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Filter width and cutting off CW

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M0XDF

Filter width and cutting off CW

I'm just finally getting into hunting for CW on the bands to listen
to, to help improve my on-air listening - I can read about 7WPM (20
char speed) and trying to find signals with my K3.
I can hear a few around on 40m with the filter set to 1.8KHz, but when
I start to reduce the filter width down, I loose it at 500Hz - I can
hear very well at 550Hz, but drop the 50Hz and it disappears - this is
after doing an auto spot.

Tuning around the frequency, I still can't find it.
Is this a combination of filter width and my sidetone pitch, which is
set to 500Hz?

I have latest beta f/w, a 400Hz, 1.8KHz, 2.8KHz and 6kHz filters
73 de M0XDF, K3 #174

--
Patience serves as a protection against wrongs as clothes do against
cold.
For if you put on more clothes as the cold increases, it will have no
power to hurt you.
So in like manner you must grow in patience when you meet with great
wrongs,
and they will then be powerless to vex your mind.
-Leonardo da Vinci, painter, engineer, musician, and scientist
(1452-1519)

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M0XDF

Re: Filter width and cutting off CW

Thanks for all the responses - to answer the questions:

Yes I'm in CW mode
yes I've used Spot and shift shows an * to indicate its centred over
the frequency
I've checked the filters and offsets, receive Filter Enables etc in
Configuration etc.

the loss of signal occurs at 500Hz, that’s before the filter switch
point at 400HZ
I have checked against RWM on 9.996 band it cuts of in the same way at
500Hz

It appears that once I go down to 500HZ, the signal is greatly
attenuated and I loose the side tone, regardless of mode, the
frequency is attenuated at that point - I can just hear the
transmission, but everything is very attenuated. I'm wondering if they
made be a bad connection of a part of the board that only comes in
below 550Hz.

When RWM is transmitting just a carrier, it gets cut off at 500Hz
--
Always remember, half the people in the world are above average
intelligence!

On 20 May 2008, at 21:46, Dave G4AON wrote:

> Hello David
>
> I don't know what you are doing wrong, my K3 works just fine right
> down to "50 Hz". I am using the latest firmware, 6 KHz, 2.8 KHz and
> 400 Hz filters. You could check on a plain carrier too.
>
> Your choice of a 500 Hz pitch works, but I don't know of anyone who
> normally uses such a low pitch. I mostly use 700 Hz but have checked
> at 500 and it worked just as well.
>
> Have you somehow got a filter incorrectly set with an offset instead
> of 0 Hz (only the cheaper 5 pole filters have an offset, 8 poles are
> zero Hz)? Also, did the loss of signal occur when the XFIL display
> showed a change of roofing filter, as the filter should only change
> when you go down to 400 Hz? Another thing, is your centre frequency
> the same as your chosen pitch (indicated by a * against the shift),
> if your filter isn't centred you would lose the audio.
>
> 73 Dave, G4AON
> ================
>
> I'm just finally getting into hunting for CW on the bands to listen
> to, to help improve my on-air listening - I can read about 7WPM (20
> char speed) and trying to find signals with my K3.
> I can hear a few around on 40m with the filter set to 1.8KHz, but when
> I start to reduce the filter width down, I loose it at 500Hz - I can
> hear very well at 550Hz, but drop the 50Hz and it disappears - this is
> after doing an auto spot.
>
> Tuning around the frequency, I still can't find it.
> Is this a combination of filter width and my sidetone pitch, which is
> set to 500Hz?
>
> I have latest beta f/w, a 400Hz, 1.8KHz, 2.8KHz and 6kHz filters
> 73 de M0XDF, K3 #174

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Don Wilhelm-4

Re: Filter width and cutting off CW

Dave,

Just as a guess (I don't have either the 500 or 400 Hz filters) - do you
have the correct filter offset entered into the K3 menu? It certainly
sounds like a conflict between the roofing filter centers and the DSP
filter centers.

You have said that the filter center frequency matches your sidetone
pitch, so that rules out a mis-setting of the SHIFT control.

I cannot duplicate your problem here, but then I am relying only on the
DSP filters - I have only the 2.7 kHz filter installed..

73,
Don W3FPR

David Ferrington, M0XDF wrote:

> Thanks for all the responses - to answer the questions:
>
> Yes I'm in CW mode
> yes I've used Spot and shift shows an * to indicate its centred over
> the frequency
> I've checked the filters and offsets, receive Filter Enables etc in
> Configuration etc.
>
> the loss of signal occurs at 500Hz, that’s before the filter switch
> point at 400HZ
> I have checked against RWM on 9.996 band it cuts of in the same way at
> 500Hz
>
> It appears that once I go down to 500HZ, the signal is greatly
> attenuated and I loose the side tone, regardless of mode, the
> frequency is attenuated at that point - I can just hear the
> transmission, but everything is very attenuated. I'm wondering if they
> made be a bad connection of a part of the board that only comes in
> below 550Hz.
>
> When RWM is transmitting just a carrier, it gets cut off at 500Hz
>

Gill W4RYW

Re: Filter width and cutting off CW

Make sure the shift is normal (press shift till you get Norm). Make sure you have gain set for narrow filters in config menu pa 43 of manual. Make sure narrow filter is set for cw receive (enabled). Make sure freq offset is set correctly. All this stuff is on pa 43 of manual. I have 500 hz and 250 hz filters and they work great!

Good luck!

Gill