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 the rest of this entry »
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.
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 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.
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 :
The DXrobot

The DXrobot

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I noticed today that the Software Defined Radio from Twente University now has six bands to play with :  0-150 kHz, 1790-1930 kHz, 3500-3760 kHz, 6990-7135 kHz,  10030-10175 khz, 14000-14290 kHz. But it lasts only a few days, so enjoy :
Last sunday I attended a hamfest in Bladel, The Netherlands, organised by PI4KAR.  From my qth it is a one hour drive to one of the niciest and last hamfests of the year. I had no special needs to look out for but after a while I stumbled on a Diamond W735 antenna. The W 735 is a 2-band loaded dipole for 80 and 40m. Overall length reduced from normal dipole dimensions by use of loading coils rather than traps. Overall length is 26m, fits just on the roof. Read the rest of this entry »