Re: Cool cheap oscilloscope for troubleshooting

Jack, W8TEE

My club has a small knot of members who enjoy building stuff. Like everyone else, most of them can't justify the expense of $250 for a decent oscilloscope. One of our "serious" builders in the club upgraded his scope and donated his old scope to the club. Now anyone can use the club's scope for a project. So far, there's not been enough members wanting to use it at the same time to be a problem. This is now a benefit of being a member..access to some pretty decent test equipment. That same member gave a presentation on how to use the scope and it was well-received.

I guess my point is: Instead of spending $25-$50 on a device and may or may not be sufficient to get the job done, consider acquiring a scope for the club. A new scope good to 100MHz is about $250, but hamfest, Craigs List, and other places have good used scopes at reasonable cost. Depending upon the size and makeup of your club, it might be a viable solution.

Jack, W8TEE

On Wednesday, July 31, 2019, 10:43:48 AM EDT, Ashhar Farhan <farhanbox@...> wrote:

An easy way to extend the upper frequency range of an oscilloscope is to use a 'down converter' - a diode mixer driven by a VFO, like a direct conversion receiver. The mixer output is fed to the oscilloscope.
About ten years ago, I wrote in a blog post that serious homebrewing needs a good scope. I must revise my claim. You need a spectrum analyzer of some sort. The reason is that our work is frequency domain.  Our circuit blocks are filters, mixers, amplifiers and oscillators. All of them have inputs and outputs specified in terms of frequencies.
It is this realization that led to the development of antuino. But that is a separate post..

On Wed 31 Jul, 2019, 6:10 PM Roy Appleton, <twelveoclockhigh@...> wrote:
"Of all the cheap oscilloscopes we have tested, we are the most impressed with this DSO188. Despite the small dimensions, the scope is easy to operate and the oscillogram is easy to interpret. It is easy to live in practice with a service life of about ninety minutes with one battery charge.
The only unfortunate thing about this beautiful device is that the DSO188 cannot be used to reliably measure the numerical values of the input signal. The manufacturer should have omitted this option, because a measurement function that is 'for reference only' is not very useful in practice. "


On Tue, Jul 30, 2019, 1:50 AM Tom, wb6b <wb6b@...> wrote:

Anyone looking for a low cost scope to trouble shoot (a least audio and low frequency such as encoders) parts of their UBitx, these little oscilloscopes were on sale. I bought one. It only has a 1 Mhz bandwidth, but that is better than the 200 Khz bandwidth on many of the other cheap tiny scopes. 

So far I've liked it and have use it for observing some pulse width modulate signals where the frequency and duty-cycle readouts were handy. It is totally isolated when running on its battery. That is a nice feature. 

I have another radio with an intermittent causing both the transmit power and receive signal strength to abruptly change. Am planning to make an RF detector probe with a diode and capacitor and just leave this little scope attached to various points in the RF chain to see where I see the signal change in step with the change in my transmit power or S meter on receive (particularly the background noise floor on the S meter). This little scope won't take up a bunch of room while doing these measurements and may provide me with a little more interesting information than a DVM.

Here is a review on a site that specializes in trying out low cost Chinese electronic gizmos. Not sure if my later model is calibrated better than the one he tested, but did not strike me as really bad.

Tom, wb6b



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