Have 2 garage door openers (Liftmaster) with 315 MHz receivers that have worked well from at least half a block away for 5 years. For past 2-3 months they have not even worked well from a foot from the door using Home Link transmitters off of car battery. Hooked up 2 different Sdr dongles today with 2 different receive software. Found very strong signal on 316.8 MHz that I suspect is desenseing the receivers. Any idea what might be the source? Problem exists at all hours and all days.