low-cost versatile APRS board – part 2

I have been using the Lilygo TWR for some weeks now. I used it mainly as an APRS-tracker, but I also tested the I-Gate and digipeater functionalities. It is amazing, that a lot of settings can be configured directly on the device, using just the small thumbwheel and the OLED-display. The Webinterface offers even more – take a look at my screenshots. The device even offers smart beaconing and different symbols (moving car, stopped car). Impressing for a software version 0.3.

The hardware seems to be the source of some issues. It seems, that even in the “low power” setting the output of the device is almost 1 Watt. In the “high power” setting it crashes when starting to transmit (= turns off). First I thought it was a software problem, but it actually seems to be a hardware problem. It was hard to get the device out of such a “crash loop”, but I managed to do so after some attempts.

There are few android devices, which can connect to the wifi access point of the Lilygo. A majority of devices fail to connect. As a workaround I configured a guest wifi on my router, naming it as the network, for which the Lilygo TWR is looking for. When it connects to my guest network, I can access the built-in webserver and the configuration menu.

I printed a case for the Lilygo TWR, which is also available on github.com. It has a version number of 0.9, so a few things might be adjusted in the future, but so far the board fits into the case and it works even without additional screws (see picture).

In tracker mode, while transmitting a beacon every 30 seconds (smart beaconing set to “off”), a 27100 battery lasts for more than 6 hours. That is a good battery life. Also the board charges the battery, when connected to a USB power supply.

In spring I would like to configure the Lilygo TWR as a digipeater and lift it up with a drone (or with a kite, when it turns out to be too heavy for the drone). So I made some weight measurements:

– bare board: 60g
– board with 21700 LiPo cell: 132g
– board, battery and case: 171g
– board, battery, case, nagoya 701 antenna: 188g

I still have to run more tests with my other radios – other repeaters and I-Gates seem to receive and decode the Lilygo TWR well. My FTM-300 seems to skip some packets, but displays most of them. The Anytone 878 receives all beacons, but the displayed symbols change (single bit errors ?). The FT-3DE decodes only few packets and I still don’t know why.