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K3 Filter Choices

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pastormg

K3 Filter Choices

Hi Guys, in my quest to purchase a new K3 I am worndering about 8 pole filter choices. I see that there is a 1.8 KHZ 8 pole ssb filter and a 250 HZ 8 pole cw filter that is avaiable. If one purchases one of these filters wouldn't that basically solve the problem of not needing all the other filters at different KHZ? This probably is a stupid question, but would really like to learn. Mark KB3Z
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Matt Zilmer

Re: K3 Filter Choices

Hi Mark,

You'll need, at minimum, a 2.7 or 2.8 KHz filter for use in transmit.
Either one is fine, and they both work quite well. This is the
"basic" roofing filter used on receive as well.

If you operate primarily SSB, the 2.7/2.8 roofing filter is usually
enough. If you're into contesting, I'd suggest 1.8 or 2.1 KHz as
well.

For CW and data modes, a smaller width filter might be helpful. I
have found that the 1KHz and 250 Hz filters are a good complementary
pair for CW and data modes like PSK31. If you only operate CW, any
filter at or under 500 Hz is fine.

AM and FM modes require wider filters (6 KHz and 15 KHz, respectively)
and this is detailed out on the Elecraft K3's web page.

A nice basic configuration would be 2.8 KHz for SSB and 500 Hz for CW.
You can always add to this since there are five roofing filter
positions.

73,
matt W6NIA
K3 #24, P3 #14

On Sun, 03 Oct 2010 18:27:50 -0500 (CDT), you wrote:

>
>Hi Guys, in my quest to purchase a new K3 I am worndering about 8 pole filter choices. I see that there is a 1.8 KHZ 8 pole ssb filter and a 250 HZ 8 pole cw filter that is avaiable. If one purchases one of these filters wouldn't that basically solve the problem of not needing all the other filters at different KHZ? This probably is a stupid question, but would really like to learn. Mark KB3Z
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Don Wilhelm-4

Re: K3 Filter Choices

In reply to this post by pastormg

Mark,

This question is asked over and over, and you will get answers all over
the board.
The real answer is that a lot of your filter choices will depend on what
kind of operating you will do and in what modes.
If you do a lot of contesting or work DX in heavy pileups where there
are a lot of strong stations close to what you want to hear. then you
should have only the 8 pole filters, their skirts are a little bit
steeper - BUT - these are only roofing filters, the DSP takes care of
most of the filtering, and does it quite well. If you will be adding
the KRX3, the filters must be matched for diversity reception, so the
simple way is just to use the 2.8 kHz filters.

In fact, the DSP filtering is good enough to be used alone, it goes down
to 50 Hz width - but the DSP can only do its job if the ADC is not being
overdriven - the hardware AGC does protect from that, but will result in
"pumping" of that hardware AGC if there a quite strong (S-9 +20 or more)
nearby signals. The K3 roofing filters will knock down the strength of
those nearby signals to a point where the hardware AGC is not activated.

Eric Swartz has posted some information for making filter choices on the
Elecraft website, I suggest you read that too.

Bottom line is that you will have to review the type of operating that
you will do with the K3 and select your filters from that information.
If your operation is rather casual, you may only need the stock 2.7 kHz
filter.

If you want to transmit either AM or ESSB or you want wide bandwidth SWL
reception, you will need the 6 kHz filter, and if you want to either
transmit or receive FM, you will need the 13 kHz filter.

Another option is to wait and see - order your K3 with the stock filter
(or perhaps the optional 2.8 8 pole filter), and operate for a while to
determine your usual DSP-set bandwidths for each mode you use - that
information will reveal the filters that you will derive most benefit from.

A word of caution on my above suggestion - if you will install the KRX3
immediately, you must remove it to add more filters, and that operation
has been referred to as a "shoehorn operation", so your choice is to
guess at the filters needed and order them up front or delay the
installation of the KRX3. Without the KRX3 installed, the filters are a
breeze to change.

73,
Don W3FPR

On 10/3/2010 7:27 PM, [hidden email] wrote:
> Hi Guys, in my quest to purchase a new K3 I am worndering about 8 pole filter choices. I see that there is a 1.8 KHZ 8 pole ssb filter and a 250 HZ 8 pole cw filter that is avaiable. If one purchases one of these filters wouldn't that basically solve the problem of not needing all the other filters at different KHZ? This probably is a stupid question, but would really like to learn. Mark KB3Z
>
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Don Wilhelm-4

Re: K3 Filter Choices

Sorry, That should have been, "so the simple way id just to use the 8
pole filters (which have zero offset)".
There is benefit in one reading your own posts - hopefully before
hitting send, but as you can see, I failed. :-)

73,
Don W3FPR

On 10/3/2010 7:59 PM, Don Wilhelm wrote:
> If you will be adding
> the KRX3, the filters must be matched for diversity reception, so the
> simple way is just to use the 2.8 kHz filters.
>
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Dave Hachadorian

Re: K3 Filter Choices

In reply to this post by pastormg

>I see that there is a 1.8 KHZ 8 pole
> ssb filter and a 250 HZ 8 pole cw filter that is avaiable. If
> one purchases one of these filters wouldn't that basically
> solve the problem of not needing all the other filters at
> different KHZ?
-------------------------------

250, 1.8, and 2.7 - perfect!

Set the 250 to switch in at dsp=400, and set the 1.8 to switch in
at dsp=2.1

That's all you need for casual or competitive cw, rtty and ssb.

Dave Hachadorian, K6LL
Yuma, AZ

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k5oai

Re: K3 Filter Choices

exactly how do you:
> Set the 250 to switch in at dsp=400, and set the 1.8 to switch in
> at dsp=2.1
>

GB & 73
K5OAI
Sam Morgan

On 10/3/2010 7:14 PM, Dave Hachadorian wrote:

>> I see that there is a 1.8 KHZ 8 pole
>> ssb filter and a 250 HZ 8 pole cw filter that is avaiable. If
>> one purchases one of these filters wouldn't that basically
>> solve the problem of not needing all the other filters at
>> different KHZ?
> -------------------------------
>
> 250, 1.8, and 2.7 - perfect!
>
> Set the 250 to switch in at dsp=400, and set the 1.8 to switch in
> at dsp=2.1
>
> That's all you need for casual or competitive cw, rtty and ssb.
>
> Dave Hachadorian, K6LL
> Yuma, AZ

Don Wilhelm-4

Re: K3 Filter Choices

Sam,

You "tell falsehoods" to the K3 when you configure the filter. If it
thinks a 250 Hz filter is actually a 400 Hz width, it will switch in at
that point.

73,
Don W3FPR

On 10/3/2010 8:34 PM, Sam Morgan wrote:
> exactly how do you:
> > Set the 250 to switch in at dsp=400, and set the 1.8 to switch in
> > at dsp=2.1
> >
>
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Jack Brabham KZ5A

Re: K3 Filter Choices

I have the 1.8 and find it to be a great all round SSB filter, although
some contesters are opting for the Inrad 1.5 instead. The 250 is a
must for CW, RTTY, PSK, etc.. There are also 500 and 700 hz 8 pole
filters around for more casual CW or the wider data modes. Haven't
heard anyone say anything positive about the 1.0 kc filter. The 6kc is
needed if you are interested in AM, ESSB, or SWL. The 2.8 "presumably"
produces a technically better TX signal than the stock 2.7 but so far I
haven't been able to justify the expense.

73 Jack KZ5A
K3 #4165

On 10/3/2010 7:37 PM, Don Wilhelm wrote:

> Sam,
>
> You "tell falsehoods" to the K3 when you configure the filter. If it
> thinks a 250 Hz filter is actually a 400 Hz width, it will switch in at
> that point.
>
> 73,
> Don W3FPR
>
> On 10/3/2010 8:34 PM, Sam Morgan wrote:
>> exactly how do you:
>> > Set the 250 to switch in at dsp=400, and set the 1.8 to switch in
>> > at dsp=2.1
>> >
>>
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