Mark
We installed a top of the line Lennox heating and AC unit 3 years ago. The PWM motors were a big concern of mine based on reports I had read about online. Lennox makes an RFI kit that they will provide if requested. There was no charge for the kit consisting of 2 toroids and an AC line filter. I had the contractor order the kit when they ordered the furnace. On installation day I asked the technician for the literature that came with the RFI kit before they left. I went and scanned the HF bands shortly after they left and was disappointed to find a number of spurious signals at discrete frequencies across the 20m - 10m bands. These signals ranged from S3-S7. I Couldn't find anything at 6m or above and my noise floor is so high on 160-80 that I couldn't hear or see anything new. After reviewing the literature that came with the RFI kit, I opened up the furnace and discovered the technician hadn't installed the items correctly. I could have fixed them but decided to call the contractor back to avoid any warranty claim issues. Once re-installed, the noise level dropped down to an S1-2 worst case on 17 and 15m. Not being satisfied, I went ahead and added some external 2.4" cores on all external wires coming and going from the furnace. The end result is a very usable spectrum with just a small handful of s0 level spurs across 17m. I have been very happy with the furnace and AC units themselves. I just wish these companies would spend the extra $10 and take care of RFI/EMI right at the source during design and production. Good luck with your search! Ed VE4EAR _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector