[Test-Equipment] Advice about used scopes

[Chris Albertson]

--- Marco IK1ODO <IK1ODO at spin-it.com> wrote:

> At 19.23 04/05/2007, you wrote:
> >Thanks a bunch for all the info.  Disagreements are good.  Let's us
> see
> >both sides of a point of view.  As for my use of the scope.  I do
> want
> >to be able to look at the waveform from  radio transmitters that
> works
> >at frequencies of up to 50Mhz.   I need to be able to design and
> test
> >RF transformers and RF mixers and filters at frequenies up to 50Mhz.
>  I
> >want to see what is being sent to the antenna (or more likey dummy
> >load)... A 20Mhz scope may not work for that
> 
> you need at least five times the fundamental frequency of a signal to
> 
> see a square wave... preferably ten times.
> The load from a simple 10x probe is around 10-12pF, and may detune 
> the circuit you are looking to. I mean, to look at real RF signals is
> 
> not a thing to do with a 100MHz scope.

"RF" frequencies, when you are working in the HF bands are between
about 1,8 Mhz at the low end up to about 30 Mhz at the high  end.

The thing about transmitters is that they don't transmit square waves.
Or at least we hope they don't.  One example. The ham 40 meter band is
just over 7 Mhz.  If the transmitter is working,  any over tones above
7 Mhz should be at least 80db below the fundamental. 

For work on the 20 meter band a 100 Mhz scope would actually be 
6x the bandwidth of the transmitter's fundamental.  


Chris Albertson
  Home:   310-376-1029  chrisalbertson90278 at yahoo.com
  Office: 310-336-5189  Christopher.J.Albertson at aero.org

__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around 
http://mail.yahoo.com