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DigitalSpy Forums | Talk Photography

psk31 - a day at the keyboard 17 Oct '09, 18:39

I know I said I wouldn't do anymore serious testing until I'd built a new PC, but I just couldn't help myself. Over the last few days I have been active on 20m with reasonable success.

After experimenting with different settings on the computer soundcard and the audio levels on my interface, I came to the conclusion that running the sound output from the PC at 100% for both the master volume and PCM volume was a bad idea.

I can't say why this didn't occur to me before especially considering I'd noticed audio distortion on other computers when listening to music with the levels at 100% - I'd always reduce them slightly with significant improvement. So it was, that after various tests I came to settle on the master volume at 90% and the PCM fader at approximately 50-60%. Further adjustments would then be made at the soundcard interface.

The other conclusion I came to - and this is almost certainly ludicrously obvious to all seasoned PSK operators out there - is that adjustments to the audio level need to be made after each change in frequency made on the computer. The higher the audio tones (higher frequencies) the louder the audio going in to the radio needs to be. When changing to lower frequencies, the audio volume needs to be reduced to maintain the same power level.

Now I've made these discoveries, I've had a lot more fun! Since I had today to myself, I decided to make it a radio day and have been pretty much stuck to the keyboard calling CQ and answering the calls of others. I'm still limited to around 10w of power since higher levels continue to interfere with the keyboard; but - and here is another revelation that will be obvious to the old-timers - power isn't everything.

To give an example of the success I have had today, I have made contacts with operators in Spain, Sweden, Italy, Poland, Slovakia, Ukraine and Russia. Perhaps that doesn't sound too remarkable, but considering my balcony mounted whip aerial I'm very pleased. To top it off though, according to the PSKReporter map, which I monitored throughout the day, my signal was reported as being heard in Canada! That is something I'm really pleased about.

What I do find strange though is this keyboard interference. All day I have been transmitting with 10w of power - sometimes creeping up to 14w. The keyboard has been fine. A key may occasionally not respond but it was easily workable. However, about half an hour ago when working RX6BH in Russia, the keys became very unresponsive making typing during transmission a nightmare - it was slower than transmission rate of PSK31! I'm not sure why this would be. Nothing had changed. The power level was peaking at 10w initially, and I even reduced it slightly to no effect.

Actually, I'm wrong. Something had changed. I'd switched on the lights in the flat. Could that be what makes a difference?

Related Blog Entries:

11 Oct '09, 18:34
PSK31 - First Experiences
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Ben 20 Oct '09, 22:09
Hurrah - I found the missing eQSL cards! Now I've got 4!
Ben M0GKY 19 Oct '09, 22:50
Already got a couple since signing up to eQSL.cc - including one from you and one from G0VHF/P both which, annoyingly, I seem to have lost. Must get some proper cards printed up at some point.
Charlie - M0PZT 19 Oct '09, 22:29
Talking of mementos, I've finally scanned in some of my old QSL cards - they're now on the M0PZT site. I shall be expecting a huge gallery on your site soon!
Ben M0GKY 19 Oct '09, 20:00
Cool - first time spotted! Being the geek that I am, I've taken a screengrab as a memento! :)
Charlie - M0PZT 18 Oct '09, 20:30
I see RN6BA spotted you on the cluster, nice one.
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psk31 - first experiences 11 Oct '09, 18:34

Over the last month, I've been preparing my station to operate on digital modes by building a radio to soundcard interface. After various hurdles I finally got the device working and conducted my first on air test yesterday, using PSK31.

Unfortunately it wasn't overly successful. I can only get the radio to output around 10-12W maximum before the ALC kicks in causing horrendous noise on the signal. I also have some interference problems with my keyboard which makes operating difficult. It was originally the case that only a couple of watts of power would cause the keyboard to lock up (and the mouse too after a bit more power). Now I've enclosed my cheap USB hub and slack cable into a metal case to improve shielding. I've also added ferrite beads to the keyboard cable, mouse cable and the USB hub cable. Although it's improved the situation significantly, when the power level gets over about 8w, some keypresses are missed resulting in "wods tped ike is" (words typed like this).

Despite these problems, I did spend a good while calling CQ and had a very brief QSO with Cris, YO5OAW in Romania. We exchanged reports and location information but due to a fading signal and the problems typing I decided not to stop and chat. PSKReporter also showed my signals being received in Portugal and Rome.

Charlie M0PZT did suggest that using a laptop could be the cause of some problems due to its unshielded nature compared to a desktop PC. I think that's quite likely considering the monitor also receives interference which disappeared when testing with a desktop machine.

So before I try another serious attempt, I think I'll replace the laptop. I'll be building a cheap PC which I reckon can be done for less than £140.00 while still being a machine of fairly modern specification (Intel Celeron Dual Core 2.2GHz, 1GB DDR2 667MHz RAM, 80GB SATA HDD, Wireless LAN, onboard Realtek 5.1Ch audio, onboard Intel graphics) with room for expansion should I need it.

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17 Oct '09, 18:39
PSK31 - A day at the keyboard
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