triadalessons.blogg.se - Helium test time calc

HELIUM TEST TIME CALC FREE

Receiving Antenna Gain (including cable loss, in this case almost nothing because it’s 4′ of LMR400) = 3 dBi.

Beaconing Hotspot Antenna Gain/Cable Loss = 6 dBi.

Beaconing Hotspot Output (US915) = 27 dBm.

I’ll call that 124 to make the math easy. What about the FSPL? I headed over to EverythingRF’s calculator for that, here’s what I got: I guarantee you I’ll get at least one snide comment about how you can’t possibly do that and live. Radio geeks will bristle at that statement, by the way. By the way, you can add or subtract all this “dBi, dB, and dBm” stuff interchangeably without worrying about the differences for now. That could be a 5.8 RAK, or it could be a 6 dBi from McGill with. Ok, so that’s cool, but where did I get the info about Amusing Eggshell Mongoose? Right off Explorer. Here’s Amateur Jade Hare with a 3 dBi HNTenna Witnessing a Beacon from Amusing Eggshell Mongoose, which has an asserted antenna gain of 5.8 dBi and is 40 km away. Since the radio models Helium uses don’t yet take vegetation or buildings or other obstacles into account, the actual results can be much weaker than predictions, sometimes by large margins. The actual path loss over 20 km may be much higher if there’s vegetation in the way (lookin’ at you, Florida) or buildings (Hi New York!). You see, as much as we’d like to think that we humans can accurately assess and calculate the world around us, we’re not always as accurate as we’d like to be. Remember that term “gobsmackingly lax” I used above? Here’s where you start to understand it. Now, there’s a problem, because there’s the theory, then there’s the real world, and then there’s our interpretation of what should “count” in the real world.

The -81 RSSI dBm that the receiving Hotspot (aka the Witness) reports is then compared against what it should have received at, given how far away it’s asserted from the Beaconing Hotspot as well as the output power for that region. It starts off with the Hotspot’s Beacon output, loses power along the cable, the antenna shapes and focuses the energy out into space, where energy is lost, the receiving antenna picks it up according to its gain, energy is lost again as it goes down the cable and is finally received in the Witnessing Hotspot. How does that look? Lemme draw ya a picture, and yes, I’ll make up a few numbers. Witness reported RSSI (at what strength did they “hear” the signal?).Witness’ reported cable loss (in the Helium app, cable loss is included in the antenna gain section).This is the loss in signal strength in “normal” clear air.

HELIUM TEST TIME CALC FREE

The theoretical amount is called FSPL, or Free Space Path Loss. The actual amount can change, sometimes drastically, depending on environmental characteristics like vegetation or building obstacles, and to a lessor extent from humidity, rain, snow, sleet, and pollution. Over any given distance a radio signal will lose a theoretical amount of strength. For example, US915 can blast at 27 dBm while EU868 is limited to 16 dBm. Knowing the Beaconer’s transmit power comes from knowing what region of the world the Hotspot is in, and what the legal limit is for power output. (in the Helium app, this is included in the antenna gain section) This is a function of cable efficiency and length. In the US, most of our hotspots transmit at 27 dBm. In order to know what the received signal strength *should* be, we need to know a few things. RSSI stands for Received Signal Strength Indicator, and, as its name indicates, is a measurement of the received signal strength. Let’s start with that signal strength, or RSSI. For now, just bookmark that idea as “work in progress.” Onward! Understanding how this works requires a little bit of radio theory, but relax, I’ll walk ya through it.Īs you read this and the example I give at the end, you’ll come to the understanding that as of now, March 2022, the RSSI limits are gobsmackingly lax. Second, we need to prove coverage in an accurate way in order to combat gaming, aka cheating. First, when businesses hear about the world of IoT and Helium, if we can show them a map of where our coverage has actually been proven to exist and at what strength, they can quickly make a decision regarding whether or not they want to use the Helium Network, and if they need to add a new Hotspot to provide coverage. We need to be able to prove that we’re actually providing coverage where we claim we are. Wait, you want more? Dawg, why didn’t you say so? Let’s dive in!įirst, let’s start with why we need an “acceptable” strength. How do you make sure a radio signal is within acceptable limits for Helium? Short version: Assert your antenna gain (including your cable loss) and location accurately and you don’t need to do anything else.