[OKDXA] Advice on placing coax in plastic pipe

[Nelson Derks]

I had a similar quandary when I put in a C-Band sat dish in 1985... This 
was an old school install involving 1.25" hardline as the RX was a 
commercial jobbie that wanted to see 4.3 GHz RF on the N connector. 
Visualize the south side of a typical three bedroom ranch house with the 
dish approximately 20" from the wall. I put in 2.5" gray PVC conduit 
from the base of the dish pad with the horizontal run approximately 30" 
deep. The PVC runs up the wall and into the attic with both ends open... 
The only weather sealing is on the exterior end in the form of an elbow 
facing downward to keep the rain out.

There is no perfect solution for this and having lived in a two story 
house I know that if you open a window on both floors there will be 
airflow from downstairs to upstairs. Same concept in the PVC conduit, 
goal is to dry any condensation that may form inside the pipe through 
natural convection. There will be condensation whenever the ground 
temperature is below the dew point of the air and that happens every 
spring. The concern with water in the pipe is that if it should freeze a 
lighter coax will be crushed as the water turns to ice, hence the ~ 30" 
depth as the official freeze line in OK is around 24" to 18" deep. In my 
case the PVC would likely burst before the hardline became damaged as 
that stuff is profoundly stout.

So... Here's the trade off: Unprotected coax in the ground will be 
nibbled on by gophers. Flooded direct burial or not, the line will 
accumulate nibbles and water intrusion over time. Then there's the 
potential for root / shovel / plow damage. Run PVC and you slow down the 
gophers but gain condensation and water issues. Leave the ends open for 
convection and you'll have condensation, seal it good and tight and the 
water that WILL get inside won't dry out. I'm not convinced a gopher 
will leave PVC alone, either... Next time you drive past a utility crew 
running fiber underground slow down long enough to check out the pipe 
they use. White, orange, blue, and from what I can tell it has a very 
thick wall.

If it were me I'd likely go with schedule 80 PVC as that has a thicker 
wall and build in 4" square electrical boxes every 60' to 80' on the 
assumption you will be pulling the coax every five years or so if only 
for a visual inspection. The access boxes will make that easier. Make it 
easier to check for water, too. Mark the tree nearest the box with spray 
paint or similar so you can find them later. An RF soak test (dummy load 
/ wattmeter on one end, TX on the other) would be a good idea annually, 
but be advised the pros use a high-dollar time domain reflectometer to 
test coax runs because anything less is "less". As for running the line 
through a wooded area... A sharpened mattock kept that way with a file 
in your pocket is a wonderful tool for cutting roots and roughing in a 
trench, but digging ~ 250" worth of trench with one will keep you 
tanned, muscular, and bored out of your mind. One word: Tylenol. The 
trade off on that is the expense of calling in a pro assuming you can 
find one willing to take on the job. They make better money trenching a 
new subdivision than they would a one-shot day job.

Best advice I can give is that there is no permanent solution and 
whatever you build make it as easy as possible to work on later... 'Cuz 
you will. ;)