KPNI exists today merely as the online radio station of Southern Methodist University (SMU). 10 years ago is was also audible inside their student center over loudspeakers, the Umphrey Lee building, but even that has ceased. Link here or here. But their web presence is scattered to say the least. Twitter pages to up... and down; pages begin tweeting and posting, then cease. But long ago, this was a vibrant and powerful Dallas radio station...supposedly.
Some reports describe KSMU as being on air as early as 1947. This is probably not accurate. In fact, by 1950 there were only seven radio stations in Dallas at all: 1080 KRLD-AM, 1040 KIXL-AM, 660 KSKY-AM, 1190 KLIF-AM, 570 WFAA-AM, 820 WFAA-AM, and 1310 WRR-AM. Only one of those was even full time, KRLD. Some of dubious sources even cite the KSMU frequency as 640 or 760, the power anywhere from 10 watts to 250 watts. No matter what the station may have later been, it was in the 1950s and 1960s, a carrier current station. But the story after 1964 is better documented. In November of that year Billboard wrote up the return of KSMU, and it's formal grand opening, just not to the airwaves exactly...
"KSMU resumed broadcasting after being off air for nine years and operates on a frequency receivable only on the SMU campus. Cables have been laid to eight undergraduate dormitories and their carrier current is transmitted into the electrical system of the buildings. cables will be laid to six graduate dormitories next month. There will be 10 student deejays to broadcast music, news and public service announcements from 5 p.m to midnight Monday through Friday and 7 p.m. to Midnight on Sunday."They used a feed from KVIL-AM to fill some of their off air time. But later in the article was a name. It is a name that comes up in every article about KSMU from the very beginning: Dr. H. Charles Baker. More about him here. But notice that first line... "off air for nine years". That would have them going dark in 1955. One more reliable source wrote on their now defunct history webpage:
"...KSMU's signal became unbalanced, creating an annoying hum heard over the campus airwaves. In 1957, the station alleviated the problem by installing an antenna that caused the AM signal to wander off campus. Unfortunately for KSMU, the signal interfered with the signal of KSKY, who immediately complained to the Federal Communications Commission (FCC). The FCC quickly revoked KSMU's FM license, making 1957 the last year for KSMU to legally be heard off campus."If it was heard off campus, it was illegally off campus. Which would have raised the ire of any licensed broadcaster receiving interference. But to reiterate, there never was a license for KSMU, no AM, no FM, no Class D license, no LPFM, not even a CP. Even their illustrious return in 1964, was still as a carrier current station. This is sometimes listed as with dates other than 1964, despite the cut-and-dry 1968 Billboard article.) It is worth noting that they may have been carried on Park Cities Cable's public access channel around 1979 but it's an apocryphal claim that I can't corroborate. More here.
So the station probably "signed on" starting around 1955. I think the pre-1950 claims are deeply dubious. It was dark from 1955 to 1964, then dark again 1980-87 returning as KPNI in 1994. The new callsign was probably to differentiate itself from the legitimate licensed 91.1 KSMU-FM in Springfield, MO. The station converted to broadcast online exclusively in 2003. The FCC never took away their license, nor did the school sell it off. They may have caused interference to KSKY around 1957, and they may even have pirate broadcast a few times... but that may be just a fish tale.