Unusual question.
Can the Meshtastic code be modified to allow a T-Beam v1.1 to operate in the 1.25 meter band?
The SX1278 operates between 150Mhz to 1050Mhz.
The RF section in the schematic seems to be generic for 433Mhz, 868Mhz and 915Mhz.
During the inital initializing of a 433Mhz T-Beam. It operates on 915Mhz until I set the region to EU_433Mhz. (And set it for Ham use)
So why can’t a T-Beam operate on 1.25 meter ham band?
Assuming you are a ham license holder, follow the instructions here to override the frequency configuration sent to the SX1278 - you should be to set it to 220 MHz.
I’m surprised to hear this. Can you link the schematics for the different T-Beam SKUs? I was only able to find one schematic for the T-Beam v1.1 on GitHub, and I assumed that the parameters were slightly different for 433 MHz vs 868/915 MHz.
Here is the Github site I use for my references:
Yes, I was there. I saw only one schematic for T-Beam V1.1, which doesn’t specify which band it’s using. You wrote,
Without actual schematics for the 433 MHz, 868 MHz, and 915 MHz versions indicating otherwise, I would assume that there are slight tuning differences in the RF section.
LoRa modules have impedance matching tuned circuits between the RF output on the Semtech device and the actual antenna connection. The matching circuit is specific to the modules intended frequency band.
Operate outside of the modules frequency band and you potentially will have a missmatched antenna, reduced RF output and possibly module damage. Also there might be excessive harmonics (interferance) produced.
Be careful with 433 MHz. There are lots of restrictions, and even more for hams. We are not a primary user for much of this, and the FCC does take that seriously.
“(e) To prevent interference to Federal Government radar systems, operation under the provisions of this section is not permitted within 40 kilometers of the following locations:”
(Several AIR FORCE BASES listed, Beale, Cape Cod, Clear, Cavalier and Eglin AFBs.)
There is also FCC Line A, which is drawn out by the FCC specifically to stop interference. If you are north of that line, which includes Seattle, Detroit, Cleveland, Buffalo, and most places within 100-200 miles of the Canada border, you are not going to push a lot of power. Hams must accept secondary status and a 5w max there.
To repudiate what someone else said, this is far more than a “rule on paper only”. You could get two countries really pissed at you for violating the terms of an agreement for interfering with either Air Force bases or Canadian stations.