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K3 Roofing Filter Gain Setup

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KD8NNU

K3 Roofing Filter Gain Setup

Gents,

I am searching without much luck for recommendations for the gain
setting recommendations for roofing filters.

Specfically I have a 700 hz 8 pole and a 200 hz filter 5 pole. There
is a gain setting in the k3 setup menue and I remember there were
recomendations on how to choose this setting. However, I have not been
able to find reference on the net.

Please can anyone provide some guidance as the performance when these
filters are engaged with digital modes is rather disapointing. What I
mean by this is that a signal can be very clean with the 2.7 or 2.1
filter engaged but if I use on of these filters the signal becomes very
poor. I want to use these to isolate close in signals but there appears
to be a lot of distortation so they are basically of little use.

I am betting that there is more to this gain setting than meets the eye
and that is where my problem is. I have put the gain for these two
filters at 1 and the 2.1 & 2.7 at zero.

I will be playing around with the settings, but there is a method to set
this parameter so I need to learn what and why so I can make them work
the way they are supposed to work.

Thanks and have a great holiday.

Don
KD8NNU
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Matt Zilmer

Re: K3 Roofing Filter Gain Setup

>From D9 Owner's Manual (may be downrev at this point), p49:

Use VFO A to set the gain in dB. In general,
youll want to add 1-2 dB for 400-500 Hz
filters, and 3-4 dB for 200-250 Hz filters.

I left the 1.8, 2.8, 6 and 13K filters alone. The 250 Hz I have set
for 3 dB gain.

matt W6NIA

--
On Sat, 28 May 2011 15:17:23 -0400 (EDT), you wrote:

>Gents,
>
>I am searching without much luck for recommendations for the gain
>setting recommendations for roofing filters.
>
>Specfically I have a 700 hz 8 pole and a 200 hz filter 5 pole. There
>is a gain setting in the k3 setup menue and I remember there were
>recomendations on how to choose this setting. However, I have not been
>able to find reference on the net.
>
>Please can anyone provide some guidance as the performance when these
>filters are engaged with digital modes is rather disapointing. What I
>mean by this is that a signal can be very clean with the 2.7 or 2.1
>filter engaged but if I use on of these filters the signal becomes very
>poor. I want to use these to isolate close in signals but there appears
>to be a lot of distortation so they are basically of little use.
>
>I am betting that there is more to this gain setting than meets the eye
>and that is where my problem is. I have put the gain for these two
>filters at 1 and the 2.1 & 2.7 at zero.
>
>I will be playing around with the settings, but there is a method to set
>this parameter so I need to learn what and why so I can make them work
>the way they are supposed to work.
>
>Thanks and have a great holiday.
>
>Don
>KD8NNU
>______________________________________________________________
>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

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Gary Hvizdak

Re: K3 Roofing Filter Gain Setup

In reply to this post by KD8NNU

Don (KD8NNU) writes ...

"I am searching without much luck for recommendations for the gain
setting recommendations for roofing filters."

=== = = = ===

Don,

See Wayne's "K3 crystal filter offset/bandwidth/gain setting guidelines"
post, dated 13 FEB 2009. You will find it in the Reflector archives at
http://mailman.qth.net/pipermail/elecraft/2009-February/105445.html

73,
Gary KI4GGX

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KD8NNU

Re: K3 Roofing Filter Gain Setup

In reply to this post by KD8NNU

Dear All

I am looking at PSK31 signals not SSB and my definition of distortion is
my visual observation on the PC waterfall in DM780 and the fact that
decode of the signal by the PC starts to fail when I engage the narrow
filters. This is observed when I have clean signals using the 2.1 or
2.7 filters and only DSP. I do understand the how strong signals can
create havoc in the band which is why I have the narrow filters. The
issue is until I get them setup to work well without interference I will
not expect them to help much when I have close signals or weak signals
that I want to pull out.

I do have all the offsets per the documentation with the filters so this
should not be the issue.

Folks have pointed to some articles regarding the setting of the filter
gain and have privided insight on how to use information on the K3
display to help quantify signals.

My biggest problem is I have zero results when I do searches on these
types of topics. One of the responses was a link directly to a writeup
that I had been searching for, go figure. :-)

All I know for sure is that again the user community has helped me get
to the info I needed and now I have a basis of logic on what I will be
looking at when I make some adjustments.

Now I need to get in front of the radio and follow the advice of the
wise ones.

Thanks Everyone!!!

Don
KD8NNU

On Sat, May 28, 2011 at 3:17 PM, [hidden email] wrote:

> Gents,
>
> I am searching without much luck for recommendations for the gain
> setting recommendations for roofing filters.
>
> Specfically I have a 700 hz 8 pole and a 200 hz filter 5 pole. There
> is a gain setting in the k3 setup menue and I remember there were
> recomendations on how to choose this setting. However, I have not
> been able to find reference on the net.
>
> Please can anyone provide some guidance as the performance when these
> filters are engaged with digital modes is rather disapointing. What
> I mean by this is that a signal can be very clean with the 2.7 or 2.1
> filter engaged but if I use on of these filters the signal becomes
> very poor. I want to use these to isolate close in signals but there
> appears to be a lot of distortation so they are basically of little
> use.
>
> I am betting that there is more to this gain setting than meets the
> eye and that is where my problem is. I have put the gain for these
> two filters at 1 and the 2.1 & 2.7 at zero.
>
> I will be playing around with the settings, but there is a method to
> set this parameter so I need to learn what and why so I can make them
> work the way they are supposed to work.
>
> Thanks and have a great holiday.
>
> Don
> KD8NNU
> ______________________________________________________________
> 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

Dick Dievendorff

Re: K3 Roofing Filter Gain Setup

In reply to this post by KD8NNU

There are recommendations in the K3 Owner's manual (see "Crystal Filter
Setup", indexed, on page 46) :

Use VFO A to set the gain in dB. In general, you'll want to add 1-2 dB for
400-500 Hz filters, and 3-4 dB for 200-250 Hz filters.

and there is a table (with essentially the same guidance) in K3 Utility Help
for the Filter Configuration page. I've lost the table formatting in
cut/paste from Help, but here's the information:

Narrow crystal filters tend to have more passband loss than wide filters.
You can compensate for this effect by specifying an amount of added gain to
use for each filter in receive mode. Enter the desired gain "boost", in
decibels, for each filter. You may specify a value between 0 and 8 dB.

Elecraft recommends using the initial loss compensation values below. You
may wish to further adjust the values for your particular filters.

Part Number Bandwidth Gain

KFL3A-200 0.20 kHz 3-4 dB
KFL3A-250 0.25 kHz 3-4 dB
KFL3A-400 0.40 kHz 1-2 dB
KFL3A-500 0.50 kHz 1-2 dB
KFL3A-1.0K 1.00 kHz 0 dB
KFL3A-1.8K 1.80 kHz 0 dB
KFL3A-2.1K 2.10 kHz 0 dB
KFL3A-2.7K 2.70 kHz 0 dB
KFL3A-2.8K 2.80 kHz 0 dB
KFL3A-6K 6.00 kHz 0 dB
KFL3B-FM 13.00 kHz 0 dB

73 de Dick, K6KR

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of [hidden email]
Sent: Saturday, May 28, 2011 12:17 PM
To: Elecraft
Subject: [Elecraft] K3 Roofing Filter Gain Setup

Gents,

I am searching without much luck for recommendations for the gain setting
recommendations for roofing filters.

Specfically I have a 700 hz 8 pole and a 200 hz filter 5 pole. There
is a gain setting in the k3 setup menue and I remember there were
recomendations on how to choose this setting. However, I have not been able
to find reference on the net.

Please can anyone provide some guidance as the performance when these
filters are engaged with digital modes is rather disapointing. What I
mean by this is that a signal can be very clean with the 2.7 or 2.1 filter
engaged but if I use on of these filters the signal becomes very poor. I
want to use these to isolate close in signals but there appears to be a lot
of distortation so they are basically of little use.

I am betting that there is more to this gain setting than meets the eye and
that is where my problem is. I have put the gain for these two filters at 1
and the 2.1 & 2.7 at zero.

I will be playing around with the settings, but there is a method to set
this parameter so I need to learn what and why so I can make them work the
way they are supposed to work.

Thanks and have a great holiday.

Don
KD8NNU
______________________________________________________________
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drewko

Re: K3 Roofing Filter Gain Setup

If I use a 50uv signal generator to set the filter gains for equal
readings on my K3's AFV meter I arrive at the following compensations:

2.70 KHz = 0db
500 Hz = 4 db
250 Hz = 8 db

This is way more aggressive than the suggested amounts but these
figures do sound equalized to my ears for real signal conditions. The
factory settings are noticeably weak. Maybe my particular filters are
just not up to par.

73,
Drew
AF2Z

On Sat, 28 May 2011 14:18:45 -0700, you wrote:

>There are recommendations in the K3 Owner's manual (see "Crystal Filter
>Setup", indexed, on page 46) :
>
>Use VFO A to set the gain in dB. In general, you'll want to add 1-2 dB for
>400-500 Hz filters, and 3-4 dB for 200-250 Hz filters.
>
>and there is a table (with essentially the same guidance) in K3 Utility Help
>for the Filter Configuration page. I've lost the table formatting in
>cut/paste from Help, but here's the information:
>
>Narrow crystal filters tend to have more passband loss than wide filters.
>You can compensate for this effect by specifying an amount of added gain to
>use for each filter in receive mode. Enter the desired gain "boost", in
>decibels, for each filter. You may specify a value between 0 and 8 dB.
>
>Elecraft recommends using the initial loss compensation values below. You
>may wish to further adjust the values for your particular filters.
>
>Part Number Bandwidth Gain
>
>KFL3A-200 0.20 kHz 3-4 dB
>KFL3A-250 0.25 kHz 3-4 dB
>KFL3A-400 0.40 kHz 1-2 dB
>KFL3A-500 0.50 kHz 1-2 dB
>KFL3A-1.0K 1.00 kHz 0 dB
>KFL3A-1.8K 1.80 kHz 0 dB
>KFL3A-2.1K 2.10 kHz 0 dB
>KFL3A-2.7K 2.70 kHz 0 dB
>KFL3A-2.8K 2.80 kHz 0 dB
>KFL3A-6K 6.00 kHz 0 dB
>KFL3B-FM 13.00 kHz 0 dB
>
>73 de Dick, K6KR
>
>

alsopb

Re: K3 Roofing Filter Gain Setup

On 5/29/2011 13:43, drewko wrote:

> If I use a 50uv signal generator to set the filter gains for equal
> readings on my K3's AFV meter I arrive at the following compensations:
>
> 2.70 KHz = 0db
> 500 Hz = 4 db
> 250 Hz = 8 db
>
> This is way more aggressive than the suggested amounts but these
> figures do sound equalized to my ears for real signal conditions. The
> factory settings are noticeably weak. Maybe my particular filters are
> just not up to par.
>
> 73,
> Drew
> AF2Z
>
>
> On Sat, 28 May 2011 14:18:45 -0700, you wrote:
>
>> There are recommendations in the K3 Owner's manual (see "Crystal Filter
>> Setup", indexed, on page 46) :
>>
>> Use VFO A to set the gain in dB. In general, you'll want to add 1-2 dB for
>> 400-500 Hz filters, and 3-4 dB for 200-250 Hz filters.
>>
>> and there is a table (with essentially the same guidance) in K3 Utility Help
>> for the Filter Configuration page. I've lost the table formatting in
>> cut/paste from Help, but here's the information:
>>
>> Narrow crystal filters tend to have more passband loss than wide filters.
>> You can compensate for this effect by specifying an amount of added gain to
>> use for each filter in receive mode. Enter the desired gain "boost", in
>> decibels, for each filter. You may specify a value between 0 and 8 dB.
>>
>> Elecraft recommends using the initial loss compensation values below. You
>> may wish to further adjust the values for your particular filters.
>>
>> Part Number Bandwidth Gain
>>
>> KFL3A-200 0.20 kHz 3-4 dB
>> KFL3A-250 0.25 kHz 3-4 dB
>> KFL3A-400 0.40 kHz 1-2 dB
>> KFL3A-500 0.50 kHz 1-2 dB
>> KFL3A-1.0K 1.00 kHz 0 dB
>> KFL3A-1.8K 1.80 kHz 0 dB
>> KFL3A-2.1K 2.10 kHz 0 dB
>> KFL3A-2.7K 2.70 kHz 0 dB
>> KFL3A-2.8K 2.80 kHz 0 dB
>> KFL3A-6K 6.00 kHz 0 dB
>> KFL3B-FM 13.00 kHz 0 dB
>>
>> 73 de Dick, K6KR
>>
>>
>
> ______________________________________________________________
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> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
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> Please help support this email list: http://www.qsl.net/donate.html
>
>
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>
>

-----
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Checked by AVG - www.avg.com
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alsopb

Re: K3 Roofing Filter Gain Setup

In reply to this post by drewko

On 5/29/2011 13:43, drewko wrote:

alsopb

Re: K3 Roofing Filter Gain Setup

In reply to this post by alsopb

Sorry guys, having trouble with email program today. Please ignore
multiple messages.

Drew,

Interesting.

Did the same with a signal generator, S3 signal, AGC off and Spectrogram
to match the peak. I'm primarily interested in weak signal CW work and
don't want to fool with the AF gain when filter settings changed.

My results:
2.7 0 db
1.8 2
400 5
250 8
200 8

Have others say they didn't think 8db gain was enough for the narrowest
filters. The only way I can see to get 4db for the narrowest filters is
to somehow set a negative value for the 2.7 filter. That might not be
all that bad to have such a capability.

I wish somebody would explain excatly what the RF gain calibration does
and how it works. This is typically done after the crystal filter gains
are set. The procedure asks one to set the filter width to 100 Hz.
That of course would kick in the 200 Hz filter here. But some have said
this procedure sets the gain of the stage before the filters. So why
specify a filter width setting? What is monitored during the RF gain
adjustment process?

73 de Brian/K3KO

On 5/29/2011 14:02, Brian Alsop wrote:

> On 5/29/2011 13:43, drewko wrote:
>> If I use a 50uv signal generator to set the filter gains for equal
>> readings on my K3's AFV meter I arrive at the following compensations:
>>
>> 2.70 KHz = 0db
>> 500 Hz = 4 db
>> 250 Hz = 8 db
>>
>> This is way more aggressive than the suggested amounts but these
>> figures do sound equalized to my ears for real signal conditions. The
>> factory settings are noticeably weak. Maybe my particular filters are
>> just not up to par.
>>
>> 73,
>> Drew
>> AF2Z
>>
>>
>> On Sat, 28 May 2011 14:18:45 -0700, you wrote:
>>
>>> There are recommendations in the K3 Owner's manual (see "Crystal Filter
>>> Setup", indexed, on page 46) :
>>>
>>> Use VFO A to set the gain in dB. In general, you'll want to add 1-2 dB for
>>> 400-500 Hz filters, and 3-4 dB for 200-250 Hz filters.
>>>
>>> and there is a table (with essentially the same guidance) in K3 Utility Help
>>> for the Filter Configuration page. I've lost the table formatting in
>>> cut/paste from Help, but here's the information:
>>>
>>> Narrow crystal filters tend to have more passband loss than wide filters.
>>> You can compensate for this effect by specifying an amount of added gain to
>>> use for each filter in receive mode. Enter the desired gain "boost", in
>>> decibels, for each filter. You may specify a value between 0 and 8 dB.
>>>
>>> Elecraft recommends using the initial loss compensation values below. You
>>> may wish to further adjust the values for your particular filters.
>>>
>>> Part Number Bandwidth Gain
>>>
>>> KFL3A-200 0.20 kHz 3-4 dB
>>> KFL3A-250 0.25 kHz 3-4 dB
>>> KFL3A-400 0.40 kHz 1-2 dB
>>> KFL3A-500 0.50 kHz 1-2 dB
>>> KFL3A-1.0K 1.00 kHz 0 dB
>>> KFL3A-1.8K 1.80 kHz 0 dB
>>> KFL3A-2.1K 2.10 kHz 0 dB
>>> KFL3A-2.7K 2.70 kHz 0 dB
>>> KFL3A-2.8K 2.80 kHz 0 dB
>>> KFL3A-6K 6.00 kHz 0 dB
>>> KFL3B-FM 13.00 kHz 0 dB
>>>
>>> 73 de Dick, K6KR
>>>
>>>
>>
>> ______________________________________________________________
>> 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
>>
>>
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>> No virus found in this message.
>> Checked by AVG - www.avg.com
>> Version: 10.0.1375 / Virus Database: 1509/3665 - Release Date: 05/28/11
>>
>>
>
>
>
> -----
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 10.0.1375 / Virus Database: 1509/3665 - Release Date: 05/28/11
>
> ______________________________________________________________
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>
>

KK7P

Re: K3 Roofing Filter Gain Setup

RF Gain Calibration measures the effect of the hardware AGC voltage on
the K3's receive gain, in dB.

It uses a narrow filter setting to improve the S/N of the signal
measured by the DSP as the gain decreases and the signal being measured
is reduced in amplitude due to that decrease.

The hardware AGC voltage is applied after the 8.215 MHz roofing filters,
so the accuracy of the filter gain compensation is of no practical
consequence as long as the roofing filter selection is not changed
during the calibration process.

Becasue the hardware AGC calibration may affect the reported S Meter
values, S Meter calbration should be checked and adjusted if required,
after RF Gain Calibration is completed.

73,

Lyle KK7P

> I wish somebody would explain excatly what the RF gain calibration does
> and how it works. This is typically done after the crystal filter gains
> are set. The procedure asks one to set the filter width to 100 Hz.
> That of course would kick in the 200 Hz filter here. But some have said
> this procedure sets the gain of the stage before the filters. So why
> specify a filter width setting? What is monitored during the RF gain
> adjustment process?

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