FCC Rule Part 15.219 Power

It would be nice if your explanation of the 15.219 rules was correct since we could operate with more power than we do, but unfortunately some of your statements regarding the power limits are incorrect.

Part 15.219 states:

Section 15.219 Operation in the band 510 - 1705 kHz.
(a) The total input power to the final radio frequency stage (exclusive of filament or heater
power) shall not exceed 100 milliwatts.
as copied verbatim from the revised Part 15 rules effective Sept. 2005, and it does indeed reference the input power and not the output power..

Notice that no distinction is made between AC or DC input power. Fortunately, with a typical high gain final stage amplifier the AC input power to the control element is small and can be practically neglected, though technically this would also contribute to the total input power. Thus the dominant input power is the DC input power to the final RF stage. Conventionally, the input power to an AM transmitter final is the DC power with no modulation and this power needs to be included in the total power calculation.

In the days of vacuum tube finals, the power delivered to the screen grid had to be included along with the plate power and the total was limited to 100 mW under Part 15. With modern transistors in the usual common emitter configuration the DC power input is the collector to emitter DC voltage multiplied by the DC collector current.

Neil

Hi Neil

Why I made those Statements is because under part 15 rule kid toy Walkie takies cannot exceed
100 mw input power either or the 100mw Walkie takies that were made in the 1960's or 1970's.
The FCC said the Walkie talkies in the 1970's could not put out 100mw on CB and if the went about 100mw
input power you had to get a FCC license for CB Radio. Alot of company started making some pretty good 100mw walkie takies back then. They use double conversion Superhetrodyne receivers with center loaded
antenna's anything to get that singnal out off such a low power.

I have one of those sets.

It acually draws around 30 to 35ma current and around 22 to 23ma on the final transistor.
Well 9volts X 23 ma= 207mW DCinput...
Yet on the box it said 100mw input and 50mw output. I called the FCC and said how can this be
Radio shack was selling Walkie talkies that were far over the 100mw input. They said it was not the DC
input they were looking at ,but th AC line of power input. I went back and looked in my engineering books
and found out the ACpower line is about 1/2 of the DCinput power...Well I took the easiest thing to test
it out on the math part I am talking about. We all know CB radios put out 4 watts of RF.
I did the math to see if this really works.

DCinput for a CB radio 12Volt X 1.35Amps= 16.2 watts DCinput Now all CB Manuals say with no Mod

Ok I cut it in half like my engineering books said to and I came up with 8.1watts ACinput Line

Then I took 50% of that because Radio shack had told me their transmitters are only 50% effient

I came up with 4.05 watts output right at FCC legal limit for CB Radio.

I really was amazed it worked,and the FCC siad that how Radio shack could say 100mw input power while
the final was accually drawing 200mwDCinput...
All the kid toy Walkie talkies sold today say FCC rule Part 15 on them and the take a 9volt battery and draw
around 30 to 35 ma with now modulation if you modulate them they draw even more... I am not saying
go make your transmitters 200mwDCinput what I am trying to show most the 100mw Walkie talkies
in the 1960s' and 1970's for CB that claim this was their input power did not do it by DCinput power but by AC
input Power which is about half of the DCinputpower.

It really amazing what companies will do to get around the law,and the FCC went for it and approved them.
They were given a FCC ID number even though they were at 200mwDC input power instead of 100mwDCinput power.

I just wondering how many of the companies that are selling AM FCC approved AM transmitters that are using this loop hold. Hey many companies did it and I will not name them because I don;t need them after
me. The FCC told me this is how they did it. Yes I read the FCC rule part 15.219,and the FCC say it does not make it Clear if it DCinput or on th ACinput...The only difference it going to make is that your transmitter may go from putting out 25mw RF to about 50MW RF output.. Really not that big of a difference. Think of this
Kids toy walkie Talkies are putting out more Power than us because they are using that loop hole.
They base the input power on the ACinput instead of the DCpower input.
I did this because I was wanting to know why these Walkie Talkies claiming only a 100mw input power
were drawing so much power off a 9 volt battery that far exceeded 100mwDCinput.. I have found
Walkie Talkies that accually drawed up to 40ma at 9 volts with just a silent dead key.
9 X 40 ma= 360mw DCinput power... I even took 10ma off to see if that would help since it had a crystal
oscilator circuit and that gives me 9 X 30ma = 270mw DC input power That still makes a 135mw ACinput
and 67.5mW RF output on a kids toy walkie talkie. Anyways I am staying at 100mw DC input,but the FCC
at one time Allowed companies to use the ACinput power to the final stage. So if you ever come accross a
100mW input Walkies talk start taking current readings. You will see most are way over 100mwDCinput.
They will also even tell you th Current draw at 9 volts is 30 to 40ma on silent key with now modulation.
I modulated one and the current jump to 100ma at 9volts .. That is 900 mw almoat one watt being drawn off a little 9 volt battery nopw wonder the 9 volt batteries went dead so fast. I agree with you neil,but I wanted people to see that we are getting different standards than the companies producing toy walkie talkies and
Walkie talkies in the 1960's and 1970's that only claimed a 100mw input power. When all realality they were
using 200mwDCinput or ever higher. They went with the AC line inputpower to get more out of their walkie talkies. I mean Radio Shack put out Space Patrol Walkie Talkie in the 1970's claimed 100mw input power and 50mw RF out put those things had a current draw from 35ma to 40ma before you even talk into them and the current would jump up to 80 to 90ma while you talked on them...On the Specification Sheet that came with them it said 100mw inputpower and output power 50mw...They used channel 11 or 14 on the CB band.
Later on they use the Frquency of 49.860 Mhz this was in the mid 80's to early 1990's. Even Wal-mart sells
Walkie talkies for kids that still work in the 49 Mhz band that exceed the the limits... Anyways the 49 Mhz band changed it to Fieldstriength now.. It use to be 100mw input power,but now it 10,000 uv@3meters...
Anyways I was just trying to show how things have changed with time,and how some companies got around that 100mw inputpower by using the ACinput power instead of the DCpower input just to get a couple extra
milliwatts to their RF output. It amazing what people will do.

Sorry I was not try to miss lead people in anyway,and I would rather
have that 100mwDCinput so the FCC does not bust me,but do not be surprise if some of these
Companies selling transmitters for $600 to $1000 have not already found this trick. I know that some
are FCC approved too. I have many friend in the FCC and one of my friends was the head of the
Part 15 devices now that all part 15 devices not just transmitters. He just retired in DEC of 2008..
Anyways he had many talks with me and said stay with the !00mw DC input Power and you will
Be safe. I made alot of my own transmitters and that legal,but just just make sure if you do to do
all the math and make good notes on your design,and they will not bust you for a home made
transmitter. I mean it in the FCC rules part 15 that you can make your own transmitter and it does
not have to be FCC certified. I had many talks with my friend about this and he was the head of the
FCC in the Part 15 devices,so he should know. Well Sorry for the Confussion neil.

I was just trying to show how many early CB Radio companies made 100mw walkie talkies
That far exceeded the 100mw DC input power,and they did this by using the ACinput power.
Which is about half of the DCinput power.

thanks SKW

Thanks for the followup post. Things might have been different then (and may still operate that way now). I had a KnightKit AM unit on the air back then but never, until recently, measured the power. It had a sticker on the bottom which said essentially "Allied Radio certifies this device meets the requirements of.....Part 15.204". The section numbers were different then and it is not clear whether it met the power restriction or the field strength restriction. A transmitter needn't meet both and judging by the RF waveform shape it probably didn't meet the out of band emission limits either (just speculating). I used a "legal" 10 foot antenna with it and the range was similar to that of my SSTRAN which I use now.

Here's a link to my post where I reported the recently measured input power of the KnightKit:

http://www.part15.us/node/1917

I had a pair of those cheap CB transceivers back then but they were toys. They had superregenerative receivers which picked up anything in or close to the CB. I was never curious enough to measure the power input. I suspect it wasn't much since the range was only 100 feet or so.

I have measured the DC input power to my SSTRAN final to be 93 mW which puts it within the limit of 15.219.

Neil

Gee, I always thought the INPUT power was a product of voltage x current. P=IV. My amateur radio amplifier, Ameritron AL-80B, shows a keydown voltage of 2700 volts and Plate Current of 450ma. 450ma x 2700V = 1215 watts INPUT power. 1215 x 70% efficiency = 850 watts out.

The same rule applies for solid state devices except the the plate is replaced with the collector. So collector current, times collector voltage = INPUT power.

There is no loophole for products like the Rangemaster 1000.

73, me 🙂

Hi Neil
Very cool on the Knight kits. I always wanted their Shortwave kit. I never got one. It had diffrent plug in
coils for each band. Anyways I think the FCC had different rules for the power back then.

Cb radio you had to have a license unless you were under 100mw inputpower and instead og going with DCinput Power they went with ACinput power..

Mine say 100mw input power but they draw 30 to 60ma on a dead key
and when modulated the exceed 100ma of that small 9 volt battery.

I measured the current and it came close to 23ma on the final transistor... well 23ma X 9 V= 207mw DCinput

That sure is not what radio shack had printed in the book. It says 100mw input power and 50mw outputpower. Now these walkies talkies I have are single conversion superhetrodyne with 1uv sensitivity..

Back around 1965 to 1968 Radio shack put out the TRC-1 and TRC-2 Walkie Talkies they were double
conversion with .5 uv sensitivity and claimed 100mw of power. Now wether this was input power or output power I have no ideal. They had a bottom and center load antenna to increase range of them. Radio shack clain 2mile range in the advertisements with thes walkie talkies. Now you did not need a license since they were only a 100mw input power. That right if you had more than 100mw input power you had to have a license. They base thes on ACinput power and not DCinput Power...I wish they would do that now that would double our power on the AM broadcast Band.

Anyways I love tube equipment over solid State. I also do Ham Radio.

I live so far in the county that there is no one to give the test out here. I have been a technition for so many years now. More than 25 years. I had my Novice before that. I heard they dropped the 13 words a minute down to 5 words a minute for General class boy what a change.

Anyways I had my novice license back when I was a teenager,and it was fun working all the CW stations.
I had a three tube Transmitter. It had two crystal Sockets. It had a 6L6 for modulator,and one tube for the oscilator,and I can't remember the Final tube. I know it would only do about 15 watts AM Max and CW
was around 50 watts max. This thing was heavy. the Power transformer must have weighed 75 pounds.
I have had a head injury since then and it hard to remember. I think it had something world in it.
Anyways it was so long ago,but I had a few crystals and work alot of stations on that thing. It was only a transmitter not a receiver.

Sean

Hi Guys it me Sean

That ransmitter had the worrd world in it. It would cover 80,40,20,15 meters I not sure it may have even done 6 meters too.

Anyways it had a 5U4 tube,(12AT7 I think ) mic amp and a 6L6 and 6CL6, 6146 tube in it.
I was tols it would do 15watts AM,but may have been less. I know the CW was round 60 to 65 watts.
It would about a 1 to1.5 feet tall and 12 inches in depth and 16 to 20 inches long. This thing was big and heavy. It had the biggest power supply transformer I had ever seen in a transmitter it was at on end
of the transmitter and that thing was very hard to move.

I THOUGHT THE Brand name was TRANSWORLD..Do you all have any ideal what I am talking about.
It was a good novice rig...Well except the AM could be used only by General Class and up.
Anyways my memory has just failed me bad.

sean

The way I see it is that the rule calls for 100 mW RF power to the final, and RF power would by definition be AC power. DC can't be RF unless you're sending out a carrier wave at 0 Hz

Rather than engage in long discussions about this I choose to refer all to my previous posts in this thread where I explained my understanding of the 15.219 power regulations. Some have stated their take on this and I have stated mine. I will respond to specific questions if asked.

Neil

Yes, Neil, I have been round in many of the discussions about what is power and dc and ac, and I have stood back to re-contemplate everything that's been said. But my poor brain cannot imagine any other kind of power than RF power being of any interest to the FCC. So, and I am locked in my way of seeing it, 100 mW input to the final has got to mean RF power, and I cannot conceive that RF power would be anything other than AC.

A comparison is an audio amp. The audio power is an AC signal. The DC powers/currents/voltages only exist to enable the various stages to generate the required AC signals.

Do I honestly have it wrong?

Hi everyone
I did not bring this subject up to get people confuse. I jsut notice Something Realistic did many years
ago,and most people know them as Radio Shack Walkie Talkies.

One thing I notice was the TRC-74 Said 100mw walkie talkie. It claim to be Only a 100mw input power
and 50mw output power... Well that walkie takie actually was 207mwDCinput on the final.

I also had the TRC-85 and TRC-89 Both claim to be 300mw Walkie Talkies. That 300mw input power
and 150mw output power. Yet this walkie Talkies has over 600mwDCinput to the final.

The FCC stated to me that these walkie talkies were not rated on DCinput power but ACinput power which is about half of the DCinput power. Anyways it seems to me that the DCinput power is what the FCC goes by for AM Broadcasting,but the Walkie Talkies sold even now a days still use the ACinput power to the Final.

I look at it this way the FCC needs to amend this rule for one reason. First it would clear up alot of confusion.
Second Companies like Range master are getting the 100mw RF output from circuits that run almost 100% effiecent...If you run a class D or E Bias set up you can acheive almost 100% of your input power to the output. Most people use Class C bias in RF circuits,but Class D uses special transformer Compling to a push
pull circuit that give near 100% effiency. Well Since Range Master has already figured this out and some other companies too. Thet are getting from 95 to 99mw RF output from their circuits.. The FCC might as well
amend this rule... Have part 15.219 simply State no more than 100mw RF output from final stage. I mean
they aready approved Range Master that putting out from 97 to 99mw RF. Yes they still have the 100mw
DCinput power,but they are getting almost all their power out too. So instead of just playing around with the
DCinput power we just need to have a max RF power set...Since people are using Range Masters that are getting near 100mw RFoutput. Let just have the FCC set a new Rule that States no more than 100mw RF
output from the final stage. You know how easy this would be to manage. They could hook a watt meter
to your transmitter and if it under a 100mw RF output your legal. I am not the FCC so getting this change would take a miracle..If my friend had not retired from the FCC I would have brought it up to him.
The FCC still says you can make a home made transmitter and be legal,so if you use one of the high effient
Bias techniques you will get near a 100mw output anyways. Look them up Class D bias and Class E bias.

If you read my CB Radio example you will see how 4 watts came the power for CB Radio.

Also P= V(squared)
----------------
impedance

13.8(squared)
----------------------
50 Ohms

190.44
----------------
50

3.88 watts RF output

This is just one formula used

the other is

12 volts X 1.35amps = 16.2 watts DCinput

ACinputpower= 1/2 of the DCinputpower
ACinputpower= 8.1 watts

CB radio circuit is 50% effient = 4.05 watts RF output.

Now these are examples of how all the power works.
I was a engineer for the United States Government/ Also Raytheon/
Advance Technologies Research Labs for NASA.

Anyways I have designed many transmitters and kept large AM broadcast Stations on the air.
Anyways as the technology gets better and designs it will not surprise me when all the small
Transmitters will be at 100mwdcinput and 100mw RF out put. If you buy a Range master
you are already there... I am only using Range master as an example because I know they
are running close to 99mw RFoutput with only a 100mwDCinput. Where most of us are running
100mwdcinput with only 25mw RF output. Some maybe getting 50mw RF output.

Anyways it fun to play with,but it may be better to change rule 15.219 just to a max RF output to
100mw.. This would clear up the rule since it does not state either ACinput or DCinput in its
Statement...It a guessing game at this point. Most people go with DC input due to it being safe.

Even companies like Range Master and Procaster use the 100mwDCinput rule ,so if they do
I would too. This keeps you on the good side with the FCC.

Anyways I brought this up to show how 30 to 40 years ago the power rating for a 100mw input
power was much different. They were actually running 200mwDCinout then. I have radios
From back then and have measured the power input to the final stages.

Well that just how things have changed over time.

Thanks SKW40

Carl, I will try to explain this further for the benefit of all reading this. First, I hope you will agree that the 15.219 rules make no distinction between AC, DC, RF, geothermal, hydroelectric, or any other type of input power....it simply says "total input power". And you are right in saying that the FCC shouldn't care about anything other than RF power, and we will see why the total power input is correlated to the RF power. We'll discuss why in a bit.

Let's start with a question: Where does the amplifier output power come from? Two sources in the typical amplifier; the input signal and the DC power supply. Under the control of the input signal, the DC input power from the power supply is converted to AC power to be used as the output. In some amplifiers (such as a common base circuit), the input signal power can be a significant source of output power as well as is the power derived from the DC supply. Now, if I want to limit the output power of an amplifier without knowing what circuit is used, the most effective way to do so is to limit the total input power to the amplifier be it from the DC supply or the AC signal input or both. By doing this the FCC effectively limited the RF output power and thus the field strength and, as you posited, they were really concerned with the RF power after all. Those folks knew what they were doing when they wrote the rules.

Another way to view this is that the amplifier converts the DC input power from the supply into the RF output power and does so at less than 100 percent efficiency. You can't get out more than you put in. Looking at the DC input power is just another way of gauging the RF output power since they are related (AC power out = DC power in x efficiency) and except for losses they are the same thing.

To measure this input power, let's ignore the signal power since, in most cases, it is insignificant. Take a DC ammeter and measure the current from the power supply and what you are actually measuring is the average DC current. Same for using a DC voltmeter to measure the supply voltage. The product, V x I, is the DC input power. True, we are not measuring the RF power output but that is not what the rules or common engineering practice requires in the case of AM transmitters. Here's the key: The RF output power will not exceed the DC input power we measure and therefore any limitation on the DC input power will also be a limitation on the RF output power. They are essentially the same thing.

Hope this helps.

Neil

Sean,

You posted while I was writing my reply to Carl so things may seem a bit out of order here.

You wrote:

Also P= V(squared)
----------------
impedance

.....snipped...

I just don't get this. I don't see any equations (formulas) here. Were you trying to write P = V^2/R? I think you were.

I have another question about what you said:

The FCC stated to me that these walkie talkies were not rated on DCinput power but ACinput power which is about half of the DCinput power. Anyways it seems to me that the DCinput power is what the FCC goes by for AM Broadcasting,but the Walkie Talkies sold even now a days still use the ACinput power to the Final.

Could you please explain what is meant by "AC input power"? If you read my post to Carl above you will see why I ask this question. I have no idea what is meant by this. I also wonder why the "AC input power" would be about half the "DC input power". I am aware of a design equation where the output power is estimated by using half the DC supply voltage squared divided by the output Z. Is this what you are referencing?

Your observation that if the rules specified maximum RF output power rather than maximum total input power would certainly make things better but such is not the case. The rules are what they are.

Neil

P = IE
P = 1 Squared R
P = E Squared/R

The above is refered to as Ohms Law. The FCC uses this strange formula for calculating power.

Thank you to all participants for entertaining my viewpoint.

I think I ran across the question of what I mean by "AC input power to the final." To my (still simple) way of seeing it, the output of the previous stage, measured following a DC blocking capacitor, would be the true RF power being applied to the final stage.