I too had a fan noise on my GR 300 repeater. As Eric instructed, I replaced the fan with a low EMI. Still had some but a lot less. Then I took the new low EMI fan and removed it from the repeater cabinet and hung it from the big cabinet, holding all the repeater items, so it still blows on the heatsink and it is almost not heard. I had two problems, 1) to high of EMI rated fan, 2) vibration noise. Thank you Eric L. for your help with my problem.
Rod KC7VQR > Doug, > > The solution is to replace the noisy fan with one that is designed for very > low EMI. The first thermostatic switch controlled fan I put on my > solar-powered UHF repeater had a whine that modulated the carrier. I then > swapped it with a Panasonic fan that was specified for low EMI. Presto! > There was no trace of fan noise on the carrier. > > Part of the problem is the basic design of some RF-noisy fans. Hall-Effect > devices are used for commutation, and some designs are inherently noisy. > Some of the noise is conducted, and some is radiated, so ferrite rings, > series inductors, and capacitors are of little value in filtering the > noise. Just choose a low-EMI fan in the first place! > > 73, Eric Lemmon WB6FLY
