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Post by End80 on Dec 22, 2016 14:04:02 GMT
An answer is revealed via the saga of Victor H. Fischer back in 1972 which eventually resulted in explaining why part 15 broadcasting is allowed when the FCC said " The intent of Part 15 is to provide the radio enthusiast with an opportunity to experiment with radio, and to entertain friends or neighbors within a very limited communication range..." I had discovered and discussed this previously at part15.us and also wrote about the whole story in a blog post at part15lab.blogspot.com/2014/03/intended-use-of-part-15-in-eyes-of-fcc.html A link to the original FCC document is also included What did our Resident Agent have to say on the subject? I don't recall if he commented or not, the discussion was 2 or three years ago. |
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Post by Boomer on Mar 22, 2017 11:05:08 GMT
Perhaps that little broadcaster you refer to in the blue box with a microphone and tape player is the Wild Planet Radio DJ. I have 3 of them. The most successful AM broadcaster I had in terms of range was a home made 1 transistor broadcaster from the book Using Electronics. I have the book and WILL build the circuit again. Click this link to Read The Book. Look for Circuit #20. I have a Wild Planet Radio DJ, it's cute, but mine just doesn't have the oomph, in fact it's pretty pitiful as far as range, 20 feet max, and doesn't go through walls, 20 feet away it's little more than a teeny whistle on a radio. I've had the urge at different times to try some mods I've seen on line, though I'm not sure I trust the circuits in the PDF I found. I've also thought of appropriating the DJ's crystal to make a real rig! That transmitter in Using Electronics, it reminds me of the circuit of my first FM transmitter, with the feedback for oscillation across the transistor's collector and emitter through a capacitor, while the base is grounded at RF. The phono oscillator in the book has a few oddities to me. One thing is there's a full DC path through the transistor, with no emitter bias, and no current limiting. My FM transmitter like this used an NPN silicon transistor, which totally needed a resistor in the emitter, as my attempts to lower the resistor to get more power blew the transistor by overheating. Maybe it's that a germanium transistor has a higher impedance and wouldn't draw excessive current. It also seems if you connect the microphone with the transformer shown, that the transistor base would have a DC short to ground. If you built it and it did well, that's great! Boomer |
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Post by End80 on Mar 22, 2017 11:28:13 GMT
To answer the question of why part15 radio is allowed.. If you go back to the original part15 rule [part24].. I found it interesting the way this new rule was conveyed; In 1938, it was foremost a "substantive" rule, IE: a public right to freely utilize. However it also emphasized an "exception" of not causing interference to licensed stations.
In essence the rules haven't really changed in the last 80 years, however now days the interference exception seems to be the foremost aspect of the rule
What's also interesting is what the catalyst had been which actually had directly prompted the rule to be written, which is something I never heard before till a day or two ago.. As discovered in a 1942 QST magazine article, it was a remote control invention of Philco Electronics that could travel 75 feet. I posted about this early yesterday morning in my blog: part15lab.blogspot.com/2017/03/thanks-philco-for-part-15-broadcasting.html |
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Post by Boomer on Mar 22, 2017 23:23:53 GMT
I like your blogs End80, actual articles, and I feel like I've accomplished something after reading them. I should set a new policy for myself, to stay out of political threads and stick with technical and science discussions, as they are truly what gets someone on to the airwaves. I do try to refrain from it already, but some bait is too tasty..  Every member of ALPB should have an outside blog, their own space, and post to it. Boomer |
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