KC Northland ARES (WØKCN)

PSK

PSK is a digital mode of radio communication enabling keyboard to keyboard communication over radio as well as small file transfer between stations. PSK has applications in emergency communication because text-based information can be more easily transmitted digitally than over voice communication. PSK stands for Phase Shift Keying which refers to the way the signal is formed by the PSK computer interface before being transmitted over the radio. Because of the nature of PSK, it is very tolerant of poor weather conditions, it requires very little output power, and due to the narrow band width of the signal, PSK makes very efficient use of the spectrum.

NLARES Standards

Northland ARES recommends NBEMS (Narrow Band Emergency Messaging System) as the defacto standard for PSK operation. There are a number of PSK interfaces available, many for free or a small registration fee. NBEMS however is written with ARES and emergency communication in mind and has been adopted by ARRL as the standard for ARES emergency communication use.

The interface is simple while providing access to a wide range of operating modes. One needs only learn the interface once and can then operate any of the additional supported modes as well. In addition, supporting one interface allows much easier training and support for users and some standardization of settings and capabilities. NBEMS consists of two interfaces, FLDigi for keyboard to keyboard communications and FLARQ for station-to-station file transfers.

For further information regarding NBEMS, please visit the application’s website at http://www.w1hkj.com.

Recommendations

Any ARES member with an interest in digital communications would be well served to become familiar with and practiced in the use of NBEMS for PSK operation. Having a good working knowledge of PSK through NBEMS provides the operator with an additional means of communication and support for ARES efforts. As this group moves into more digital communications responsibilities, increased demand for digital communications will be seen. The need for qualified operators is ever-growing so increased use, knowledge, practice, and implementation of this mode is a must. Members interested in this capability should make use of the software and should participate in any activities incorporating PSK into their communications needs.

Software:

Windows:

fldigi from http://www.w1hkj.com/Fldigi.html

DigiPan from http://www.digipan.net/

Multi-PSK from http://f6cte.free.fr/index_anglais.htm

Mac OS:

fldigi from http://www.w1hkj.com/Fldigi.html

cocoaModem from http://homepage.mac.com/chen/w7ay/cocoaModem/index.html

PC/Radio Interfaces

West Mountain Radio RIGblaster

Recommended RF Settings

Primary VHF operating frequency: 145.750 Mhz FM Simplex

Getting started

Getting started in PSK operation is easy. There is a wealth of information on the Internet for PSK or Phase-Shift Keying. PSK is very tolerant of poor operating conditions, and it makes very efficient use of the bandwidth. Along with the NBEMS website (http://www.w1hkj.com/), there are a number of websites devoted to general PSK usage and operating principles. A Google search of PSK should reveal a long list of support options for the reader. In short, a computer, 2-meter radio, and a simple interface to connect the two are all that are needed. A wide range of interfaces and prices exists from a simple cable to more sophisticated units. Prices and capabilities vary and are beyond the scope of this document. Seek out opinions on sound card interfaces before getting started. Nearly any Northland ARES member who participates in the digital work will be able to provide assistance.

What is a waterfall and what are the different modes.

The NBEMS interface provides for a variety of different transmission modes. For example, PSK31, PSK63, MT63, Olivia, and others are available under the PSK interface. A pull-down list simply makes each of these modes available. A common characteristic of soundcard modes and soundcard interface software is a waterfall. A waterfall is a graphical representation of the signals heard on a particular frequency. Since PSK has a narrow bandwidth and makes very efficient use of the radio frequency spectrum, many separate signals can occupy different hertz values within the same frequency. Each signal appears as a pair of closely spaced vertical lines or a “waterfall” on a spectrum display. Well formed PSK signals have a very definitive appearance on the waterfall and this can be used to help an operator tune their signal by adjusting their volume level to improve the signal quality.

How do we interface this with the counties and Hospitals?

Both Clay County EOC and the Mobile Incident Command Post have PSK capabilities. A PSK station consists of a computer with PSK software such as NBEMS, a soundcard interface, and a transceiver. Volunteers anticipating serving at either station are strongly encouraged to become familiar with PSK operation.

Why would we use this in a disaster or emergency over Winlink?

Although serving similar functions, PSK and Winlink function in different ways and serve different purposes. For example, PSK is a keyboard to keyboard mode for one-to-many communication in which text-based data can be transferred efficiently. When using PSK, the exact list of recipients need not be known. Anyone able to receive a transmitted signal can, with the appropriate PSK software receive and understand the transmission. Likewise, Winlink offers a means to communicate text and files, but it does so over the Internet so the recipients must be known at the time the message is formulated. Also, unlike PSK, Winlink is not for immediate 2-way communications. Just like conventional email, the recipient must actively query an email account for new messages while PSK communication is live immediate interaction. In short, in a disaster, any text-based communication in which the recipients are not known or are part of a disaster response and are directly available for live communication, and in which the nature of the communication is not sensitive, private information, PSK is a means to make such a communication. When the nature of the information is sensitive or private, and/or when the recipient(s) is known and a live two-way communication is not needed, then Winlink can fill that role.

How do I send a picture to the county?

Using NBEMS, a picture or other small file can be sent to County Emergency Management. The FLARQ interface in NBEMS allows for a station to broadcast its willingness to share a file, in this case a picture. Such a broadcast is called a “Beacon”. A beacon is an invitation to connect for a file transfer. When a beacon is heard on the sending side, a station using the FLARQ interface can reply to the beacon with a “Connect” transmission. Once transmission is answered, a negotiation ensues and the two interfaces determine the right speed to use to make the transfer. The rest of the process is automatic. A file is transferred from PC to PC over RF and the mission is accomplished.