It would be difficult to detect such signals hence the size of the radio telescopes and networks combined with the large amounts of computing assets marshaled by the SETI project.
However, the last article I read stated that close to 1200 signals had been detected that can not be attributed to any known natural source. Which could mean that there are natural sources yet to be discovered or understood to account for these signals....or that there may be a few of those 'alien Pioneer' craft being noisy.
I am in the middle of a software test. Sigh. Will answer all posts this evening. :-)