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filters

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john@kk9a.com

filters

400Hz is definitely my favorite CW and RTTY filter. I also use the 250Hz
roofing filter (switched in at 350Hz) when the QRM gets bad, what document
shows that this offers little improvement?

John KK9A

K9MA wrote:

Assuming it's for a K3(s), I don't think you will find the 250 Hz filter
very useful. The response that both Elecraft and I measured shows that
the narrow filter really isn't much better. Were I to do it again, I
would only use the 400 Hz ones.

73,
Scott K9MA

On 12/31/2017 17:02, doug dietz wrote:
> Guys
> i ordered a 400hz filter by mistake. I have use for a 200h or 1k, 18.k
> What ya got
> doug49707 at gmail.com Doug WD8Z

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K9MA

Re: filters

I use similar settings for CW, with both filters. I haven't tried DSP
bandwidth of 250 Hz with the 400 Hz crystal filter, but based on the
filter characteristics, I don't think it would make much difference.
Also, the 250 Hz filter drifts around so much with temperature that it's
hard to keep it centered properly.

Compare the responses here:

http://www.elecraft.com/K3/K3_filter_plots.htm

Anyhow, all I'm saying is that even for a pretty hard-core CW contester,
I'm not sure the narrow filter is worth the investment.

Now, my previous rig, an FT-1000D, which is inferior to the K3 in almost
every other way, actually has better skirt rejection on CW, but that's
with cascaded crystal filters, both of either 500 or 250 Hz bandwidth.
I'm not sure that's because of an inherent limitation of the K3 DSP, or
just the filter algorithm chosen (perhaps to limit latency?).

73,
Scott K9MA

On 12/31/2017 21:32, [hidden email] wrote:

> 400Hz is definitely my favorite CW and RTTY filter. I also use the 250Hz
> roofing filter (switched in at 350Hz) when the QRM gets bad, what document
> shows that this offers little improvement?
>
> John KK9A
>
>
> K9MA wrote:
>
> Assuming it's for a K3(s), I don't think you will find the 250 Hz filter
> very useful. The response that both Elecraft and I measured shows that
> the narrow filter really isn't much better. Were I to do it again, I
> would only use the 400 Hz ones.
>
> 73,
> Scott K9MA
>
> On 12/31/2017 17:02, doug dietz wrote:
>> Guys
>> i ordered a 400hz filter by mistake. I have use for a 200h or 1k, 18.k
>> What ya got
>> doug49707 at gmail.com Doug WD8Z
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--
Scott K9MA

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Ed Muns

Re: filters

In reply to this post by john@kk9a.com

The actual passband of these two filters is more important than the
marketing name. The "400 Hz" filter is about 435 Hz wide at the -6dB
points. The "250 Hz" filter is about 380 Hz wide. Look at the graphs on
the Elecraft website.

Ed W0YK

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of [hidden email]
Sent: Sunday, December 31, 2017 7:32 PM
To: 'Elecraft Reflector' <[hidden email]>
Subject: [Elecraft] filters

400Hz is definitely my favorite CW and RTTY filter. I also use the 250Hz
roofing filter (switched in at 350Hz) when the QRM gets bad, what document
shows that this offers little improvement?

John KK9A

K9MA wrote:

Assuming it's for a K3(s), I don't think you will find the 250 Hz filter
very useful. The response that both Elecraft and I measured shows that the
narrow filter really isn't much better. Were I to do it again, I would only
use the 400 Hz ones.

73,
Scott K9MA

On 12/31/2017 17:02, doug dietz wrote:
> Guys
> i ordered a 400hz filter by mistake. I have use for a 200h or 1k, 18.k
> What ya got
> doug49707 at gmail.com Doug WD8Z

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Bob McGraw - K4TAX

Re: filters

In reply to this post by K9MA

I prefer the 500Hz filter over more narrow ones. Less IMD on the RX signal.

Bob, K4TAX

Sent from my iPhone

> On Dec 31, 2017, at 9:55 PM, K9MA <[hidden email]> wrote:
>
> I use similar settings for CW, with both filters. I haven't tried DSP bandwidth of 250 Hz with the 400 Hz crystal filter, but based on the filter characteristics, I don't think it would make much difference. Also, the 250 Hz filter drifts around so much with temperature that it's hard to keep it centered properly.
>
> Compare the responses here:
>
> http://www.elecraft.com/K3/K3_filter_plots.htm
>
> Anyhow, all I'm saying is that even for a pretty hard-core CW contester, I'm not sure the narrow filter is worth the investment.
>
> Now, my previous rig, an FT-1000D, which is inferior to the K3 in almost every other way, actually has better skirt rejection on CW, but that's with cascaded crystal filters, both of either 500 or 250 Hz bandwidth. I'm not sure that's because of an inherent limitation of the K3 DSP, or just the filter algorithm chosen (perhaps to limit latency?).
>
> 73,
> Scott K9MA
>
>
>> On 12/31/2017 21:32, [hidden email] wrote:
>> 400Hz is definitely my favorite CW and RTTY filter. I also use the 250Hz
>> roofing filter (switched in at 350Hz) when the QRM gets bad, what document
>> shows that this offers little improvement?
>>
>> John KK9A
>>
>>
>> K9MA wrote:
>>
>> Assuming it's for a K3(s), I don't think you will find the 250 Hz filter
>> very useful. The response that both Elecraft and I measured shows that
>> the narrow filter really isn't much better. Were I to do it again, I
>> would only use the 400 Hz ones.
>>
>> 73,
>> Scott K9MA
>>
>>> On 12/31/2017 17:02, doug dietz wrote:
>>> Guys
>>> i ordered a 400hz filter by mistake. I have use for a 200h or 1k, 18.k
>>> What ya got
>>> doug49707 at gmail.com Doug WD8Z
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to [hidden email]
>
>
> --
> Scott K9MA
>
> [hidden email]
>
> ______________________________________________________________
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Re: filters

In reply to this post by K9MA

There is a newer 200HZ filter with more poles and does a great job in
contest situations,

I have a FT-1000D with a Inrad 125hz filter in 455khz cascaded with a
250HZ in the wide IF,
and the 1000D cannot hold a candle to a K3 skirt selectivity, that is
the one major reason
I bought the K3 after using one, the difference in skirt selectivity
was so apparent it was
not even a question, I had several ft-1000D and none of them were even
close,
If your ears cant hear the difference try measuring it.
Plus the 1000D filters cause IMD up the wazoo, and by the way I also
had the Inrad roofing
filter in the 1000D, so actually 3 cascaded.

Merv K9FD

>
> Now, my previous rig, an FT-1000D, which is inferior to the K3 in
> almost every other way, actually has better skirt rejection on CW, but
> that's with cascaded crystal filters, both of either 500 or 250 Hz
> bandwidth. I'm not sure that's because of an inherent limitation of
> the K3 DSP, or just the filter algorithm chosen (perhaps to limit
> latency?).
>
> 73,
> Scott K9MA
>
>
> On 12/31/2017 21:32, [hidden email] wrote:
>> 400Hz is definitely my favorite CW and RTTY filter. I also use the 250Hz
>> roofing filter (switched in at 350Hz) when the QRM gets bad, what
>> document
>> shows that this offers little improvement?
>>
>> John KK9A
>>
>>
>> K9MA wrote:
>>
>> Assuming it's for a K3(s), I don't think you will find the 250 Hz filter
>> very useful. The response that both Elecraft and I measured shows that
>> the narrow filter really isn't much better. Were I to do it again, I
>> would only use the 400 Hz ones.
>>
>> 73,
>> Scott K9MA
>>
>> On 12/31/2017 17:02, doug dietz wrote:
>>> Guys
>>> i ordered a 400hz filter by mistake. I have use for a 200h or 1k, 18.k
>>> What ya got
>>> doug49707 at gmail.com Doug WD8Z
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to [hidden email]
>
>

Joe Subich, W4TV-4

Re: filters

In reply to this post by Ed Muns

On 12/31/2017 10:58 PM, [hidden email] wrote:
> The actual passband of these two filters is more important than the
> marketing name.

The "marketing name" on the <Inrad> filters is effectively the -1dB
bandwidth. The name is derived from their original use in Yaesu rigs
and Yaesu's marketing where there were two filters in cascade and
represents the final effective bandwidth of the cascaded pair. Plot
the cascaded bandwidth of the Inrad #701/#703 pair (400 Hz), #708/#704
pair (250 Hz) or the #711/#714 pair (1800 Hz) and see how that works.

When one has only the first IF filter, the "cascade" is provided by
the 2nd IF DSP. In the K3/K3S what does the "WIDTH" display actually
show - the -0dB, -1dB, or -3dB point of the 2nd IF response? Then,
how does that match with the first IF filter and what is the composite
response.

73,

... Joe, W4TV

On 12/31/2017 10:58 PM, [hidden email] wrote:

> The actual passband of these two filters is more important than the
> marketing name. The "400 Hz" filter is about 435 Hz wide at the -6dB
> points. The "250 Hz" filter is about 380 Hz wide. Look at the graphs on
> the Elecraft website.
>
> Ed W0YK
>
> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of [hidden email]
> Sent: Sunday, December 31, 2017 7:32 PM
> To: 'Elecraft Reflector' <[hidden email]>
> Subject: [Elecraft] filters
>
> 400Hz is definitely my favorite CW and RTTY filter. I also use the 250Hz
> roofing filter (switched in at 350Hz) when the QRM gets bad, what document
> shows that this offers little improvement?
>
> John KK9A
>
>
> K9MA wrote:
>
> Assuming it's for a K3(s), I don't think you will find the 250 Hz filter
> very useful. The response that both Elecraft and I measured shows that the
> narrow filter really isn't much better. Were I to do it again, I would only
> use the 400 Hz ones.
>
> 73,
> Scott K9MA
>
> On 12/31/2017 17:02, doug dietz wrote:
>> Guys
>> i ordered a 400hz filter by mistake. I have use for a 200h or 1k, 18.k
>> What ya got
>> doug49707 at gmail.com Doug WD8Z
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html Message
> delivered to [hidden email]
>
> ______________________________________________________________
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john@kk9a.com

Re: filters

In reply to this post by Ed Muns

So I guess you're saying that there is not much difference, only 55Hz, so
maybe it is not worth the cost of having both. My K3S's are programmed to
switch these roofing filters in closer to their actual passband. The cost of
the 250Hz filter is a small percentage of the transceiver cost so I do not
mind having this option. I see it being far more useful than the 1.0Khz
filter. WD8Z said that he ordered the 400Hz by mistake and my initial
comment was that it is a fantastic CW/RTTY filter. I have two in each of my
K3S's.

John KK9A

-----Original Message-----
From: [hidden email] [mailto:[hidden email]]
Sent: Sunday, December 31, 2017 10:58 PM
To: [hidden email]
Cc: 'Elecraft Reflector'
Subject: RE: [Elecraft] filters

The actual passband of these two filters is more important than the
marketing name. The "400 Hz" filter is about 435 Hz wide at the -6dB
points. The "250 Hz" filter is about 380 Hz wide. Look at the graphs on
the Elecraft website.

Ed W0YK

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of [hidden email]
Sent: Sunday, December 31, 2017 7:32 PM
To: 'Elecraft Reflector' <[hidden email]>
Subject: [Elecraft] filters

400Hz is definitely my favorite CW and RTTY filter. I also use the 250Hz
roofing filter (switched in at 350Hz) when the QRM gets bad, what document
shows that this offers little improvement?

John KK9A

K9MA wrote:

Assuming it's for a K3(s), I don't think you will find the 250 Hz filter
very useful. The response that both Elecraft and I measured shows that the
narrow filter really isn't much better. Were I to do it again, I would only
use the 400 Hz ones.

73,
Scott K9MA

On 12/31/2017 17:02, doug dietz wrote:
> Guys
> i ordered a 400hz filter by mistake. I have use for a 200h or 1k, 18.k
> What ya got
> doug49707 at gmail.com Doug WD8Z

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K9MA

Re: filters

A quick look at the Elecraft filter response plots for the KFL3A-250 and
KFL3A-400 shows these bandwidths:

dB      -250     -400

-6       400      420
-20      480      530
-40      600      700
-60      780      920

So, the narrow filter won't make much difference close in, but may
provide more rejection more than 200 Hz from the center frequency.
(Assuming it hasn't drifted too far.) Another way to look at it is that
the narrow filter has about 10 dB more rejection beyond +/-200 Hz.
This, of course, adds to the DSP rejection, and may prevent overloading
of the DSP by a strong adjacent signal. How often this makes any
difference is hard to say.

I can say that I can't recall ever switching to the narrow filter to
reduce QRM from a signal more than about 400 Hz away. I frequently do,
however, for those less than 200 Hz away, in which case the extra
rejection must come almost entirely from the DSP.

Scott K9MA

On 1/1/2018 13:35, [hidden email] wrote:

K9FD

Re: filters

In reply to this post by john@kk9a.com

KFL3C-200 200 Hz

Look at that one instead of the 250hz if your going to put a narrow one in.
I have both and the 200 is more xtals and is better.
73 Merv K9FD

> So I guess you're saying that there is not much difference, only 55Hz, so
> maybe it is not worth the cost of having both. My K3S's are programmed to
> switch these roofing filters in closer to their actual passband. The cost of
> the 250Hz filter is a small percentage of the transceiver cost so I do not
> mind having this option. I see it being far more useful than the 1.0Khz
> filter. WD8Z said that he ordered the 400Hz by mistake and my initial
> comment was that it is a fantastic CW/RTTY filter. I have two in each of my
> K3S's.
>
> John KK9A
>
>
> -----Original Message-----
> From: [hidden email] [mailto:[hidden email]]
> Sent: Sunday, December 31, 2017 10:58 PM
> To: [hidden email]
> Cc: 'Elecraft Reflector'
> Subject: RE: [Elecraft] filters
>
> The actual passband of these two filters is more important than the
> marketing name. The "400 Hz" filter is about 435 Hz wide at the -6dB
> points. The "250 Hz" filter is about 380 Hz wide. Look at the graphs on
> the Elecraft website.
>
> Ed W0YK
>
> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of [hidden email]
> Sent: Sunday, December 31, 2017 7:32 PM
> To: 'Elecraft Reflector' <[hidden email]>
> Subject: [Elecraft] filters
>
> 400Hz is definitely my favorite CW and RTTY filter. I also use the 250Hz
> roofing filter (switched in at 350Hz) when the QRM gets bad, what document
> shows that this offers little improvement?
>
> John KK9A
>
>
> K9MA wrote:
>
> Assuming it's for a K3(s), I don't think you will find the 250 Hz filter
> very useful. The response that both Elecraft and I measured shows that the
> narrow filter really isn't much better. Were I to do it again, I would only
> use the 400 Hz ones.
>
> 73,
> Scott K9MA
>
> On 12/31/2017 17:02, doug dietz wrote:
>> Guys
>> i ordered a 400hz filter by mistake. I have use for a 200h or 1k, 18.k
>> What ya got
>> doug49707 at gmail.com Doug WD8Z
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html Message
> delivered to [hidden email]
>
> ______________________________________________________________
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K9MA

Re: filters

On 1/1/2018 15:09, K9FD wrote:
> KFL3C-200 200 Hz
>
> Look at that one instead of the 250hz if your going to put a narrow
> one in.
> I have both and the 200 is more xtals and is better.

When did that one become available?

Scott K9MA

--
Scott K9MA

[hidden email]

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Re: filters

Some time ago, bought some when they first came out, swapped
them in instead of 250HZ.
May have been in 2016 not sure.

Merv K9FD

> On 1/1/2018 15:09, K9FD wrote:
>> KFL3C-200 200 Hz
>>
>> Look at that one instead of the 250hz if your going to put a narrow
>> one in.
>> I have both and the 200 is more xtals and is better.
>
> When did that one become available?
>
>
> Scott K9MA
>

Petr, OK1RP/M0SIS

Re: filters

In reply to this post by john@kk9a.com

Hi all,

the interesting think is to check the first -30dB attenuation skirt first.
(After about -30dB down from the peak of the crystal filter response curve
the DSP handles the remaining signal rejection for very strong signals that
are inside the filter response curve, effectively sharpening the remaining
filter response and limiting the b/w to that point)

Just the 2c...

Happy and healthy New Year 2018 to all over there!

73 - Petr, OK1RP

-----
http://ok1rp.blogspot.com
--
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73 - Petr, OK1RP
"Apple & Elecraft freak"
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