...are we saying we can add more RF power in the final?
Yessir, that is the purpose of the final amplifier. In many AM transmitters it is also the stage where the r-f carrier is modulated.
Carl - The FCC will have to initiate and author any changes they see fit in the wording of § 15.219. It is extremely unlikely that anything appearing here will prompt this.
P=VI
So if it is a tube, Plate Voltage * Plate Current = Input Power
Yes, John, so why does 15.219 mention filaments?
Attention deficit city.
In Post # 19 Rich(F) wrote:
IMO § 15.219(a) and (b) need to be re-written to clearly state their meanings, especially given that unlicensed users of radio transmitters sometimes don't have the technical backgrounds the FCC may have assumed for those users when § 15.219 was added to the Rules.
That was an interesting provocation, so I invited Rich(F) to present an example of such a simplified version of Part 15, which he side-steps by writing:
Carl - The FCC will have to initiate and author any changes they see fit in the wording of § 15.219. It is extremely unlikely that anything appearing here will prompt this.
As an intellectual exercise we are free to author a common man's explanation of what 15.219 says without the FCC being involved.
I wonder if you really could write something understandable to the untechnical. Most of what you do write shifts the topic away from what's currently under discussion and interupts continuity. This is your chance to demonstrate an actual communication skill down here at the part 15 level.
... This is your chance to demonstrate an actual communication skill down here at the part 15 level.
For obvious reasons your post was not much of an incentive to me, sorry.
You are correct, Rich(F), you are no incentive.
Hi Carl, Let me edify you. As you know there are several types of vacuum tubes. Tubes have elements. Tubes may have cathodes. These cathodes can be heated or "directly heated."
A directly heated cathode is the filament. Do you see where I am going?
Hope this helps.
Cordial to offer edification, but I am not hungry at this time.
Telling me what a filament is might be snooty, but why is filament referenced in 15.219?
"but why is filament referenced in 15.219?"
Simply because if the final RF stage uses an electron tube the "heater" or "filiament" which is an element in the tube consumes power. That is power applied to the "tube" as power to operate the "heater" or "filament".
That being the case the power to operate the "heater" or "filament" is not being included when considering the power input to the final RF stage.
It is generally accepted they are referring to the DC Plate voltage and current when calculating the final stage input power.
Depending on the final output, the power to drive the grid could be considerable but I don't think their definition of "input power" includes that.
Telling me what a filament is might be snooty, but why is filament referenced in 15.219?
Carl - why not take up your case with those actually responsible for the text in FCC § 15.219(a), rather than the many times you have done so with readers of a thread on a Part 15 website?
Only the answer you get from the FCC will be credible (if credibility is what you are seeking from your posts here).
The explanation by MRAM 1500 is probably as close as it's going to get to a "reasoning" for mention of filaments in relation to "input power."
I am not able to be as dogmatic as all of the commenters seem to be regarding 15.219.
To me it could mean several different mutually exclusive things.
Thank you for participating.
The explanation by MRAM 1500 is probably as close as it's going to get to a "reasoning" for mention of filaments in relation to "input power."
Carl -- Why would you not ask the FCC about this rather than to ~accept any unofficial response to your query posted on a Part 15 website?
Rich(F) wrote -
Carl -- Why would you not ask the FCC about this rather than to ~accept any unofficial response to your query posted on a Part 15 website?
Two reasons. The whole purpose of a Part 15 website is open discussion of related issues which often yields worthy results.
And because, unlike yourself, I have no contacts at the FCC.
It would be helpful if you took it up.
Carl, when the rule was written way back when, tubes were the common active device used in electronics...amps, transmitters, hi-fi, radios, TVs etc. Transistors didn't really take over till the late 60s. So, the rule which hasn't been re-written to reflect modern day times when of course the transmitters we are using are all transisters and ICs, still refers to tubes and tube terminology. The FCC should update the text to reflect that everything is not tubes anymore. That's a question that should be put to the FCC with an explanation of how the rule applies to transisters. But till that happens just assume the rule is DC into the final power amp(unmodulated...no signal applied) is 100 milliamps max. applied to the base of the transister for example. forget about the tubes...doesn't matter.
Mark
I have no contacts at the FCC.
Neither do I.
The FCC website provides venues to ask such questions, but they DO take some effort to find on the part of those seeking FCC answers to the questions they have.
It would be helpful if you took it up.
Helpful to Carl Blare, no doubt, but he is asking me to take up his "cause" even though it is of no technical concern.
I decline to do so.
Everything you say is true, Mark, and I appreciate your input. But there's more to it.
Let's say it was still the age of tube transmitters (and by the way, as shown by the links presented by WDCX there are still plenty of Part 15 tube transmitters), there would be no reason to mention filaments in relation to the input to the grid of the RF final stage, because the existence of filaments is incidental to the input of a vacuum tube amplifier.
Therefore the question always comes back to "WHY, oh WHY, does the FCC mention filaments in relation to 15.219, EVEN IN THE CASE OF TUBES?
As to Rich(F), you may enjoy having a dance partner, but I don't dance, a deficiency that cost me plenty on Pat Shannahan's prom night.