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One of my dream purchases for radio is a functional spectrum
analyzer that is reasonably accurate. I use a dongle right now as
a 'poor man's spectrum analyzer", although it has some serious
limitations - like taking things in a 1mhz 'bite' at a time, plus
compression of the signal makes db measurements only an estimate
at best. It works for checking for deviation or for spotting
unwanted signals, but not that well.
The bottom end of my dongle is also around 25mhz... I have some
parts to cobble together an up-converter, but haven't had the time
to work on that (first I need to get my old HF rig going again).
I know that there are some kits out now (plus units from China)
that work, but their price is outside of my reach. Maybe things
will get better!
On 7/31/19 10:43 AM, Ashhar Farhan
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..
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.
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@...
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.