This post is taken from my old website. I’m still dismantling that site.
What is PMR446 anyway ?
PMR446 stands for Personal Mobile Radio and is a license free radio in the 446 MHz UHF band. That is about 6 Mhz above the 70cm amateur radio band. There are 8 channels starting at 446.00625 MHz and ending at 446.09375, spaced 12.5 kHz apart. Read more
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 :
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.
So 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.
I just noticed in Google Analytics that I passed the 10,000 visitors benchmark. My blog started in March 2008 and I installed Analytics around March 22.
So from March 22 2008 till now (Feb 3 2009) I had 10,381 visitors.
About 75% comes from search engines and merely 18% via other sites. This is a figure that can be better. Work todo !
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 WSPRnet.org site : http://wsprnet.org/drupal/node/384
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 :
On several sites you’ll find some html code showing the Aurora status, European and North American Eskip status. These images are created by the DX robot, maintained and ran by Allard Munters PE1NWL. You know what I mean if you can see it :