[Elecraft] IF xtal replacement mod

[Phil Wheeler]

Ron D'Eau Claire wrote:

>Several months ago when I replaced my filter crystals I saw a message
>that caught my eye. I believe that it was from Eric or Wayne, pointing
>out that with good i-f filter crystals the attenuation increases sharply
>down near 200 Hz. That was why they recommended 400 Hz as the "narrow"
>CW filter bandwidth. I haven't saved the message so I must work from
>memory. It raised some questions because, apparently, somewhere in the
>Elecraft documentation an example of 100 Hz for the narrow filter is
>mentioned.
>

Interesting input, Ron.  I hope someone can resurrect that message.  My 
current settings are (CW) OP1, 700, 400 and 100 -- and i have no 
substantial attenuation and no harshness at 100 Hz.

>
>I noticed the message because I had used my FL4 at 200 Hz until I
>replaced the crystals, but found that I did not like the sound of the
>filter at that bandwidth with the new crystals installed. It wasn't so
>much the attenuation, although I did notice that, but more the "sound"
>of the filter. QRN and signals near the edge of the bandpass had a
>"harsh" quality that I attributed to the distortion produced by the
>steeper slopes at the edges of the passband. In my experience, there
>really IS a place in this world for filters whose sides are not
>vertical. 
>
>It didn't matter to me since I normally operate CW with a bandwidth of 1
>or 1.6 kHz or greater and do the filtering in my head. I just set my
>"narrow" filter to 400 Hz. 
>

Interesting point.  In the mid-sixties I lost the hearing in one ear. 
 Aside from not hearing music in stereo anymore, the most noticable 
effect was loss of the ability to filter sounds well, both for CW on the 
radio and in focusing on one person's speech in a noisy room.  So I find 
myself much more dependent on filters than I was before.  Technically, 
that makes no sense, since the tranceiver output is not stereo -- but 
that is the subjective impression I have.

73, Phil