[ARC5] Frequency shift with percussion

[Charles]

>I use a NEScaf filter at the audio output. That functions much as a
>'Select-O-Ject" would with it's variable center frequency and variable
>width passband.

That will work well for CW, but for voice, once past the detector, the 
interfering signals are already in the audio passband along with the desired 
signal, and can't be removed... that's why I can hear them!
So an audio filter won't help (except for notching out a heterodyne)... the 
only cure is more selectivity before the detector (i.e. in the IF).

>I have considered inserting a small converter to move the IF signals to
>a frequency where xtals and entire filters are more available and then
>back to the IF chain after filtering.

A good idea, and one I've  also considered... although it would still 
require a non-stock crystal for the mixer oscillator, and room to mount the 
board. At some point the ARC-5 will have turned into my grandfather's axe 
(new head, new handle). I'm just looking to make it usable for occasional 
80/75m use, not to replace a $10k Yaecomwood DSP rig (which I don't have 
anyway).
:)

-Charles
WB3JOK/0