[R-390] Filter Options II

[Perry Sandeen]

List,

Wrote: With the exception of watch crystals, the whole industry of sub 1 MHz crystals is pretty much a thing of the past. Yes, there are a couple of people who will make you this or that. You better have deep pockets to get them interested in whatever you need done. Yes, one of them is a buddy, but that only goes just so far.

Yea verily.

My take of the group’s replies is that:

1. Crystal filters are out of the question unless one does and up converter/down converter to use some of the commercial filters used in the rice box radios.  Probably a real PITA.

2.  While ceramic filters can be used, the supply is probably extremely limited, even worse that getting a original Collins replacement filter for the “A”.

3.  Use the Lankford roofing filter mod and stick to a 6 KHz or less bandwidth. For a $100 or so it is probably the most cost/time effective solution.

4.  Convert your “A” to a R-725 and selling your remaining good filters on epay to help offset the conversion cost.  Takes a lot of time and patience to convert the I.F. to 6 volt filaments. (Yes Tisha, I have 3 to do when I get a-round-to-it.)

5.  Something microprocessor based would be too complex for the vast majority of us.

Regards,

Perrier