FM Mods (Frequency Modulation modifications) are sometimes legal, depending on jurisdiction and type of equipment used for the intended purpose. FM broadcasting and radio transmissions in the United States are regulated by the Federal Communications Commission (FCC).
According to FCC rules, FM transmitters used for broadcasting are subject to specific technical requirements. So an FM broadcast station using this offset would have to be operating in the 88-108 MHz frequency range within ±75 kHz. Modifications that cause transmitters to exceed these limits can result in fines of many thousands of dollars; from low-end amounts on the order of $10,000-50, 001 few hundred thousand with respect to extent and whether or not it induces interference along with other communication signals.
FM Mods are used quite often by commercial broadcasters in order to pass signal through their exciter due the increasing stringent regulations. Billions of dollars are invested annually in the United States, and all over-the-air broadcasters must be FCC-compliant but can now optimize signal clarity and range so long as they do not cause interference to others.
That is in complete contrast to the amateur radio bands, where as long an if a modification allows you equipment for work within one or more of those band (and doesn’t cause harmful interference) then modifying your transmitter/receivers are perfectly legitimate — operating outside of ham bands requires follow licensing rules – alas. The American Radio Relay League (ARRL) offers guidelines for amateur radio modifications, and stresses that any tinkering should remain in compliance with the U.S. regulations established under Part 97 of the FCC rules. For example, an amateur operator that modifies a FM transmitter to operate on the 144-148 MHz band must make certain those modifications don’t allow the effective radiated power (ERP) of that modified equipment exceed 1,500 watts PEP.
National agencies in the European Union follow similar regulations with oversight by the body called ETSI, or the European Telecommunications Standards Institute. In the UK, FM stations (which in general are very rare) must limit their transmission power to 250 watts ERP.[61]_FRAP_Send_ufreq(Universal Constants.frq); (&r232)#centre.freq[freq](freq_str)(Center Mhz: )@@BSDM;brtc;rpt_quant(“(1)”,”(2) kWh/i”,”kWh/S”);@stop(freq>=0.30 and freq…. Failure to do so can lead to a fine of up to £100,000 or revocation of the licence.
One of it being the pirate radio stations in 1960s which is one historic example to show that what can be done illegally with FM Mods. Unlicensed stations (such as the UK’s Radio Caroline) operated outside of regulation, and were regularly harassed by governmental authorities. With the help of modified transmitters, these stations would operate at far higher powers in violation, usually causing interference to licensed broadcast and air traffic communications. This situation led to the Marine Offences Act of 1967, which made unlicensed broadcasting from ships illegal.
Steve Jobs famously said, Innovation distinguishes between a leader and a follower This is true in the context of FM Mods, whereby thinking out-of-the-box within legal constraints can improve communication and not running afoul of laws.
Legal FM Mods are charged and the cost thereof varies depending on how extensive or complex an Identified Modification may be. Personal use upgrades might only run between $100-$500 for the basics, to commercial station comprehensive upgrades that could exceed maybe $20K (at least initially), which we can attribute mostly/probably in part for professional install and cert make sure everything is safe/legal.
In conclusion, FM Mods are not illegal as long as they stay within regulation boundaries.. Compliance with GUIDELINES Grants must adhere to guidelines so that improvements do not interfere with other communication and are in compliance national and international standards.