Message-ID: <5B7F1211.1000109@posteo.de>
Date: Thu, 23 Aug 2018 21:59:13 +0200
From: DK7FC <selberdenken@posteo.de>
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To: rsgb_lf_group@blacksheep.org
References: <1613303827.20180823120801@gmail.com> <88af04ed-ef1c-03e3-464f-fc5e4155d0eb@n1bug.com>
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Subject: Re: LF: Anyone good with Elsie?
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Chris,

I think it's time to show us a photo of your BPF construction :-) Don't 
hesitate to leave all the stuff on the workbench as it is ;-)

73, Stefan

Am 23.08.2018 20:26, schrieb N1BUG:
> Hi Chris,
>
> I sent an earlier reply which seems to have gone into the bit bucket
> somewhere, possibly to due to server settings in my mail client
> which I've just now changed back to what was working previously.
> That first reply was mostly off topic so if it does show up, please
> ignore it.
>
> I've been following the comments on your topic and just wanted to
> toss something in the mix. It appears the response of your actual
> filter is more rounded and the skirts less steep than the model. I
> leave it to those with more knowledge to correct me, but I believe
> this suggests Q of components in your filter is significantly lower
> than Q assumed by the model. Using higher Q components, if possible,
> may give you more attenuation of unwanted out-of-band signals. I
> built one of these filters and my response appears to be in closer
> agreement with the model.
>
> Not speaking to a solution but a possible cause of the unexpected
> filter response: If you used capacitors with reasonably good
> tolerance, perhaps the inductors came out a bit low in value. I've
> forgotten whether you used pre-made inductors or wound your own
> using cores of some type. If the latter and the cores are ferrite,
> the specific batch of cores might be enough to throw it off. I
> believe ferrite materials typically don't have tight tolerance.
>
> Paul
>
>
>
> On 08/23/2018 07:08 AM, Chris Wilson wrote:
>    
>>
>> Hello  LF'ers
>>
>> Is anyone able and willing to advise on my band pass RX filter design
>> please? I have made a band pass filter for 137kHz reception and
>> checked it with my SDR in real time. It is shifted a little high and I
>> am wondering what I need to change to pull it a bit lower? Any
>> practical advice or component values welcome. Adjustability would be
>> nice! Thanks
>>
>> Filter design is at http://www.chriswilson.tv/lf-circuit.jpg
>>
>> Real world results at : http://www.chriswilson.tv/passband.jpg
>>
>> ELSIE plot at : http://www.chriswilson.tv/lf-plot.jpg
>>      
>