I want to create a short (2-3 mile) PtP link using XR9s. One end will go up maybe 200ft on a tower. The other end will be on top of a small building (maybe 30-40ft.)

I have a budget for the tower climbers but my company is very adverse to paying for future climbers so any problems that require them will draw strict scrutiny and unhappyness.

200ft of LMR400 @ 900MHz produces approximately 8db of loss. But since this is such a short link, I am thinking I could get away with just putting the dish on the tower and running LMR400 feeder cable down to the Routerboard on the ground. This way if there was a problem with the unit we could fix it without getting climbers. I realize that if the antenna gets knocked down we will still need climbers.

Does this seem like a good idea? Besides the loss issue, what are other problems I have not considered?

I plan to use either two 900MHz parabolics or perhaps one parabolic and one panel antenna. Not sure yet.

One bit of info, I had 35ft of LMR400 and 70ft of half inch hardline. According to the math, if I remember correctly, should have been something like 4-6dB loss. I had over 4dB loss on the LMR by itself.

The line loss will not kill you at 900MHz, but expect it to be worse than the calculations show.

Definitely get a 900MHz filter. Anytime you have 900MHz above trees it is going to catch a huge amount of out of band interference.

With the radio on the ground, you can always add the filter later, but, from experience, I wouldn't even try without it. Streakwave has a 900MHz bandpass filter for about $50 that I've heard works well.

Does the path require you to be at 200'?

Do you have a dish? A yagi or panel is more than sufficient at this range and should be drastically cheaper.

If loss is a concern, step up to 600 instead of 400.