Archive for the Digital Mode Category

When watching a documentary today I noticed that the makers used the very known rtty sound when they are talking over wireless communication. I remember that in the James Bond films of the 60’s and probably the 70’s also they use the same sound. I guess it is a 75 or 100 baud rtty sound.

Even in modern shows or films it is used.  Who has a better and more up to date sound that can be used ?

My top 5 of my best dx using wspr. On 20m the antenna is a half wave vertical. On 80/40 and 30m I used the Diamond W735 with an extra dipole for 30m. This antenna hangs just 2 meter above the lawn.


Ham radio operators interested digital modes will often use these computer interfaces to automate CW contacts (send morse code from the PC), use the PC soundcard for RTTY and control push-to-talk functions among other things.
Many of the PTT interface drawings  found on the net suffer the same problem. Well it is not really a problem.

Let’s have a look at a typical interface :interface_before.jpg
You have the RTS and DTR line tied together with diode, then comes a transistor that operates as a switch. And finally the ptt line from you transceiver. So when the RTS or DTR signal goes high, you are on the air. So what is the catch ? Ever booted your computer or used other software besides your regular hamradio soft ? Of course you did 🙂 and what happened ? My transceiver went in to TX on the wrong antenna / receive converter / mistuned antenna. Luckely the radio was set in SSB and no harm done without modulation. But it could be worse.

interface_after.jpgSo what have I done ?
A simple modification that costs almost nothing : add a simple switch in the PTT line. See the red switch in the interface drawing.

That’s it. When the computer has booted and ready to use, I toggle the switch and can operate the digital modes.

A friend of me asked if I could detect some WSPR signals on 20m. He has been monitoring it a while without any activity.
I also read the comments of G4ILO on the site :
I must admit that I was also stuck on 30m.
He made a statement and yesterday I had a day off. A whole day of listening later this is what passed my screen :

Timestamp        Call   MHz       SNR Drift Grid   Pwr Reporter RGrid  km    az
2009-01-21 10:48 EA1FAQ 14.097137 -24  0    IN71op 0.5 ON3JT    JO21fe 1274   30
2009-01-21 09:58 VK6BN  14.097091 -23 -1    OF88ac 10  ON3JT    JO21fe 14167 313

Not much.

Hey guys, if you want that propagation monitoring works, we need to activite all bands.

ON3JT_WSPRTonight I used WSPR again to see the activity on 30m. Now I received about 7 stations from the USA, Hungary, Spain, Switzerland, UK and the Czech republic. After a few hours I ticked the 20% T/R option. This switches the transceiver on for 20% of the time and the remaining 80% listening.

And yes, my signal gets out. Using only 2 watts my signal is picked up by VK6KHD, Nigel in Australia. My first.
That is about 14190 km or 7095 km per watt or very very far from my qth 🙂

Last saturday night my computer has been running all night long the WSPR (whisper) software from ….. to see if I could receive that mode too. My wife had the night shift in the hospital and could not argue that the computer is making too much noise in the bedroom 🙂 That is the downside of having the shack in the bedroom.
I set the receiver to 10.138.7 in the 30m band and went to bed.


After reading this site : I modified my Icom IC725 with a similar capacitor. It worked more or less. Switching to the CW-N mode on my trx and decoding with Dream I could listen to some DRM radiostations. At that time the only antenne I could use was a magnetic loop, mounted near the window. Not the setup that everyone dreams of 🙂