1M Watts of RF – How the FM Supertower Works
jeffgeerling.com
jeffgeerling.com
Sort of like saying a flashlight is 100W because its as bright as a 100W bulb when looking right into it even if the flashlight itself is only putting out 30W, the reflectors in the flashlight direct the 30W of light in one direction making it brighter.
The gain listed on antennas is really just telling you how directional it is, any gain above 0 means it has directionality over a perfect omni and must be oriented properly to take advantage of it.
Antennas with a non-uniform horizontal radiation pattern do need to be correctly oriented. A simple example of a directional antenna is a Yagi, where more energy comes out the front than the back and sides.
Many small antennas like say for cellular use will list large gain numbers, and many people will buy based one having more gain than another. The ones with more gain typically have radiation patterns less uniform than a dipole and may pick up better to certain sides, even though they aren't an obvious single direction antenna like a Yagi or marketed as such.
This is of course true! I wish it didnt need to be said, but I work in radio and I have absolutely seen people install antennas incorrectly (installing Yagi antennas with the wrong polarity or facing the wrong direction is reasonably common). Hopefully that wouldnt be an issue at FM broadcast sites though.
This is generally correct, but for more context ERP uses a gain in dBd which is decibels relative to a dipole antenna. A dipole is not a perfect omnidirectional antenna.
A perfectly omnidirectional antenna would be an isotropic or point source antenna, which is only theoretical (no truly isotropic antenna can actually be built as far as I know, but dipoles are simple to build and widely used). Gain is measured in dBi when comparing to isotropic antennas, and EIRP (Effective Isotropic Radiated Power) would be used, not ERP.
This may sound like a small nitpick, but its a pretty huge difference in practice! 1MW ERP is approximately 1.6MW EIRP.
A theoretical perfect dipole has 2.15 dBi gain over the perfect theoretical isotropic, but again only in certain directions.
Perhaps the article would have been even more impressive titled 1.6 MW transmitter then just listing EIRP down in the article instead of ERP.
Either way its actually only a 330KW transmitter.
As a proprietary system, HD Radio involves costs that can be prohibitive to small broadcasters. I do not know of any attempts to reverse-engineer the HD Radio system, nor am I qualified to guess at the workload involved, but an open license alternative is a nice dream that would enable a huge quality and capability improvement for even the smallest radio stations.
I know my Dad has a lot of experience on both sides of the licensing (both large radio conglomerates and smaller independent broadcasters) and I think having a discussion on the history and implementation of HD Radio in the US could make a good follow-up video at some point.
If I'm understanding you, a clean sheet implementation of "HD Radio-compatible" digital broadcasting using open source and open hardware techniques over a federally licensed station would contravene the proprietary system's license?
https://github.com/argilo/gr-nrsc5
A lot of the ibiquity patents are expiring this year or have already expired as well. I haven't been following the patent situation on this as closely as I used to, but needless to say I will be very excited when they all finally expire. Digital radio would have been awesome had it become pervasive in the late 90's when it should have.
Imagine trying to screw one of those into your cable modem!
300 thousand kilowatts? (300 MW?) No wonder they need such massive cooling.
You also get to look inside an old tube transmitter; all the ones I've seen these days are solid state, though in our second video I did mention a couple tubes they had at the site they now use as doorstops!