Re: [Repeater-Builder] Problem with fan noise in power line.
I would suggest you try a 100uH inductor and as well as a 1000uF capacitor as an L/C filter. You may need 2 sets in series depending on how bad the noise is. On 4/17/07, Doug Hutchison [EMAIL PROTECTED] wrote: Have a system comprising 4m simplex link and 2m repeater running from same PSU. Tried using a brushless fan to boost cooling but when running and connected on the same PSU as the RF kit, the noise generated on 4m TX audio (not 2m), a very loud buzz, is incredible. Obviously the inverter noise is being carried back into the PSU so some sort of filtering is needed as, when the fan is run on a separate supply, there is no problem. Has anyone encountered such a situation and if so what circuit or device was used to cure the noise (other that a second PSU)? Regards, Doug - GM7SVK Yahoo! Groups Links
RE: [Repeater-Builder] Problem with fan noise in power line.
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 -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Doug Hutchison Sent: Tuesday, April 17, 2007 7:09 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Problem with fan noise in power line. Have a system comprising 4m simplex link and 2m repeater running from same PSU. Tried using a brushless fan to boost cooling but when running and connected on the same PSU as the RF kit, the noise generated on 4m TX audio (not 2m), a very loud buzz, is incredible. Obviously the inverter noise is being carried back into the PSU so some sort of filtering is needed as, when the fan is run on a separate supply, there is no problem. Has anyone encountered such a situation and if so what circuit or device was used to cure the noise (other that a second PSU)? Regards, Doug - GM7SVK
RE: [Repeater-Builder] Problem with fan noise in power line.
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
