[PCR-1000] Filter Modifications for CW

Tue, 21 Oct 2003 16:59:38 -0400

Someone did this a loooong time ago.
Let me see if I can find it.

----- Original Message ----- 
From: "Martin Francis" <[email protected]>
To: <[email protected]>
Sent: Tuesday, October 21, 2003 10:59 AM
Subject: [PCR-1000] Filter Modifications for CW

> Hi there,
>
> this is my first posting to this list (I am an active member of the
> ndblist), and having read through your archives and been unable to answer
> my question that way, I wondered if any of the list members might be able
> to help me with this query:
>
> I'm using my PCR-1000 for logging NDBs in the range 198 - 430KHz. NDBs
have
> a channel separation of 1KHz and I would like to fit a much narrower
filter
> to deal with this (perhaps 250Hz or even less). Presently I'm tuning to
the
> carrier frequency, switching to either LSB or USB (Canadian beacons are
> generally only LSB), then using audio DSP filtering to try and isolate the
> tone I'm looking for.   Problem is, if there's a local station on an
> adjacent channel, the AGC pulls right down and it's very hard to hear the
> DX.   With a much narrower filter I could use CW mode instead and tune to
> the mod offset frequency (e.g. for 1020Hz modulation this would be + or -
> 1020Hz on nominal carrier)
>
> Does anyone have any experience of fitting a narrower (e.g. crystal)
filter
> to this set?   Is there any easy way to change the third IF frequency from
> 450KHz to 455KHz, for which filters are more widely available (can this be
> done through slight adjustment of firmware variables?)
>
> Would it make sense to apply narrower filtering to the 10.7MHz stage as
> well, and perhaps reduce some of the AM BC breakthrough I often have to
> deal with on LF?   Please note I'm already using a low pass filter between
> set and antenna
>
> Can anyone help?
>
>
> Best wishes,
>
> Martin Francis
>
> =======================================================
>  Martin Francis
>
>  NDBList:   Official Mapmaster + Country Co-ordinator
>  Location: Richmond Hill, ON, CANADA
>  Lat / Lon: 43.53'08"N / 79.27'30"W / FN03GV
>  Beacons: 312 received since May 7, 2003
>
>  Antenna: Twin K9AY 85' loops on 300 feet of coax
>  Receiver: ICOM IC PCR1000 with 2.8KHz filter
>  Software: NDBWebLog / WWSU / Argo / SR5 / Goldwave
>  Web Site: http://www.classaxe.com/dx
>  NDB Log:   http://www.classaxe.com/dx/ndb/log
> =======================================================
>
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