FCC cite for both 15.209 and 15.219

Sounds like the field inspectors/agents gave every benefit of the doubt and looked to see if there was any way it could be considered compliant. Running over a watt, though? Pretty much no way it was going to come in as legal under part 15 on the AM BCB.

Still, sounds like the FCC gave it every chance they could.

Daniel

This is the latest in what has been going on for quite some time now. it started with oldies 102.3 @ 40w ERP @ 60ft HAAT and seems to have ended with WCBO AM 1700 @ 1200mW input, 3m antenna, 6 meter ground.

He did not tune the Tx. the engineer that turned him in installed it that way. I tuned it back the right way and the next time i came back it was back to 8 volts. suffice to say i left it that way. and the engineer and station that gave him all his equipment and set up the tx to illegal power levels is the same engineer that turned him into not only the FCC but BMI.

Thank You,

Rev. Robert P. Chrysafis
Universal Life Ministries
http://www.ulc.org

Moderator Hunterdonfree
http://groups.yahoo.com/group/hunterdonfree

Since we hobbyists rarely have access to accurate field strength readings, it is difficult to appreciate just how inefficient a Part 15 AM installation can be. The installation discussed here uses a radiator nine meters long, forming a grounded dipole antenna fed at two thirds of the total height. The radiation resistance is about twenty times higher than for a three meter radiator fed at its base. The input power to the final transmitter stage is twelve times what is allowed by Section 15.219(a). Even so, the FCC field strength reading corresponds to only 22.2 uW radiated from an electrically short vertical monopole. This is an efficiency of only .00183 %!

I presume that this is a particularly poor system. It should be possible to get more than this amount of radiated power from a very ordinary system with a three meter antenna and 100 mW of input power to the final stage. A really good system should be able to get ten times the radiated power calculated here.

Rev.,

Thank you for your insight into this cite. As Rattan posted, I too find it interesting that the FCC agents examined both 15.209 and 15.219 and apparently tried to cover both rules. That is to their credit in my book.

As far as the "engineer" who set up this station and then set up the operator by reporting to the FCC is concerned this demonstrates unethical practice on his part, and I am not talking about the whistle blowing but rather maladjusting the transmitter to violate the rules. Is this person a real engineer or just a wannabee? A licensed Professional Engineer would most likely lose his license if he knowingly enabled someone to violate the law as you have described.

I presume there is more to this story than has been disclosed, but the so called "engineer's" conduct as reported in your post is shameful.

The other important message here is that the enablers were not cited. The operator is ultimately responsible for the legal operation of a part 15 station, not the consultants and not the manufacturers.

Neil

he's cheif engineer for a local broadcast cluster. there is a long story behind these two that starts about 30 years ago in a CB radio club and the story would require a multipage blog to tell.

Thank You,

Rev. Robert P. Chrysafis
Universal Life Ministries
http://www.ulc.org

Moderator Hunterdonfree
http://groups.yahoo.com/group/hunterdonfree

Rev,

It is not necessary to go into the details. Thanks for what you have already posted. It is disappointing that some folks behave that way.

Neil

Just picture Jack Lemon and Walter Mathaeu on Stereoids and supplant the woman with a Radio Station and you get the picture.

Thank You,

Rev. Robert P. Chrysafis
Universal Life Ministries
http://www.ulc.org

Moderator Hunterdonfree
http://groups.yahoo.com/group/hunterdonfree

ok - that was the most awsome description of a situation as I've ever read.

As Neil said, low-power AM enforcement actions are rare, but here is another one that was issued recently:

http://www.fcc.gov/eb/FieldNotices/2003/DOC-279229A1.html

This one was issued to a college radio station. Interestingly, educational institutions can use the Section 15.221 rules, which allow a school AM station to use any amount of power, provided that that the Part 15.209 field strength limits are met 30 meters outside of all of the border of the campus. Unfortunately, the Part 15.209 limits are so low (corresponding to 2.2 nW from an electrically short antnna), that, unless the campus is larger than Rhode Island, it is not possible to use an antenna to get a useful signal in a significant area of the campus. If a campus uses an antenna (or preferably multiple transmitter and antenna combinations) it is much better to use Section 15.219 rules rather than Section 15.221 rules. LPB lobbied for for Section 15.221, and got it in 1990. But it did not help them sell many transmitters with antennas at schools. Section 15.221 also permits the use of buried leaky coax cable, and LPB was able to sell some buried leaky coax installations, such as at Disney World.

The field stength measured at the college charged in this particular NOUO corresponds to a radiated RF power from an electrically short antenna of 469 mW. This clearly exceeds Section 15.219 limits, since the input power that is allowed by Section 15.219(a) is only 100 mW, and the antenna length limit of Section 15.219(b) results in an astonisingly low radiated power (even if there is cheating), as I showed in another post in this thread.

Thanks, Ermi, for the link and for doing the math.

What follows is some rambling memories of my campus carrier current adventures (from the '60s) which is primarily for entertainment and to describe what can go wrong.

Some of you might remember my mentioning in other posts that I was involved with the carrier current operation on the university campus when I was a student. We did a lot of things right but at times things went wrong. Mostly, the five or so transmitters around campus were built, maintained, and operated by ham radio folks from the electrical engineering student pool, but with the post Sputnik emphasis on engineering rigor the students found it almost impossible to continue in this role and only I was left after a while and that lasted about six months.

The studios were located at a conservatory of music about 1/2 mile off campus and everything was audio linked by leased phone lines. The transmitters all were loaded into the power system in each dorm and the field strength just a few tens of feet from the dorms was not enough for the signal to be usable on a portable radio even though the transmitters were rated from 5 to 25 watts input. The signal for a line operated radio in the dorm was really good though.

Here's what went wrong. I was in a co-op program, three months at school, three months away working. I was on the engineering staff and knew the faculty advisor and the "jocks" so when one of our transmitters went wacky while I was on work section, listeners heard the university's name on the ID and called the full power licensed FM campus station to complain about their signal being heard all over the AM band in one of the dorms. The FM staton called the advisor who gave them my name and from campus records they found and called me at my work residence some 60 miles away. Uh Oh...now what do I do?

Since it was a weekend, I drove to campus to investigate and found the 25 watt tube transmitter which I had built and tested to be engaging in Barkenhausen oscillation. Not good! Never happened before. So I retuned the transmitter and the loading and all was well, but I still did not know what went wrong. I did notice that the tuning was off quite a bit and it took a lot of adjusting to get it right. Was someone else messing with the transmitter?

Yep. The station's "chief engineer", a music performance major with no ham or electronic background, had performed "routine maintenance" on the unit. We later had a staff meeting and reorganized a bit with a new "chief engineer"....me!

Things went pretty smoothly thenceforth until the day that I was either fired or quit...probably both. I had gone to the studio to find out why all the audio feeds to campus were distorted and had been that way for weeks. The leased phone lines were connected to a patch panel in a rack in the studio and at the top of the rack was the "audio distribution amplifier", a tube type Heathkit Mono HiFi amplifier. Inspection revealed that the glass envelope on one of the push pull output tubes was broken. I unpatched the feed and removed the amplifier so I could clean it and replace the tube. Had I known then what I know now about politics, I should have at least told the faculty advisor what I was doing, but I didn't and he walked in and went ballistic when he found out that we were "off the air".

Another five minutes and it would have been fixed but due to the verbal abuse I walked (or was fired) and I don't know what happened after that.

I have been told that a few years later the FCC shut them down for a year because someone had taken the 25 watter and used it to feed an antenna strung between the light poles at the campus stadium. Rumor has it that they were heard at the FCC monitoring post some 40 miles away. It is surprising that someone smart enough to make this work was dumb enough to try it. As far as I know, the station is operating to this day. When the conservatory was moved onto main campus there was a major infusion of money for the performing arts and the station benefitted with new equipment. They have a website up so I presume all is well with them.

Thanks for letting me recall fond memories and I hope it wasn't too boring for you. If you read this far then I guess it wasn't.

Neil

FCC NOUO: "Your operation on frequency 1620 kHz was measured at 65,000 microvolts per meter (uV/m) at 100 meters. This exceeds the allowable unlicensed limit of 14.8 uV/m at 30 meters established in 47 C.F.R. S: 15.209(a). Thus, this station is operating in violation of 47 U.S.C. S: 301."

Ermi Roos: "The field stength measured at the college charged in this particular NOUO corresponds to a radiated RF power from an electrically short antenna of 469 mW. This clearly exceeds Section 15.219 limits, since the input power that is allowed by Section 15.219(a) is only 100 mW, and the antenna length limit of Section 15.219(b) results in an astonisingly low radiated power (even if there is cheating), as I showed in another post in this thread.
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If I did this right, the numbers are even worse, Ermi.

Generating a 65 millivolt/meter groundwave field 100 meters from a ground-mounted, base-loaded Part 15 AM setup on 1620 kHz with 20 ohms total of coil and r-f ground loss would take an applied power of almost 80 watts. The r-f voltage at the base of the 3-m whip would be in excess of 6,000 volts !

The above system elevated so that the base of the 3-m whip and transmitter was 6 meters above the earth, and was connected by a 6-meter vertical conductor to the same r-f ground would need about 13 dB less applied power for the same measured field strength. A -13 dB ratio converts to a power multiplier of about 0.05, so the power needed then would be a bit less than 4 watts. The r-f voltage at the base of the whip would be about 330 volts.

Even a perfect 1/4-wave monopole over a perfect ground plane would need about 1/2 watt of applied power to produce this measured field at 100 meters.

It would be interesting to learn what their configuration really was.

Rich

At the risk of violating MLR's request that we refrain from the much discussed ground lead topic I just want to point out that Rich's post shows the astounding effect on field strength which can result from the contribution of a ground lead.

The FCC knew very well what they were doing when they limited the lengths of RF conductors.

Neil

A casual reading of Rich's post might cause some of the audience to think that he and I disagree about our numbers. Actually, we are in complete agreement. Rich is illustrating how difficult it is to get good efficiency from a 3 meter whip at ground level, and even from a 3 meter whip elevated 6 meters. The radiated power that corresponds to the field strength reported by the FCC is 469 mW from an electrically short antenna, as I stated in my previous post. Rich reports that, to get this much radiated power at 1620 kHz, it is necessary to apply about 80 watts to a 3-meter antenna with 20 ohms of loss resistance, and about 4 watts when the antenna is elevated 6 meters. This implies an increase in efficiency by a factor of about 20 for the elevated antenna.

In my post, I mentioned only the radiated power, and not the power that has to be applied to the antenna to get the radiated power. Rich also says that about a half watt applied to a lossless 1/4 wave monopole produces the field strength the FCC measured. This is true, because a lossless electrically short antenna has only slightly less gain than a lossless 1/4 wave monopole (469 mW is about a half watt).

As I said, there is no disagreement. I just wanted to clarify the two posts.

Adding a bit more detail:

Ermi wrote "Rich reports that, to get this much radiated power at 1620 kHz, it is necessary to apply about 80 watts to a 3-meter antenna with 20 ohms of loss resistance, and about 4 watts when the antenna is elevated 6 meters. This implies an increase in efficiency by a factor of about 20 for the elevated antenna.

Just to remind that the added efficiency is not produced because the Part 15 tx and 3-m whip are elevated, per se, but because of the added radiation from the long conductor(s) connecting the tx chassis to the buried r-f ground.

Some believe that the added signal strength from elevated (whip/mast) Part 15 AM systems is due to better line-of-sight paths from the 3-m whip. But a NEC evaluation shows that it is due to radiation from the longer conducting path to r-f ground.

Rich also says that about a half watt applied to a lossless 1/4 wave monopole produces the field strength the FCC measured. This is true, because a lossless electrically short antenna has only slightly less gain than a lossless 1/4 wave monopole (469 mW is about a half watt).

NEC shows that a lossless 3-m monopole system on 1620 kHz has a peak gain of 4.77 dBi. This value is 0.38 dB less than that for a lossless 1/4-wave monopole. So if this 1/4-wave system needed 1/2 watt of applied power to produce a given field strength at a given distance, then this 3-m monopole would need about 9% more, or 0.545 watts.

So we are in essential, but not exact agreement.
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