Re: {Collins} Using Oscilloscopes for Collins Equipment



Yup,  The 1X was a typo and if you look right beyond that typo where I again
referred to the probe it said 10X,  as it should have to start with..  Sorry
for the confusion Robert.

Bill

-----Original Message-----
From: Robert Thomas [mailto:ve3tou@xxxxxxxxxxxxxxxxxxx] 
Sent: Saturday, May 30, 2015 8:35 AM
To: Bill Carns
Subject: Re: {Collins} Using Oscilloscopes for Collins Equipment

I agree with Bill re the scope -- and bear in mind that a scope with this
kind of performance would have been considered "high end" in the 1950's,
when much of our Collins gear was produced.

But I have a different take on the subject of probes. The 1x probe will load
the circuit under test with tens of picofarads, thus affecting the signal
you're trying to measure. A 10x probe reduces the load on the circuit to
10-15 pF, and also brings the voltages found in vacuum tube gear into the
range the scope can handle. To me, this is the "default" 
probe.

A basic understanding of probes is essential (IMHO). Tektronix has a
monograph called "ABC's of Probes", which is useful but pretty overwhelming.
For a shorter primer, go to www.treetopcircuits.com, download the manual for
the LC-2 active probe, and look at the "Probe Basics" section, particularly
the bits about passive probes, adjustments, and ground leads. Read the bit
about ground leads twice. 
BTW, I emphatically do NOT recommend getting into active probes in most
situations.

73
Bob

On 2015-05-30 8:41 AM, Bill Carns wrote:
> Not familiar with that scope, but if it is a triggered sweep scope of 
> any decent quality, the 20 MHz bandwidth is going to do for the IF and 
> VIF diagnostics and alignment and be decently useful for RF work up of 
> course to about 15 MHz.
>
> The big question is what kind of probes came with it..  Hopefully 
> there is a low capacitance probe and hopefully a 1-X associated with 
> it but the 10X is not really critical.
>
> Bill
>
> -----Original Message-----
> From: Collins 
> [mailto:collins-bounces+wcarns=austin.rr.com@xxxxxxxxxxxxx] On Behalf 
> Of Robert
> Sent: Friday, May 29, 2015 11:54 PM
> To: CCA Reflector
> Subject: {Collins} Using Oscilloscopes for Collins Equipment
>
> Fellas, I need some advice.  I have an Instek GOS-620 (20 MHZ)
> oscilloscope with several probes.   How sufficient will be this
> instrument with its limits be in diagnosing problems, performing 
> alignments with my S lines, A-4's and 32V's?  In all my 51 years of 
> being a ham I've never been taught nor versed in how to really use a 
> scope.  Kinda like not learning how to play the piano when in earlier
years wishing I had now.
>
> Also, any suggested basic text/tutorial books on the market that would 
> help me out?
>
> Many thanks es 73,
>
> Robert Lawson
> W4RL
> CCA Member
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