HFU HF Underground
Technical Topics => Part 15 AM and FM Station Operation => Topic started by: ThaDood on December 17, 2025, 1729 UTC
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This exchange on this post , https://www.hfunderground.com/board/index.php/topic,155420.0.html , reminded me of another project in the works, an 11M transmitter for Part 15 levels from the FREQ of 25.670MHz - 26.100MHz. If, I finally get around to doing this project, I'll put it up on my Archive page. So, stay tuned!!!!!!
ADDITIONAL 12/21/2025: Upon looking up the permissible Field Strength Emissions for Part 15 use in the 11M INT BC Band, it appears to be a measly 30uV @ 30M, 30 mircovolts measured at 30 meters away. (Or, several "S" units to a portable at around 100ft.) This does indeed seem like a ridiculously low Field Strength, where maybe the signal would reach a couple close back yards. However, on the receive side of things, consider that of all the bands that listeners would be using outdoors antennas, this band appears to to have some nice prospective. On the 11M INT BC Band, listeners would most likely be using Ground Planes, like 1/4-wave, 1/2-wave, and 5/8-wave, antennas, as well as Beam Antennas. Given these possible considerations to extend the range, at the receiving end, Part 15 operations may have some possibilities after all. Certainly, would make for an interesting experimental transmitter. Passing contemplation...
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Sounds promising
What would that tx power be in mW?
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Hmmmmmmmmmmm... Good question, since to meet the Part 15 Field Strength for 26MHz, of 30uV @ 30M away, the power would probably be in pW, picowatts. Local coverage??? Very local, like a few hundred feet at the most to portable. However, with decent CB base station antennas, at the receiver's end, that range could be from 1/4 mile to 1/2 mile. Even further to those receiving with beam antennas. Hey... It's a Part 15 Loophole that exists, albeit a small one, but might as well try and take advantage of it. Right???? Anyway, THANKS for asking.