Need help in creating a bug detector.

[counterespionage]

I really don't know if this is the right forum, I found about this forum when I searched for an up converter for software defined radio. I don't have an SDR and I don't know if it is a good investment, even $70 is a lot of money for me, so I want to think this through thoroughly before I buy anything.

Is a regular RTL-SDR good enough to detect bugs when they are operating by transmitting and receiving data. Like for example if a smartphone or IoT is secretly sending data when it isn't supposed to, or any just to scan for bugs when I go to unknown places, like hotels, etc. I want to use this RTL-SDR as a spectrum analyzer and take it around to find about all the frequencies around me. The regular RTL-SDR only covers frequencies between 24MHz - 1.7GHz, that is a pretty narrow window of the radio space, I want to increase the frequencies it can cover at the lower end and higher end.

Will it be difficult or expensive to create an upconverter and downconverter which increases it's range to maximum and minimum allowed by it.

[Kage]

SDR receivers would be a good start and with one of those super cheap TV dongles plugged into a tablet computer through one of those USB OTG adapters you can run some of the popular android SDR packages for ultra portability.

Another option is getting a cheap or used portable scanner radio that has a "close call" feature where it can automatically identify and tune to the strongest nearby signal, then you can take the radio and wand it around until it captures something hidden. My Uniden BC72XLT has that feature and I picked up that radio at a garage sale in a freebie box

There used to be kits to detect bugs, I think Ramsey Electronics might have even had one at some point.

Most pedestrian bugs are likely going to be on VHF on up through UHF because of the need for compact antennas so anything like an SDR will be helpful. Three letter agencies are likely using something far more sophisticated that would be really hard to find and probably using spread spectrum technology or even more complex. Only ones I ever looked into that were low frequency were ones in project DIY books to tap phone lines and send RF down the actual telco wire but I'm not sure if those were a joke or real.