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RF stopping axial fan.

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Just looking for some information, if anyone has any idea what is going on with a linear 12 Volt power supply. I'm using a high current linear power supply to run a 100 watt linear amplifier. But when I key the microphone it's stopping the two cooling fans, if I let the key go, the cooling fans come back to life. I've checked for voltage drop, there isn't any that would stop the cooling fans. If I try a different load (halogen lamps) The fans stay on and run fine. Do you think this could be an RF thing, where the linear amplifier is near the power supplys cooling fans. Is it possible for stray RF energy to interfere with the axial fans functioning ? I'm really at a loss to why the cooling fans stop on transmitting on a HF transceiver and linear amplifier. Thanks for reading, any thoughts appreciated.

Assuming the fans run on 12V DC, they probably have a cheaply-designed transistor inverter inside the plastic case to drive an AC motor (rather than a brushed DC motor).  With no RF shielding from the amplifier and its tank circuit, it could easily be interfered with, since this is an untested susceptibility case.  Can you install a “cane metal” or other perforated metal shield between the RF stuff and the fans?

All 12 V fans I know of use brushless DC motors with integrated controller. Brushed DC motors I've only seen in equipment from the 60s and 70s. Even the early PC-XTs had brushless fans.

Yes, your RF can certainly disturb the BLDC controller (and a lot of other things as well).

Also, in the vicinity of an RF power amplifier, you are almost certainly in the “near-field” region, where the energy stored in the EM field is large.

Thank you for your replies, I think it must be RF interference. I will try and put together some shielding, the fans where cheap ones, but they cool the PSU well enough. I've noted other weird stuff using linear amplifiers over the years, from wiping out televisions to affecting sound systems etc. But will try the shield idea.


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