Where can I get instructions to build a very good Bug RF detector?

Good Bug detectors are very expensive and those selling cheap in the Internet are not good; is just waist of money.

Someone knows how to build one with low and high frequencies together?

Thanks.

What is a VPN?

VPN is (Virtual Private Network) were first used by companies to enable their employees to securely access internal systems such as email remotely (e.g. from home or while on business trips). Today they are increasingly being used for personal use by individuals to protect their privacy while online in public places (e.g. when using the wi-fi connection in a cafe) or in a country where the internet is censored / blocked (e.g. China, Saudi Arabia…).