[Collins] 51J4 audio improvements??

[Joel R. Hallas]

My 51J4 didn't come with the 6 KHz filter and I did jumper across with a
capacitor  to use the IF transformers to give a suitable  AM bandwidth.
I don't have the schematic in front of me, but remember that the coils
at the ends of the mechanical filter provided the dc path for at least
one side and thus I used a resistor (or two) to complete the path. I
forget which side, but it was clear from the schematic. Note that if the
plate circuit, it will have B+ on it, so route carefully.

I staggered the IFs to give a flat 6 KHz response, without much loss of
performance.

If you want to find a new home for that 6 KHz filter, let me know.

73, Joel Hallas, W1ZR

Glen Zook wrote:

> The 6 KHz filter is fine for AM contacts on the
> amateur bands.  However, for short-wave listening,
> broadcast band, etc., it is WAY too sharp for anything
> like "hi fi".  You need to get a broader filter.
>
> I don't know how putting a capacitor across the filter
> connections will work in the 51J4.  However, the
> previous owner of my 75A3 had done that in the second
> filter position (for an optional filter, not included
> with the basic receiver) and it works fine for AM if
> you don't need the selectivity that the filters
> provide.
>
> Glen, K9STH
>
> --- Paul <pwende@arrow.com> wrote:
>
> It may just be the nature of the 6KC filter as well. I
> am going to do an alignment on it over the holidays
> but I have a few questions.
>
> Can I pull out a mechanical filter and just feed in to
> out with a .01uF cap? The xstal filter may be enough
> for hi fi listening.
>
> =====
> Glen, K9STH
>
> Web sites
>
> http://home.attbi.com/~k9sth
> http://home.attbi.com/~zcomco
>
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