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Receive digital text and images via 144/440 MHz FM


kd9xb
 

Hello friends,

On 2 meters and 440 MHz FM, in addition to our usual voice QSOs, we can also receive and transmit text and images, using software now available free to the amateur radio community.

A few years ago, I conducted a digital "after net" following the Tuesday evening Arlington ARC 2M net. I'm planning to resume these digital transmissions (digital via analog FM, actually). To decode the digital modes, and perhaps even to try transmitting them yourself, please download and install the Fldigi software ...

http://www.w1hkj.com/files/fldigi/

or here:

https://sourceforge.net/projects/fldigi/files/

For decoding, all you need to do is get the audio from your radio into your PC. This usually involves a patch cord from your radio's headphone or audio output, into the mic jack of your PC. You can also try "acoustic coupling," which can be accomplished by placing your HT's speaker next to the mic on a laptop.

Then configure Fldigi for the appropriate audio device. If you have a newer transceiver with a USB connection, Flidigi might recognize your transceiver as an audio device.

When using Fldigi, select RxID at the top right. That will automatically detect the mode being used, and the correct audio frequency (usually 1500 Hz).

If you want to transmit digital modes, an interface such as the SignaLink or RIGblaster is very helpful, although if your transceiver has the aforementioned USB connection, you may not need the interface.

I recommend Fldigi for relative east of use and installation, but you might also want to look at MultiPSK ...

http://f6cte.free.fr/index_anglais.htm

MultiPSK has some modes and features not included in Fldigi.

Android apps

There are also apps for Android that will decode the modes.

AndFlmsg encodes and decodes, so it can be used for transmitting as well as receiving. And it has recently been updated. It can be downloaded from ...

https://sourceforge.net/projects/fldigi/files/AndFlmsg/

TIVAR, a simpler receive-only, decode-only version of AndFlmsg is available here ...

https://sourceforge.net/projects/fldigi/files/AndFlmsg/TIVAR/

For decoding using Android, patch cords can be problematic, so it might be easiest just to use acoustic coupling, i.e. placing the HT next to the Android device (radio's speaker near Android's mic).

HF digital nets

In addition to receiving and decoding the modes on 2 meters and 440 MHz FM, there are some HF amateur digital nets that can be decoded using Fldigi and the Android apps. These NBEMS (Narrow Band Emergency Messaging Software) nets usually take check-ins in the Thor22 mode (78 wpm), and messages in MFSK32 (120 wpm). If your radio has a digital (dig) mode, use it. Otherwise, use USB. If you can, feel free to check in!

Nets in our region:

New York NBEMS Net
Saturday 0800 EDT
3584 kHz USB (sometime difficult to hear in Virginia during the summer)

Pennsylvania NBEMS Net
Sundays 0730 EDT
3584 kHz USB

US East NBEMS Net
Wednesdays 1900 EDT
3536 kHz USB
Check-ins in MFSK16, messages in MFSK32

Most evenings you can hear and decode similar nets and digital QSOs around 3585 kHz, plus or minus a few kilohertz.

Shortwave Radiogram

Another workout for your Fldigi software or apps would be my Shortwave Radiogram project. Digital text and images are transmitted by shortwave broadcast stations in Florida and Pennsylvania. Information is at http://swradiogram.net .

Shortwave Radiogram Schedule
(days and times EDT; frequencies in kHz):

Thursday 7:30-8:00 pm 9265 from WINB Pennsylvania
Friday 9:00-9:30 am 15770 from WRMI Florida
Friday 11:00-11:30 am 15750 DRM from WINB Pennsylvania
Friday 10:30-11:00 pm 9265 from WINB Pennsylvania
Saturday 9:30-10:00 am 15770 from WRMI Florida
Sunday 4:00-4:30 am 5850 and 7730 kHz from WRMI Florida
Sunday 7:30-8:00 pm 7780 from WRMI Florida

(Here in Arlington, because we are only 75 miles from their transmitter, WINB is usually difficult to receive.)

Let me know if you have questions: kimelli@...

73
Kim
KD9XB