[Hallicrafters] Test equipment

[Kenneth G. Gordon]

Bil Barfield wrote:

> Ken Gordon did a great job of describing a good basic setup of test
> equipment.

Aw, shucks. :-)

> Many thanks. I'm kinda new to this and enjoy all the help I can
> get.  I especially liked his rundown of the value of tube checkers. I just
> bought a Knightkit unit, but have not had a chance to use yet.

Those are quite adequate, in most cases, for what we need them for.

> 
> He stated that an oscilloscope is the handiest piece of equipment in his
> shack.  I know a few things to do with an O-scope, but would love to learn
> more.

As someone else mentioned here, one of the very best small books on 
the subject is "101 Things to do with your oscilloscope" or similar. You 
can find them on that watery place often.

> 
> Ken, could you please give us a quick rundown of all the stuff you can do
> with a scope.  I want to be sure I use them all.

Gosh, Bill, to do an adequate job of that here would require a pretty 
long e-mail, although I can give a short list here.

You can measure the following parameters with one, although some of 
these also require additional external components, such as power 
supplies, resistor decades boxes, signal generators, etc:

Voltage
Current
Phase
Frequency
Distortion
Resistance
Capacitance
Inductance
Passband shape of IF strips
Gain of amplifiers from DC to daylight.
Linearity of amps.
Harmonic content of oscillators or amps.
And many others.

One use for a scope that I have found to be particularly impressive is in 
properly aligning IF strips. This is the so-called "visual method". It 
requires both a sweepable function or signal generator with a 
synchronizing output and a good low frequency 'scope with the 
capability of connecting an external horizontal sync source.

Using this setup, you can actually SEE the complete shape of a 
receiver's IF passband, and watch, in real time, the effect of any 
adjustments you make. The first time I got it to work properly, I was truly 
amazed. I no longer use the "connect a VTVM to the diode load, and 
peak everything for max" method as it can very easily give erroneous 
results. This is especially true in those receivers that require stagger-
tuning of the IF cans.

Once you use this method to align a receiver IF, you will NEVER go 
back to the simpler method unless you are stuck without a scope and 
sig gen and have to get a receiver working.

BTW, for those wishing to try this method, the single most important 
factor to keep in mind in order to get this to work properly is to use the 
slowest sweep rate you can. Since most scopes have a fairly short-
persistence trace, you will find that it is easiest to use in a darkened 
room, with directed lighting onto those portions of the receiver where 
you have to make the adjustments.

Ken Gordon W7EKB