[ARC5] AM broadcast reception on BC-453

[K5MYJ]

You are having a problem with the narrow bandwidth of the BC-453 IF amps.

Pulling the slugs out gives you  the narrow bandwidth. Pushing them in gives 
the wider bandwidth.

If you really want to listen to AMBC on an ARC-5/ATA/SCR-274 receiver you 
should try a BC-454 (3MHz to 6MHz) receiver. It has a wider bandwidth IF.

Bob Macklin
K5MYJ
Seattle, Wa.
"Real Radios Glow In The Dark"
----- Original Message ----- 
From: "Leslie Smith" <vk2bcu at operamail.com>
To: "ARC-5 List" <arc5 at mailman.qth.net>
Sent: Thursday, March 19, 2015 12:31 PM
Subject: [ARC5] AM broadcast reception on BC-453


>  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
>
> -- 
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