I have a ton of Tzadik stuff. (And a lot of it is really nice-sounding!) I haven't heard Radar, and they are proving difficult to google... radar, no. Radar band, no. Radar music band, amazingly still no... LOL. File under "what not to name your band," I guess! (I did find it eventually, listening to samples now...)
You can't really pin Tzadik down genre-wise, I have very wide-ranging tastes so it doesn't bother me. But they are not a "jazz label" or anything like that. Lots of jazz, but also avant garde and contemporary classical and metal(ish) and world music and klezmer and etc... they're all over the map.
Off the top of my head, some of my favorite Tzadik stuff:
Bar Kokhba Sextet (their live album on Tzadik is one of my all-time faves, but sound is not perfect... studio album "Lucifer" has great sound)
The Dreamers - all their albums have really beautiful sound and they have some fancy vinyl releases, too. Ipos and their debut self-titled album are my faves.
Les Rhinoceros
Some of the John Zorn Filmworks albums - Belle de Nature, The Nobel Prizewinner, El General
The Cracow Klezmer Band - love them... "De Profundis" is my favorite
Book of Angels series is amazing... favorites are Malphas, Volac, Xaphan, the aforementioned Lucifer, Haborym, Stolas (that's a great one if you like fairly straight-ahead jazz). I had one of my defining audiophile moments listening to Xaphan some years ago...
Richard Crandell - Spring Steel ... this one is amazing to listen to on good headphones. Not everyone's idea of a fun listen but I find it very beautiful and meditative.
I pre-ordered via Kickstarter Zion80's debut album which is coming out in April. Seen them in concert four times, excited to hear their album.