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

[Dennis Monticelli]

For a marker you could use a level triggered one-shot.  I think it is
possible to wire up a single IC comparator to do this, If not a dual
comparator should do the trick.  The sawtooth ramp would feed the
comparator.  For two independent markers a quad comparator could be used.

Dennis AE6C


On Thu, May 23, 2013 at 2:39 PM, Kenneth G. Gordon <kgordon2006 at frontier.com
> wrote:

> 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
> ______________________________________________________________
> ARC5 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/arc5
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:ARC5 at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>