Mike, You might want to compare the Bitscope 310 with the Velleman PCSU1000 60 MHz PC-based scope. Depending on where you buy it, the Velleman is about half the price of the Bitscope. It doesn't have the eight separate logic channels and built-in function generator, but it has most of the rest of the features of the Bitscope, and more. The Velleman software appears to be superior, too, thought I'm only basing that on the feature lists -- haven't actually used the Bitscope software.
I'm pretty pleased with the Velleman PCSU1000, but there's one task I haven't been able to get it to do yet: display the CW envelope. I'm not sure if this is due to not feeding it a clean trigger signal (I think the output from my keyer needs to be buffered) or if scope sample rate isn't high enough. I don't know the exact technical details of how sample rate figures into these PC-based scopes, but I imagine like any A/D converter they periodically sample the waveform. The higher the frequency and resolution, the higher the sample rate required. The Bitscope 310 lists a 40Ms/s maximum sample rate, and the Velleman has a max of 50Ms/s. The sample rate used depends on the sweep rate (lower sweep rate = lower sample rate.) But the Velleman has a 1Gs/S rate that can be switched on for four of the highest sweep rates (.2us, .-1us, .05us and .02us.) When viewing a 7MHz signal from my K3, I found the waveform "wobbled" unless I used the 1GS/s modes. Then it was rock steady. When displaying the K3 CW envelope, I fed the signal from my keyer into one channel and the RF into the other channel (I use a Bird RF sampler between the K3 antenna port and antenna or dummy load.) The keying signal displays fine, but the CW envelope doesn't. Depending on the volts/div, the display is anywhere from a random-looking splotch of dots to the waveform you would expect, but with gaps and holes. The only way I can display the waveform properly is to use the software's Persist mode, which keeps all traces on screen. Eventually, the gaps in the trace fill in and I see the waveform displayed as it should be. But there are limitations when doing this: it's hard to line up the waveform with the graticule to estimate time duration, and the Velleman software Waveform Parameters page, a great feature which displays many measured and calculated values for the waveform, shows a bunch of question marks. Obviously, the Vellemen doesn't quite know what to make of the composite waveform. I mention stability of the keying signal because even when I do this test on my old HP 1725A 275 MHz scope, the CW envelope wobbles back and forth. I'm pretty sure this is due to the keying signal not providing a clean trigger source. I'm planning on building a little buffer circuit for the keyer to clean up the signal. If the HP can display a steady CW envelope, it's possible the Velleman can. Otherwise, it may have something to do with the sample rate being too low. at the slow sweep speed required to display the CW envelope. Hope this is helpful. 73, Dick WC1M > -----Original Message----- > From: Mike Walkington [mailto:[EMAIL PROTECTED] > Sent: Friday, September 12, 2008 10:06 PM > To: Elecraft-Reflector > Subject: [Elecraft] OT - PC Oscilliscope Performance > > All, > > Just found this PC based oscilloscope > http://www.bitscope.com/product/BS310/ > and wonder what you think of it. Yes you are limited by needing a PC, > but > the waveform generator, spectrum analyser and logic analyser > functionality > seem to be most versatile. > > Mike > VK1KCK > K2 #2599 > _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
