[ARC5] Visual alignment of BC-454

[Kenneth G. Gordon]

OK. Looks to me as though I finally have what I wanted.

"Photos at noon". or as soon as my dear wife gets off the web.

There are several issues I finally found and eliminated.

1) I yanked the detector tube and coupled to the detector input, pin 4 of the 12SR7 socket. 
Taking the signal from the detector load resistor was not working at all. There was simply too 
much noise introduced which was masking what I wanted.

2) I used my Heathkit PK-3 RF probe as the detecting device.

3) The 1st IF was oscillating when the gain/regen control was just at max...I backed it off until 
that went away. That was causing jitter and widening of the trace.

4) I had the BFO on (I'm a dumb ass....) :-( ...so I turned that off. What I was seeing last night 
was simply the BFO swamping everything. At my age, it is obvious that I shouldn't be working 
on this sort of thing when I really should have been in bed a couple of hours ago...

5) I was apparently feeding a bit too much signal to the mixer grid...reduced that a bit.

6) Signal generator was NOT centered on the IF passband. Adjusted that to center.  I was 
much too low. Center frequency of the IF appears to be very close to 1417 KHz, not 1413.5 
as I thought it was.

7) The passband is definitely skewed to one side. However, this MAY be due to the fact that 
my sweeper does not put out a very good sawtooth. It certainly is not linear!

8) I increased the sweep rate a bit. It is still less than about 30 Hz. No ringing or other 
artifacts are visible.

Things I still need to do:

1) Sweep "wider" in order to see the whole passband. 10 KHz isn't quite enough. However, if 
I crank up the "gain" of the modulation on the HP-8640B, the "Reduce" light comes on. 
However, I suspect that this is related to the frequency that is being "FMed" and I can safely 
ignore it in this case.

2) Build a better probe.

3) Simplify all connections.

4) Build or buy a MUCH better sweeper. (Model suggestions gladly accepted.)

I still cannot quite figure out why I cannot use the diode load resistor as the source. Perhaps 
someone here can advise?

FYI, the passband shape is pretty "classic", and the over-coupled look is not immediately 
obvious. However, this MAY be simply because I am not providing a high enough signal level 
input to the mixer grid.

Adjusting the IF can tuning capacitors radically changes the shape of the passband. I'll 
include photos of that with details later.

I'll need some help to interpret exactly what all those will mean. 

I am VERY, VERY suspicious that the quality of the sawtooth from the sweeper is a very 
significant factor in the apparent abberations I am seeing.

Ken W7EKB