There are no windows? For FM it only has to be a few feet (fraction of meter) of wire. I've got a 80's JVC receiver that came with an AM antenna that's only several loops of wire on a bobbin with perhaps a
6" (15 cm.) diameter. Works great here in the sticks.
Get a car radio or tuner . . . Great! I say, - easiest way to get stereo FM into my shop (metal building) using low loss coax aimed at the automobile market (12' - how'd you think those stretched limos do it?) plus, after-market car radios are built with sensitivity in mind, and not terribly expensive.
Concrete is not necessarily a signal stop, the amount of moisture in it may be. If the concrete is concrete blocks with a modicum of moisture protection, no problem. Add real concrete with reinforcement bar anchored in mother earth and kept wet and you have a problem.
If you already have and love a receiver (one presumes the FM is the real problem, AM should go through concrete)_you need to get outside the building. Laws, lease agreements, rental agreements, etc. be damned. A simple folded dipole made from 300 ohm twin lead should be enough (search for it - takes roughly 4' of TL plus lead-in to the receiver). Throw it out the window.
Still not happy?
Read up on multi path (FM) and which directions the stations you want are in.
Then it gets more hinky . . . ditto HDTV. Then a shield that blocks an interfering signal (or multi path) may reduce average signal strength, yet improve reception. (read about multi path to understand how that works). All to do with geography and location and signal reflectors (buildings, water towers, mountains, hills, etc.)
And last but not least . . . a lot of FM receivers and tuners with outdoor or "compromised" antenna inputs (say from walking across a rug on a dry day and touching the antenna input) may be faulty. The junction field effect transistor is susceptible to static electricity.
Mainly outdoor antennas. from my repair experience. JFETS are great for FM front ends, but not bullet proof. The problem is, you need a good voltmeter and experience to troubleshoot them.
Generally you hear about, or have a customer who used to get WXXX but can't any more (or not since that big thunder storm last year . . .)