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> I wrote a book on low power AM broadcasting. Sound great. I hope you'll post a link. > they operate at very low wattages (sometimes 100 watts or less) Sinc
by cf100clunk 3y ago
> I wrote a book on low power AM broadcasting.
Sound great. I hope you'll post a link.
> they operate at very low wattages (sometimes 100 watts or less)
Since the original article is about a station on the shoulder of the TV VHF-Low and FM bands here's my take on it.
Even a very low power transmitter rated <5 watts in the FM band can have its ERP (Effective Radiated Power) multiplied greatly by the combination of a good antenna and altitude above average terrain. A pirate with a small transmitter cabled to an omnidirectional antenna mounted atop a high apartment block can easily output a >100 watt ERP. Frankly the pirate's rig might even achieve ERP levels in the 6-8kw range if they get lucky, enough to cover a medium sized city. Interference issues crop up because the pirate broadcaster likely did not have the engineering knowledge or resources to analyze and predict problems in that chain, even if the transmitter is itself quite clean. That's why we have strict broadcast licensing technical requirements almost everywhere in the world.
- ooterness 3y agoSorry, but no. EIRP is actual power plus antenna gain; ERP is the same thing minus 3 dB. By definition, an omni antenna has low gain. Narrow directional antennas will have high gain, resulting in higher EIRP, but would not be suitable for covering a whole city.
- cf100clunk 3y agoI now realize that I should have replaced ''the pirate's rig might even achieve ERP levels in the 6-8kw range if they get lucky'' with ''the pirate's rig might even achieve ERP levels in the 6-8kw range if they get better gear''. Anyway.
- quesera 3y ago> Interference issues crop up because the pirate broadcaster likely did not have the engineering knowledge or resources to analyze and predict problems in that chain In this case, in Boston, the FM band is full. No new licensees can be fit in, due to the dearth of open channels and minimum power regs. So any pirate is likely to be stepping on someone. Maybe not in protected contours, but I'm willing to bet that the complainants are not actually measuring interference anyway.