Understanding the 25mW cap on Analog Video Transmitters or VTX - Why it is there and What is the situation in India?

 VTX is the most important component of an FPV drone. It helps transmit the image as seen by the camera back to the pilot who views it on an FPV Goggle or Monitor. Usually it will be a single tiny chip with a metallic heat sink and will run warm. It consumes lots of battery power. As the distance between the Video Transmitter and Video Receiver increases, more power is required by the VTX to transmit the image till a point that there will be a break in transmission. 

The most popular FPV systems are the 1S Tiny Whoops which come with an AIO board containing the Flight Controller, Electronic Speed Controller, Receiver, Video Transmitter and On Screen Display are on a single board. Best example of such a system is the BetaFPV Meteor75 Pro ELRS. 

Such a system has the minimum power requirement of the VTX at 25mW giving a range of 100 to 200 meters, perfect for indoors, parks and spaces around a house. 

Pushing the output of 100mW is easy and many brands allow it. This will give a longer range but drain the battery faster. Between 100mW to 200mW you might get a range of about 1 Km.

Meteor72 Pro offers increments in power levels of the VTX from 25mW to 100mW to 200mW to 400mW

VTX is considered by many to be the weakest link in the FPV system. Recreational FPV Pilots like to tinker with their gear and the urge to push limits is always there. 

The analog FPV system is pretty old but stable. It allows drone pilots to quickly get into learning FPV Flying without putting a dent in the savings. In this article we shall understand why there is a cap on the VTX pumping power. 

Local Regulations

Most countries including India have a cap on the drone weight and many other parameters like VTX power. The current standard is 25mW.

To understand the cap, you have to go back to the days of long forgotten radio transmission tech. At some point it was analog and then it went digital and further now it is mostly data packets. 

5.8 GHz is the transmitting frequency of the VTX. It is a public band and license free and used by many devices. In the good old days of Ham Radio, a power of 25mW as considered good enough to work without interfering others. That limit stayed. 

Many commercial establishments use the same band for their equipment like CCTVs. A higher power will cause signal interference. Plus, higher power with VTX will interfere with other VTXs if drones are flying together like in FPV Racing competitions. With the airwaves getting crowded, there will be more heartburns along the way.

What should you do?

As a responsible Recreational Drone Pilot, you need to stay within the limits of your local laws. Follow the regulations. In the case of this article, 250 grams for the weight of the drone and 25mW for the power of the video transmitter has been set by law. 

These two and many other limits apply in India. If you want to go anything higher, get the Remote Pilot Certificate from any of the DGCA Authorised Remote Pilot Training Organisation and do register your drone with Digital Sky Portal.