[ARC5] Visual alignment of BC-454 - more photos

[Kenneth G. Gordon]

OK, gang, here are two more photos for your viewing pleasure.

http://www.w7ekb.com/Personal/BC454/BC454IF-3.jpg

http://www.w7ekb.com/Personal/BC454/BC454IF-4.jpg

This third photo was taken with the normal room-lighting left on. Before I took this one, I 
increased the deviation of the signal generator's swing. This confirms what I first thought that 
the "swing" was too narrow to properly show the IF passband. As you can see from this one, 
the "bottoms" of the IF passband can begin to be seen and the overall shape looks much 
more "reasonable". Also, if you look closely, you can see that the over-all passband is 
skewed to the left a bit.

I have yet to experiment with increasing the IF signal input level to see what that does.

As Dennis and I have agreed, the skewing is obviously an effect of the single-coil 
regeneration.

After I have worked out some other matters, I think I will indulge in experimenting with 
regeneration at both IFs. Pehaps by proper alignment using the sweeper, I can achieve 
better skirt selectivity.

Also, it looks as though the IF center frequency is 1416.9 KHz.

The fourth (and the first) photos were both taken with the room lighting off. The primary 
reason I did this was to see the retrace more clearly. Otherwise, the situation with photo 4 
was identical with the third photo.

At this point, it looks to me as though I can stop worrying about the "shape" of the 
sawtooth/ramp from the sweeper, at least for the time being.

With the room lights on, the retrace is not particularly "interesting" any more.

I have been working at this procedure for one very good reason: I intend to now experiment 
with varying the spacing between the IF coils to see what effect that has on selectivity.

However, before I do that, I may have to build or buy some sort of marker generator so I can 
accurately measure the bandwidth.

Although the present 'scope pictures are very informative, they aren't as informative as they 
need to be.

Perhaps I can "modify" the output of one or the other of my really cheap "signal generators" 
(Eico 324s or Heathkit SG-8) or one of my BC-221-AKs (I have two) or one of my two LMs as 
the source for some sort of pulse-generator/converter to use as a marker generator.

Lessee...I could square up the output of a BC-221 with a Schmidt trigger, then follow that with 
something that would give me a narrow pulse.

Suggestions?

Ken W7EKB