Frequency options: I can't decide 433Mhz or 868Mhz

Hello Radio Lovers,

Just for fun I am planning to set up a communication bridge
between two Android phones using 3 of these LILYGO® TTGO Meshtastic T-Beam V1.1 ESP32 433/868/915/923Mhz WiFi BLE Lora ESP32 GPS NEO-6M SMA 18650 Battery Holder With OLED
devices.

One of them should act as a repeater on the rooftop of my house, this should work shouldn’t it ?

                                         rooftop repeater
                                           +-----------+ 
                                           | meshtastic| 
                                          /| node2     |\
                                         / +--------- -+ \
                                        /                 \
                                       /                   \
+--------+           +------------+   /                     \   +-----------+           +--------+
| phoneA | bluetooth | meshtastic |--+                       +--| meshtastic| bluetooth | phoneB |
|        |-----------| node1      |                             | node3     |-----------|        |
+--------+           +------------+                             +-----------+           +--------+
          

Here in EU I can choose between 433Mhz and 868Mhz.
I can’t decide which one is better.

Some say 433Mhz is crowded with tire pressure sensors, temperature/humidity sensors and garage door remotes.
But if I scan with my rtl sdr 868Mhz seems to be crowded as well.

868Mhz seems to be the more popular and “modern” frequency for lora, 25mW is allowed but only a duty cycle of 1%, correct ?

433Mhz on the other hand is better to get a bit around corners (this is what i googled), or through trees and bushes, and there is no duty cycle limit, but only 10mW are allowed, right ?

868Mhz at 25mW versus 433Mhz at 10mW,
thats the question, which one works better in the woods ?

Since I already own a lot of nice 433 Mhz antennas
I tend to buy the 433 Mhz version but I am not sure if I will regret this soon.

I have got a Diamond X-30 2m/70cm antenna (144Mhz/433Mhz) mounted on a hight mast on my rooftop with 25m Aircell 7 coax cable which ends in my basement.
Is it sufficent/clever to use this for 433Mhz lora ?
Or will all 10mW be lost in the 25m coax cable ?

Or better mount the complete small lora device (which is supposed to be the repeater) including antenna on the Mast ?

Some advice is really appreciated.

Thanks in advance
Lixus

25m of Aircell7 is going to reduce your ERP by a factor of about two at 433MHz. You can check your local regulations, 500mW of ERP are allowed in the 869.4MHz to 869.65MHz region as per ETSI norm.
This wikipedia page Short-range device - Wikipedia as a nice overview regarding the regulations.

Do not use 25mtr aircell… nothing left on the end. Put in IP65 box in top of mast or roof and if you need, use a USB extender over LAN. I use USB extender over LAN for all my SDR hardware. USB extender over LAN max length is 30 meter. I buy from Reichelt.de.

1 Like

there is no need for an USB over LAN extender since you can remote connect to any ESP32 based hardware via wifi:

meshtastic --host HOST

Bu… you cant power or charge Tbeam over wifi :slight_smile: Or when live in heavy city area, like in the netherlands, WiFi bands is very, very, very, busy who have very limited range. Again, you cant charge or power over WiFi so you need USB and use a LAN extander :wink:

Ok, I got it, using 25 meters of aircell 7 is not clever.

But can’t i compensate the loss of the coax cable by increasing the tx_power ?

I assume that the LILYGO TTGO T-Beam V1.1 433Mhz
can provide up to 500mW ?

But still I am not sure if should buy the 868Mhz or the 443Mhz
version of the LILYGO TTGO T-Beam V1.1

where are you located?

I am located in Germany.

I wrote 500mW but 100mW is correct.
20dBm is 100mW, right ?

In the meanwhile i found these similar threads:

I now belive that I am going to prefere the 433Mhz Version over the 868Mhz version of the LILYGO TTGO T-Beam V1.1

I started the thread you mentioned.
Yes, 433mhz has double the penetration of 868mhz.

You can set the power to 20dBm through the Python CLI.

I would have suggested the T-Beam SX1262 M8N board to you, but they are not available in the 433mhz version anymore. They have way better capabilities.

You might wanna check how noisy/congested 433 is in your area first.

Strongly consider the 868MHz variant since in germany 500mW of ERP is totally legal in a specific band (869,40MHz - 869,65MHz):

With 433Mhz you are limited to 10mW ERP which is next to nothing and does not compare to any gain in range related to the frequency.

1 Like

Right, for this use case only 10mW ERP in the 433Mhz range is allowed.

Thats Germany, everything that would be fun like sending with 500mW in the 433Mhz is not allowed :wink:

Fun Fact, according to this document page 8 bottom and page 9 (which is from 2008, so perhaps not valid any more)
licenced radio amateurs are allowed to work with 20 Watt FM or even ALLMODE in the same frequency range 433.050 - 434.790 MHz while me ( not licenced but interested radio amateur ) is only allowed to do 10mW. Thats not fair. Or am I wrong ?

From the mentioned document about allowed 868 Mhz power in Germany
Allgemeinzuteilung von Frequenzen zur Nutzung durch Funkanwendungen geringer Reichweite SRD

I do not understand what now applies to this Meshtastic Lora project.
They mention 25mW but also 500mW and even 2 Watt

865 - 868 500 mW
865 - 868 2 Watt

Why I am not allowed to to 2 Watt for Lora in the 865 - 868 range ?

@kokroo , thanks for the hint about T-Beam SX1262 M8N
Is this the right device ? It seems to be available in 443 Mhz TTGO T-Beam V1.1 SX1262 LORA 868/915MHZ ESP32 WiFi Wireless Bluetooth Module GPS NEO-M8N IPEX 18650 Battery Holder
You recommend it because it can do power up to +22dBm ( ~ 160mW) ?

I first felt in love with the LILYGO TTGO Meshtastic T-Beam V1.1
borad because it looked like an easy plug and play variant to get into the topic
even without a case for the device.
But I really dislike the antenna position, the T-Beam SX1262 M8N would make it possible to put it in a tube (water pipe) as a case more easily.

Lixus

This is totally fair since HAM and short range devices are two separate things. Also, short range devices have no privileges per definition, which means that they have to live with the fact that somebody else might stomp on their transmission.
You are not allowed to use meshtastic in the 865-868MHz region since this band is reserved for Geräte zur Funk-Frequenz Kennzeichnung (RFID)5
You are allowed to use 500mW ERP (this includes antenna gain!!) in the 869,40MHz - 869,65MHz region, but be aware that you are limited to a 10% duty cycle (interval 1 hour, so 360s of transmission time per 1 hour). The next generation of meshtastic software is going to include breaking changes that will adress EU regulations, either duty cycle and/or “polite spectrum access” as per ETSI (ich bin mit dabei meshtastic offiziell “EU konform” zu machen, aktuell kannst du dir mit neu kompilieren behelfen da die Frequenzen “hart” im sourcecode stehen).

You can check out our (up to) +30dbm core pcb:

We are really close to releasing the second generation which will be fit for production.

And regarding the t-beam antenna position: on your “older” non sx1262 is a footprint for an u.fl connector right underneath the SMA connector footprint. Desolder the SMA connector, solder on an u.fl connector and use u.fl to SMA (or whatever) pigtails.

1 Like

@PlumRugOfDoom I like your idea. Are you going to produce a batch of your boards?

I’d love to see a device like the T-Echo with 1W transmit power and a bigger battery case.

Iam retired and plenty time, always interested in testing.
BTW i build the Tbeam in IP65 case and upload pictures soon.

I have 6-8 433mH bought accidentally. Needed 915 here in Arizona. May trade for technical help with Meshtastic.

Just get your US ham license (technician is good enough) and turn off encryption and you’re good to go in AZ.

OK, thanks. But the whole point is everyone has a phone, not a license.
Thanks,
Larry

Yup. Just depends on what you want to do. :slight_smile: