[Elecraft] OT mechanical v crystal filters OT

[Brett gazdzinski]

Its my understanding that they are not great other than
they do have steep skirts. 

The R390 used IF transformers (tuned circuits) while
the R390A had mechanical filters.
The R390 was judged to work better, and the R390A was actually
designed to reduce cost through the use of the mechanical
filters.

Although it is meaningless in an 8 MHz IF radio, I think at
50, 100, 262, or 455 KHz, tuned circuits may be best, but you
likely need to design the circuit parts very carefully, and they 
might take up a lot of space, and be hard to adjust.

Brett
N2DTS






> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net 
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of David Cutter
> Sent: Monday, May 07, 2007 1:43 PM
> To: Elecraft
> Subject: [Elecraft] OT mechanical v crystal filters OT
> 
> Off Topic but with so much expertise flying around I thought 
> I would ask how mechanical filters compare with crystal filters.  
> 
> I think they were fairly low in frequency (455kHz?), so, not 
> suitable in the present discussion,  but it would be good for 
> our education at least.
> 
> David
> G3UNA
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