Wednesday, 5 February 2014

40m WSPR beacon now QRT

I shut down the 40m WSPR beacon at exactly 22:00 after a successful test this evening. The USB sound card is behaving and working quite well. Both transmit and receive were doing good throughout the evening since switching over to the new soundcard, so I decided to call it a day at that point. I just had a brief nosey at what was going down on 40m PSK before closing the shack.

Ive now been awake 30 3/4 hours, including working a night shift, a hospital visit and a karate training session, and think I really ought to stop playing radio and get some kip.

So of course, before shutting everything down I popped into the workshop to take those modem cards and the new 3.5mm stereo jack sockets and put them in stock, and to move the 4m transverter out of its box and onto the bench ready for some more work tomorrow. I had noticed a musty smell and discovered that all the recent heavy rain had seeped in in one corner and the bag for the Larkspur mast kit was damp, thats now been moved and I will run the heater tomorrow to help dry everything out.

Whilst in there I took the meter to the potentiometer on my mocked up level control. Hmmm, its a 100k pot and it reads - 100k. Checked the wiper action and wherever on the track I had the wiper the value came out about right. So not the pot then. I then tested the jack plug... bugger, open circuit to the center pin! This isnt the first of these ive had that with, this particular batch had a few duffers in it. It seems for whatever reason the center pin isnt properly crimped onto its solder tag. I dont know if its salvageble, perhaps the center pin can be soldered to directly. So I will make up another plug for it tomorrow and retry the maximum value setting exercise. I now have a rough maximum level to aim for, a mere 10mV, and the design of a suitable 40dB 'T' attenuator to make a fixed maximum control. I need to do this exercise on the soundcard mic input as well, to nudge the noise level down a bit closer to the ideal of 0dB. I dont think that will need as much attenuation though!

I also need to dig out a big heatsink and plan a board layout for a build of ON6MU's 7W HF linear amplifier design. This is a 10dB gain linear that I intend driving with a 500mW input, or theres about, from the 10m Wispy. Once Mark has had it on his test bench I should know just what power I have available as drive for the linear, and hence my maximum power. David G4HMC has very kindly offered me a VN66AF power MOSFET, which is the active device. I dont wish to go too high, as Wispy is a DSB transmitter, and the lower sideband will become a nuisance to others at more than a few watts. I'd like an ideal of 5W SSB equivalent, but will see what I can drive the linear to. IF I can hit 3.5W equivalent (7W DSB) then that will do fine.

And now, children...

Boiiiiinngggg, said Zebedee, time for bed.

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