[ARC5] AM broadcast reception on BC-453

[Scott Robinson]

Hi Keslie,

This kind of problem is why I keep a sweeping function generator (Leader 
LFG-1300, 0-2 MHz) in the shop.

I think your IF is not perfectly tuned, so either you tune the whole 
thing for maximum smoke as was probabnly originally done, or, if you 
want a wide band IF, you need the sweeper to guide the stagger tuning.

In any case, yo umay need to either unstick that one IF adjustment or 
find another IF can.

Good hunting!

/scott

On 3/19/15 12:31 PM, Leslie Smith wrote:
>    G'day fellow list-readers,
>    I built a converter to listen to the AM broadcast band on a BC-453.
>    I have a question about sound quality and IF response.
>
>    But first - some extra info.
>    About 2 years ago I built a converter to 'move' the 80m band to the
>    ARA nav band.
>    (In this case I used an older ARA, not a BC-453.  And yes, I do
>    understand the '453 is almost the same as the ARA set.)
>    The point here is that when I listened to SSB (converted from 80m) the
>    voice sounded as expected.
>
>    Now, listening to AM BC broadcasts this is what I hear:
>    When the '453 is tuned to what I judge to be the 'middle' of the
>    signal (here it's 480kHz) the sound is muffled.
>    To get natural sounding voice quality I must tune the '453 a little
>    'high'.
>    When I tune the '453 'low' the muffled quality is less, but not so
>    clear was tuning 'high'.
>
>    Important info.  The slug in the second I.F. transformer is 'stuck'.
>    By that I mean I can't pull it out.  The first and third slugs are
>    "out".
>    I haven't tried to align the I.F. transformers.  (How stable are these
>    sets over 70 years?)
>
>    I'm interested to know how many here listen to the BC band using one
>    of the 'nav' sets?
>    What quality of sound is heard?
>
>    Other comment.  I'm using a circuit that is somewhat like a JFET
>    version of the Pullen - except I don't attempt to 'mess' with G(m) -
>    it's just a long-tailed pair.
>    The signal goes to the LH JFET gate, is source-coupled to the RH JFET
>    gate and thence to the drain (and untuned transformer).  From the
>    transformer the signal goes to the '453.
>    The L.O. switches the RH FET gate.
>
>    With this arrangement I have excess gain.  Don't even think about
>    using this arrangement as a converter to feed a 'command' radio.
>    From memory, I think I'm using a one-turn link with the output
>    transformer, so I'm attenuating the signal a good deal before the
>    '453.
>
>    73 de Les Smith
>    vk2bcu at operamail.com
>