I have a 5.8dB 32" antenna mounted in my attic at a height of about 10m. It’s connected to a Heltec V3 with LMR-400.
I’ve done some range tests and can only get about 1 to sometimes 2 km to a another unit w/ an upgraded whip antenna.
What can I do to test my setup to find out where the issue is?
I’ve thought about buying one of those NanoVNA analysers, but not totally sure how useful it would be in this case.
How long is the LMR-400 run?
In these tests are there good line of sight between antennas?
Lora can get good range, but still needs mostly line of sight. If there are lot of buildings wont work. Which is why height is important to get over top of buildings/trees.
A nanoVNA could be useful in checking that each antenna is properly tuned for the frequency using. Despite claims many are not actually tuned to the claimed frequency.
… they (as long as dual port!) can also test signal loss on cable runs, so that actually might be the most useful test. Could potentially isolate a bad connector or similar.
A SDR dongle might be (in some cases anyway) useful, to get a more ‘realtime’ view signal strength. Meshtastic app is not ‘real time’ enough to really test the signal very easily.
I’ve also built my own Arduino App, that can be flashed to a Heltec Lora V3 (only device tested on anyway) - that shows RSSI/SNR of received packets in real time on streen.
… maybe should release the code.
… but actually a nanoVNA can functional as a signal strength indicator too. (note I am only talking in theory, havent actully got one to see how well works in practice for testing!)
You could in theory test signal strength at other end of attic, to just to just outside, to see if getting much annenuation though the roof tiles for example.
I would be interested in that Heltec V3 app
Have just put it here:
Its a self contained file - other than needed the Heltec ESP32 library (I installed it with the Arduino IDE, and then created this script based on the example codes)
… it was actully created for testing signals transmitted from my own code running on some RP2040-Lora devices, from before I used Meshtastic (code also in the same github repo). Got the Heltec to test Meshtastic and realized it was a nice device to work with, so created a receiver for the Heltec Lora V3.
… so then adapted my original code to then show reception of ''proper" meshtastic packets. Its unable to decode them, so it only really useful for showing the RSSI/SNR, but that it does well, just showing in large font on screen.
Its a self contained script for the device, although it needs some other Meshtastic Node(s) transmitting to do anytthing useful (use the Range-Test module to have the node send periodic packets)
If too complicated could perhaps par it down a bit. Actully the three modes not that useful with meshtastic, could be greately simplifeid to only include mode 1 (the most useful with meshtastic)
Before spending any money, have you used any of the online tools to calculate Line of Sight? There are a few out there, but I really like this one:
But if you don’t have true geometric line of sight between points, you’re likely to experience very poor range-performance.
Have you used the Range-Test module to do any range walks? I’ve found that to be one of the best tools out there to do real world side-by-side comparisons of different antenna configurations and locations.
Come up with a standard walking route that, to the best of your ability, skirts the edge of your reception range. You can dump those results into Google Maps and create some really neat plots, but that’s a longer discussion…
But by mapping out the furthest reaches of your range like that, you’ll see where things are failing. A good hint that LoS is a problem is if you have relatively good Signal to Noise numbers, anything positive, let’s say, and you still lose link back to the base station. That’s typically an indicator that while your signal strength may be solid, you’re likely standing in an radio frequency “shadow” without true Line of Sight.
I use these range-walks to establish a baseline so that whenever I make any changes, say I buy a new antenna or hoist my rooftop node up another 10 feet…I can repeat the same range-walk using the range-test module, export the data and do an objective, real-world, side by side performance comparison.
Consider the nature of the upgraded antenna too…if it’s a monopole, it likely needs some level of ground plane to achieve rated performance numbers…I only use dipoles for that reason…
Finally, I’ll echo what someone else said, if your antenna is at the end of any length of cable, you’re likely suffering significant signal loss in the cable. If at all possible, stick with 4"(or less) pigtails.
Lastly…are you certain the antennas connectors are correct? SMA versus SMA-RP have bitten many folks before, it’s an easy thing to do…easy to check, just make sure one side of your antenna connector has a pin, and the other side as a recess for the pin. Two pins, or two recesses…bad times 
Best luck, let us know how it goes,
Pol
Whenever there is a question regarding range, my number one thing to check is to be sure the LoRa device is actually outputing the power it should be.
OK, so I have one of those small RF power meters, it measures up to 3000Mhz, but they only cost £25 on Ali etc.
indeed an SDR can give you a good indication too, if you are able to compare several devices to see what a normal transmission looks like at a particular distance.
Over the years I seen several LoRa devices go low and sometimes very low output, my not taking acare to be sure there is always an antenna connected perhaps. Dont recall having a LoRa device go low receive sensitivity though.
If your prepared to re-program (temporarily) your Heltec or Lilygo device you can put a transmitter program on one and an RSSI meter on the other and check the performance over a local flat field at a standard distance. You will soon get to know what the expected RSSI is and that is an indication of how much the transmitted power actually is.
Before spending any money, have you used any of the online tools to calculate Line of Sight? There are a few out there, but I really like this one: heywhatsthat.com
That one looks great, but it looks like every location requested is then made public. So putting your house in would show all the users the location of your house?
I have a similar setup. I also get about a 1 Kilometer range. This is just the line of sight issue.
I suppose technically yes.
But dont have to give any details, ie dont need to put an identifiable name. So its just a point on map.
Plus unless it only listed on the ‘All panoramas’ if specifically use ‘make public’.
… otherwise the only way to access the panorama would be to ‘guess’ the URL - which is an opaque key. WOuld have to do a lot of ‘hunt and pecking’ to find actual panoramas, which even if find one would lack context.
It’s ~5m long. I thought LMR-400 was good enough to not be an issue. I’ll test it once I get my NanoVNA.
Yes, looked at sites like the one @polamnus linked to check for coverage areas.
That’s what I’m hoping to eliminate. I grabbed the Seesii Upgraded NanoVNA-H4. Hopefully it’s a good one.
I have another Heltec I could use. Do you have a guide on how to use this?
I wish RSSI/SNR was part of the built-in range testing!
I have. There are areas 10-30km away that should be LoS.
That’s what I’ve tried. Although I was driving, not walking, but assume that would be ok?
This is the antenna I’m using. [LINK] Is there another antenna you could recommend?
I could mount the heltec in the attic but wonder about heat. I’ve been thinking of building a Rakwireless PoE node for that. I’ll check with the Nanovna and see how much the LMR400 is affecting my signal.
As a sanity check I did verify my attic node and it’s SMA to SMA, but noticed that one of my Lilygo nodes had a mismatch. I’ve been using it for a month or so… Is it fried? Is there any way to check if it has burned out?
Loads of really great info in these posts, thank you guys!
30km ?
Whats the height\altitude differance between the antennas at your location and the other ?
I’m in an area that is ~110m ASL and ~30km away there are peaks around 350m ASL.
Looks like a good antenna, I don’t suspect that’s your problem, but it sure never hurts to check/test…but that’s a Rak braded antenna, so I don’t think that’s apt to be a problem…if you’d said it was some eBay white-label model, then I’d be more worried, but that Rak oughta do you well.
I don’t think you fried that radio, but a mismatched connector will definitely see range drop to near nothing I just went on a “range walk” the other day and noticed my SNA had dropped to -16 just 20 feet or so from the house…turned out the IPEX connector had come unseated from the board, so it’s safe to say the range without any antenna is truly horrible, but a mismatched SMA connector would be the equivalent of no antenna at all.
I doubt you fried the radio…I really think (but don’t know) the “danger” of running these without antenna is not all that great. I wouldn’t tempt fate, certainly, but a little bit of run-time without an antenna isn’t going to kill it…I don’t think anyway. I’ve accidentally ran more than one of mine without an antenna and I’ve not seen any drop-off in performance or range. I say that only ever having worked with Rak boards though so can’t speak to the other manufacturers.
If it’s not too difficult, go ahead and mount that node in the attic…doesn’t have to be pretty, just has to not fall apart long enough to test. But give that a go and see if you notice anything different.
I know you said you tried a range-test while driving, but since you’re only getting ~1Km anyway, set the broadcast rate to 30s and start walking until it stops pinging. If you’re feeling spry, walk in the other direction and likewise stop when it stops pinging…in theory you should be able to “draw” a set of pins which represent the entire circumference of your base station’s range.
Also, range-tests do contain RxSNR. It’s super useful too since when you plot it on Google maps you can use the RxSNR number as a way to color the pins so you can get a sort of heat-map showing a range of strong to weak signals.
Here’s a snippet showing two different receiver antennas as an example:
The relative colors depict the SNR values, two different color sets depict the data sets from the two different antennas.
I might put together a whole post on how to do that if others would find it helpful or useful.
Best luck, keep us posted!
Regards,
Pol
I’ve added a bit more information about installing the app on the homepage GitHub - barryhunter/lora-tester
But does assume familiarity with the Arduino IDE.
… not a power user myself, so might be forgetting some steps, but need ESP libraries. But in theory can just copy the code from github as a new project, build, compile and send to device.
Idea being have one normal Meshtastic device transmitting, probably using Range-Test module to send periodic messages. Then this code on a second device, and it will show you the RSSI/SNR of messages as received.
I get about the same range.
I have 11.5dBi, antenna at home in a window about 5m above the ground.
Heltec V3. 2m coax.
I also get about 1km range.
You need perfect line of sight fro more range I suppose.
I will move my antenna outdoors up above the roof line in the future and that will most likely improve things.
I think the long range claims we hear about are for setups from hilltop to hilltop.
These are microwave transmissions after all, they are true line-of-sight devices not like HF and VHF transmissions were you can get past obstacles without loosing all the signal.
//Harry
There is another issue with using frequencies around 900 MHz. Leaves on the trees will absorb the RF and create additional loss. Cellular phones experience the same problem. The coverage area changes with the season. Living in a semi-rural area with lots of trees, I found this problem. Cellular phone coverage is better in the winter. I hope this is a help.
And the absorbtion is higher when the leaves are wet.
I am not sure on the wet leaves. But, I do know heavy rain can affect UHF propagation.
I believe that may be a large portion of your issue there. We start off with about 0.07 to 0.06 watts of power.
If you are getting 86% efficiency from your cable then yo are already knocking that power down to 0.05 watts. The cable run basically schwacked a tenth of a watt right off the top.
best bet is to move the Heltec to the attic and give that antenna all the wattage you can.
Next best is to get the antenna outside of the attic. We have a lot of RF Garbage in our attics here. Roofng nails all over the place holding tiles on the roof. Metal flashing, some people have metal roofs, then there is all of the electrical wiring and plumbing and HVAC air handling duct work. All of that can cause issues too. But start out by removing the cable from the equation.
And do post up the Nano VNA results. Test it with and without the cable.
