[ARC5] Visual alignment of BC-454

[Kenneth G. Gordon]

On 23 May 2013 at 9:21, Ian Wilson wrote:

> Hi Ken,
> 
> You will see the envelope if you are looking at the output of
> an AM detector.

I tried that Ian, and got nothing but a big blob. I still can't figure out why that 
didn't work. I only got what I have been expecting after I began to use one of 
my Heathkit RF probes to connect to the X-axis input.

> If you are looking at the IF then you should see
> a symmetrical, "filled-in" display.

I don't quite follow you here, Ian. What sort of probe or connection to the 
o'scope X-axis would I use? A straight 11 meg resistor-probe?

> If you have an asymmetric
> display with fill-in then you are probably looking at the output
> of a not very linear detector with inadequate filtering :)

Indeed...or an off-center signal generator....or both.

> 
> If you can access the Z axis then you can blank the retrace
> and clean up the display significantly.

I can access the "Z" axis all right, but I have always presumed that if the 
ramp generator had an infinitely-fast return-to-zero, "Z" axis access wouldn't 
be necessary.

> You will still have to wait
> for the transient response to die away before starting a new sweep.

Yes. That has been clear since the beginning of this experiment.

> It
> is very easy to do experiments like this if you are messing around
> with PICs or whatever. It is somewhat more challenging if you are
> doing this the fun way with 555's, etc.

Yes. From my reading, 555s as ramp generators leave a lot to be desired. 
They need a near-perfect current source instead of a resistor in the RC 
circuit for one thing. And their power output is low.

Well, I am going to continue to play with this setup as it now is in order to 
figure out how to get the most out of it.

Have you yet had a chance to look at my latest photo?

Ken W7EKB