HFU HF Underground
Technical Topics => Part 15 AM and FM Station Operation => Topic started by: ThaDood on August 31, 2025, 1643 UTC
-
https://antiqueradios.com/forums/viewtopic.php?t=450003&sid=976d48f56b147cabc80491723266eee8 But, you can download this dude's .PDF direct, https://worldphaco.com/uploads/THE%20LOW%20POWER%20MW%20AM%20TRANSMITTER-ANTENNA.pdf Nice read & system explained, and rare INFO for anyone to write about today. YES!!!!!!! Even, if you don't do everything from scratch here, you could add improvements to what you may already have and use. Lots of great INFO here. (Thank you Boomer for the link!)
-
I've read the first three pages and only skimmed the rest so far, but those first three pages where captivating!
I don't know who Dr. H. Holden is but like his writing style, and I never knew the term "Pantry Transmitter" is what they call a part 15 transmitter in the UK! That's a cool bit of trivia. However, he said something else that I found peculiar - in that it's flat out incorrect, - or maybe I just missed a context somehow, but here's the quote from page 2:
"•••••
"Although these regulations don’t apply in all countries, the USA’s FCC’s Part 15.219 Regulation Transmitter Specifications do provide a useful “metric” to avoid interference to others.
Obviously any MW band AM transmitter circuits, regardless of their RF amplifier design, combined with some design of Antenna structure, must never be allowed to transmit a higher actual electromagnetic (EM) wave power than the “FCC’s regulation transmitter-antenna arrangement”
"••••••
Am I misunderstanding what he's saying? To me it sounds like he saying that regardless of the circuitry or an alternate antenna configuration that it obviously must still adhere to a certain field strength - "EM wave power" - Is that what he's saying? Or am I misinterpreting?
I mean several FCC documentations clearly state 15.219 has no field strength limits associated with it. I mean that's almost the exact words (I can pull something up in short order if need be). The are no field strength limits associated with 15.219
Or am I making a fool of myself and that's not what he's saying at all? I read the above quote 3 times, maybe I'm just experiencing a brain fart or something.
-
Well, one of the simplest things that I've seen under FCC Part 15 Rules was this rip:
Section 15.209:
9 KHz-490 kHz: 2400/F(kHz) uV/M, 300 M
490 kHz-1705 kHz: 24000/F(kHz) uV/M, 30 M
1.705-30 MHz: 30 uV/M, 30 M
30-88 MHz: 100 uV/M, 3 M
88-216 MHz: 150 uV/M, 3 M
216-960 MHz: 200 uV/M, 3 M
960 MHz and above: 500 uV/M, 3 M
I'm looking at the 490-1705kHz: 24000/F9kHz) uV/M, 30M. (Yeah, for ease, I ripped from https://sandersrfconsulting.com/fcc-part-15-intentional-radiators/ , from the https://www.hobbybroadcaster.net/resources/FCC-Part-15-regulations.php link.) Somewhere, I have downloaded on my storage computer hard drives the full FCC Part 15 Rules. But anyway, I thought that I've seen something upon RF Field Strength Limits. Sanders RF Consulting is certainly right about one thing, "A simplified cheat-sheet is needed.". Then again, I've quoted the Part 15.209, and not .219. So, you bring a good-point. Still, this dude, Dr. H. Holden, does provide some nice, useful, INFO, to soak-up. BTW also, I don't take that ripped chart as a gospel-truth, but as another reference. Case in point for the Part 15 FM Band FS Limits, I seem to remember being 250uV at 3M away measured. Still, that one is ridiculously limiting, but it is at least a documented 'Limit'.
-
Now that I've read the rest of it I realize he appears to fully comprehend 15.219 but for whatever the reason his objective was for his designed and constructed "Pantry Transmitter" to simply conform more to 15.209. I guess because from outside the USA.
The PDF is very interesting but I still feel like I'm missing something. I know I'll be taking a second look at it. It stands out as significant to me, but a little perplexing at the same time. But its it's definitely worth reading.