Digital Modes

Having recently returned to the hobby one of the first things I noticed was the popularity of digital modes. When I  stopped operating in 1998 digital modes were still costly to operate. Now with soundcard interfaces, digital modes can be operated with little investment as almost all computers have SB16 compatible soundcards.  Well, upon seeing all that was available I dove right in of course and enjoy it quite a bit.

So far I have stuck mostly to PSK31 operation. I'm amazed at how well PSK31 gets through even the noisiest band conditions. I am currently using PSK31 Deluxe  that is included in the Ham Radio Deluxe software suite, but have tried DigiPan, MultiPSK, and a couple of others. So far for PSK operations I have preferred the PSK31 Deluxe.

After reading a post from KD5DE - Mel, Digital Awards Manager for Ten-Ten, on the tenten list server I have learned a little about Feld Hell. Feld Hell has been around for awhile and is a fun mode to operate. If you suffer from poor eyesight you will enjoy it's large text and double lines. There is also a Feld Hell Club that issues operating awards for Feld Hell contacts. I use MultiPSK software for Feld Hell.

RTTY is the mode that is next on my list to operate. This mode seems to be just behind PSK in popularity. I have monitored some RTTY but have not jumped in and made any contacts yet.

If you would like more information on the following modes click on read more to continue where I will give brief descriptions and operating frequencies of each of these modes.

PSK means Phase Shift Keying at 31 baud.

It is a digital communication mode developed by Peter Martinez. It modulates the phase of a single audio tone, transmitted normally in USB mode. The transmission is always at 31.25 baud, with a variable length code (Varicode), where characters used more often have shorter bit codes. As a result, the mean transmission rate is about 50 words per minute.

When you plan to run PSK:

• Keep your macros short. 
  • PSK is about 1/3 slower than RTTY; you can really impact your rates with wordy macros
• Use lower case letters wherever possible. 
  • PSK is a varicode mode. That means that characters contain a variable number of bits, unlike ASCII characters that have a fixed number of bits. Most lower-case PSK characters have fewer bits in them than their upper-case equivalents, so lower-case (in general) transmits faster.

On the radio make sure:

• Audio processing is off
  • Speech processing is off
  • Hi boost is off (Kenwood radios)
• Radio should be in USB mode
  LSB is also possible but normally USB is used.
• Don't overrun your finals from the transceiver and/or amplifier
  • 50 percent duty cycle is mostly ok Using lower case letters instead of all caps, will increase speed and reduce TX time.
• Only 100 Hz is needed as channel separation.
• Example filter usage:
  • Available 2.4 kHz / 250 Hz /100 Hz filter bandwidths.
  • 2.4 kHz is used for monitoring the PSK area of band when in search and pounce mode.
  • 250 Hz and 100 Hz filter bandwidths are used when in run mode.

Operating frequencies for PSK31

1838.150
3580.150
7070.00
10142.150
14070.150
18100.150
21080.150 (although most activity can be found 10 kHz lower)
24920.150
28120.150

HELLSCHREIBER is a method of sending and receiving text using facsimile technology. This mode has been around along time; the recent use of PC sound cards as DSP units has increased the interest in Hellschreiber. The single-tone version (Feld-Hell) is the method of choice for HF operation. It is an on-off keyed system with 122.5 dots/second, or about a 35 WPM text rate, with a narrow bandwidth (about 75 Hz). Text characters are "painted" on the screen, as apposed to being decoded and printed. A new "designer" flavor of this mode called FM HELL has some advantage for providing better quality print, at the expense of a greater duty cycle. As with other "fuzzy modes" it has the advantage of using the "human processor" for error correction.    Article from Feld Hell Club and Murray Greenman ZL1BPU  www.qsl.net/zl1bpu

Frequencies for Feld Hell

160 METERS  1.804   
80 METERS   3.574  
40 METERS   7.084 7.039 (DX)
30 METERS   10.134 10.144 (Region I)
20 METERS   14.074  
17 METERS   18.104  
15 METERS   21.074  
12 METERS   24.924  
10 METERS   28.074

The RTTY mode is a traditional mode used by radio-amateurs and use two frequencies which are filtered, each one corresponding to a binary digit (1 or 0). These two frequencies, separated by a shift, modulate the RF when transmitted and the modulation is called Audio Frequency-Shift Keying (AFSK), otherwise the modulation can be done directly on the RF carrier and it is called Frequency-Shift Keying (FSK).

Frequencies for RTTY

80 meters: 3580 - 3650 (3520 - 3525 in Japan)
40 meters: 7080 - 7100 in the US
30 meters: 10110 to top of band
20 meters: 14080 - 14099 (avoid the beacons at 14100)
15 meters: 21080 - 21100
10 meters: 28080 - 28100

Introduction to PSK31

Sample of 20 meter PSK31 Activity

Soundcard Interfacing