KJET 1590 wasn't much, an IGM Instacart that notoriously missed voicetrack cues and got out of synch with the rest of the playlist at least once daily. It was mono, had a crazy narrow bandwidth even ordinary, non-radio oriented listeners noticed. But after the demise of KYYX, it was a lifeline for Modern Rock fans who wanted to keep up with emerging new music.
Outside of a handful of Alternative-AOR crossovers and Sunday night shows, there wasn't much KISW and KXRX could do. KCMU was trying to impress everybody with John Cage and Diamanda Galas. KNHC had the Old Wavers and trendy Dance music, but not a whole lot of new Indie and College Rock.
And you had to pick up a good book and sit through Steely Dan, Phoebe Snow, Michael Tomlinson, Toni Childs, Crosby Stills & Nash, Steve Winwood, Matt Bianco, Joni Mitchell, George Winston, Uncle Bonsai and Lyle Lovett to get to a Roxy Music or Peter Gabriel song on KEZX (No "Sledgehammer", "Big Time" or "Shock The Monkey" either.)
KJET 1590's rated audience was small. But they were quite popular in the 1980s. Many members of Seattle's grunge bands listened to KJET.
And in another phenomena I've observed over the years; KJET 1590 was perhaps the most listener airchecked Seattle radio station of the 1980s. Over the years, various KJET tribute sites, tribute radio stations and aircheck sites have come and gone that hosted a lot of KJET aircheck tapes and I've heard KJET material ranging from their earliest days. With Rick Shannon (Rick Riley) voicetracking as The Unknown Announcer (1982) to their last goodbyes. From unlistenable (Certron LN-60/Soundesign) quality to the surprisingly good. Some of it is on one of my old hard drives.
So it wasn't just me and many I knew in high school and around Puget Sound doing this. And these were the ones who kept their KJET tapes and didn't re-record anything over them.
Why? Some tapes ended up in places of the country where there was no local Alternative rock station at the time, sent through snail mail by Seattle friends/relatives. KJET also played pre-release album cuts and imports and until listeners could buy the real thing, these lo-fi mono recordings carried them over. (In the days before streaming everything, people did what they had to do, the best that they could do it. AM or not.)
I believed then (and even more so now) that KZOK/SRO management back then didn't know what they had. But SRO were getting ready to sell KZOK/KJET and they probably thought an Oldies combo (with the relaunched Classic Rock KZOK and KJET becoming '50s-'60s KQUL) would look more corporate-buyer friendly.