Topband: Xtal Filter

[Bill Cromwell]

On Wed, 2012-01-04 at 09:38 +0800, Anton Moehammad wrote:
> Hi everybody,
> 
>  I believe there is a 1825 KHZ xtal filter sell somewhere, can any body share their experience about put a narrow XTAL filter in front of their recv ? (CW works only)
> 
> 
> 
> Ir Moeh AntonHendra
> Jambon Tengah no 290 RT1/RW3
> Magelang 56121
> Indonesia
> Mobile : +6285292611160
> email   : moehanton at yahoo.com
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> UR RST IS ... ... ..9 QSB QSB - hw? BK

Hi Anton,

It will work very well but your receiver will only hear 1825 kHz. Most
of us would like to have a receiver that can be used on our entire band
assignment...at least as much of it as we use. Depending on the
bandwidth of the filter (you mentioned CW) you would not be able to hear
1826, 1824, or any other 160 meter frequency. There have been some
receivers, dedicated to a single frequency, that used that approach, I
read about them years ago. It's not something you would probably want to
spend money, time, and other resources to acquire.

You can see that more clearly if you think of the I.F. strip in a normal
receiver as the entire receiver. Remove the RF amp and the mixer stages
and feed the input of the I.F. amp from the antenna with perhaps a tuned
circuit (at 1825 of course). Your approach would be exactly the same.
You won't have the option tuning around the band. You'll have a fixed
frequency I.F. strip at 1825 kHz with perhaps a conversion to yet a
different I.F. frequency.

73,

Bill  KU8H