[R-390] Preselector

[Roy Morgan]

At 08:03 PM 8/19/2004 -0700, Dan Merz wrote:

>... what if the preselector  that I add has narrower bandwidth than the 
>front end of the receiver I'm using but is still wide enough for what I 
>want to hear?  Won't
>I see a benefit by adding this preselector?

Dan,

The preselector is operating at the received frequency, and will almost 
certainly have a bandwidth wider than the IF if the receiver.

The IF bandwidth is set by the mechanical or crystal filters (and by the 
whole IF strip for those with "the MAN's R-390".)  The Preselector is a 
tuned circuit (or maybe two) at the normally much higher received 
frequency, and the Q needed for, say, 4 Kc bandwidth is not practical to build.

The situation is different at LF and VLF, and in particular with TRF and 
regenerative detector receivers (such as the RAK/RAL at lower frequencies.)

Roy

- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
7130 Panorama Drive, Derwood MD 20855
Home: 301-330-8828 Work: Voice: 301-975-3254,  Fax: 301-948-6213
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