f loss in the loading coil was 15 ohms, and the loss in the r-f ground connection also was 15 ohms, then NEC shows that the gain of that system in the horizontal plane is about -5.9 dBi.

Using an equation relating antenna gain in dBi, applied power, and field intensity from a monopole at a given horizontal distance shows that the applied power needed for this set of conditions is about 635 mW.

NEC analysis alone shows that a radiated power of 54 mW is needed from this system to produce 73,800 µV/m at a distance of 30 meters over a perfect ground plane, which is in good agreement with the previous post of Mr. Roos. NEC also shows that 635 mW of applied power is required for that system to produce that radiated power.

The FCC measurements were taken over an imperfect ground plane in Nebraska, but the groundwave propagation loss over that 30-meter path would be very little more than for perfect earth.
 
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At the time the Liberty 1640 NOUO was discussed previously on this board, emotions were running high because of a perceived injustice to the station by the FCC. For that reason, it was necessary to tread carefully when commenting in order to avoid fights. Now that some time has passed, it may be possible to be more frank:

Supposedly, the transmitter was a Rangemaster, but an unmodified Rangemaster, even when elevated 20 feet, could not have produced the field strength that was recorded by the FCC. Either the FCC agents made a large measurement error with their FIM, or there were modifications to the Rangemaster circuit to increase the power of the transmiter considerably.
 
Another possibility could be the use of a linear amplifier driven by an unmodified Part 15 AM transmitter.
 
The analysis and results concerning the Liberty 1640 NOUO were not created just recently, but were discussed and debated in a long thread on this board called "Liberty 1640 Ordered Off the Air," beginning nearly four years ago, on April 16, 2010, and continuing for months afterward.
 
Ermi Roos said:
... or there were modifications to the Rangemaster circuit to increase the power of the transmiter considerably.
Click to expand...

@Ermi: at what power level would you estimate would produce this sort of field strength assuming the transmitter was otherwise installed in a compliant manner?
 
RadioCityBill said:
@Ermi: at what power level would you estimate would produce this sort of field strength assuming the transmitter was otherwise installed in a compliant manner?
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Bill,

I think that the input power to the transmitter final stage was in the vicinity of a watt, or so. I don't agree with Fry's analysis. This thread has become a continuation of the Liberty 1640 thread, in which Fry claimed back in 2010 that the radiated power corresponding to the field strength recorded by the FCC is 301.5 mW. I'm glad that he now agrees with my posted calculation at the time of 54.5 mW. But I also believe that his additional analysis in this thread is in error. I'm not sure I want to deal with this latest paper blizzard, however.
 
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Yes, because current drops to near zero and voltage is maximum at the top of a monopole antenna.

I computed it for the base of the antenna because the impedance at the top of the antenna is pretty much unknown.
 
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On another site, I read about the use of elevated "ungrounded" Rangemasters, and the poster noted that the range is significantly reduced when there is no ground lead compared to when a ground lead is connected. Actually, if the transmitter were truly "ungrounded" he would have obtained practically no range at all instead of the reduced range of "only a few blocks" that he describes. For the transmitter to function at all, there has to be some sort of return path for the dispacement current from the antenna to the circuit ground of the transmitter. In this case, the return path to circuit ground was probably through the transmitter power and audio input cables.

In the Liberty 1640 NOUO discussed previously in this thread, the FCC measured 73,800 uV at 30 meters from what was said to be a Rangemaster; but with the 20 foot ground lead disconnected, the field strength was reduced to 19,700 uV/m, which is still a very strong signal. This is a reduction of signal strength of about 11.5 dB, but some of the lost field strength might have been recovered if the transmiiter had been retuned after disconnecting the ground lead. So, there really isn't any "no ground" elevated installation unless extraordinary measures are taken.
 
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Ermi Roos said:
On another site, I read about the use of elevated "ungrounded" Rangemasters, and the poster noted that the range is significantly reduced when there is no ground lead compared to when a ground lead is connected. Actually, if the transmitter were truly "ungrounded" he would have obtained practically no range at all instead of the reduced range of "only a few blocks" that he describes. For the transmitter to function at all, there has to be some sort of return path for the dispacement current from the antenna to the circuit ground of the transmitter. In this case, the return path to circuit ground was probably through the transmitter power and audio input cables.

In the Liberty 1640 NOUO discussed previously in this thread, the FCC measured 73,800 uV at 30 meters from what was said to be a Rangemaster; but with the 20 foot ground lead disconnected, the field strength was reduced to 19,700 uV/m, which is still a very strong signal. This is a reduction of signal strength of about 11.5 dB, but some of the lost field strength might have been recovered if the transmiiter had been retuned after disconnecting the ground lead. So, there really isn't any "no ground" elevated installation unless extraordinary measures are taken.
Click to expand...

Hey Ermi, I think the transmitters were mis-tuned as well.
 
Thanks for your comment, John. I think we need some standardization in the unit of distance called the "block." To me, a "few blocks" does not sound like a terribly low distance for part 15 AM, especially if no explicit ground lead is used. I think of a block as 0.1 miles because that is the nominal length of city blocks in the the area I know; although at particular locations, blocks vary greatly from the nominal length. To me, "few" is more than a "couple," which makes "few" 3, or maybe 4. 0.4 miles is not a bad distance at all for "no ground" Part 15 AM. In Manhattan, on the other hand, the blocks can be very long. It is a hike to walk between 5th Avenue and 6th Avenue, and so the distance has to be appreciably more than than 0.1 miles. Instead of blocks, I'd rather that some actual unit of distance were used for estimating distances. Even "furlongs" would be more meaningful to me than "blocks."
 
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