[R-390] 60 Hz on Audio

[Jon Schlegel]

Not So Anonymous,

Thanks for your reply.  Actually the 4 and 2 kHz filter show similar 
behavior as the 8 kHz filter does.  All I can offer about the 
mechanical filters is that I had originally removed them from the 
module swept them and they all performed well inasmuch as their 
stopband attenuation typically was pushing 90 dB.  After reinstalling 
the filters into the module I again swept the four bandwidths and 
found the stopband attenuation to be better than 75 dB.

Regards, Jon



At 01:39 PM 6/9/2009 -0600, w9ya wrote:
>And by this I mean the filter and circuit associations unique to the filter
>either by only being used with that filter setting as opposed to another
>filter that does not show such association OR because this particular filter
>is somehow accentuating this effect in other components that might be at
>fault.
>
>In any event, like ALL troubleshooting, keep narrowing down your focus until
>the answer is obvious. i.e. Keep taking measurements that you make sure are
>being taken properly.
>
>Not So Anonymous
>
>
>On Tue, Jun 9, 2009 at 1:35 PM, w9ya <w9ya at qrparci.net> wrote:
>
> > I am going to go out on a limb here and answer your question: "
> > If not acceptable, what could be causing the distinct difference of
> > 60 Hz level just by changing the BW setting? " <- The filter.
> >
> > Not So Anonymous
> >
> >
> >
> >
> > On Tue, Jun 9, 2009 at 1:30 PM, Jon Schlegel 
> <ews265 at rochester.rr.com>wrote:
> >
> >> All,
> >>
> >> Please check out these photos of the output of my R-390A IF Module.
> >>
> >> This first image shows the audio output from the Diode Load signal
> >> line.  Input to the IF module is 455 kHz modulated 30% with a 1 kHz
> >> tone.  The 16 kHz mechanical filter is selected in this image.  The
> >> audio looks pretty clean.  Any 60 Hz that might be there really isn't
> >> visible.
> >>
> >> http://www.vecnav.com/R-390A_IFmodule/DiodeLoadOut_16kHzMechFilter.jpg
> >>
> >>
> >>
> >> This second image was made with the identical conditions as above
> >> except that the selected mechanical filter is now 8 kHz.  A 60 Hz
> >> component is now easily visible.  In fact it's about 25 dB or a
> >> factor of about 18 times worse than with the 16 kHz setting.
> >>
> >> http://www.vecnav.com/R-390A_IFmodule/DiodeLoadOut_8kHzMechFilter.jpg
> >>
> >>
> >>
> >> Is this kind of behavior acceptable for these receivers?
> >>
> >> If not acceptable, what could be causing the distinct difference of
> >> 60 Hz level just by changing the BW setting?
> >>
> >>
> >> Thanks and regards,
> >> Jon Schlegel WA3MVM
> >>
> >>
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