I’m trying to make transmitter that fulfills the following criteria:

• Radio frequency: 150 MHz
• Audio: 800 Hz bip. 1 second ON, 1 second OFF
• Weight (without battery): < 0.5 g
• Board size: <= 8.5 * 20 mm
• Range: >= 50 m
• Battery life: >= 1 day
• Should work with the following battery: Renata CR1025

Prototype 1

150 MHz transmitter based on this design

• The received audio is only static noise (150 MHz carrier wave without audio). I need to investigate further why this is not transmitting a bip
• I can receive the signal on my UV-5R radio.

Resources

• Sender used for wildlife monitoring - white paper
• RF beacon made with 2 555’s and a 433MHz module
• 433 MHz modules used in previous circuit
• Schematic of 433 Mhz module above
• Tiny spying transmitter
• Interesting forum discussion
• RC lost model beacon
• Simples RF transmitter circuit
• Tiny 433 MHz transmitter open source
• simple miniature FM transmitter without crystal

Commercial beacons

• https://www.telemetrie-service.de/telemetrie-sender-2016
• https://www.holohil.com/transmitters/lb-2x/
• https://www.lotek.com/products/vhf-avian-tags-for-smaller-species/

Use microcontroller to generate audio

It’s easy to generate audio with the microcontroller as done in this RC lost model beacon video

Possible microcontroller options:

• ATtiny412: 2.7-5.5V power supply, weight 400 mg
• ATtiny20: weight 2 mg

LC resonator

F = 1/(2*PI*sqrt(L*C))

import math
1/(2*math.pi*math.sqrt(1*10**-6*15*10**-12))