The final RF stage was also something particularly interesting briefly discussed in that same thread..
■Carl:
"My interpretation of part 15.219 has always been literal.
The rule states "100 mW into the final RF stage".
It does NOT say "100 mW into the final amp".
The final amp is not the final RF stage.
The loading coil is not the final RF stage.
The antenna is the final RF stage.
■Mark:
I think that since part of the wording is "excluding power for the filament" for tube amps the meaning of stage is the final amp.
■Rugster:
I was about to say the same thing. Also, it is commonly understood convention to use the term "final RF stage" to refer to the PA...
■Carl:
@ Mark You said: "I think that since part of the wording is "excluding power for the filament" for tube amps the meaning of stage is the final amp."
But that is not logical. If it were true, then all of the tubes in a 'tube-type' phono oscillator would be final RF stages.
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There was no more talk in the thread about it and I for one would like to know who was right.. Where is the final RF stage?
The wording maybe should be input to the final RF amplifier stage which would then imply an input, amplification(active component) and a load which would be the antenna but the word amplifier is left out to create the question of what is a stage. But I still stand by what I said back in the post. The give away is not including the power for the filament which refers to an active device like a tube. Even though it may be a transistor or an IC chip the final RF stage refers to the final amplifying stage before the antenna. That is sort of understood but a good lawyer may make it an interesting case. A final RF stage is referring to an active component like a tube, transistor, IC and related components. The antenna isn't an active device. It doesn't need power to work so like a capacitor or inductor or resistor it's passive.
Now if the wording not including the power for the filament wasn't there then there would be no specifying whether a stage would be an amplifier or not. A stage could be anything, even the antenna. But the wording definitely refers to an amplifier stage.
antenna. That is sort of understood but a good lawyer may make it an interesting case. An final RF stage referring to an active component like a tube, transistor, IC and related components. The antenna isn't an active device. It doesn't need power to work so like a capacitor or inductor or resistor it's passive.
I'm not a good liar, uh, lawyer, but I play one on part15.org. Define "active".
@centinel An active device in electronics is a component that need a power source to work.
https://www.arrow.com/en/research-and-events/articles/active-vs-passive-components-in-electronics
A whip antenna needs power to work. it wont do anything without it.
Same goes for the ground lead, it's part of the system, the only time the antenna and ground lead are not active components is when it hass no power supplied - just like the rest of the components of a transmitter.
It seems pretty clear that the antenna is an active device.
@richpowers A whip antenna like those on our transmitters are passive antennas as they don't have active devices(transistors) the amplify signals themselves but just act as a load for an amplifier and just radiate by electromagnetic radiation, but not needing power themselves. The antenna if just a rod is not active. The antenna is not the final amplifier stage. The antenna relies solely on the signal it is fed.
Words words words.
You can read pretty much anything you want into words.
I believe that it is intent that matters. And that the FCC intended the final stage of the transmitter to be the amplifier just before the antenna. You can maximize the efficiency of that final stage with a Class E amplifier (like the SSTran 5000) or accept the usual efficiency of around 50%. The Talking House + Range Extender takes the intent of the rules way beyond, not only potentially increasing the output of the transmitter to 100mw, but also adding a feedline to the antenna system as well, making it well over 10 feet or 3 meters. The Range Extender can be grounded as well, so if you aren't "by the book legal", as some put it, you've added even more length.
I know that the system is certified, but will never understand how they did it. And given that in the U.S. the operation of a Part 15 system has to be compliant, I don't know how they get away with it in the field.
@mark Come on Mark; you said the antenna "just radiate by electromagnetic radiation, but not needing power themselves." '
If applying power results in the antenna raidiating electromagnetic radiation, then the antenna is clearly an active component.
@artisan-radio The TH has been certified around 40 years, it was certified to be grounded via the power outlet,- But it's important to note that so had all the others part 15 AM transmitters that had been certified during that time period... and it started even before that with the New Pilot Communications xmtr which may have been the first back in the early 1980s..
The Talking House is/was not the only certified transmitters to utilize its power cord as ground, they all did, with exception to the outdoor units like the LPBs (TransAMs) and the Billboard USA transmitters (which I think were exclusively only for lease and not sale - and the leases were top dollar expensive)
Now the Range Extender didnt get certified until, when? about 20 years ago? - So far as I know there have never been any othrr similar part 15 device manufactured to compare to it.
@richpowers I don't know how to explain an active/passive device better than I did. The AI here explains it very well.
https://www.google.com/search?client=firefox-b-d&q=examples+of+passive+transmitting+antennas
@mark Just a few minutes ago I was reading this well written, enjoyable even article, not long, which I'll go ahead and post the link to now in regard to this, but it also brings up another interesting topic which I'll post in a new thread..
https://www.rfvenue.com/blog/2014/12/15/active-v-passive-anntennas
@richpowers You just beat me to it as this has started to get way off the topic of what is a "stage"
Please, start another topic if you want to talk about passive or active electronic devices.
@richpowers You just beat me to it as this has started to get way off the topic of what is a "stage"
Please, start another topic if you want to talk about passive pr active electronic devices.
Off topic? The question from the start has been is the final stage the final amp or the antenna itself. The argument is that it can't be the antenna because it's not an active component, and so raises the question "but isnt it?"... And that's where we're at now.
I fail to see at what point it went off topic at all??
Well I guess Artisian and mine little side topic about the Talking House drifted off topic a bit, but regarding if an antenna is an active component or not is right on par with the subject
For present and future reference,.. This discussion continues from this point and concluded (or almost concluded anyway, I guess, maybe, I dont know) here: https://www.part15.org/community/postid/60454/