Greetings all. Here are a few pics of my current build. I can provide a parts list if there is an interest.
What do you have between the TTGO’s transceiver and the Antenna?
I would be interested in a parts list!
It’s a ‘Tiny Low Noise Amplifier’ from GPIO Labs (GPIO.com). What’s great is it’s wide input voltage range (+3.6 VDC to +24 VDC).
With some cable loss probably 15 dB gain. It uses a Mini-Circuits PSA4-5043+ Chip.
The bulk of the info is on my work machine. I will try and post it Monday or Tuesday.
Is this the ampifier you used? I am very interested in this setup if it can boost range by adding it inline like you have shown.
It’s this one:
Also note- it comes with SMA female on both ends. You will need a SMA male to male adapter to connect with the TTGO.
Cool! What voltage are you running the amplifier on? What kind of current does it draw when in use?
Is that bidirectional? It’ll amplify both the receive and transmit?
Nice project, I’d be interested to hear how the range compares with that amplifier! It has a max power output of 21dBm though which is similar to the T-Beam. It also has an absolute max power input of 17dBm so you will want to reduce the T-Beam power output.
It would be interesting to know how it affects the receive sensitivity.
After inspecting what I am calling the waterproof RPT unit, I realized the plastic case is diminishing the contact point of the SMA female connector to antenna (picture 1). So it will need a SMA Male to Female Barrel Adapter to properly seat the antenna. Or use it with the low loss cable (picture 2).
Parts List for waterproof RPT Unit:
TTGO Meshtastic T-Beam V1.1 ESP32
Voltaic Systems 6 Watt-Panel
Voltaic Systems 3.5x1.1mm - extension cable
SparkFun MMPT Solar Charger
2x - Screw Terminal 3.5m Pitch (2-Pin)
Lithium Ion Battery 6Ah
SMA Male Radio Antenna TWAYRDIO - In retrospect I would purchase another brand. Need antenna analyzer before I can recommend.
SMA Male (right angle) to SMA Female Low Loss Cable
Nanuk 903 Small Waterproof Hard Case
GIPO Labs Tiny Low Noise Amplifier
SMA Male to SMA Male Barrel Adapter (Connector)
On Off Switch
Fender Washer (ground plane) for antenna
Non-acidic silicone sealant (outside holes)
Epoxy (inside holes)
Thanks for the heads up on the max power input.
Unfortunately it is not bi-directional. The diode is powered on transmit. To receive, you need a good, well grounded antenna. My thoughts on this, its more important to receive a message from say HQ to the working field in an emergency. Or possibly have one at the end of the HQ mesh and one at the end of the field mesh.
I am running the amp on + 3.7 VDC from the Lithium Ion Battery. I have not measured current yet. The specs from the Mini-Circuits site: “Low, small signal operating current of 53mA nominal maintains junction temperatures typically below 125°C at 85°C ground lead temperature.”
This conversation is making me want to design a bidirectional 900mhz amplifier.
I’ll look into that after I finish my current list.
Hmmm, I’m going to hazard a guess this will hinder your performance not help it unfortunately. For example the SX1262 TBeam has 22dBm transmit power at 130mA and a receive sensitivity of -139dBm. If the power amp only puts out 21dBm and likely has an amount of insertion loss, you have reduced the delta between transmit power and receive sensitivity while adding additional current consumption.
Understood. I am newer at this frequency transmit process. When I have some time - hopefully this weekend - I will try some real world tests. I came across the amp and thought for $24 it’s worth checking it out.
Thanks for the input.
Anyone seen these in action? Do they just pick up any random signal in the 35cm range and retransmit indoor? Or can they be made to do that?!
The cell network uses different frequency bands for uplink and downlink. My assumption is it won’t work for Lora.
Do have the schematic for putting this together. Really want to try this. Thanks