Digital Voice Modes for VHF/UHF Ham Radio

Ham radio already makes use of many digital modes such as RTTY, PSK31, AX.25 Packet, etc. Another wave coming is a true digital voice mode, especially for the VHF and higher bands. Currently, most of the activity on the VHF and higher bands is FM (or SSB), both analog modulation. Virtually all of the mobile phone formats have gone digital and good old analog FM is being phased out. Many land mobile users such as police and fire radio are also moving to digital. I suspect it is a question of when (not if) ham radio VHF/UHF will go digital.

The two competing formats emerging in the ham radio world are D-STAR and APCO 25. D-STAR is a digital radio standard developed by the Japanese government under the direction of the JARL. ICOM is the leading proponent of D-STAR and has several transceivers and repeaters available that conform to the standard. The ICOM web site has the best information on using D-STAR. The ARRL recently did a review of a few ICOM D-STAR products in QST.

Any new technology has to overcome the fear that it won’t be broadly adopted and will die an early death. One concern is that only ICOM has D-STAR radios in the market today. Recently, there have been sightings of a D-STAR radio from Kenwood, which could indicate momentum behind the D-STAR standard. The ARRL has also reported activity from Kenwood on D-STAR transceivers.

APCO 25 is the digital radio standard aimed at police/fire/emergency responders developed by the Association of Public-Safety Communications Officials (APCO) International. APCO calls this format “Project 25” or P25, which is described here. Some hams argue that hams should once again follow the tradition of adopting commercial/land mobile developed standards for ham use. There is merit to this argument as the VHF/UHF FM gear is based on commercial standards. Even today, many repeaters are made up of commercial gear deployed on the ham bands.

Which is better, a standard developed for amateur radio use or one that leverages off commercial standards and technology? The debate is on in the various online ham forums. (Don’t expect consistently brilliant discussion of the topic.) VE7TKO has been a vocal supported of D-STAR on digital forum and

Stay tuned. This will be a hot topic in the years to come. And it will probably take years for digital to overtake analog….the installed base is just too large and it will take time for it to convert over.

2 Replies to “Digital Voice Modes for VHF/UHF Ham Radio”

  1. What is really needed is free software that combines 3 existing pieces of software into one package. (1) Speech recognition software will let you speak into a microphone and write a letter on your computer without typing on a keyboard. (2) PSK31 software and an add-on card in your computer will allow you to use your existing radio and antenna to communicate with a 30 Hz bandwidth by typing on your keyboard and receive text on your monitor. (3) Software exists for blind people to read books by scanning the text and hearing the words from a speaker connected to the computer. That text could come from your computer monitor.

    Speech could be converted into symbols. The symbols could be communicated by radio with almost no bandwidth. The symbols could be converted into sound. But if the symbols are encrypted by hardware (APCO-25) or by software (D-Star), the people who have the encryption keys could make big bucks.

    Could someone please write the software that is needed for us?

    Mike n6ief

  2. The technique you have described is very interesting. As I think about it, it is all about coding of the message. The technique you describe essentially encodes the message in English as ASCII characters. This would result in a lower bandwidth signal as you described but it would lose the characteristics of a person’s voice. It all depends on what the communications objective is….in ham radio, lots of people would find this unacceptable for “voice” communication.

    Another thought is that there is probably a more efficient coding scheme that ASCII/English,since the English language has lots of redundancy.

    -Bob K0NR