Then what if we *deliberately* inject hundreds, if not thousands of discrete RF carriers into our SDR receivers from say...an internal RF carrier or noise generator, mixed with the desired RF signal to mitigate OL caused by a few strong carriers? It would be interesting to see the math and note what, if any reasonable limits apply, even if the amount of OL protection is small but there nonetheless. If this is a viable form of OL mitigation, then by now, someone must have already addressed this, possibly in an academic or IEEE paper? Paul, W9AC
That roughly describes the FM broadcast band near San Bruno Mountain, south of San Francisco, which is chock full of FM transmitter sites. It is an extremely difficult RF environment. The picket fence spectrum definitely is not beneficial. Instead, the stations mix with each other in the receiver front end and fill in any clear channels with garbage. I did some consulting for a company that made FM-SCA receivers and developed an 8 stage voltage tuned preselector for their receiver that worked as well as the six stage air variable preselector in my circa 1978 Technic's tuner that sold for $450 at that time. I also tried a WJ mixer with 1/2 watt LO drive as the front end of a superhet, but without a preselector. There was no comparison; the non preselected high power mixer was nowhere near as good as the preselected receivers. Of course, an ordinary car radio driven near the mountain is far worse than than any of the above. At the Maker Faire a couple of years ago, they had a start up company that was exhibiting an FM receiver that digitized the entire FM band. I'd like to see what that would have done around San Bruno Mountain. Rick N6RK _________________ Topband Reflector Archives - http://www.contesting.com/_topband