https://www.electronicdesign.com/technologies/communications/article/21755680/220-mhz-transmit-combiner-cuts-intermodulation-interference
220-MHz Transmit Combiner Cuts Intermodulation Interference | Electronic Design
The DB4370-DPM series of transmit combiners for the 217- to 221-MHz range uses high Q tuned cavities to greatly reduce intermodulation (IM) interference in...
220 mhzintermodulation interferencetransmitcombinercuts
https://www.arrl.org/Groups/view/220-mhz-spectrum-management-asson/type:club
ARRL Clubs - 220 MHZ SPECTRUM MANAGEMENT ASSON
The American Radio Relay League (ARRL) is the national association for amateur radio, connecting hams around the U.S. with news, information and resources.
220 mhzspectrum managementarrlclubsasson
https://www.law.cornell.edu/cfr/text/47/part-90/subpart-W
47 CFR Part 90 - Subpart W - Competitive Bidding Procedures for the 220 MHz Service | Electronic...
https://www.aanda.org/articles/aa/ref/2016/09/aa28702-16/aa28702-16.html
Subarcsecond international LOFAR radio images of Arp 220 at 150 MHz - A kpc-scale star forming disk...