The Rode NT1-A microphones are excellent, low noise, studio microphones. But, they suffer from two issues due to their large diameter elements if used outdoors. They are sensitive to wind and susceptible to moisture condensation. I will write about solving the moisture issue here.
If you are recording outdoors, during high humidity conditions of early mornings or during the night, moisture can condense on the microphone element, causing complete microphone failure, popping, or noisy recordings. Once the microphones dry out, they return to normal operation. Try to keep the microphones as dry as possible, and don’t keep them in moist conditions. As one who records nature sounds, I need to be recording during the early mornings, which is sometimes very humid or foggy. So, I came up with a way that solves this moisture issue by making some resistive heaters assembled to the back side of the microphone screen, under the windscreen.
As you can see from the photo. I wired five, 560 ohm, two watt resistors in parallel to two wires. Those wires will be powered by a 12-volt battery, since I already use a 12-volt battery to power my recording equipment. This provides around 1.5 watts of heating. Using the finished heaters installed on the microphones, under the windscreen, I measured the following temperature rise from 66F degrees ambient: 20 minutes- 9F degrees, 1 hour- 16F degrees, 1.5 hour- 17F degrees, 2 hours- 19F degrees. This temperature rise seems adequate for my purposes and gives a good trade off to battery life. You may change the resistor and voltage values to meet your requirements. Remember, we are looking for some heating to raise the temperature enough to remove condensation and limit the effects of continued high humidity conditions. You may need more power, since I use a three layer windscreen, I have some extra insulation and isolation from the atmosphere.
Now, since the Rode NT-1A microphones have a metal screen, we can’t just attach the resistors there or they will short out. What I did was encapsulate the resistors in silicon gasket material available at any local auto parts store. I used black. To give the silicon more rigidity, I wrapped a small piece of fiberglass window screening over the resistors, retained by a little tape, before applying the silicon. I applied the silicone to both sides of the resistor array, then wrapped it with kitchen, plastic wrap, to form to a nice shape. Let it dry for 12 hours, remove the plastic wrap, trim thin edges, and you have your heating element.
I attached the heater with a tie-wrap to the lower part of the metal microphone screen, on the wire end of the heater. There is no need to hard attach the heater to the screen better, the windscreen, that came with the microphone will hold it quite well.
In use, it may take a few minutes to heat enough to resolve moisture issues, and you will have to keep the heaters on until atmospheric conditions dry out. I have had no issues with moisture causing problems while using the heaters, even in high dew points to foggy conditions. Try to start off with dry microphones, it will make it easier to keep ahead of the condensation. This can be difficult if you are camping.
I hope this information helps all who use the Rode NT-1A microphones for recording outdoors. They are the lowest noise microphones, and are great for recording nature sounds when their outdoor issues are solved.