I found the following 915MHZ RF 4W power amplifier:
This would certainly push transmission, but would it be capable to transceive also? If not, does anyone know of an alternative 915MHZ power amplifier that can transmit and receive? Thank you
Edit 1
Would adding a diplexer make the amplifier capable of receiving and transmitting? Also, I know adding a PA is illegal; this is strictly research.
Edit 2
I added a schematic; would this work? I am trying to a compatible diplexer.
The amplifier needs to have an attenuator to bring the TX signal from the LORA radio down to below 1dbm or it gets some nasty harmonics and signal reflections, as seen on a spectrum analyzer. I used a -20db attenuator for that.
The amplifier also needs to have a power mosfet to switch it on and off. It gets insanely hot when not transmitting. The code (from above) will need to be modified to give it a few ms to power up when it’s first turned on. It also uses a logic inverter, configured to match the truth table of the RF switch, to drive the RF switch from one GPIO rather than two. It also allows for faster switching than what can come out of the very slow Arduino digitalwrite function.
The code from above will not be merged into the main meshtastic code. It’s a bit of a hack. I could see it going into a power amplifier plugin.
I greatly appreciate your shared research. The feedback I was receiving on reddit didn’t seem hopeful. I love the picture also, but could you possibly share a schematic? I think I have an idea of how you have the parts arranged, but all the cables have me confused.
BTW, I found several suppliers for the RF switch, but had trouble finding a -20db attenuator; mind sharing a link of where you found your attenuator?
One last question…when you turn off the amp, will the ESP32 still function at its regular capacity via meshtastic?
Sharing a schematic or diagram would mean having to make one. I threw that together in an evening. I’d like to have it (eventually) manufactured, but got distracted with other things. It’s very close to the block diagram you posted on Reddit with the attenuator coming in between the switch and the amplifier. The other wires are for power and control.
I made the attenuator myself using the Pi configuration, you’re welcome to use my design.
Thank you for helping. I was looking at antennas as well to further improve performance. Would these antennas drastically improve performance & be worth the extra money for farther/reliable range?
I took the chance and purchased a pairf (got the covid relief check, so less than $20.00 won’t upset the household budget and spouse).
I’ll make some measurements, comparing them against the half wave “rubber ducky” verticals that Heltec furnishes with thier ESP32 modules using an SDR and RTLpower to see how they look before doing a field test. and post the results.
Using a 5 element yagi on one end didn’t make much of an improvement (at SF12 and minimum data packet settings), so I’m not expecting miracles.
Hello, is there an amplifier that I can plug in, between my ttgo tbeam and my antenna, and not have to rewire, reduce, reprogram, or rewrite a rats nest worth of wires? I am not an inventor, or a programmer, and I can not read schematics beyond oh hey look here’s a resistor. (I had someone else solder the screens on my tbeams) I’m looking for a simple, plug and play USB powered amplifier to get more power and range from my 915Mhz tbeam.
I appreciate any help I can get.
Jeff
No idea your situation or what you like for range, put your antenna higher up? Or using a directional antenna as option?
More power not always bring solution.
If there is it would likely be rather expensive as it would would have to have the RF bypass switch and attenuator built-in, and have a way of managing power states and automatically sensing transmit.
Wow, 600 bucks, for 5 watts… The only word that comes to mind is piracy. Thanks though, I do appreciate you taking the time. I guess there is a lot more to an amplifier than I thought. You have a good weekend.
WiFi amplifiers have solution
Again repeat, more power not always give more range.
Antenna just 2 or 3, 4 , 5 meters higher up, give much more effect in range improvements.
Just try it, you find out it works.
Just try 1 - 2 meter or more you notice differenc let me know you thank me afterwards, 100%.
The actual max rf radiation is where the coax go in to antenna. Now you radiated against the rooftop So that part must way way up.
Lowloss cable and short as possible
Here is the amp I am messing around with, it is a bi-directional amp and its supposed to automatically switch between transmit and receive mode based on the what is being supplied at the input, the Meshtastic LoRa devices I am using seem to be with in spec to properly activate it.
The problem I am having is I get almost zero reception with it in place? The transmission seems to be working well and it really improves the range.
Any idea why I might have trouble with this blocking reception? According to the LED status it is usually in reception mode as it is supposed to be and periodically goes into transmit mode on its own or when I send a Meshtastic message.
