# Equations to calculate range?

• posted

Hi,

I actually found a use for a clear LOS shot, so started giving it some consideration. I am unclear as to what equation that can be used to predict (to an extent) range? From googling, I've found many of them -- which all yields different results.

I'm trying to "baseline" what is possible, starting with the upper range antennas that are approachable (cost-wise). Two 32 dBi parabolics would run me just over \$500, which is about high as I'd be wanting to invest.

Its unclear to me how to calculate and predict (to an extent, of course), what "real world" expectations could be.

The shot would 802.11a (5Ghz) and for simplicity lets assume that it is a completetly clear LOS shot with absolutetly no obstacles and in clear weather with no (or very little) RFI.

Is it possible to calculate a ball park figure for range, given:

Transmit power before hitting the antennenas: 18 dBm (63 mW, 802.11a, 5Ghz)

Antennas: parabolic on both ends, giving 32 dBi gain each

Receive sensitivity: -73 dBm to -84 dBm (It could lower, but this range, based on specs, should yield acceptable data rates)

Thanks!

(Or, should I say, thanks in advance, Jeff!) :^)

• posted

Oh, these this was the antenna I was eyeballing:

(I'd get two, of course.)

• posted

The Ham Radio folks know how to do this and there are charts in one of the handbooks. If youir numbers are sccurate you get genuine results.

Google for "pass loss calculation". There are all sorts of solutions. SOme may work for you.

• posted

No way today. Billing, taxes, one crisis, and a evening antenna project in the rain.

Start here: |

are at least a dozen posting in the last few months where I've walked someone through the link calculations. Any one of these can be used as an example: |
it a try, post your calcs, and I'll check your work (later).

• posted

There are at least a dozen posting in the last few months where I've

Give it a try, post your calcs, and I'll check your work (later).

Thanks.

You got me pointed in the right direction.

I definetly will read everything, starting off there. I'm planning on weather-proofing and mounting the AP's as close to the antennas as possible, hopefully right on right on their "support structures", to minimize cable-loss as much as possible.

Wow, don't know if I'm doing the numbers completetly correct yet (I will be familiarizing myself), but some playing around is showing that 32 dBi gain gives much more range than I thought. I would guessing like maybe a mile and a half. LOL

• posted

Thanks, I'll google that and lurk around Ham radio sites as well!

• posted

> There are at least a dozen posting in the last few months where I've

> Give it a try, post your calcs, and I'll check your work (later).

Oh, pretty cool too, springboard'd from there to a site that calculates azimuth/elevations based on two Lat/Longs. Didn't even think about that. That'll give me an excuse to finally do something worthwhile with my GPS. :^)

• posted

I use a map, SA Topo! program, Delorme Street Atlas, Topozone, Google Earth, or anything else that gives Lat-Long. There are lots of web sites that will calculate distance:

's the easy part.

Next, you get to calculate the Fresnel Zone clearance to make sure there's nothing in the way. Minimum is 0.8 times the Fresnel Zone clearance. I suggest downloading and doing battle with Radio Mobile:

do the point to point freznel zone calcs, see: