Broadcast Blow Torches need blown out.

Most portable radios can easily receive signals of around 100uv, and many good radios, i.e., home stereos, go down to 25uv or so.

The discussion in this thread is about the fields of AM broadcast signals.

With more research, one might learn that the ambient r-f noise floor in the AM broadcast band existing in many urbanized areas can require a received field intensity greater than 20 mV/m for useful reception, no matter the r-f sensitivity of the AM receiver.

Such fields are much greater than suggested in the above quote.

Ok, I CAN'T be the only one here who thinks this whole thing is just ridiculous.

"You don't need 50k watts to cover a metropolitan or extended metro area"
Oh believe me, Yes you do.
You have any idea how TRASHED the AM band is now?
Here in DFW (we have GREAT ground conductivity by the way) Its not uncommon for our local 50kW stations to get buzz or static during storms, or driving through town.
Head up to the really crappy ground in the northeast where it takes 50kW just to go 50 miles! WBZ Boston is a great example. (local WBAP goes 130 miles with 50 kW)

If anything, this is quite simply the most disgusting topic I've ever seen here.
The magic of AM radio is the skywave!
I LOVE getting distant AM signals.
Killing off our legendary 50kW clear channels is an absolute waste of time! (For what its worth, theres no such thing as a clear channel frequency anymore anyway)
If we want AM to be clean again, the FCC is going to actually have to enforce the damn Part 15 laws intended for unintentional radiators.
Killing our blowtorches isn't going to help anybody.

Sorry if you found this thread problematic @mighty1650.

You brought up WBZ out of Boston as an example of "need" to push 50Kw out to cover 50 miles. I call this claim utterly bogus. Unsure who at CBS Boston perpetuates this fiction.

That is the station I referred to as being heard in 38 US States. Clearly, 35 US States are outside the 50 mile listening range in accordance with reality of their bragging about the 38 states can hear them.

Look at their radio signal:
http://radio-locator.com/cgi-bin/pat?call=WBZ&service=AM&status=L&hours=U

Seems like they are broadcasting VERY close to or right in salt water. This map of their tower proves this:
http://binged.it/13p0UGW

Now, saying there is lots of "noise" and interference in the asphalt jungle, well, yes, true.

Wouldn't the more prudent thing here be to setup multiple much lower powered transmitters instead of a major blow torch?

CBS station out of NYC is probably the same power, salt water, large coverage, etc.

Major interference issues should be something FCC or state equivalent plus the actual station should be working to clean up. Drive the areas, field complaints, identify emission sources, resolve. I take it stations don't do this?

This is like someone at end of a water pipeline complaining about water pressure, so they start pumping 2x, 3x, 10x until pressure issue is resolved. They end exploding the water mains, create flooding, property damages, etc. Solution was then and now to install new mains, upgrade main trunks, etc. to service end of line.

AM Skywave? Yes, it is a cool effect. But it isn't impressive with 50Kw and the same content you hear on 100 other stations. It is impressive when it's a 1Kw or less station that you are exceeding broadcast range by a big factor.

Part 15 broadcasting isn't causing the interference issues. Other sources are responsible for ground level "noise". Saying one in the same is kind of true as Part 15 broadcasting remains a fringe noise allowance and nothing more.

"Here in DFW (we have GREAT ground conductivity by the way) Its not uncommon for our local 50kW stations to get buzz or static during storms, or driving through town."

What your leaving out is the heavy infrastructure of high voltage lines carrying 450,000 VAC on them that run right over densely populated and congested areas, and Dallas is not an open wide field, but a cluster of glass, metal and concrete, and adding in the population produced noises besides the lightning zaps heard on the radio, which happens ANYWHERE on ANY frequency and on ANY station at ANY power level.

"Killing off our legendary 50kW clear channels is an absolute waste of time! (For what its worth, theres no such thing as a clear channel frequency anymore anyway)"

If we want AM to be clean again, the FCC is going to actually have to enforce the damn Part 15 laws intended for unintentional radiators."

The Part 15 laws cover BOTH intentional and unintentional radiators.

The latter, "unintentional radiators" comprise of about 90 percent of everything in use today, in both industry and consumer level. To effectively enforce the Part 15 rules applying to the unintentional radiator specifically, that means you would have to remove that 90 percent of technological wonder that is in use and depended on in order to remove only a third of the introduced noise in the MW band. Which BTW, those unintentional radiating devices spread their splatter across far more than just the MW band.

There is no way that the FCC can enforce those rules effectively without having to remove those devices completely from both industry and the public. Would you be willing to give up your computer and digital cameras and chargers and LCD TV and X-Box and iPad and neon light signs and LED traffic light systems and those energy saver swirl light bulbs?

I seriously doubt it..all for the sake of helping your local 50Kw station from the once in a while crackle and pop coming from a lightning bolt or a nearby welding shop or a switching power supply gone amuck?

Now let's talk about intentional radiators and their serious lack of impact on a 50Kw blowhoe.

Well..not much to be said about that..considering it would take a tiny flea 100mW signal sitting practically next to the radio receiver tuned to that 50Kw station and the tiny flea transmitting on that same frequency to be of any REAL effect or noteworthy concern of enforcing Part 15 rules!

Why wouldn't removing the 50Kw levels to more realistic levels not help anybody? Apparently at 50Kw, it's still not good enough because of those lightning bolt jolts heard on their signal, and all the modern tech noises produced that still interfere with that 50Kw signal. So what is the point then of 50Kw maintaining that power level at night when 400 miles away the mentioned noise sources would dampen that signal even worse, but remain the same tiny level of crackle pop locally at lower power levels?

Why would Odessa/Midland need to hear WBAP when WBAP's programing is local to Dallas/Ft. Worth and Odessa/Midland have KCRS 550 providing that localized programing..plus network programing that is also heard on WBAP?

Rush Limbaugh heard on WBAP? It is on KCRS. So why would Odessa/Midland want to tune to a noisy 50Kw station located in Dallas/Ft. Worth to hear Rushie when they got KCRS in their back yard?

And KCRS effectively covers (including at night) well out to Pecos Tx to the west, Hobbs NM also to the west, Brownfield to the north, Colorado City to the east, and Iraan to the south, and does all that with a mere 5Kw!

RFB

Oh no!
No no no!
You folks totally got me wrong.
I am in NO way blaming our 100mW stations!
We actually follow the rules!

I'm talking about our technological wonders that are grossly out of Part 15 specs.

There is no reason for a plasma TV to spew garbage all over the radio spectrum for blocks.

Now as to our 50kW blowtorches.
Yes the same programming is heard on just about all of them. Do I like this? No I don't.
But I don't see this as a reason to kill them off.
If anything, the radio regulations need to go back to the way they USED to be. It was deregulation that allowed the Clear Channels and the Cumulus companies to gobble up all the stations.

Now, on the subject of using multiple low power transmitters instead of one high powered.
I believe economically, this wouldn't be a smart move.
For every transmitter, you need a tower site. AM tower sites aren't cheap, neither is the electric bill to the keep the sites on the air.

Now on the link you provided yourself, the map even says 50 miles on it! The 38 states they boast about? that's nighttime skywave coverage. Their daytime signal is pitiful for a 50kW AM station, but that's due merely to their ground conductivity in the area.

As to interference,
I did consider the Dallas jungle of power lines, homes, buildings, ect. If 50kW has a hard time punching through that, wouldn't a lower power be even worse? I mean, my little AM station (even the FM) gets fuzzed out at traffic lights!
So do I think AM stations need more power? actually yes I do. For the same reasons I think Part 15 intentional radiators need to be allowed more power.
The AM band's noise floor is not what it used to be, its not the 40's anymore. The noise floor is terrible.
The noise floor is horrific all the way up into the VHF bands! There's a reason many two-way communications are moving to UHF. They first went from Lowband to VHF now to UHF as the noise floor has steadily gotten worse.
Why has the noise floor gotten worse? Florescent lights, computers, TVs, cell phones, switching power supplies, leaky cable lines, leaky power lines.
How can this be fixed?
Two options.
Allow power increases across the board for broadcasters (and Part 15 guys like us alike)
or actually enforce the damn rules already in place!
I think the FCC should inspect every new product that gets put out on the market, to make sure it doesn't trash the band.
There is no reason that something can't be engineered to not make a mess of the radio spectrum.

I'm not a corporate defense whatever, nor anti Part 15. and I'm a bit surprised considering my history here to even be remotely considered as such.

On a side note...

I'm considering all stations in the spectrum.
Not just the 50kW.

The less noise total the better 🙂

Unintentional radiators can kill you.

I've been building another computer, as backup (more accurately, I'm building a computer to build a backup computer that gave up the ghost hardware-wise).

I was using another failed computer as a base (I keep the power supply, replace the motherboard and various other pieces). I got it up and running, and then went to listen to my local AM news station - it was completely covered up by noise!

Suspecting the new computer, I turned it off, and the noise disappeared. Turns out it had one of those generic, no name power supplies; when I replaced it with a Corsair, it ran quietly (RF-spectrum wise).

So yes, there is a lot of noise from these unintentional radiators. Interestingly enough, it was only on AM 1130 +/- 10 Khz, which just happens to be the frequency of the news station.

Please provide a reference, Rich, for that 20mv noise floor assertion.

"No no no! You folks totally got me wrong.
I am in NO way blaming our 100mW stations! We actually follow the rules!"

My bad! Apologies for misunderstanding your post.

"I'm talking about our technological wonders that are grossly out of Part 15 specs."

Agreed. Most of the consumer products today are manufactured on mass scale and using very loose tolerance components, which are also manufactured on mass scale. The variance between like components are not really within their claimed 5 or 10 percent. Much much more variable. It's amazing stuff even works, but it also explains why these devices put out such blatant noise and interference and why they don't last very long..if lucky they last just barely past their 1 year warranty!

But the big problem is this. People want cheap and have demanded it since the 80's. Back in the 80's when people were screaming for lower priced commodities such as electronics and even larger ticket purchases like vehicles and household items, the manufacturers were more than happy to oblige and produce cheap stuff..flooding the markets everywhere with it, and down the prices went. At first when new stuff was introduced, they would be quite expensive, but still cheaply built. Then after 6 months or so, those prices would drop because of market saturation of the product. This has continued ever since.

Remember those good ol electronics that did cost a pretty penny..like the Realistic and Pioneer and Samsung and Kenwood stuff? Built in metal frames and 1/4 inch wood sides and weighed 60 pounds or more?

Try to find equipment like that these days brand new. Even those back in the day with metal coverings were made of higher grade metals than the cheap thin junk today.

Bumpers on cars used to be metal coated with chrome plating. Now all there is is plastic covering over a thin skinny low grade metal bar behind it. Dash boards used to have high grade metal in them covered with padded and insulated covers. Today...it's all plastic.

Anyway much of the stuff producing radio spectrum interference cannot be helped. To relieve some of it, those devices would have to be built and designed with greater quality components and the price would go up..and people don't want that.

Society asked for cheap..and they got it. Too late to cry foul over it because not only did it saturate markets with cheap commodities, it closed down domestic manufacturing and the jobs went along with the closings and overseas relocating.

Cheaper is not better. We get what we pay for. We also get the side effects..such as interference from those things that did not exist a short 30 years ago and is why the radio spectrum then was a bit cleaner than today.

"I did consider the Dallas jungle of power lines, homes, buildings, ect. If 50kW has a hard time punching through that, wouldn't a lower power be even worse?"

Actually no. Receivers can be designed to filter out those crackles and pops. Also with better designed devices that are connected up to the power grid system. All those neon lights driven by switching supplies, traffic light systems, home electronics..all of it can be better designed and fitted with better filtering.

Those high tension voltage lines have been there for a very long time, far longer than our computers and cell phones and plasma tv's. True those devices do generate problems, but they only added to the existing causes of interference not so noticed in years past like today. So having stations increase their power will not solve the once in a while crackle and pop. Those kinds of interference..ie from mother nature in the form of lightning, and our own man made stuff even 30 years ago, is a must accept fact and jacking up power to a station won't cure the problem.

The issue isn't about a 50Kw's local coverage concerns. The issue is those 50Kw stations occupying spectrum in areas where they should not be, and the likelihood of remote listeners in another city or town tuned into that 50Kw station when there is one much closer providing a clearer signal is next to nill. Then at night those stations really have no right to be shoving their local programing or weather reporting or local news into 5 other states, along with duplicate network programing on frequencies where more local stations could be on the air providing jobs to the local economies.

Those 50Kw stations should be required to kick back their power levels so that they maintain their daytime coverage contour during the overnight hours. There is no need for that daytime coverage to extend out 700 miles or more reaching into other states and cities where local stations are already there, and those frequencies occupied by those clear channel stations can have local stations on them, again providing more local jobs and growth to those communities.

A town 500 miles away with businesses would rather advertise on a local station than expect some station 500 miles away be willing to run said advertising on their airwaves for a business 500 miles away. Imagine what the listeners of WBAP would think or say if they heard a commercial for La Bodega located in Odessa. And La Bodega can advertise on KCRS and pay the local market rate and get their ad heard where they want it..in the area where the business is located.

Same is true in reverse, if KCRS was a 50Kw clear channel station. What business in Dallas/Ft. Worth would be willing to advertise on KCRS when WBAP is there? And business in Dallas/Ft. Worth won't bother calling up a 5Kw station in Midland/Odessa to advertise, even if KCRS was 50Kw clear channel!

"I think the FCC should inspect every new product that gets put out on the market, to make sure it doesn't trash the band."

Looks good on paper and sounds good. But again 99 percent of the electronics..including those noisy plasma tv's are NOT built here in the US. The DUT submitted might show and test to have low interference potential..and pass muster..but the plasma tv's beyond the unit submitted for test wont and usually don't. Inspecting each and every item as it comes off the assembly line belt before they are boxed up and shipped out is impractical in today's mass production factories. Perhaps if it was implemented, it would have to be done domestically as the FCC has no jurisdiction in countries like China or Korea, where most of this stuff is manufactured. And to un-box stuff as it is unloaded from cargo ships just to test would be a logistic nightmare.

"There is no reason that something can't be engineered to not make a mess of the radio spectrum."

100 percent in agreement! But the bottom line is this...manufacturing and design are in business to maximize their bottom line. If their products can just meet the minimums, that's all they are concerned about and move on. Again it is a matter really outside of the arm of the FCC and even US government. The only way to return to the high quality products we used to find in stores 30 years ago is to return that manufacturing and design engineering BACK to the US..where it belongs.

Those things that are designed and built here in the US..such as broadcast electronic devices using switching power supplies and CPU's etc, do not produce that garbage because they ARE constructed with higher standards and higher quality components made HERE. That is but one example of the differences.

RFB

ArtisanRadio wrote Please provide a reference, Rich, for that 20mv noise floor assertion.

What I actually wrote was this (in post 16 in this thread): "the ambient r-f noise floor in the AM broadcast band existing in many urbanized areas can require a received field intensity greater than 20 mV/m for useful reception, no matter the r-f sensitivity of the AM receiver."

This does not state that the noise floor is 20 mV/m. It states that it can require an AM broadcast signal to have a field intensity of 20 mV/m or more for an acceptable signal-noise ratio as heard by the radio listener.

FCC regulations applying to licensed AM broadcast stations use a ratio of 26 dB to a co-channel signal, for acceptable reception. So a radio noise voltage field of 1 mV/m would require the desired field from the radio station to be 20 mV/m.

The radio noise generated by devices in a home and nearby it such as SCR light dimmers, switching power supplies, arcing insulators on power lines etc can produce a total noise voltage in the AM broadcast band of 1 mV/m and more, at the antenna of a local AM receiver.

For those wanting more detail, please refer to the paper linked below. Figure 10 (b) there shows a median noise voltage as measured in Mexico of almost 60 dBµV/m, which is 1 mV/m.

http://www.ehu.es/tsr_radio/images/International_Journals/PRIE-07-01.pdf

So I won't necessarily find a noise floor of 20mv/m. Rather I need a signal that is 20mv/m stronger than whatever the noise floor is for a usable signal.

So if the noise floor is 0mv/m, I'd need a 20mv/m signal to receive it. If the noise floor was 50 mv/m I'd need a 70mv/m signal to be usable. Yes?

Actually, you need a signal which is 20 times stronger than the interference (noise floor). So, if the noise floor is 1 mv/m, you would need about 20 mv/m. This is how AM daytime signals are allocated. They are usually protected from interference from other stations to their 0.5 mv/m contour. So another station can't overlap your 0.5 mv/m signal with anything stronger than 0.025 mv/m (usually called 25 microvolt/meter).

So, in your example above if your noise floor is 50 mv/m (a REALLY high noise floor!) you need 1000 mv/m to override the noise. That's 1.0 VOLTS/meter! The kind of level you would expect within a few blocks of a licensed AM station.

If the noise floor was 50 mv/m I'd need a 70mv/m signal to be usable. Yes?

Sorry, but no.

According to the FCC, a 26 dB ratio is needed between desired and undesired co-channel signals for good reception of an AM broadcast station, regardless of the absolute value of the noise voltage at that receive location.

So that value is not fixed to be 20 mV/m greater than whatever noise voltage exists at that receive location.

The useful value needed for the desired, received signal depends on the r-f noise present at that receive location.

Good points @RFB.

I don't think the FCC wants to clean the spectrum up. They've been dead weight living off hand out paychecks for too darn long.

You can add the AM band to the long list of FCC intentional disasters. The FCC should be disbanded or everyone fired. I mean really, what have they done of real benefit to the populace in the past 30 years?

What do you expect when the FCC is filled with lobbyists from big corporations, all of which seem to import JUNK from the far east and sell at arguably high prices considering the true craftmanship of the products.

Inspecting cargo containers should be routine. Masses of electronics should be sub-sampled for compliances, thresholds, etc. If a single unit fails, test a few randoms and if they fail impound the cargo.

Needless to say the shipping of cargo is a big dark mystery government and industry doesn't want the common man to know about. I suspect you could smuggle an elephant in that way and corporations bring hordes of out of compliance electronics in this way as well as more illicit problem causers.

I was out walking with my radio in hand earlier (really nice day here today) and I cause that 600 watt station out of Toronto along with two others that are around 1000 watts and that was before dusk.

WBZ I probably can pickup in broad daylight 300 feet underground in a mine. Those clowns are on my short list of complaints to file. Any broadcaster that boasts about coverage like them needs their watts snipped. They already are broadcasting over salt water and getting that advantage. They could make due with 10Kw or 5Kw and cover Boston metro no problem.

Biggest issue in Boston for them likely is their distance of broadcast tower outside of the city. Perhaps if they were "central" to the area broadcasting to, many of the urban atmosphere issues could be better handled with less.