Do you think radio signals aliens have sent reached us before we had the technology to receive them

Flabbergasted.

you really believe that in that stuff

Our radio technology is what's called narrow band communication where we only transmit in a very narrow range of frequencies. Early on, the governments stepped in and divided the frequency space into ranges and licensed each range out so we've stuck with narrow band. However we have since discovered that spread spectrum is the way to go where you transmit on as many frequencies as possible. Such a transmission would only look like static to someone without the appropriate codes. Even with our licensing of frequencies, we've discovered spread spectrum helps us transmit more data so we use spread spectrum in a limited sense, WiFi uses spread spectrum which is why it has narrow band beacons to synchronize the codes, CDMA came out after TDMA ( GSM ) because it took us longer to work out spread spectrum technologies. If the aliens are smarter than we are ( that should not be difficult ) and didn't tie their hands with government licensing of bandwidth, they may be using spread spectrum and not only does their communications look like static to us but ours would look like unintelligent chirps and beeps as surely no intelligent civilization would use narrow band. We probably aren't communicating with aliens by radio because we're stupid, have governments and manage our resources in a currency based economy and therefore have selected an inferior method of radio communication.

In the span of about 150 years, we humans went from wires and telegraph code keys to radio and TV communications to digital computers. Do you really believe that extraterrestrials will be communicating across the vastness of the Universe with electromagnetic waves? Of course not, and nether will humans in another 100 years or so. I have a feeling that there's new physics on the horizon that will make communications at the speed of light all but obsolete. I believe that new physics will be based upon scalar fields and scalar energy, and communications, perhaps even space travel, will be instantaneous across many, many 1000s, if not millions, of miles. And that is just the beginning.

The chances of accidentally hitting upon just the right frequency with just the right demodulator to 'hear' extraterrestrials is highly unlikely. Even if they were communicating in the conventional sense, there are way too many particulars (variables) involved that would have to be in perfect order, such as frequency, demodulation, bandwidth, selectivity and sensitivity, etc. Probably will never happens by way of conventional radio communications.

Best regards