Vocal Keyer Project
Build this stand-alone contesting accessory for your radio and conserve your voice
The June 2008 VHF contest provided a golden opportunity to try my newly assembled Elecraft 222 MHz transverter and homebrew Yagi. The equipment performed well but points for this band were hard to get as repeated CQs over the contest period netted a raspy voice and only five contacts.
After the contest I began looking at commercially available voice keyers to take the brunt of calling CQ. Most keyers are now of the PC soundcard variety but I wanted the ability to operate without a computer. Searching the internet I found an assortment of voice recording chips. The HK8281 caught my eye with claims of multiple messages and an 8 KHz sample rate. Unlike the popular ChipCorder® devices by ISD, this chip can be easily configured for 2, 4, or 8 fixed duration messages without a microcontroller.
I ordered the required components and bread-boarded the circuit. A printed circuit board was then developed and the assembled board was mounted in a small enclosure. Connection to my Yaesu FT-857 was made using a short CAT-5 cable. The keyer was built with all new parts for about $75 and boasts the following features:
- Two 16-second messages with an 8 KHz sample rate and 4 KHz bandwidth (or four 10-second messages with a 6.4 KHz sample rate and 3.2 KHz bandwidth)
- Built-in audio amplifier and speaker
- Message pushbuttons
- Play/Record switch & LED
- Transmit On/Off switch
- Uses the radio microphone
- Transformer isolated audio output with level control and automatic PTT switching
- Message-1 repeat with 2-25 second delay interval
- Suitable for any radio with appropriate RJ-45 adapters for the microphone and radio
The HK828 provides high quality, single-chip record and playback for 32-60 second messaging applications. The device includes an oscillator, microphone preamp, automatic gain control, antialiasing filter, smoothing filter, speaker amplifier, and a high density multi-level storage array. Recordings are stored in nonvolatile memory which provides zero power message storage.....