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 The charts below are no longer valid, but I’ll leave ’em up for posterity.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


144 responses to “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. Jared Sherman Avatar
    Jared Sherman

    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. Get high­er; that’ll do way more than the anten­na you have.

  4. Jared Sherman Avatar
    Jared Sherman

    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

  5. Jared Sherman Avatar
    Jared Sherman

    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.

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

  7. 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

  8. 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. 🙂

  9. 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?

  10. Hi Shien, try check­ing Wish­plor­er’s dash­board to dig into your data.

  11. 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

  12. 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

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

  14. Oth­er hotspot around me have very good scal and wit­nessed perfect

  15. 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

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

  17. 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

  18. 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.

  19. 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?

  20. 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.

  21. 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 !

  22. Ah, right on! Hap­py to help mug, keep charging!

  23. Baron Lopez Avatar
    Baron Lopez

    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?

  24. Hi Baron, check out our Hotspot Deliv­er­ance series on YouTube, start over here.

  25. Tim Van Geertruyen Avatar
    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)

  26. 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.

  27. Tim Van Geertruyen Avatar
    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.

  28. You installed 2 hotspots or 2 anten­nas 4m apart?

  29. Tim Van Geertruyen Avatar
    Tim Van Geertruyen

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

  30. 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.

  31. 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.

  32. 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.

  33. 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

  34. 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

  35. 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

  36. Hmm, that might work but pret­ty close to gam­ing. You might try a low­er gain antenna.

  37. 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.

  38. 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.)

  39. 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

  40. The green & pink one is the old PoCv10 chart, not the new PoCv11, which is the cur­rent version.

  41. Simon Avatar

    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



  42. 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.

  43. 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.

  44. I ran 2 hotspots 1 meter apart, assert­ed 1.1km apart. POC is VALID by keep­ing the RSSI val­ues between ‑80dBm to ‑90dBm

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