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The beatings will continue until the morale improves...

audioguy said:
I cannot recall a time in recent history when the EB has so aggressively targeted Part 15 operators.
Click to expand...

Just curious, audioguy -

Both of your quoted NOUOs referenced not only an apparent violation of 15.219(b), but also to emissions from those operations that could "...present a safety hazard to the operation of aircraft..."

Can these FCC actions truly be characterized as unduly aggressive?

Some may see them as being mindful of the public interest, wouldn't you agree?

RF
 
Under Part 15 rules for this type of transmitter, spurious emissions are only required to be suppressed by 20 dB, which is not very much. Certainly these harmonics will propagate for short distances. The notices do not state what values were measured, so no conclusion can be drawn as to whether they were in compliance or not. The mere fact that they were observed does not mean that they were in excess of the limits. One gets the impression that the inspector was searching for anything he could find to add to the record, whether significant or not.

Part 15 transmitters typically do not have low pass filters (there are exceptions). They mainly depend on the Q of the output matching network for harmonic suppression. Although greater attenuation would be desirable, this would significantly reduce transmitter efficiency because of the way transmitter power is specified and measured.

It is a matter of conjecture as to whether the low order harmonics of an AM band transmitter would pose any risk to an aircraft. I personally rather doubt it.
 
It would seem odd since from what I know he is using the Hamilton Rangemaster which had been certified. There are plenty of them in operation and while a fraction of them may have been subject to FCC examination on installation issues I haven't seen any cited for spurious radiation issues. The only thing I could assume is that there was a tuning issue that exacerbated the problem, or, undue pressure was applied to the FCC by perhaps a commercial broadcaster fearing that the Part 15 operator would take away their audience.
 
audioguy said:
Under Part 15 rules for this type of transmitter, spurious emissions are only required to be suppressed by 20 dB, which is not very much.
Click to expand...

Three observations:

1. Neither of those FCC NOUOs found those setups to be operating legally under either Part 15.209 or 15.219. Therefore the harmonic suppression required by Part 15 in that spectrum for legally operating, unlicensed devices is of little value in the defense of those operations.

2. Even if the 2nd and 3rd harmonics of 1640 kHz that were mentioned in these NOUOs actually were 20 dB below the carrier at the distances shown in the NOUOs, they would still be greater than the value permitted for unlicensed operation in that spectrum by Part 15.223 (see clip below).

Sec. 15.223 Operation in the band 1.705-10 MHz.

(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.
However, if the bandwidth of the emission is less than 10% of the center
frequency, the field strength shall not exceed 15 microvolts/meter or
(the bandwidth of the device in kHz) divided by (the center frequency of
the device in MHz) microvolts/meter at a distance of 30 meters,
whichever is the higher level.

3. If these setups really met Part 15 for unlicensed operation, then the field intensities of the 2nd and 3rd harmonics at the distances shown in the NOUOs would mean that the harmonics would be buried in the ambient r-f noise at those distances, and unlikely to be noticed by an FCC inspector.

RF
 
Bill DeFelice said:
..The only thing I could assume is that there was a tuning issue that exacerbated the problem, or, undue pressure was applied to the FCC by perhaps a commercial broadcaster fearing that the Part 15 operator would take away their audience.
Click to expand...

Regarding the "or" part of the post clip above, it should be noted that the FCC will have no technical or legal basis to issue an NOUO or worse to an unlicensed operator of a setup that is in functional compliance with Part 15 -- no matter how much that operation might aggravate a commercial broadcaster.

Accurately researching, understanding, and using a functionally compliant system will avoid such FCC actions -- if that is what their operators wish to do.

RF
 
The field strength reading for the transmitter operating on 1610 kHz corresponds to a radiated power of 8.16 mW of radiated power from an electrically short vertical monopole over ground. For the 1640 kHz transmitter, the apparent radiated power is 9 mW. These two radiated powers are fairly close to each other.

This compares to an apparent radiated power of 3.34 mW for the KENC transmitter operating on 1620 kHz, which was mounted on a 40-foot tower.
 
It should be noted that WDCF 1350 in Dade City, FL has a spur on 2.7 MHZ that can be heard 1.5 miles away from the station. Also WWJB 1450 in Brooksville, FL also has a spur that can be heard on 2.9 MHZ. Am I to assume these stations also pose a threat to public safety?
 
druidhillsradio said:
It should be noted that WDCF 1350 in Dade City, FL has a spur on 2.7 MHZ that can be heard 1.5 miles away from the station. Also WWJB 1450 in Brooksville, FL also has a spur that can be heard on 2.9 MHZ. Am I to assume these stations also pose a threat to public safety?
Click to expand...

Actually, these are harmonics, not spurs (spurious emissions). When I learned my radio theory years ago, multiples of the fundamental frequency were designated as harmonics, and spurious emissions were emissions that were mathmatically unrelated to the fundamental. Interesting to note in both NOUOs, although the two frequencies listed are clearly harmonics, the FCC inspector describes them as spurious signals.
 
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