Hello everone!

I've been looking for a cheap way to record ultrasonic frequencies and I am getting a little frustrated.. I've been studying this (http://www.richardmudhar.com/articles/technote/micdesigns/index.html) tutorial for a while after this (https://www.wildlife-sound.org/resources/equipment/2-uncategorised/76-recording-ultrasonic) article and while I think I could rebuild it, I wouldn't know which recorder to use with it since none of the ones I saw mentioned in forums etc (that will supply plug-in power from their mini jack which apparently works best with these capsules) are available to buy anymore - generally I keep finding mostly old information on the matter.

I understand that being able to record and handle frequencies of up to 60 if not 90 kHz is not a particularily sought-after trait in a microphone/recorder but are there any late developments in that area? I would really appreciate a simple, or at least somewhat relyable combo that doesn't leave a lot of room for me to ruin stuff with my lack of electrical knowledge - I literally just want to record rat noises.

And honestly, it's alright if I have to build the microphone as shown in the links above - as long as I find a recorder it will work with. Maybe someone has some experience with recording ultrasounds? I would really appreciate to know whatever works for you! And thanks for stopping by, I'm at my wits end.

-Calla