People who like to experiment with microphones

What are you talking about?

Common scopes have over 30mhz of bandwidth, uncommon ones that are expensive have over 5ghz of bandwidth.

Anyone with any means of buying a good signal generator used, can afford a good scope that works well with CB radios.

 

Why?

Explain it.

 

Rule of thumb for the bandwidth of an oscilloscope has always been to use one that has at least 3 times that of the frequency being examined.

If all you want to do is measure the frequency than you can do that accurately well beyond the rated bandwidth but you could also just do that with a frequency counter.

The article at https://blog.adafruit.com/2012/01/27/why-oscilloscope-bandwidth-matters/ can explain why you need bandwidth beyond the frequency you are looking at to get any sort of accurate measurement of amplitude.

 

Thanks Ubu. I read that a while ago but very helpful.

OK here is the thing, I am asking so others can figure it out.

IF we take lady Ada's post at face value, then there is a 70% (-3db) compensation at frequency that is needed so why I questioned Rabbi is that his claim of 80 mhz is needed in order to compensate for that loss. However if we take the 70% rule as mentioned, that works out to be a little under 50 mhz to achieve that needed compensation at the CB frequencies.

Now taking another issue in account, the user of a CB isn't using the scope to measure voltage levels at RF test points at CB frequencies but rather to observe waveforms of a modulated signal, leaving the needed -3db loss insignificant.

Many use scopes for IF alignment and PLL alignment but overall those are not what I'm talking about.

 

For the audio waveform you would want more than just a X3 headroom for bandwidth as anything other than a true sign wave is made up of the sign ware and the even and odd harmonics of the sign wave so the higher the bandwidth the better for seeing a true representation of the actual audio waveform. A 30MZ or 50MHz scope is more than enough to see just the audio waveforms though.

If you’re looking at the modulated waveform in the IF it would depend on what frequency or frequencies the IF(s) of the radio are and you would want at least a scope rated at 3x of it or them.

For aligning the PLL a frequency counter would be more accurate than a scope but a scope should be used for checking the actual final output waveform for clipping. For a CB 50MZ is really not enough as its highest frequency is 27.405MHz so 3x that would be 82.215MHz. You would probably be best off using at least a 100MZ scope to get a true look at the final output.

 

Ok I guess I have been wrong for the past 40 years and will mention to the guys over at textronix who I deal with that mark and the other CB'er supertechs are right, they can see the video for themselves.