The antenna itself won't be significantly affected by the water.
However, waterproofing the coax connection is essential. If this is not done, water will creep inside the coax by capillary action and ruin the coax.
There are several products that can be used, for some examples see 3M's application guide. However all have three elements:
- An underlying insulating layer which covers exposed conductors and/or facilitates removal of the outer layers of tape later.
- A sealing layer of rubber or mastic tape.
- An abrasion and UV protective top layer.
Step 0: clean the connection
Remove any dirt or oil with a cloth and alcohol. You'll notice I skipped this step in my photos :)
Step 1: Courtesy Wrap
This makes the waterproofing much easier to remove in the future. If this isn't done, over time the sealing tape will creep into the connector, making it nearly impossible to unscrew.
I used Scotch Super 88 because it's what's on hand. Some people like to wrap with the adhesive side up so it doesn't leave goo on the connector. There are also tapes designed for specifically this application which remove cleanly. Stretch the tape to get it to conform to the connector. You'll find cheap electrical tape does not conform nearly as well.
Step 2: Sealing Layer
For this I used 3M 2228 rubber mastic tape: it's a sticky mastic with a UV protective layer on one side. The nonsticky side goes out. I prefer mastic tapes in permanent installations since it flows better into tiny cracks, though it can be quite difficult to remove.
An alternative to mastic tape is rubber tape. It's not sticky but still fuses to itself over time. I use it if I know I'll need to dismantle the connection in less than a year.
Proper application is important:
- Stretch the tape as you wrap it such that its width is 75% or less of its original width.
- Be sure to get the tape really well into the exposed threads of the female connector.
- Each wrap should overlap the previous wrap by half the tape width.
- Extend the wrap past the connector, and if your connector has any kind of shrink wrap on it, past that as well.
- If this connection is going to be vertical with the coax coming from the bottom when installed, consider wrapping in the other direction such that water would have to travel upwards to get in.
Step 3: Protective Layer
3M 2228 has a UV protective layer built-in. It's the non-sticky side of the tape, so ensure that side is facing out.
Had another kind of tape been used, or if extra protection is desired, a final wrap or two with some vinyl electrical tape would be appropriate. Don't use cheap electrical tape! It will turn brittle and peel off when exposed to the elements.
As before, stretch the tape to get good conformance, though a reduction in tension on the final wrap helps prevent the tape from peeling itself off. For the same reason, it's good practice to cut the tape, rather than to pull it until it breaks.
Use N Connectors if Possible
The PL-259 / SO-259 or "UHF" connector common on ham equipment provides no waterproofing whatsoever, which is why it's so important to get the sealing tape into the threads.
On the other hand, male N connectors have a gasket inside which seals against the face of the female connector. It's the red thing inside:
This prevents moisture ingress through the threads.
N connectors are often installed with what looks like heatshrink over the barrel that crimps over the shield. This should be not just ordinary heatshrink but one with a waterproofing adhesive. If done properly, this combined with the gasket should make an N connector waterproof with no taping. However I still tape them for extra protection unless it's a very temporary installation.
As a bonus, N connectors are good up to 11 GHz.