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Your posts are very insightful !

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Thank you Vikram, this is very good introduction into the topic.

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"Angered by this, Sarnoff used his influence to ensure that the Federal Communications Commission (FCC) changed the FM radio spectrum so that Armstrong’s company could no longer use it, rendering the company useless."

The osensible reason for the shift from "low-band" to "high-band" FM was to minimize skip, https://en.wikipedia.org/wiki/Skywave , which is a propery seen as a feature rather than a bug by users of the 6 meter band https://en.wikipedia.org/wiki/6-meter_band and https://en.wikipedia.org/wiki/AN/PRC-77_Portable_Transceiver , but was suboptimal for localized broadcasting.

"One area of concern was the effects of tropospheric and Sporadic E propagation, which at times reflected station signals over great distances, causing mutual interference. A particularly controversial proposal, spearheaded by the Radio Corporation of America (RCA), which was headed by David Sarnoff, was that the FM band needed to be shifted to higher frequencies in order to avoid this potential problem. Armstrong charged that this reassignment had the covert goal of disrupting FM radio development,however RCA's proposal prevailed, and on June 27, 1945 the FCC announced the reassignment of the FM band to 80 channels from 88–106 MHz (which was soon expanded to 100 channels from 88–108 MHz), while allocating the former FM band frequencies to "non-government fixed and mobile" (42–44 MHz), and television channel 1 (44–50 MHz), controversially ignoring the effect of tropospheric and Sporadic E propagation on those services." https://en.wikipedia.org/wiki/FM_broadcasting_in_the_United_States

That said, the prevailing view view that Sarnoff lobbied for the change in order to ruin Armstrong appears to be accepted, as it de facto did "The dual band transition period ended at midnight on January 8, 1949, at which time all low band transmissions had to end, making obsolete 395,000 receivers."

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Wow, there are so many nuances to this story! Thanks for sharing Gunnar!

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Thanks for sharing this useful history

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