[R-390] Interested in R390A Filters?

[Charles P. Steinmetz]

Chuck wrote:

>FWIW, I have one of his 6 kc filters that was installed in place of 
>the, (IMHO) "useless" 16 kc.  It works wonderfully !!  There have 
>been several people who have picked up completed radios from me and 
>I make it a point to demonstrate the filter.

I agree regarding the 16 kHz filter.

In today's band conditions, 6 - 6.5 kHz is (IMO) the optimum AM 
filter.  For very noisy conditions, 4 kHz is about optimum.  If you 
live down the street from a strong AM station you like, 8 - 9 kHz 
with a relaxed shape factor (better group delay) than a mechanical 
filter is about the best you can do.

If I were choosing four *mechanical* filters with a clean slate, they 
would be 2 - 2.3 kHz (for SSB and desperate-measures AM reception), 4 
kHz, 6 kHz, and 9 - 10 kHz.  If I didn't care about SSB but wanted to 
copy CW, I'd install a filter in the 250 - 500 Hz range instead of 
the 2 - 2.4 kHz filter.  If I didn't live down the street from a 
strong AM station I loved, I'd omit the 9-10 kHz filter and install 
both the 250-500 Hz and the 2 - 2.3 kHz filters.

If I were making OEM-format replacement filters, I think I'd look 
hard at ceramic filters instead of the Collins "low-cost" mechanical filters.

Best regards,

Charles