Perhaps a better way to think about it IF scheme wise is that
the Corsair is like the Omni A/D/C series but has the 6.3MHz
IF (started with the 580 Delta) for PBT and narrow BW IF
filtering. Once out of the 6.3MHZ IF it is converted back to
9MHz where the product dector is located at. So the Corsairs
have 2 IF frequencies but three actual mixers/conversions. On
the TX side the 6.3MHz IF is not involved in the signal path
at all and everything is done at 9MHz.
For grins you can take the entire 6.3 MHz IF out of line in
the Corsairs quite easily. I did that a year or so ago as an
experiment, the results were interesting. Search the archives
if you want to know how to do it. Needless to say all the
narrow filter positions and PBT go away if you do this.
So in reality there is very little that is directly the same
as the Omni A/D/C series in the Corsairs. There is a lot of
design similarities but many differences in detail and
component choices.
The Corsair was factory standard with 4 pole (8 pole
optional) 9 MHZ 1st IF filter. The Corsair II's all had the 8
pole 9 MHz IF filter in the 1st IF.
Duane
N9DG
--- Craig Roberts <crgrbrts@verizon.net> wrote:
> As I understand it, one of the major differences between
> the Corsair and
> Corsair II is the roofing filter (4-pole vs. 6-pole). Can a
> Corsair be
> retrofitted with the later filter easily or are there other
> circuit changes?
>
> Thanks,
>
> Craig
> W3CRR
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