APALink

APALink is an external C utility designed to keep an AP FPV video link usable under changing RF conditions. It can switch to a lower bitrate when signal strength becomes weak.

What it does

APALink monitors the link and applies fallback logic. For example, it can reduce video bitrate to 2 Mbps when the signal drops below a configured threshold.

Installation summary

1. Open the APALink source repository: CaraSandbox.
2. Follow the README in that repository.
3. Copy the ap_alink binary to /usr/bin.
4. Copy ap_alink.conf to /etc/.
5. Optionally copy vtxmenu.ini to /etc/ to enable an AP FPV menu.

Make the binary executable:

chmod +x /usr/bin/ap_alink

Configuration

Edit /etc/ap_alink.conf:

bitrate_max=22
bitrate_min=2
dbm_threshold=-47

Settings:

• bitrate_max: bitrate used under good signal conditions.
• bitrate_min: fallback bitrate used under weak signal conditions.
• dbm_threshold: signal threshold where fallback starts.

A lower threshold keeps higher image quality for longer, but may increase lag or freezes under weak signal. A higher threshold triggers fallback sooner, usually reducing lag at the cost of image quality.

Example settings

BL-M8812EU2:

bitrate_max=12
bitrate_min=2
dbm_threshold=-52

BL-R8812AF1:

bitrate_max=10
bitrate_min=2
dbm_threshold=-48

VTX menu

With vtxmenu.ini, AP FPV settings can be exposed through an MSP-style menu. Typical items include:

• TX power: min/max presets such as 1500 or 2000.
• Channel: available 5 GHz Wi-Fi channels.
• Auto power: enable or disable automatic TX power behavior.