SAWDIS Share Buttons

SAWDIS Share Buttons:

29 July 2011

PSKmail – Another Emergency Response Tool

(Click on images for larger view.)

In times of crisis and natural disasters, amateur radio is often used as a means of emergency communication when land line, cell phones, Internet and other conventional means of communications fail. This was the case recently when heavy snowfall closed several roads and trapped 100's in their vehicles in the Eastern Cape and Kwazulu Natal provinces

Unlike commercial systems, amateur radio is not as dependent on terrestrial facilities that can fail. It is dispersed throughout a community without "choke points" such as cellular telephone and Internet sites that can be overloaded. Amateur Radio operators set up and operate organized communication networks locally for governmental and emergency officials, as well as non-commercial communication for private citizens affected by the disaster.

Many radio amateurs are active as communications volunteers when radio towers and other elements in the communications infrastructure are damaged.  Luckily this does not happen quite often in South Africa but we as radio amateurs should be ready at any time should our services be needed.  Amateur Radio operators use various modes and radios to get the message out.  Amateur Radio operators have informal and formal groups to coordinate communication during emergencies. At the local level, radio amateurs may participate in local emergency organizations, or organize local "nets" using VHF (very high frequencies) and UHF (ultra high frequencies). At the government level, radio amateurs are often involved with Disaster Management operations. In addition, radio amateurs operate at the national level through HAMNET, which is coordinated through the SA Radio League (SARL) and its field volunteers. Many radio amateurs are also involved in weather and disaster observation, operating under the SA Weather and Disaster Information Service (SAWDIS) and provide emergency weather and disaster information to the general public for dissemination.

Having realized the shortcomings of current emergency messaging systems in South Africa, including those that utilize voice, CW, or email robots, I started a topic on the SARL Forum called Emergency Communications in South Africa. A few radio amateurs in South Africa realized the need for fast, reliable, emergency message transfer that would not be subject to any errors in translation from the spoken word to the written word, or from Morse Code to the written word, or wind up in an email inbox that nobody notices until it may be too late. The primary criteria that needed to be satisfied is that any message that was sent must be without any errors. If a single number within a phone number to be called is in error, the entire message is undeliverable. So, more than anything else, the delivered message must be an exact duplicate of the original.

To accomplish this, a verification approach, called “ARQ” for Automatic ReQest, must be utilized, and the system needed to be staffed with live amateur operators, who can verify message delivery to the intended recipient, and not depend upon any email “robots” which cannot obtain such verification in a timely manner. In addition, the system had to be capable of using very little of the radio spectrum so that there was more space left for other emergency communications activities, along with other amateur radio hobby activities.

Much talk resulted on the SARL Forum but nothing constructive was forthcoming.  I decided to grab the bull by the horns and started to experiment with  PSKmail client and server the past few weeks.  PSKmail is a narrow band arq system for use by amateur radio operators via short wave (HF)radio communication. It does not use a special controller, you just need a computer with a sound card and an amateur radio station.

PSKmail uses the fldigi program as a modem, and can use most any digital mode supported by fldigi, including the new robust PSK modes which include soft viterbi decoding and interleave to increase immunity to qrm and qrn. The operator can choose several mode profiles to match channel conditions.

The system uses adaptive mode control to use the channel capacity efficiently. When channel quality changes during a connected session the system changes speed to accommodate the new circumstances.

PSKmail has a client/server architecture. PSKmail protocol only allows 1 connected client at the time. Bandwidth (3dB) using the maximum speed (PSK500) is max. 500 Hz, providing a net throughput of ~400 wpm. The multiplatform PSKmail client is written in Java, and runs on Windows, Linux and OSX. The server is written in Perl. Applications include a Mailbox (port 24) allowing down/upload of local mail and mail from the Internet, downloading information from the web (ASCII text only), position update and station-to-station messaging via APRS(port26), and chat mode (between clients).

Even if the local internet is down, the long range on High Frequency (HF) radio guarantees a connection to the Internet. And it is child's play to set up an ad hoc server. I setup the first ever PSKmail server in the Western Cape called the ZS1I PSKmail Server. This server is currently operational on 7045 Mhz and situated in Mossel Bay and default listening mode is PSK500R.

The following radio amateurs call signs are currently listed on the ZS1I PSKmail Sever:


I would like to thank these amateurs for participating in constructive testing and experimentation. Your participating is highly appreciated.

Now what is PSKmail? 

PSKmail is a system that allows access to internet services such as email and web independent from infrastructure. Example: A sailboat on an ocean can read and send email, fetch weather reports, send direct messages and update the ships position through the APRS system. Friends and family can stay in touch and can also follow the ships movements seconds after position updates are sent from the ship.

PSKmail can provide access to internet services in rural and otherwise isolated areas of South Africa. Perhaps you'd like internet access on the North pole? No problem, pskmail provides that. Wait, did I mention its free and open source?

Infrastructure independent ?

PSkmail clients access servers using HF. A mobile station can be battery operated, solar powered, and can be located somewhere off the beaten track (in a jungle or on the high seas for example). Naturally the servers need to be connected to the internet to fetch internet email. But, the servers can even be used without internet connection (where that is not allowed or for special purposes such as emergency systems). The servers are independent and do not fail if a central system should be unreachable. Should one server be off the air then feel free to use another.


E-mail is an essential communications medium. PSKmail allows mobile clients access to their e-mail whenever and wherever necessary. With PSKmail you access your email providers' pop server, meaning that your normal email account can be used. Support is also in place for popular services like gmail. The pskmail client application features a settings dialogue where your service providers' email settings can be entered, these settings can be sent on the air during a connection with a pskmail server. You can also store your settings in a centralized database and the server will use that if available.

Surfing the web

PSKmail provides text based web surfing. Clients can access their favourite web sites and, in order to save bandwidth, pskmail delivers these in text form (with images removed). This is a very useful feature. The sailor can, for instance, access weather reports, navigational warnings etc. News sites can be browsed and I can fetch the match report from my hockey teams latest game.


The Automatic Position Reporting System was designed to support rapid, reliable exchange of information for local, tactical real-time information, events or nets. PSKmail is able to send position reports and exchange station to station aprs messages. One nice way to use this is for instance to send the current position every ten minutes from a mobile station. Friends and family can follow the movements of the station on a graphical display (see the wiki for more on this).

Emergency support

PSKmail is an outstanding tool in emergency situations. The server network is loosely tied together and that means that if a server, or even large parts of the network, should be out of service then the remaining servers carry on business as usual. Of course one weak link is your email provider, should that server be out of service then fetching mail from it will be difficult.
But, you may have another account? Just point the server in that direction then and carry on.
What if the entire internet shuld go down then?
Well, all servers have local mailboxes that can be used to store and forward your messages to other pskmail clients.

So, how can I try this then?

To use PSKmail you need:

A ham radio license
An hf transceiver with a working antenna solution, for boats that may include an antenna tuner and an isolated backstay or a whip antenna.
A computer running Linux, Mac OS or Windows.
FreeBSD should also be fine but we lack test reports there.
An interface for connecting the computer soundcard to the hf transceiver
A narrow filter (500 Hz) in the transceiver is highly recommended. A dsp may be nice but is normally not a replacement for a real filter.

The SAWDIS will incorporate PSKmail into it's already well established networks.

Further updates to be posted as PSKmail is rolled out in parts of South Africa.

Johan Terblanche
Founder: SAWDIS
Mossel Bay
29 July 2011