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Filter problems

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Jim AB3CV

Filter problems

I think I've figured out why my subrx seems to be much less sensitive than
the main. I was playing around with the bandwidth control today while
having the VFOs linked.

I have the same filter setup in main and sub, a 2.8K and a 250hz, both 8
pole. I have both main and sub set to cut to the 250 at 350hz. I do most of
my Dx activity with the BW set to 350 so engaging the 250hz filter.

What I noticed is that although the sub is much less sensitive than the
main with the 250 engaged it is just fine just above where the filter kicks
in.

This tells me that something is wrong with the filter or the socket it is
in. The balance control has to be set past 3 oclock to even out the signals
with the 250 engaged in the sub. The balance is just fine however when that
filter isn't engaged.

I'm going to try moving the filter to another socket in the sub to see what
effect that has.

I can also try swapping the 250 between the sub and the main to see if the
loss of sensitivity tracks the filter placement.

Any other ideas?

It could be a bad filter. I don't think the filters should be that
different in loss when in spec.

jim
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Jim AB3CV

Re: Filter problems

Just used the K3 utility to disable the 250 8p on the sub and the audio now
is balanced regardless of sub bandwidth. Of course the noise level changes
but no imbalance with strong or weak sigs between the two.

Now to figure out if it's the socket or the filter at fault.

jim

On Tue, Mar 26, 2013 at 8:22 PM, Jim Miller <[hidden email]> wrote:

> I think I've figured out why my subrx seems to be much less sensitive than
> the main. I was playing around with the bandwidth control today while
> having the VFOs linked.
>
> I have the same filter setup in main and sub, a 2.8K and a 250hz, both 8
> pole. I have both main and sub set to cut to the 250 at 350hz. I do most of
> my Dx activity with the BW set to 350 so engaging the 250hz filter.
>
> What I noticed is that although the sub is much less sensitive than the
> main with the 250 engaged it is just fine just above where the filter kicks
> in.
>
> This tells me that something is wrong with the filter or the socket it is
> in. The balance control has to be set past 3 oclock to even out the signals
> with the 250 engaged in the sub. The balance is just fine however when that
> filter isn't engaged.
>
> I'm going to try moving the filter to another socket in the sub to see
> what effect that has.
>
> I can also try swapping the 250 between the sub and the main to see if the
> loss of sensitivity tracks the filter placement.
>
> Any other ideas?
>
> It could be a bad filter. I don't think the filters should be that
> different in loss when in spec.
>
> jim
>

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Vic Rosenthal

Re: Filter problems

Make sure the filter gain compensation is set properly for the 250 Hz filter. The easiest
way to do it is from the filter configuration screen of the K3 utility.

On 3/26/2013 5:44 PM, Jim Miller wrote:

> Just used the K3 utility to disable the 250 8p on the sub and the audio now
> is balanced regardless of sub bandwidth. Of course the noise level changes
> but no imbalance with strong or weak sigs between the two.
>
> Now to figure out if it's the socket or the filter at fault.
>
> jim
>
> On Tue, Mar 26, 2013 at 8:22 PM, Jim Miller <[hidden email]> wrote:
>
>> I think I've figured out why my subrx seems to be much less sensitive than
>> the main. I was playing around with the bandwidth control today while
>> having the VFOs linked.
>>
>> I have the same filter setup in main and sub, a 2.8K and a 250hz, both 8
>> pole. I have both main and sub set to cut to the 250 at 350hz. I do most of
>> my Dx activity with the BW set to 350 so engaging the 250hz filter.
>>
>> What I noticed is that although the sub is much less sensitive than the
>> main with the 250 engaged it is just fine just above where the filter kicks
>> in.
>>
>> This tells me that something is wrong with the filter or the socket it is
>> in. The balance control has to be set past 3 oclock to even out the signals
>> with the 250 engaged in the sub. The balance is just fine however when that
>> filter isn't engaged.
>>
>> I'm going to try moving the filter to another socket in the sub to see
>> what effect that has.
>>
>> I can also try swapping the 250 between the sub and the main to see if the
>> loss of sensitivity tracks the filter placement.
>>
>> Any other ideas?
>>
>> It could be a bad filter. I don't think the filters should be that
>> different in loss when in spec.
>>
>> jim
>>
> ______________________________________________________________
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--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/

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Jim AB3CV

Re: Filter problems

I spent some time last night playing with various filter settings via the
K3 utility. What I found is that the 250 8p filter in the main required no
boost to maintain signal level as I dialed down the bandwidth and engaged
it. The suspect one in the subrx required 6db of boost.

Has anyone else seen this level of boost required?

With the subrx bandwidth increased to be just above its 250hz8p filter the
receiver comes alive nicely.

I'll open up the K3 this weekend and do a filter inspection to see if there
is some crud on the pins and try a filter swap to the main just to verify
my suspicion of a bad filter.

I may have to order another...

jim ab3cv

On Wed, Mar 27, 2013 at 12:55 AM, Vic K2VCO <[hidden email]> wrote:

> Make sure the filter gain compensation is set properly for the 250 Hz
> filter. The easiest way to do it is from the filter configuration screen of
> the K3 utility.
>
>
> On 3/26/2013 5:44 PM, Jim Miller wrote:
>
>> Just used the K3 utility to disable the 250 8p on the sub and the audio
>> now
>> is balanced regardless of sub bandwidth. Of course the noise level changes
>> but no imbalance with strong or weak sigs between the two.
>>
>> Now to figure out if it's the socket or the filter at fault.
>>
>> jim
>>
>> On Tue, Mar 26, 2013 at 8:22 PM, Jim Miller <[hidden email]> wrote:
>>
>> I think I've figured out why my subrx seems to be much less sensitive
>>> than
>>> the main. I was playing around with the bandwidth control today while
>>> having the VFOs linked.
>>>
>>> I have the same filter setup in main and sub, a 2.8K and a 250hz, both 8
>>> pole. I have both main and sub set to cut to the 250 at 350hz. I do most
>>> of
>>> my Dx activity with the BW set to 350 so engaging the 250hz filter.
>>>
>>> What I noticed is that although the sub is much less sensitive than the
>>> main with the 250 engaged it is just fine just above where the filter
>>> kicks
>>> in.
>>>
>>> This tells me that something is wrong with the filter or the socket it is
>>> in. The balance control has to be set past 3 oclock to even out the
>>> signals
>>> with the 250 engaged in the sub. The balance is just fine however when
>>> that
>>> filter isn't engaged.
>>>
>>> I'm going to try moving the filter to another socket in the sub to see
>>> what effect that has.
>>>
>>> I can also try swapping the 250 between the sub and the main to see if
>>> the
>>> loss of sensitivity tracks the filter placement.
>>>
>>> Any other ideas?
>>>
>>> It could be a bad filter. I don't think the filters should be that
>>> different in loss when in spec.
>>>
>>> jim
>>>
>>> ______________________________**______________________________**__
>> Elecraft mailing list
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>> Help: http://mailman.qth.net/mmfaq.**htm<http://mailman.qth.net/mmfaq.htm>
>> Post: mailto:[hidden email].**net <[hidden email]>
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
>
> --
> Vic, K2VCO
> Fresno CA
> http://www.qsl.net/k2vco/
>
> ______________________________**______________________________**__
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Vic Rosenthal

Re: Filter problems

I don't have a 250 Hz filter, but both of my 400 Hz ones do require a few dB. I am more
surprised that your main filter requires NO boost, than that your sub requires 6 dB. How
much do others who have 250 Hz filters use?

On 4/3/2013 6:32 PM, Jim Miller wrote:

> I spent some time last night playing with various filter settings via the K3 utility.
> What I found is that the 250 8p filter in the main required no boost to maintain signal
> level as I dialed down the bandwidth and engaged it. The suspect one in the subrx
> required 6db of boost.
> Has anyone else seen this level of boost required?
> With the subrx bandwidth increased to be just above its 250hz8p filter the receiver
> comes alive nicely.
> I'll open up the K3 this weekend and do a filter inspection to see if there is some crud
> on the pins and try a filter swap to the main just to verify my suspicion of a bad filter.
> I may have to order another...
> jim ab3cv
>
>
> On Wed, Mar 27, 2013 at 12:55 AM, Vic K2VCO <[hidden email]
> <mailto:[hidden email]>> wrote:
>
> Make sure the filter gain compensation is set properly for the 250 Hz filter. The
> easiest way to do it is from the filter configuration screen of the K3 utility.
>
>
> On 3/26/2013 5:44 PM, Jim Miller wrote:
>
> Just used the K3 utility to disable the 250 8p on the sub and the audio now
> is balanced regardless of sub bandwidth. Of course the noise level changes
> but no imbalance with strong or weak sigs between the two.
>
> Now to figure out if it's the socket or the filter at fault.
>
> jim
>
> On Tue, Mar 26, 2013 at 8:22 PM, Jim Miller <[hidden email]
> <mailto:[hidden email]>> wrote:
>
> I think I've figured out why my subrx seems to be much less sensitive than
> the main. I was playing around with the bandwidth control today while
> having the VFOs linked.
>
> I have the same filter setup in main and sub, a 2.8K and a 250hz, both 8
> pole. I have both main and sub set to cut to the 250 at 350hz. I do most of
> my Dx activity with the BW set to 350 so engaging the 250hz filter.
>
> What I noticed is that although the sub is much less sensitive than the
> main with the 250 engaged it is just fine just above where the filter kicks
> in.
>
> This tells me that something is wrong with the filter or the socket it is
> in. The balance control has to be set past 3 oclock to even out the signals
> with the 250 engaged in the sub. The balance is just fine however when that
> filter isn't engaged.
>
> I'm going to try moving the filter to another socket in the sub to see
> what effect that has.
>
> I can also try swapping the 250 between the sub and the main to see if the
> loss of sensitivity tracks the filter placement.
>
> Any other ideas?
>
> It could be a bad filter. I don't think the filters should be that
> different in loss when in spec.
>
> jim
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email] <mailto:[hidden email]>
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>
> --
> Vic, K2VCO
> Fresno CA
> http://www.qsl.net/k2vco/
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email] <mailto:[hidden email]>
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>

alsopb

Re: Filter problems

8 db.
This number was obtained by observing a signal generator carrier signal
in Spectrogram (AGC off) with the 2.7 KHz filter. Then each
progressively narrow filter was kicked in and the gain adjusted for the
same peak value.

The 200 Hz filter also needs 8db and perhaps a bit more.

The method leads to no loss in signal audio as the width control is
progressively decreased.

73 de Brian/K3KO

On 4/4/2013 03:30, Vic K2VCO wrote:
> I don't have a 250 Hz filter, but both of my 400 Hz ones do require a
> few dB. I am more surprised that your main filter requires NO boost,
> than that your sub requires 6 dB. How much do others who have 250 Hz
> filters use?

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Jim AB3CV

Re: Filter problems

I'll use Spectrogram and the XG2 with AGC off when I redo it. Good ideas.

I only have the FM filter, 2.8khz8p and 250hz8p in the main RX and a
2.8Khz8p and 250hz8p in the sub RX.

I'll also give a look with an N-gen to compare filter shapes.

73

jim ab3cv

On Wed, Apr 3, 2013 at 11:43 PM, Brian Alsop <[hidden email]> wrote:

> 8 db.
> This number was obtained by observing a signal generator carrier signal in
> Spectrogram (AGC off) with the 2.7 KHz filter. Then each progressively
> narrow filter was kicked in and the gain adjusted for the same peak value.
>
> The 200 Hz filter also needs 8db and perhaps a bit more.
>
> The method leads to no loss in signal audio as the width control is
> progressively decreased.
>
> 73 de Brian/K3KO
>
>
> On 4/4/2013 03:30, Vic K2VCO wrote:
>
>> I don't have a 250 Hz filter, but both of my 400 Hz ones do require a
>> few dB. I am more surprised that your main filter requires NO boost,
>> than that your sub requires 6 dB. How much do others who have 250 Hz
>> filters use?
>>
>
>
>
> -----
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 2012.0.2240 / Virus Database: 2641/5722 - Release Date: 04/03/13
>
>
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>
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> Please help support this email list: http://www.qsl.net/donate.html
>
>

Arie Kleingeld PA3A-2

Re: Filter problems

Hi all,

Just for the record:

K3 #1255:
for main RX:
BW: 2.7k - 2.1k - 400 - 200
gain: 0 - 4 - 6 - 8 dB

Sub RX:
BW: 2.7k - 2.1k - 400
gain: 0 - 3 - 6 dB

Measured with XG2 on 50 uV, AGC-off - dBV indicator of K3
With above settings, output is nearly constant.

If there is still too much deviation, think about the following solution:
Make sure your SSB filters are gain-matched as a group, and do the same
for the CW filters.
Ofcourse this will depend on the filtercombination in your K3 and the
filters you use for different modes.

73
Arie PA3A

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Bill Frantz

Re: Filter problems

In reply to this post by Vic Rosenthal

On 4/3/13 at 8:30 PM, [hidden email] (Vic K2VCO) wrote:

> I am more surprised
> that your main filter requires NO boost, than that your sub requires 6 dB. How much do others who
> have 250 Hz filters use?

I have 6dB in the configuration. I usually increase the RF gain when I narrow the bandwidth too.

Cheers - Bill, AE6JV

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