Can I Get A Witness?

Having trouble understanding why your hotspot isn’t getting a Witness? Are you seeing messages about being above or below the bounds of an RSSI metric? Let’s dig in!

There is an UPDATE to this post over here. Feel free to read on, but the rest of this post talks about a system that is no longer being used by Helium (PoCv10). The charts below are no longer valid, but I’ll leave ’em up for posterity.

We’ll start with this, the infamous PoC V10 SNR limits graphic. This is NOT, by the way, the system Helium now uses, which is PoCv11. Still, it’s useful to understand the concepts.

I’ll explain the X and Y axis in a bit, but at first glace it’s pretty basic.

Green = Good, Red (pink?) = Bad. Find the numbers reported for your specific Witness event, see where they intersect, and you’ll know why you have an Invalid witness. Yes, yes, yes, if you’re a “radio head” you instantly see something wrong, but for now let’s keep it simple.

We’ll go through two examples; 1 invalid, and 1 valid. Here’s an invalid witness.

Three things are listed:

  • The distance in meters. This is used to calculate FSPL, or Free Space Path Loss. More on that in a sec.
  • The signal strength in dBm (RSSI)
  • The level of signal above the noise floor, in dB. (SNR)

Here’s how that witness charts out:

With a high SNR (anything above 0 is high for Helium), at only 914 meters this signal is basically too good for the distance.

Ok, so what does it look like if the witness is valid?

We’re looking at the same three things, but now we’re at about twice the distance, and if you remember your dB strength rules (every 3 doubles or halves), about a quarter of the SNR.

Easy enough to read a chart, right? But what does it mean, and how can you get more valid witnesses?

We’ll start by defining two things first: RSSI and SNR.

RSSI = Received Signal Strength Indicator. In very simple terms, RSSI measures the strength of the radio signal you’re receiving.

In RSSI measurements, the larger the negative number, the weaker the signal. -130 is weaker than -100. In general, in the land of Helium, you want your RSSI to be between -82 and -134.

SNR = Signal to Noise Ratio. This is a measure of the quality of a signal compared to the background radio “noise”. It’s expressed in terms of dB (decibels), and the bigger the number, the better. Except when it’s not.

Wait, a signal can be too good? Yep.

When Helium started (and basically, up until the present, August 2021), Helium had a problem: They were selling radio devices. Why is that a problem? This’ll get more complicated before it gets simple, so buckle up and pay attention.

Everyone (in the US, and in most countries) selling a radio device has to have it certified by some national body. In the US, that body is the FCC. One of the things they check during certification is that your device doesn’t break any emission-strength rules (technically EIRP, more on that here.)

Helium is required to stay within the limits of the rules. To do that, they used a low gain antenna (1.8 dBi gain) and a reasonable amount of energy output (-27 dBm). That put them at -28.8 dBi for max EIRP, well within the limits for the US, which is a max EIRP of -36 dBi.

The FCC also requires a manufacturer to build units that “prevent” the consumer from changing the antenna. Helium accomplished this by using RP-SMA connections. Yep, that counts as prevention. It’s an outdated system, for sure.

An additional measure taken to ensure there was no encouragement to “improve” your antenna (and even they acknowledge it isn’t a great one) is to set fairly strict and sometimes unreasonable rules regarding what a received radio signal should be in terms of the signal strength and quality.

This is accomplished in part by measuring ALL antennas (even your high gain fancy wazoo antennas) AS IF THEY WERE THE HELIUM STOCK ANTENNA.

No, that doesn’t make sense. Yes, it was reasonable at the time. Yes, it will be changed.

How did Helium come up with those rules, and why? I’ll start with the Why: To stop cheaters, also known as “gamers” because they game the system without providing any actual benefit.

Cheaters used to be able to just plug in a bunch of hotspots stacked on top of each other. Those hotspots would witness each other from inches away while reporting falsely asserted locations that made them seem to be much further apart. It appeared they were providing great coverage. So they earned. Massively earned.

One of the most egregious examples happened in a little town called Modesto, in California. At the peak of the cheating, in late summer 2020, a group of hotspots (probably in a closet, and not even in Modesto) were earning thousands of HNT per day. Yes, per day.

Helium has since worked to combat gaming in more and more nuanced ways, but the way they approached Modesto was with a giant radio-signal measuring hammer: The RSSI/SNR chart. This was created by a Helium employee who analyzed almost half a million PoC receipts and looked for outlier results.

He was approaching this in classic Silicon Valley fashion: Look at the actual dataset, don’t rely on “old” thought, and figure out a new way to do a better job. Admirable, but it turned out to penalize not only egregious gamers, but many of the rest of us who just wanted to do an above average job.

The Modesto cluster was gutted, but the RSSI/SNR chart stayed in place. Other changes (HIP 15 & 17) entered into the system and incentivized spreading out and being rewarded for providing better and better coverage, but the RSSI/SNR chart stayed.

It wasn’t because the Helium team was ignoring it. They had much a bigger challenge to surmount: Getting Validators online so the blockchain could stop suffocating itself. With that mission-critical task accomplished, they can now (summer/late summer 2021) turn to making sure the blockchain improves in accurately rewarding superb coverage.

Which brings us, almost, to today, sometime in August of 2021. With PoCv11 (Proof of Coverage Version 11) on the horizon, we’re about to take a strong step in the direction of rewarding strong & clear signal coverage over short and long distances.

As you’re seeing in the app, Helium is offering you the chance to enter your antenna gain and elevation. This will help them more accurately assess whether or not your witnesses are valid. As of today (Aug 4th, 2021), those two metrics don’t actually make a difference for you, the hotspot owner, but…they will.

In the future, when PoCv11 comes online, the details you enter will be applied to your witness receipts. In order to combat gaming (essentially to stop everyone from just saying they have a 50 dBi gain antenna so all of their witnesses are good), Helium will simultaneously apply your gain AND decrease your transmit strength. That’s fair, by the way, and you should want that to happen.

I know, I know. Nobody likes decreased strength. Trust me on this one: LoRa already gives you TONS of range. Your goal is not long range, it’s increased earnings, and earnings come from valid witness receipts.

What will that look like? Full details over here, but for those of you who aren’t deep into radio geekery, the big picture is that Helium will drop SNR and just use RSSI and distance. Here’s a proposed chart. Meters on the Y axis, RSSI on the X axis.

Ok, so you’ve got three lines on there: Red, Yellow, Green. The lines represent the current cutoff (Red) for a valid witness as well as proposed future cutoffs (Yellow and Green).

You’re also seeing a bunch of blue dots. Those blue dots represent reported witness metrics of RSSI at some distance. The green line is the most restrictive, but is based on actual values of RSSI at some given distance, which is far more accurate than the current RSSI/SNR curve.

To keep it simple, this means that in the future, when PoCv11 replaces the current version, a hotspot using a non-stock antenna will not be penalized for it. Whether the yellow, or green, or some other line is used is still up for debate.

We’ll wrap this up with one of the most important takeaways: What antenna will help you stay within the proposed limits? Easy: It’s the LOWEST gain antenna you can use. See how the curves all shoot up at a fairly defined RSSI? That’s the key. If your RSSI is even a few points “to the left”, you can be on the wrong side of the line.

This helps explain why in many cases, when you get that fancy super high gain antenna, your valid witnesses disappear. So what antenna should you buy?

My recommendation is still the HNTenna, but any of the low gain (4 or less) antennas in your countries frequency, from a wide variety of sources like McGill, Parley Labs, L-com, or Laird will be fine.

If you’re willing to explore your inner geek and you like to tinker, take a look at attenuators. They’ll attenuate (or weaken) the signal (both tx & rx), but they’ll also increase the SNR, so experiment cautiously. Here are a few options:

Expensive (~$400) and unnecessary, but hey, if you want a great unit – Fairview 0-11 dB Step Attenuator

Cheaper ($25), less precise without extra measuring equipment – ATM RF Variable Attenuator AF033-10 DC-1000 MHz 50 Ohm

An attenuator decreases your signal strength both ways. They’re not a great long term option. The best option is to use a low gain antenna and get it up high in the right location. If you see that the Nearson 9 or RAK 8 that you bought when you were in “Bigger is better” mode gets more valid witnesses once you’ve taken a little sauce out of it, well, you’ll have some useful data points (that I’d love to hear about.)

Want to go deeper? Consider hiring me to help you out; I love helping people crush with Helium.

Happy Witnessing!

**This post was written with technical oversight from @jerm on Discord. He is an absolute wizard with this. All righteous accuracy is his, any errors are mine. -Nik@GKI

143 thoughts on “Can I Get A Witness?”

  1. Hi Nikolaos, I haven’t heard of anyone successfully doing a split antenna set up. I’d pick one antenna, get it high, and call it good.

  2. this is my dilemma getting whether I need to get my antenna high enough or getting a stronger one. (Cuddly Misty Otter) im at roughly 25ft/7.5M but the tree line maybe causing issues to my signal. I had the hntenna but never got witnessed I swapped to a 8dbi and I have witnessed others (still no witness to my beacons) and also now get the fun witness_rssi_below_lower_bound response. so I dont know what to do. I’m looking at maybe getting the Rohn H50 43′ telescoping mast to try and clear some height. just not sure.

  3. Thanks Nik I figured that would be the option I need to go with just not sure I need to keep the 8dbi or go back to the Hntenna 3dbi I guess I will have to test with each to see which would work best for my area being at that height and based on the other miners in my area

  4. do you think having a network frequency analyzer is a good component to have on hand? been researching those to understand more and analyze the antenna signal.

  5. They’re fun if you’re a geek, but not necessary. Remember, antennas are something like 5% of the earning equation. 🙂

  6. I have problem with sent beacon , just 2-3 get my sent beacon , so what’s the problem in this case?
    I changed location , anntena , still same problem

  7. How close are they? How many? What’s line of sight like? What antenna are you using? How is it connected? Is your miner connected via WiFi or Ethernet? Lots of questions to answer there amigo. 🙂

  8. So a month ago I set up my bobcaand well I wasn’t witnessing or being witnessed, got a new antenna, and still nothing, and one update yesterday I am witnessing, but still no witnesses, where can I find something that tells me Ihave invalid RSSI?

  9. Hello Nik
    My sent beacon always 0
    Just 3 time have seen by 1 or 2
    I changed location , antenna , tried everything but same problem

  10. And Im using 5.8 dbi , i tried 2 different 5.8 dbi , also i tried original 2.8 dbi , still sent beacon 0 witness (just 2 times i get 1 or 2 witnesses) , and im using real ip (Ethernet) all ports are open , and the hotspot in a verygood location and view. And I’m alone in me hex , scale 1.0 nearest hotspot to me is far by 800 m

  11. Depends on other hotspots around you as well. If they have a poor setup they won’t be able to witness you.

  12. Hi guys I have one question.
    Since December 13th with the changes that have taken place, I find myself having 4 or 5 invalid transactions.
    Reading here and there, I think the problem is the too many db declared by my workstation.
    I really have 8 db and the antenna is at the right height (12 mt).
    The question is:
    I have an 8 db antenna and a 10 meter LMR 400 cable with one plug on the antenna and one on the bobcat.
    considering the dispersion, between the cable and the couplings, I lose about 1.8 db and therefore I should declare 6.4 db.
    Do you advise me to change the antenna value on the app?
    In your opinion, if I lower the db I solve this problem?
    Thanks for your availability and assistance.
    I accept any suggestions

  13. Hi Damiano, def include cable loss in your declared antenna gain, you’ll need to use the Custom option in the app.

  14. Hey gristle. Set up a miner at my sisters house at the hexagon next to me. From actual miner to miner. I use explorer to calculate the meters apart and it’s about 250 meters. When I set up my location for the miners at my sisters place I put it about 100 meters further away from the direction of my house. In the app where it says witnesses the distance between my miner and sisters miner is 800m. But it says it’s invalid due to miners being too close. Is there a way to make it work ? Do I have to relocate the location even a bit further ? Thank you

  15. Hi Johnn, the app (once you’ve asserted) won’t show you the actual location, just the center of the res 8 hex it’s in. I’d use HeliumVision to determine correct placement for this. Sounds like you’ll have to relocate a bit further.

  16. It looks like from the miner mine to my sisters house is about 250meters from the miner at my sisters house is asserted at. Which is 70 meters away from the actual miner. If I move it a bit further away. To 150metres. Will that be okay for poc 11?

  17. Hi Johnny,
    Two things: First, you just have to test this stuff. Second, moving a miner 150m for privacy reasons is totally fine in my book. Moving it solely to clear a hex is technically gaming. The goal with the network is to provide WUPU coverage, and in general, 2 miners within even 500m of each other is usually too dense. I’d consider moving the miner to a totally different location where it’ll help expand network coverage.

  18. Gotcha. I do have multiple miners definitely spread out in different cities. I guess I should rephrase what I was saying . The miner itself cleared a hex by itself without me taking the location in the first place. I was only moving it so it’s not too close to my own miner to which I didn’t wanna cause no witness, which is also in a hex of its own legitimately. I didn’t move it a hex just to get gains without actually being in that hex ! Just wanted to clarify so you didn’t think ima dick lol.
    Second. Thank you for referring that site. It was a huge help. I also got an enclosure and following your poe set up for my first try at at. Excited to let you know how I do !

  19. Hi Nik,

    One thing I didn’t see addressed in your example was witness_too_close (same hex), where I live is completely flat (Houston, Texas) and have two hotspots in neighboring hexes, both have an 8dbi antennas mounted above the roof line and those two HS are working well together — that’s not my problem. The issue is one of those hexes I am 1 of 2 in the same hex where my other HS is all by itself in it’s own hex. My HS that is not alone keeps getting invalid witnesses from the HS from it’s own hex, which it says it’s using a 1.2 dbi at 0 m, why do I get penalized for a HS that wouldn’t be valid in the first place since we are in the same hex anyway?

  20. Tim Van Geertruyen

    Hi Nik,

    What is your opinion on using a bandpass filter?
    I’m breaking my head over why my 9dbi antenna’s 130 ft high on a Church Tower don’t earn as well as equal hight and antenna setups I know of.

    I’m in Europe (Old Seafoam Chinchilla)

  21. Could be overshooting. Bandpass filters can sometimes help if you’re right next to high output antennas (let’s say less than 10m, though that’s rough.) Better to get vertical standoff. The first thing I’d try is a lower gain antenna.

  22. Tim Van Geertruyen

    I see. I don’t think that we’re overshooting, because we’re witnessing and being witnessed close by , if that’s what you mean. However I forgot to mention that we installed 2 of them 4m apart from each other, with another 433Mhz antenna in the middle.

    Other antenna’s are more than 100m away.

  23. Tim Van Geertruyen

    2 hotspots with 2 9dbi antennas 4m apart. Someone’s 433mhz antenna right in the middle!

  24. Hi Tim, I’d recommend getting those hotspots way further apart; 1,000m or more ideally. The antenna in the middle probably isn’t causing problems unless it’s pushing out a ton of power.

  25. Hello Nik,
    very interesting and practical text. In my case, at 12 meters high outdoors with the internal RAK 2.8dBi antenna I was reaching other hotspots more than 200Km away (across the sea). I decided to raise it to 20 meters and change the antenna for a 5.8dBi antenna (also from RAK) to try to witness with them and now I only reach the closest ones, I get the message “2 x Witness rssi too high”. Is this the same case you are dealing with here right? do you recommend me to go back with a 3dBi antenna?, I’ve tried to modify it in the configuration without success.

  26. Hi Alex, yep, I’d go back to what works from a gain (3 dBi) perspective. I bet the extra elevation isn’t the issue.

  27. hi NIK, I started with bobcat with indoor 4dbi, i have metal roof and my house is in the low, have trees around me. after a week of doing nothing, i replaced my antenna with 5.8 rak outdoor and elevated 4m higher and i added 38ft of lmr 400, now i can witness one , but no1 can witness my beacons, should i try to switch to 3dbi ? Also im running of WIFI

  28. Order of importance is probably:
    1) Connect via ethernet
    2) Check your line of sight to other hotspots, and if getting your antenna higher will provide more clear Lines of Sight, then
    2) Get the antenna higher

  29. Hello,
    Thank you for all the information up there.
    I have a Nebra hotspot, set up in my roof, which is 55m up from the ground, the building I am in sits on top of a hill, a bit like SF hills, which is in the middle of the city, there are almost no buildings higher than mine, fewer than 10/15. So basically my line of sight is endless. I set up a 5.8dbi antenna on the roof.
    The problem is I am getting invalid witnesses because of how good the signal is with far away hotspots. I came across a fix; change the dbi on the app without actual king changing it physically. Meaning, say my antenna is 9 dbi when it is actually 6. Does that work?
    Thank you for your help

  30. Hello Nik!

    My beacons (one per day?) get sometimes up to 14 witnesses and some even 23km away. But when it comes to me witnessing, I get maybe one per day and this is from hotspot from the same Hex, any idea what could be wrong?
    Unfortunately I am relayed, waiting for VPN setup..(router is still on transit).
    Setup: Sensecap M1, height 90m, 180degrees open view, 2.8db stock antenna.

    Thanks in advance for your time.

  31. Hmm, sounds like your antenna may not be well placed, OR the antennas of Hotspots around you aren’t well placed. 14 witnesses is the max per beacon, and 23 km is well within normal limits for LoRa. Get your antenna outside and up high. The Helium Basic Course is an excellent walk through of making sure you understand how the whole thing works (so you can optimize.)

  32. I had a null witness that was 6 dBI RSSI, and -103 dBm. According to that chart it should have been valid. Is that plot a rough estimation? It was pretty close to the border but still clearly within the limit

  33. Hi Nik

    Thanks for all the info you provide on your blog and in videos. One thing I see asked a lot on various discords is when entering your antenna gain in the app, do you put the actual gain of your antenna or do you take into account cable loss etc. so a 9db antenna with 2db cable loss, do you put 7db? Everyone seems to have their own different view on this

    Thanks

    Simon

  34. Hi Simon,
    Take into account cable loss. The Network wants to know the signal strength to expect from your miner. The more accurate that is, the more likely you are to have valid witnesses.

  35. This article is a bit misleading. Further distance is in fact ideal for those many miners in densely populated areas. Lower reward scales nearby being avoided and witnessing those further out higher reward scale equals greater earnings.

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