[ARC5] Dumber than a rock....

[Kenneth G. Gordon]

Well, I certainly have learned a lot today: mostly about how damned stupid I can be.

1) I have NOT been connecting to the diode load (R-18 in the BC-454)...because I moved 
that to the front panel to use as my AF gain control a month or more ago. Dumb ass trick #1.

2) The 12SR7 works just fine, thank you. Dumb ass trick #2.

3) The trace in Photo 5 was NOT gotten with my scope probe connected to the diode load: it 
is connected directly to the cathode of the 1N34A. Dumb ass trick #3.

Now for the accurate knowledge gained:

1) One CAN use a standard 'scope probe connected across the diode load to get the correct 
display. See photo 6. One uses the diode load since connecting there results in an "outline" 
trace since the diode load resistor(s) and associated capacitor(s) form an LPF to pass the 
audio and reject the IF.

2) One CAN use the sweeper to sync the scope. However the display is more "interesting" in 
that case. Again, see photo 6. Actually, I prefer the X-Y mode as it results in a more easily 
adjusted trace, and it is cleaner. (Compare photo 3 and photo 6)

3) For the BC-454, I cannot get enough "swing" out of my HP-8640B/sweeper-combo to 
properly display the ultimate IF passband shape, since I would need a "swing" of at least 30 
KHz, and at this frequency (1415KHz) the 8640B bitches if I exceed about 15 KHz and simply 
won't "FM" above that width.

All I have left to do now is to figure out how to 1) add markers, and 2) calculate the actual 
passband attenuation so I can tell exactly how much my selectivity enhancement actually 
helps.

However, first I think I will go dig out the bottle of Single Malt and take a good wee dram. 
Maybe then I won't feel so stupid. :-(

Ken W7EKB