[ARC5] Subject: Re: Wobbulators, and IF alignment.

[Ian Wilson]

Hi Ken,

There are two approaches here:
  - use a slow sine wave (e.g. 50Hz). If slow enough, the up and down
    responses will overlap, more or less
  - use a sawtooth, blank the retrace, and delay until the fast transient
    response has died away before starting the next sweep

For older gear, the first approach is very simple and works fine. You don't
even
need a sync connection to the 'scope, since they all have a Line sync input.

For more selective gear, the first approach runs into persistence problems.
You can fix this with a long-persistence display, or use a storage scope
(in which case you may as well go the whole solid-state hog and use a
DDS to generate your frequency sweep).

73, ian K3IMW




On Fri, May 10, 2013 at 12:29 PM, Kenneth G. Gordon <
kgordon2006 at frontier.com> wrote:

> On 10 May 2013 at 7:25, Ian Wilson wrote:
>
> > I like the convenience of this unit especially if you want to align
> > several receivers with the same IF. Very handy.
> >
> > 73, ian K3IMW
>
> IMHO, one of the (to me) big problems with a wobbulator (my RSGB
> Handbook from many years ago has one in it) is that in those cases in which
> the wobbulator has a horizontal scope sync output, that output is a
> triangle
> wave.
>
> It should be a very fast rise-time sawtooth instead.
>
> Otherwise, the scope trace shows a double-hump which makes it
> considerably less easy to interpret.
>
> Ken W7EKB
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