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

----- Original Message -----
From: "Martin Francis" <no.spam@mail.pls>
To: <no.spam@mail.pls>
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
> =======================================================
>
> ______________________________________________________________
> PCR-1000 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/pcr-1000
> Help: http://mailman.qth.net/faq.htm
> Post:

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Post:

Many thanks Mike, I appreciate you trying to help me with this.

If I have a try myself, I will certainly post my results to the list for the next person who wishes to try.

Best wishes,

Martin Francis

-----Original Message-----
From: Mike Curtis [SMTP:no.spam@mail.pls]
Sent: Tuesday, October 21, 2003 5:00 PM
To: no.spam@mail.pls
Subject: Re: [PCR-1000] Filter Modifications for CW

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

----- Original Message -----
From: "Martin Francis" <no.spam@mail.pls>
To: <no.spam@mail.pls>
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
> =======================================================
>
> ______________________________________________________________
> PCR-1000 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/pcr-1000
> Help: http://mailman.qth.net/faq.htm
> Post:

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Help: http://mailman.qth.net/faq.htm
Post:
______________________________________________________________
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Post:
.

Ok, these posts are from September 1998.
A guy named "Odo" from Gremany did it.
no.spam@mail.pls
Good luck.

Here are his posts:

this makes sense. Because the built-in IF-filters are not good enough
for receiving amateurs in the HAM-bands or for receiving digital modes
on shortwave. If there is no SSB/CW-option there is no need for better
IF-filters. I tried hard to get better IF-filters all around the world
but I couldn`t get because of IF-frequency !!450khz!!. This is a big
mistake from Icom. Even the 2.8 khz Filter is manufactured especially
for Icom and not available for someone else. The best you can get is a
4khz-filter CFWS450IT from Murata. I had luck to get 3 of them free for
developers from a Murata Distributor here in Germany. So I changed the
6khz-filter to 4khz and changed the 15khz-filter to 6khz. Maybe I will
change the 6khz to a 9 or 10khz-type when I get one. But the changes I
made seemed to improve better Performance for all shortwave-listenings
and the 15khz you dont need really.
When anybody KNOWS (securely) an Manufacturer who builds 450khz
IF-filters with bandwidth less than 2,8khz and an acceptable shapefaktor
of 2.5 or better please post it or send me email. With two additional
filters of 300/500 and 1800/2200 Hertz it would be the very best
receiver for shortwave you could get for this low price. BUT WHERE TO
GET ???
best regards to everybody joining this list

odo
-

I removed the 15khz filter and put the 6khz in. In the hole from the
6khz I put a 4khz CFWS450IT from Murata with 4khz. It seemed to me that
it improved performance for all over the shortwave ham-bands wich I
prefer listen to. The "Big Guns" in the broadcast-bands I prefer to
listen with my (modified) Sony2001D/2010. :-))
But I`m trying to get another 9 or 10khz IF-filter to change the 6khz.
I`m also working to get (or build) another small IF-filter with
preferably 2.2khz bandwidth, but it is hard work to get the parts you
need.
But there is also lots of fine software for PCs with (original)
SoundBlaster-Soundcards available wich helps a lot (such as dspblast).
So it was a very big mistake from Icom to build !!450!!khz IF-filters
into the PCR1000. In other case you could increase performance up to a
really professional receiver close to the NRD545 with some better
filters and a better (more programmable) DSP-unit. I really miss an
adjustable and switchable notch/peak filter like some extern DSP-units
have.
best regards
odo -from good old germany

----- Original Message -----
From: "Martin Francis" <no.spam@mail.pls>
To: <no.spam@mail.pls>
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
> =======================================================
>
> ______________________________________________________________
> PCR-1000 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/pcr-1000
> Help: http://mailman.qth.net/faq.htm
> Post:

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