A word on the usage of fans... This comes from personal experience, I have found that there are a great deal of fans that like to create electrical noise that comes out of their power leads. If this fan is connected to the same DC supply that has the transmit radio connected to it, and it is producing high amounts of noise, it can and will introduce this noise onto the output of the transmitter. Sometimes this noise can be solved to putting the correct value capacitor across the fan's DC power leads. Sometimes this works and sometimes it doesn't and from my experience you are faced with two choices if it doesn't work, one is to find a fan that doesn't make noise and the other which I have done on many occasions, is run the fan on its own dedicated power supply. Typically, I use a small 1 Amp, 12V wall wart power supply to run the fan and the issue is solved. I have found that some of the noisiest fans that I have used were salvaged from old computers.
Power Supply Considerations Once again, in my experience I have found the best practice is to run your GPS oscillator(s) and anything else that is providing a reference signal that contains an OCXO or TCXO to your transmitter and/or your RTCM/Voter Board on a separate power supply from your TX radio and amplifier if you're using an amplifier. The reason for this is due to the relatively high current draw from the transmit side of things, you may see a small voltage sag. This drop in voltage may be for only a moment or for the entire time the transmitter is keyed. If everything is connected to the same power supply, your reference oscillator(s) will experience this drop as well. What can happen is that this may shift the frequency output of the oscillator that is being disciplined by GPS, or another high accuracy source to shift, which will cause a shift in the output carrier frequency of your transmitter and/or your PL tone frequency. The vast majority of the time if this does happen, you may notice some slight distortion when the transmitters key. This is really only noticeable in overlap areas and may be so quick that it is not noticeable on the air at all if everything recovers fast enough. With a well regulated power supply, appropriately sized for its intended use, this should not be an issue. Even with an appropriately size power supply, the tolerance of the some supplies can be surprisingly generous. If this is something you are experiencing in your system, take a look at the power supply output voltage under TX load. If the output voltage sags more than 1 volt, then I would consider using a separate power supply for your transmitter assuming the power supply has the correct current capability for what you are trying to use it for. The other issue could be that the power supply in question may have old electrolytic filter capacitors that are no longer up to the task, in that case, repairing the power supply or replacing it is in order.