Signal Levels

Ok so I did a site survey a few month ago for a remote tower location, things looked good, standing in the back of our pickup I was able to get a signal of -69 which is exactly what Radio Mobile told me I should get. We finally got power to the location today and are about ready to put up our tower and did some more testing tonight. We can’t even hardly see the tower now. Signal levels are at best -91 using the same antenna. The site is 13 miles aways using 900Mhz. When we did our initial testing we we had 2 links active on the AP and now we have 10. I’m still too new to all this to really know where to start looking. First time we tested we used a stinger and a 14db yagi, this time was with a stinger and a 17db yagi, the yagi improved the signal to -87 so I don’t think it is the SM antenna. I will be trying a diffrent SM this weekend to rule that out. One other odd thing is that I changed the AP from 924 to 906 to make sure it wasn’t a freq problem and about 10 minutes after the change the AP started dropping SM’s, it did this the other day also when it was on 915, that night I turned the AP into a SM and did a spectrum anaylisis and there is nothing out there that should be causing us problems. Our noise floor is around -83 to -85 everytime I check it. The AP antenna is a cyclone 9dbi Omni.

Where should I start looking for the problem?

Here is a link to a google earth kml of the link and what radio mobile says it should do.


What’s the foliage like between you and the tower? 13 miles is a pretty long shot, even with a 17, unless you have a crystal clear fresnel zone. Depending on where you’re located, the trees leafing out can have a huge effect this time of year.

You mention that this is a “remote tower location.” Are you planning on deploying a new site there? If so, you’d be WAY better off putting in a backhaul. You really want to get out of the band you’re serving users with for site-to-site. And DON’T neglect sync. If you do, you’ll be sorry.


Okay, just looked at your radio mobile shot. Is there any way for you to get higher? That fresnel zone is pretty occluded. And if there is tree cover in that 13 miles, I’d wager that you’ll not get a reliable shot unless you gain some height on your remote end. You gotta get the fresnel out of the dirt.