ACR PLT CONCERNED WITH ZLC FREQ CONGESTION WHEN OPERATING IN WYOMING AREA ARPTS.

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EXCESSIVE FREQ SATURATION: ALL OF NW WYOMING IS WORKING JUST ONE ATC SECTOR AND COMMON HIGH; LOW ALT; AND LOCAL FREQ OF 133.25. AS A CONSEQUENCE; ALL USERS ARE TRYING TO TRANSMIT AND RECEIVE ON SAME FREQ AT SAME TIME. VIRTUALLY EVERY XMISSION IS BLOCKED BY ANOTHER XMISSION. LOCAL ACFT ON GND AT NW WYOMING ARPTS ARE CALLING FOR ATC CLRNC; NOT REALIZING THEY ARE BLOCKING HIGH ALT; SLC XMISSIONS DUE TO TERRAIN MASKING. THE FREQ CONGESTION HERE IS WORSE THAN ANY LOCATION ON THE EAST COAST! RECOMMEND SLC CENTER SPLIT THE LOW/HIGH ALT SECTORS WITH SEPARATE FREQS; AND A 3RD FREQ FOR ACFT ON THE GND TO PICK UP THEIR IFR CLEARANCES/VOID TIMES. DURING HIGH VOLUME WEEKEND TIMES; THE CENTER HAS TO REPEAT ALMOST EVERY XMISSION 3-4 TIMES BEFORE THE RECEIVING ACFT WILL ACKNOWLEDGE IT. THIS RESULTS IN OVERLOADED CTLRS AND DEGRADED ATC PERFORMANCE. WE WERE 'LEFT' ON A SEQUENCING VECTOR TWICE ON THIS FLT; HAD TO REMIND THE CTLR FOR ADDITIONAL INSTRUCTIONS. SLC THEN FORGOT TO HAND US OFF TO THE NEXT SECTOR 124.35. WE FINALLY SWITCHED OURSELVES TO DEN CTR. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR ALLEGES THAT THE FREQ CONGESTION PROB IS MARKEDLY WORSE ON THE WEEKENDS; LATE MORNING THROUGH MID AFTERNOON.