An amplifier is an active device. "passive amp" would be synonymous with 'passive active device'...
The closest thing I can think of that would fit the description of a 'passive amplifier' would be an antenna with relative gain. Antenna gain is better than amplifier gain. Antenna gain offers additional signal power with no additional noise or distortion of the signal. Amplifiers also offer additional signal power but add noise and distortion.
If the old cable has been damaged by water, corrosion or physical cuts or crushing, etc. it needs to be replaced. The same is true of the antenna.
The least effective solution is the addition of an amplifier near the receiver. All of the noise, distortion and interference up to that point will be amplified as well... then the new amplifier will add its noise and distortion on top of that.
Focus on the antenna, if it's not up to the task, you won't fix the situation with down stream accessories. Once you have a quality signal from the antenna, then focus on the need for a preamp or distribution amp. If amplification is needed, the right choice is important, you need to know how strong the signals are going into the amplifier and you need to know how much loss is down stream of the amplifier. You may not need any amplifier. Finally, cable and splitters need to be chosen and installed correctly.
As JC has requested, you'll need to provide a link to a TV Fool report for the location along with a complete description of existing antenna(s), combiners, receivers, muxes, modulators, amplifiers, cable lengths, numbers of sets connected, etc. Do you have access to the existing hardware in place, and the right to adjust, replace or repair all parts of the system? This sounds like a system owned and maintained (though not very well) by the building owner, not your friend.
Without full access to the system, your friend may be stuck, depending on the owner of the system to make repairs or adjustments.