Tuesday Digital Modes And Morse Net

Following last night’s experiments on 10m by a few club members, it was decided to start a regular digimodes net, beginning next Tuesday evening, at 2100 local, on 28.115MHz¹.

The initial mode we will be using on Tuesday will be PSK31. In the main, signals will be horizontally polarised². Most participants will be using FLdigi, and 5-10W of power to the antenna, although this is in no way mandatory – use whatever you have that will allow you to send/receive using this mode.

Anyone in the SW region is welcome to participate – we have very little idea at the moment of how far our signals may propagate.

We have also done some experimentation on the 28th June with using FLdigi generated Morse as an alternative. Using Morse has the advantage that people learning Morse can catch the odd letters by listening to the incoming signal, while FLdigi then shows the decoded character on the screen just after hearing it. For Morse, our settings are 18wpm and Farnsworth timing OFF. 18wpm is fast enough that you don’t end up counting dits and dahs. Without Farnsworth timing it’s hard to catch the characters, but you do slowly get used to them, and get to hear the sound of some common words and callsigns. You don’t have to listen to the signal if you have no interest in learning Morse. Although not designed as such, with the improved performance of computer decoding - it is a serviceable datamode in its own right.

If you use the recommended method of running a second sound card³ or digital interface for the radio, or a modern rig that presents a USB audio interface, then you can listen to the received signal via FLdigi’s monitor mode. This allows you to listen to either the unprocessed signals or just the bandwidth you are looking for, effectively a downstream CW filter on the received 3kHz wide USB signal.

1. That is the signal frequency - if you use the typical FLdigi sweet spot frequency of 1.5kHz and USB on the rig, then you will have to set the dial frequency to 28115kHz-1.5Khz, ie 28113.5 kHz. 1.5kHz is a bit high for listening to Morse - we normally use 750Hz, so you will need to set up Morse for a sweet spot of 750Hz and a dial frequency of 28.114250 MHz (USB) if you want to listen to the signal. FLdigi lets you configure the sweet spot differently for the various classes of modes. If you simply want to use Morse as a datamode, there’s nothing wrong with leaving things set to 1500 ↩

2. in practice, within the Glastonbury area cross-polarisation is not a problem, so if you want to use an old CB groundplane vertical antenna it will work fine on the groundwave signal with the link budget of digital modes and QRP power levels. ↩

3. using a dedicated sound card for the radio is recommended so that you don’t risk splurging Windows sounds onto the air, in this case you can also take advantage of FLdigi’s monitor facility and filtering as described. ↩