Liberty 1640 Ordered Off the Air

[Carmine5]

A little item from Inside Radio:

http://www.insideradio.com//Article.asp?id=1772580&spid=32061

I was under the impression that this was a Part 15 station. So was it the station's politics or was it a violation of FCC rules that forced Liberty 1640 off the air?

c5

 

[Tom Wells]

I watched a YouTube they shot in a car (It was someone with the described format) and was very happy for them with
the coverage they demonstrated. I suppose we need to wait for the FCC info.
Hope they find a way to satisfy the inspectors quickly and return to the air.
The "P" word being used is not a good sign. Particularly if the FCC sees it this way instead of being a Part 15 with a simple
field intensity "misunderstnding" via a "questionable grounding issue".

In 1991, I had few segments on the Chicago Tunnel Company shortwave pirate, that were called
"Now it's time to crank about the Government", over dramatic symphonic music.
I think that helped bring about more efficent and prompt FCC action.
On HF, such opinions could easily extend beyond the US borders, and of course be heard by too many people, potentially.

 

[RadioMan203]

Here's the NOUO from the FCC site.

 

[Tom Wells]

Here's the NOUO from the FCC site.

Ouch.

 

[Deleted User]

They hand those NOUO's and NOV's out like food stamps here in Boston and we still have Pirate Operators that have the bleeping Mayor of Boston on as a guest.

Short of crashing in the doors, smashing the gear, jailing anyone found there, seizing assets, and deporting people, nothing is going to change

THE FCC DOES NOT CARE

http://www.fcc.gov/eb/FieldNotices/

 

[Carmine5]

Here's the NOUO from the FCC site.

Ouch.

According to the NOUO:

"Specifically, the agents measured the field strength of 19,700 microvolts per meter (uV/m) at 30 meters with the 20 foot ground wire detached. This shows that the ground wire was radiating and exceeds the 3 meter combined maximum length of all radiating elements permitted under Section 15.219"

If the ground wire is "detached" how could it be radiating?

 

[rfry]

If the ground wire is "detached" how could it be radiating?

The FCC first states in the NOUO that the field strength was 73,800 microvolts per meter (uV/m) when measured at 30 meters. Then later in that same NOUO they state that the field strength was 19,700 uV/m at 30 meters with the ground wire detached.

With due respect, wouldn't common sense then indicate that the ground wire was contributing significantly to the 73,800 uV/m field measured before the ground wire was detached?

Further, a "best case," functionally compliant Part15 AM setup on 1640 kHz would produce a groundwave field intensity of about 3,000 to 4,000 uV/m at 30 meters, which is quite a bit less than shown in this NOUO even with its ground wire detached.

RF

 

[stormy01]

Can someone tell us what kind of power in watts this "station" was outputting? What is the mathematical formula to determine power output in watts based on a field strength at a certain distance from the transmitting antenna?

By the way, the website for this 'operator', http://liberty1640.com/station_location.htm claims they are 100mW, Part 15...what are they smoking??? :

 

[rfry]

...What is the mathematical formula to determine power output in watts based on a field strength at a certain distance from the transmitting antenna? ...

That calculation is based on a fairly large number of variables including:

1. the a-c resistance in the r-f ground system, which itself depends on many variables

2. the length(s) of the conducting path(s) from the transmitter chassis r-f ground terminal to the functional r-f ground (typically, something buried in the earth). The top of grounded conductors such as towers, massive wires, flagpoles, billboards, water towers etc and/or the "ground" of an a-c outlet are not functional r-f grounds.

3. the r-f resistance of the loading coil

4. the frequency, which determines the radiation resistance of the antenna system for the total radiating length of the 3-m whip and the conducting path(s) to a functional r-f ground

5. the degree of impedance match between the transmitter r-f amplifier and its output circuits to the antenna system load impedance

Accurate knowledge of all of these numbers is not practical for a Part 15 AM system operator/analyst, even when all the equations are known. But some perspective on the answer to your question can be generated based on a given set of conditions. This was done to produce the chart linked below.
.
Using the methods/equations for a 10-meter ground conductor as shown in that chart (the blue curve), then the radiated power needed to produce an inverse distance, h-plane field of 73,800 µV/m at 30 meters on 1640 kHz would be about 300 milliwatts. A field of 19,700 µV/m at 30 meters would take a radiated power of about 21.5 milliwatts (other things equal).

Given typical losses in the antenna system, typical efficiencies of the output stage of the transmitter, and allowing for some matching loss would mean that the DC input power of the transmitter would be considerably higher than the radiated power.

Of course, we don't know the specifics for this or any other operation in an FCC NOUO, so nothing specific about the transmitter power of any particular operation can be inferred from the comments in this post.

http://i62.photobucket.com/albums/h85/rfry-100/Part15AMSystemComparison.gif

//

 

[Timewarp]

Oh my God! The FCC has charged a part 15er as a pirate because his ground wire was 18 feet
too long on his FCC type certified devices. You know what? There are part 15 devices in use in
just about every home in America. Maybe the government will just start knocking on all
Americans doors to make sure everyone's part 15 devices are in full compliance.

I am a disabled VET. They told me I fought for freedom!!!!

 

[Bongwater]

"Liberty"'s been up here a few times. Though I imagine his lawyer might advise him not to comment at this time (which is wise.)

However, he's been on down there for a few years with no static. I think "somebody" heard 1640 and thought "This guy is competing for listeners" and ratted him out. It's not very often the FCC nails Part 15 AMs (It does happen, but if you REALLY want to shake a hornets nest, just go one milliwatt over the limit for FM and....)

There's also the fact he's been actively promoting "Liberty 1640" -to the point he has "affiliate" stations. Not a smart move. It's a bizarre thing. Radio stations NEED to promote themselves to get listeners. Something licensed stations never do often enough. But if a Part 15 station does it - WHAM! You're busted.

Politics? Perhaps. I'm not a fan of Alex Jones and the usual stuff on GCN. Much of their stuff is too unbelievably radical for my taste. But it might have made someone else nervous enough to call Uncle Charlie.

But I wouldn't rush to blame the nearest "godless pinko New World Order commie". You see, radio (especially the big guys) are smarting from the loss of listeners to other mediums (web, iPod, satellite, Music Choice, etc.) Anything that cuts into that bottom line - especially something that probably got a little loose with the rules of Part 15 AM - is fair game. And far easier.

It's a web of things really. But it's a reality check......

 

[Bob1370]

Let's do some comparisons here. The guy is putting out a field strength of 73 mv/m a good 100 feet away from the antenna with nothing more than a wire antenna and a ground strap presumably hooked up to a stake driven into the dirt. It's a highly inefficient plant by licensed broadcast station standards to be sure. (A licensed class B or C AM station with a quarter-wave antenna and a typical 120-radial ground system will put out that kind of field strength two or three miles away feeding 1000 watts into the antenna.) But it's apparently more efficient than Part 15 allows and probably running more power. If you use that 1000 watt licensed station as a benchmark, then scale it back, ratcheting back both the power and the probable efficiency of the antenna, it's conceivable that he was feeding that thing with 50 to 100 watts transmitter power, enough to reach a lot of people and cause a lot of interference to stations licensed to be there either on the channel or within a couple of channels. So he may have been way over the Part 15 limit in terms of allowable power. He's on a frequency where Class B stations are licensed with up to 10,000 watts daytime and 1,000 watts non-directional nights, and he's probably posing a significant interference problem for such stations. There is a second-adjacent-channel station on 1620, KOZN, less than 10 miles away from him and something like this could cause significant problems to KOZN's nighttime 1000 watt signal.

Political content probably has nothing to do with the effort to shut him down (there's content just as crazy, or crazier, being carried on syndicated shows with hundreds of licensed affiliates and being uttered by cable hosts and members of Congress)--but signal strength and interference potential has everything to do with it.

 

[Ermi Roos]

The mathematical formula for finding the radiated power from an electrically-short vertical monopole over a perfectly-conducting flat ground plane for a particular electric field intensity at a particular distance is

Pr = 1.111(10^-11)[(Ed)^2], where

Pr is the radiated power in milliwatts,
E is the electric field strength in uV/m, and
d is the distance in meters from the antenna to where the field strength measurement is made.

If E = 73,800 uV/m and d = 30 m, Pr = 54.5 mW.
If E = 19,700 uV/m and d remains 30 m, Pr = 3.88 mW.

So, the radiated power of the Liberty 1640 AM transmitter with the ground lead connected is approximately 54.5 mW; and with the ground lead disconnected, it is approximately 3.88 mW. I say, "approximately," because the field strength reading, even with a calibrated FSM, could off by +/- 2 dB (or so).

"Electrically-short" means much shorter than a quarter wavelength. The Liberty 1640 antenna, including the ground lead, is about 9 m long, and a quarter wavelength at 1640 kHz is about 46 m. Therefore, the 9 m antenna can be considered to be electrically short. The 30 m field strength measurement distance is so short that there will not be any significant reduction in field strength due to attenuation by low ground plane conductivity. Therefore, the assumption of a perfectly-conducting ground plane is valid. The formula is valid in the far field, and the 30 m measurement distance, while not in the near field, is a bit too close at 1640 kHz.

 

[rfry]

The mathematical formula for finding the radiated power from an electrically-short vertical monopole over a perfectly-conducting flat ground plane for a particular electric field intensity at a particular distance is....

I haven't investigated why our answers disagree, but below is a paste from my spreadsheet exercise based on an equation from an engineering reference, that is applicable to this situation.

The term dBi (below) refers to the h-plane antenna system gain in decibels relative to an isotropic radiator, and which includes the effect on radiation resistance of a 10-meter, unfiltered/unchoked, vertical "ground" conductor attached to the r-f ground terminal of the elevated transmitter with a 3-m whip attached to its antenna connector.

NEC-2 was used to calculate the radiation resistance of the elevated whip and 10-meter ground conductor, which along with the other ohmic losses in the antenna system resulted in the antenna system net gains in dBi cited below.

EQUATION:

Field Intensity in mV/m = 1000 / Distance(m) * SQRT(30 * Power(watts)) * 10 ^ (dBi / 20)

30 Distance, meters

-2.66 Antenna System Gain, dBi

0.3015 Power, watts (about 300 milliwatts)

Ans. 73.80453203 mV/m, which is about 73,800 microvolts/meter.

That ~300 mW value of radiated power needed is significantly higher than that posted using the equation Pr = 1.111(10^-11)[(Ed)^2].

For confidence, below is the calculation using that same spreadsheet for the h-plane field for 1 kW radiated by a perfect 1/4-wave monopole driven against a perfect ground plane:

1000 Distance, meters

5.15 Antenna Gain, dBi

1000 Power, watts

Ans. 313.372316 mV/m

That ~313 mV/m value is the value for such a configuration shown in standard antenna engineering textbooks.

And of course, none of this is sufficient to determine the input power of the transmitter needed to produce that radiated power for any specific "Part 15" AM system -- which necessarily includes all of the unknown factors given in my post in this thread of today (18 Apr 2010) at 11:20:47 CDST.

RF

 

[Ermi Roos]

It appears to me that Mr. Fry is calculating the input power applied to the antenna by the transmitter, not the radiated power generated by the antenna. The clue is that he is using an antenna system gain of -2.66 dBi. A lossless electrically-short antenna has a gain of +4.77 dBi, not -2.66 dBi. The difference between the antenna gains Fry and I used is 7.43 dB. 7.43 dB happens to be the difference between my results and Fry's, expressed in dB.

I am calculating the total RF power generated by the antenna. By taking into account the losses in the antenna system, Fry is calculating the amount of RF power required to be applied to the antenna by the transmitter in order to get the radiated power that I calculated. The great majority of the transmitter power is consumed as heat in the losses in the antenna system, and does not become radiated power.

Actually, Fry's calculations of the input power to the antenna system are very interesting, because he shows that the measured field strength cannot be produced by a transmitter with 100 mW input power applied to the final stage, even if the transmitter were 100% efficient.

 

[Carmine5]

Radio Ink published a little item on Liberty 1640. According to the station's website:

"Yes, we have been visited by the FCC, but they and we are very cooperative." The station calls the grounding issue a "gray area" and says the matter is being corrected, adding that a new transmitter will improve its signal in Omaha.
The complaint to the FCC, says Liberty Radio, "came from a bitter man who didn't want to hear that his politician was a puppet and that someone in Nebraska could operate a radio station without red tape."

So while politics may not have motivated the FCC to investigate, that certainly was the case with a disgruntled listener who complained.


http://www.radioink.com/Article.asp?id=1773640&spid=24698

c5

 

[druidhillsradio]

Mr. Disgruntled would probably be shocked to hear that lots of licensed AM radio station carry broadcasts the he would find politically objectionable, including GCN and Alex Jones.

 

[Hamilton]

I’m amazed by the incorrect information I have read here! I have spoke to the “Main man” involved, have know him for years, I know the agent involved. This same agent inspected another customer and passed him a couple days before the Liberty 1640 thing. I understand the Liberty 1640 customer is going to build the AM1000FER filter (instructions on the website), the agent told him if he installed a filter he was good to go, that was my understanding, the “Liberty 1640 shut down by FCC” is just news hype. Same old thing, the FCC comes by, if you have a certified transmitter no sweat, and if they find something they don’t like, they will work with you to fix it, no big deal. And you are good to go.
As reported the FCC did not care about the content, which I think was the Alex Jones program? I understand the visit was pleasant with lots of joking around.

About the new ground test, it is my understanding, they do not care about the radiation level, they take a comparison between the transmitter with and without ground, if you are a certain amount over with the ground then you need a filter. How much over you can be, I don’t know, but I have heard there is some sort of 1 meter “ground” allowance.
Contrary to what you may read here, not all ground systems radiate. Of course some do. Towers and billboards are notorious ground radiators. I have had two pole mount transmitters pass FCC in the last few weeks with no filter needed, the FCC found there was not enough ground radiation to need a filter. So if your ground wire system looks like an antenna, it probably radiates, and if you get an FCC visit, you will probably need a ground filter to comply with the new interpretations.

 

[rfry]

Contrary to what you may read here, not all ground systems radiate ... So if your ground wire system looks like an antenna, it probably radiates, and if you get an FCC visit, you will probably need a ground filter to comply with the new interpretations.

Physics shows (even for Part 15 AM) that all unchoked/unfiltered conductors connected to the chassis/r-f ground terminal of an elevated transmitter will produce radiation -- in many cases more than the 3-meter whip considered to be "the antenna." Such conductors include the lightning ground, DC power, and audio conductors connected to the transmitter.

Conductors don't need to look like antennas to function like antennas. For example, the grounded steel frame of a billboard does not look like an antenna. But if an unfiltered/unchoked "ground lead" of a transmitter connects to that frame then as Mr. Hamilton writes, the frame is a "notorious" radiator (along with all other physical forms of a conductor).

Even using a shielded conductor such as the center wire of a coaxial cable, or an insulated wire installed in metal conduit where both the ground conductor and its supposed shield are connected to an earth ground at their lower end does not prevent radiation from the shield itself, unless some means is provided to prevent r-f current from flowing on the outside surface of that "shield."

The responses above are not a matter of opinion or interpretation, from the viewpoint of physics.

RF

 

[Hamilton]

That is not what I said Rich, I won’t be getting into endless rabbit trail discussions that go nowhere about that

You are free to your opinion, kindly allow me to have mine.