I’m having a really hard time getting reliable messaging 800m to 1km… Even with a rooftop solar router.
Are the supplied antennas correctish?
Are my expectations out of line?
I’ve got a python script sending the time once a minute and I’m getting 30% of the messages on a 3km round trip dog walk, 1km max distance.
Few things come to mind
I use this website for a basic LOS calculation I do not believe it takes into account buildings/trees etc just terrain. (trees like to absorb radio waves, buildings can reflect abit depending on material they are made from)
http://heywhatsthat.com/
Also could be interference from other sources around the area leaking radio waves into the spectrum you are using. (Poorly made radio equipment can do this even if it operates at a separate frequency)
I am using the sx1262 chipset on my tbeams that put out around 158mw (on paper) the older versions on most tbeams use the sx1278 around 100mw so that might help range abit.
Just my 2c.
The supplied antennas are usually ok if they actually match the frequency of the device you are using. But I’ve noticed that sellers don’t seem to have different antennas for 868Mhz and 915Mhz so over all they are poorly tuned.
Have you tested them on a VNA?
No, I don’t have access to one here, we’re in lockdown in rural southern Mexico, as our Panamerican road trip is currently paused, So I’m trying to keep myself occupied with what we have along with us.
These are newish, how do I determine the chipset?
It will state it on the lorachip itself if you are using tbeams:
I took two T-Beams on the dog walk again today, The Solar Router was on the 10m rooftop.
The Base Station was sending the time every minute. I received 15 of 45 messages sent.
It’s a relatively short walk, the furthest distance being 1km away. Relatively flat Mexican Farmland a few 0.8 story farm houses…
Did you double check the solder connections on your repeater antenna? Maybe try using a different, stock device up there/
This is the older SX1278 chipset I can not really comment on the range difference between the two as I do not have the older chipset except on 433mhz.
Im assuming you do not have the tbeams in your pocket?
Do you have an SDR?
That picture shows that it says 433Mhz on the chip, which is actually the frequency for use in Asia.
Anyway, try adding a ground plane. You can use the lid from a jar and put a hole through it for the antenna.
Better yet, to make your own antenna for 433Mhz you want it to be 17.3cm for 1/4 wave or 34.6cm for 1/2 wave.
From your picture it looks like the antenna is only maybe 2cm, not a good length. You can make a dipole antenna with 2 pieces of wire of the above lengths, one going from the center pin and the other from the ground (shield) and run them in opposite directions.
https://www.easycalculation.com/physics/electromagnetism/antenna-wavelength.php
Although if your transmissions interfere with shipping containers, which is what 433Mhz is used for in North America, you might get an unfriendly visit.
It was originally a stock device, it showed 30-40% signal strength on the T-Beam screen during the walk, now it shows 80-90% - I’ll consider reverting to stock. Thanks
No, It’s held at head height for the duration of the walk…
Correct, One of the 5 was delivered 433Mhz - But as we are traveling and have no fixed address in Mexico I can’t wait any longer for a replacement. That 433Mhz unit has been relegated to a receiver only. Seems to receive fine running 915Mhz code.
Thanks, I’ll build a 1/2 wave dipole for tomorrow’s walk and report back…
So for 915Mhz 1/2 wave each leg should be 16.4 cm
Would soldering directly onto the board cause any issues as there is no protection against RF leakage from the connection point?
The shielding is soldered against the board in the same way the SMA connector was, I can’t see the difference…
I’m wondering if you have a cold solder joint that has increased resistance. Maybe try and check with a multimeter. Should be around 50 Ohm
Thanks for that! I built one this morning and mounted it to my largest sombrero for tonight’s walk… This one was paired to my phone. I also carried a second one with a stock antenna with the brass tube as shown before.
I still had many missed pings (guessing 50%), but it was interesting that both units seemed to get all the received messages and they both missed all the missing messages. I suppose the one that was received could have relayed it to the other.
But what was also interesting/sad is that I left another T-beam with a stock antenna 3 meters from the one transmitting the time and it too missed many of the same messages that I missed while walking. It did catch a few that I didn’t.
The server sent these every minute… I have to trust the script actually works each time…?
Current Time = 16:06
Current Time = 16:07
Current Time = 16:08
Current Time = 16:09
Current Time = 16:10
Current Time = 16:11
Current Time = 16:12
Current Time = 16:13
Current Time = 16:14
Current Time = 16:15
Current Time = 16:16
Current Time = 16:17
Current Time = 16:18
But the receiver 3 meters away doesn’t catch them all:
Received: {'from': 3186665228, 'to': 4294967295, 'decoded': {'data': {'portnum': 'TEXT_MESSAGE_APP', 'payload': b'16:10', 'text': '16:10'}}, 'id': 2850509587, 'rxSnr': 7.25, 'rxTime': 1613686246, 'hopLimit': 1, 'fromId': '!bdf0a70c', 'toId': '^all'}
Received: {'from': 3186665228, 'to': 4294967295, 'decoded': {'data': {'portnum': 'TEXT_MESSAGE_APP', 'payload': b'16:11', 'text': '16:11'}}, 'id': 1882057581, 'rxSnr': 7.0, 'rxTime': 1613686293, 'hopLimit': 1, 'fromId': '!bdf0a70c', 'toId': '^all'}
Received: {'from': 3186665228, 'to': 4294967295, 'decoded': {'data': {'portnum': 'TEXT_MESSAGE_APP', 'payload': b'16:12', 'text': '16:12'}}, 'id': 3660720756, 'rxSnr': 8.0, 'rxTime': 1613686366, 'hopLimit': 1, 'fromId': '!bdf0a70c', 'toId': '^all'}
Received: {'from': 3186665228, 'to': 4294967295, 'decoded': {'data': {'portnum': 'TEXT_MESSAGE_APP', 'payload': b'16:16', 'text': '16:16'}}, 'id': 3608628701, 'rxSnr': 4.0, 'rxTime': 1613686611, 'hopLimit': 1, 'fromId': '!bdf0a70c', 'toId': '^all'}
Received: {'from': 3186665228, 'to': 4294967295, 'decoded': {'data': {'portnum': 'TEXT_MESSAGE_APP', 'payload': b'16:17', 'text': '16:17'}}, 'id': 3643319722, 'rxSnr': 5.25, 'rxTime': 1613686668, 'hopLimit': 1, 'fromId': '!bdf0a70c', 'toId': '^all'}
Received: {'from': 3186665228, 'to': 4294967295, 'decoded': {'data': {'portnum': 'TEXT_MESSAGE_APP', 'payload': b'16:18', 'text': '16:18'}}, 'id': 1110682246, 'rxSnr': 8.25, 'rxTime': 1613686773, 'hopLimit': 1, 'fromId': '!bdf0a70c', 'toId': '^all'}
Received: {'from': 3186665228, 'to': 4294967295, 'decoded': {'data': {'portnum': 'TEXT_MESSAGE_APP', 'payload': b'16:19', 'text': '16:19'}}, 'id': 3030548374, 'rxSnr': 9.0, 'rxTime': 1613686861, 'hopLimit': 1, 'fromId': '!bdf0a70c', 'toId': '^all'}
Received: {'from': 3186665228, 'to': 4294967295, 'decoded': {'data': {'portnum': 'TEXT_MESSAGE_APP', 'payload': b'16:21', 'text': '16:21'}}, 'id': 1596524341, 'rxSnr': 9.0, 'rxTime': 1613686944, 'hopLimit': 1, 'fromId': '!bdf0a70c', 'toId': '^all'}
Also weird that the hopLimit is 1 on all these messages when it was just the 2 units in the area…
I’m starting to think it’s not all the fault of the antenna… But I’ve run out of ideas on what to try next.
What version of the firmware do you have on your board? A recent build fixed a problem with retransmission of packets.
1.1.48 on these, the Solar Repeater is stuck on 1.1.32 and will not update over USB:
While it was able to update it once via OTA, it will not update to 1.1.48, it moves the progress bar about halfway and then quits. Sometimes it tries twice - but it still fails. As I link that thread I remember that I thought it was USB power that helped it succeed last time. Might need to fire up the rescue drone and get it down from the rooftop tomorrow…