Sunday, 23 February 2014

PSK-20 working, plus Sudden -2 and a voice keyer

Most of today was taken up with Sams karate grading, so it was very late that I was free to play with any projects. Sam passed and is now 8th Kyu, which meant I had to cook his favorite tea - lasagne. With a good meal and a few bevvies in me, I found a few moments to complete the modifications of the PSK-20 transceiver.

The RF sniffer circuit needed to be as small and as close to the antenna connector as possible. So I decided to build it 'ugly' with all the parts having their leads cropped back as far as possible. The 2k2 resistor is soldered directly to the pin of the BNC socket, and the ground connections are straight to the ground-plane of the PCB.

With the mods done and a power cable made up, it was time to add power!. Always a daunting time, she fired up with no obvious signs of distress, and a healthy green power LED. I had calculated the current limit resistor for the power LED based on a 13.8v supply, which came out as 1k2, so I bumped that up to 1k5 to give a bit of leeway.  I then connected the audio out to the USB sound-card on the laptop. Hmm, nothing? Ah, plug it into the microphone port! Despite it being late evening, several PSK signals began to scroll down the FLDIGI waterfall.

Whilst connecting the antenna patch lead from the rig to the ATU, I had to move a few half finished projects out of the way. One is a Kanga Kits Sudden-2 receiver. This is effectively 'finished' apart from a case and knobs,

but it has provision on-board for an audio filter. After contacting Kanga, I now have the schematic of the filter, and as its pretty simple im sure I have the parts somewhere already, so I intend fitting that before boxing the project up. I already have a large plastic box for this, selected with the intention of it having an internal battery.

Also knocking about on the desk was this little digital voice recorder that cost me about two quid from Hong Kong a good few months back

 This was supposed to have been wired up to the headset system of my mobile installation, so I could call CQ whilst driving and not worry about my throat drying out! But when the rig went faulty this got forgotten about. I really ought to get it finished!

Ive run the PSK-20 now into test load, and also a quick test burst to air. No QSOs as yet, as I want to check the levels etc first and make sure every things aligned properly. In idle mode, with full audio drive the power meter was reading a good steady 3W. As idle mode is a 50% duty cycle, I need to back the audio drive off to a point where an actual data transmission gives 3W, which I think means idle should be about 2W. I'll sort that tomorrow and give it its first real run out on air.

The rather out of focus picture above shows the PSK-20 on receive, with the power LED lit. On Tx, the red LED below is driven by the RF sniffer and lights brightly, flickering slightly with data modulation. I will put the case back on tomorrow. My only concern is that the PA heat sink does get bloody hot. Perhaps the addition of a small cooling fan could be useful here.

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