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CW Transmit Filter Bandwidth

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Byron Peebles-3

CW Transmit Filter Bandwidth

I have noticed that Elecraft K3/K3S defaults to setting the wide SSB
filter as the CW TX filter.

Is there a technical reason for doing this? Would it be better to use a
1kHz filter or one of the narrow CW filters?

Thanks, in advance.

73, Byron NZ3O

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Don Wilhelm

Re: CW Transmit Filter Bandwidth

Byron,

The K3/K3S is designed to use the filter that is installed "stock" in
all transceivers, so you need to select the 2.7 (or 2.8) filter for CW
(or any other mode except AM, FM or ESSB) for transmit.

Requiring a 1kHz filter for CW transmit would require that filter be
included in the basic package and would increase the price of the
transceiver.

This sounds like a 'curiosity' question - the K3/K3S works fine with the
2.7/2.8kHz filter for CW transmit.

73,
Don W3FPR

On 8/21/2018 4:03 PM, Byron Peebles wrote:
> I have noticed that Elecraft K3/K3S defaults to setting the wide SSB
> filter as the CW TX filter.
>
> Is there a technical reason for doing this? Would it be better to use a
> 1kHz filter or one of the narrow CW filters?
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Byron Peebles-3

Re: CW Transmit Filter Bandwidth

Don:

I do understand it works, since every unit is shipped that way.

My question is more in the vein of wouldn't using a 1kHz or less filter
be safer/cleaner/logical for CW?

Obviously, not as a factory default, since only one filter is sure to be
there, but on a per-user basis.

I thought years ago (before I had Elecraft) I read that a narrower TX
signal made for a stronger signal within that narrower bandwidth.

73, Byron NZ3O

On 08/21/2018 04:33 PM, Don Wilhelm wrote:

> Byron,
>
> The K3/K3S is designed to use the filter that is installed "stock" in
> all transceivers, so you need to select the 2.7 (or 2.8) filter for CW
> (or any other mode except AM, FM or ESSB) for transmit.
>
> Requiring a 1kHz filter for CW transmit would require that filter be
> included in the basic package and would increase the price of the
> transceiver.
>
> This sounds like a 'curiosity' question - the K3/K3S works fine with
> the 2.7/2.8kHz filter for CW transmit.
>
> 73,
> Don W3FPR
>
>
> On 8/21/2018 4:03 PM, Byron Peebles wrote:
>> I have noticed that Elecraft K3/K3S defaults to setting the wide SSB
>> filter as the CW TX filter.
>>
>> Is there a technical reason for doing this? Would it be better to use
>> a 1kHz filter or one of the narrow CW filters?
>

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Byron Peebles-3

Re: CW Transmit Filter Bandwidth

In reply to this post by Don Wilhelm

I would add that changing the TX FLT to something else generates an
error when I try to use it. 73, Byron

On 08/21/2018 04:33 PM, Don Wilhelm wrote:

Don Wilhelm

Re: CW Transmit Filter Bandwidth

In reply to this post by Byron Peebles-3

Byron,

You are assuming that the CW signal shape is controlled by the TX filter.
It is not - that is done in the DSP and produces a clean single
frequency signal that is quite good at TX phase noise and keying artifacts.
As long as that signal fits within the bandpass of the filter all will
be well. In other words, a 1kHz filter would not produce an improvement.

It might with some other rigs, but not with the K3/K3S because the
filter is not the limiting factor - the DSP shaping and the low TX phase
noise of the K3/K3S are the determining factors.

73,
Don W3FPR

On 8/21/2018 4:42 PM, Byron Peebles wrote:

> Don:
>
> I do understand it works, since every unit is shipped that way.
>
> My question is more in the vein of wouldn't using a 1kHz or less
> filter be safer/cleaner/logical for CW?
>
> Obviously, not as a factory default, since only one filter is sure to
> be there, but on a per-user basis.
>
> I thought years ago (before I had Elecraft) I read that a narrower TX
> signal made for a stronger signal within that narrower bandwidth.
>

Don Wilhelm

Re: CW Transmit Filter Bandwidth

In reply to this post by Byron Peebles-3

Byron,

Yes, if you select anything other than the 2.7/2.8 filter for CW
transmit, you will receive an error.

73,
Don W3FPR

On 8/21/2018 4:48 PM, Byron Peebles wrote:

> I would add that changing the TX FLT to something else generates an
> error when I try to use it. 73, Byron
>
>
> On 08/21/2018 04:33 PM, Don Wilhelm wrote:
>> Byron,
>>
>> The K3/K3S is designed to use the filter that is installed "stock" in
>> all transceivers, so you need to select the 2.7 (or 2.8) filter for
>> CW (or any other mode except AM, FM or ESSB) for transmit.
>>
>> Requiring a 1kHz filter for CW transmit would require that filter be
>> included in the basic package and would increase the price of the
>> transceiver.
>>
>> This sounds like a 'curiosity' question - the K3/K3S works fine with
>> the 2.7/2.8kHz filter for CW transmit.