[ARC5] Dumber than a rock....

[Geoff]

Nice to know Im not the only one getting old....

Carl


----- Original Message ----- 
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: "ARC5" <Arc5 at mailman.qth.net>
Sent: Friday, May 24, 2013 7:29 PM
Subject: [ARC5] Dumber than a rock....


> 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
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