Message-ID: <50565EF3.9020809@iup.uni-heidelberg.de>
Date: Mon, 17 Sep 2012 01:21:23 +0200
From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= <Stefan.Schaefer@iup.uni-heidelberg.de>
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To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: Re: RE: MF tonite
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Hi Ken,

My thoughts,

Am 16.09.2012 22:07, schrieb Ken:
> Hi Stefan.
> Thank you for all the filter info, definitely interested in them, at pr=
esent
> for 500kHz I have a homebrew filter using two Toko transformers in betw=
een
> the antenna socket and two stage rx pre-amp.
What RX are you using? And what type of antenna?
>   There are GE protection diodes
> across the input,
I should think about that too. 3x Si diodes in series, 2x, antiparallel.

>   the pre-amp gain is 0 - 18dB with a variable capacitor to
> peak at the operating frequency.
What is the BW of that peak?
>   I was thinking of replacing the 500kHz
> filter with this mechanical one, it would save work, just need an input
> matching Xformer and change the gate resistor on the input FET.
>   =20
Yes, the input resistor value can be choosen in a very wide range. Yes,=20
you can use a input Xformer to get some gain.

73, Stefan/DK7FC


> Your thoughts please Stefan.
>
> 73.
>
> Ken
>
> M0KHW
>
> -----Original Message-----
> From: owner-rsgb_lf_group@blacksheep.org
> [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Stefan Sch=E4f=
er
> Sent: 15 September 2012 01:07
> To: rsgb_lf_group@blacksheep.org
> Subject: Re: LF: Re: RE: MF tonite
>
> Hi Ken,
>
> I just tried to use the 500 Ohm input and the 18k Ohm output. It works
> UFB but then i got worried about destroying the filter due to the
> up-transformation on the input (the max. input voltage is 2 V rms). Thu=
s
> i decided to rebuilt the circuit as it has been before and will
> eventually use an uptransformer behind the filter. But probably this is
> not necessary because the MF noisef floor is still 20 dB above my
> RX+soundcard noise floor...
>
> After readjusting the C, now the passband ripple is<  0.5 dB.
>
> This is the schematic:
> https://dl.dropbox.com/u/19882028/MF/MF%20Filter%20schematic.png
> (You know, someone has done it all before and it is nothing new ;-) ).
>
> Will you order and use some of them?
>
> 73, Stefan/DK7FC
>
> Am 13.09.2012 21:47, schrieb Ken:
>   =20
>> Hi Stefan.
>> Fully understand.
>>
>> 73.
>> Ken.
>> M0KHW
>>
>> -----Original Message-----
>> From: owner-rsgb_lf_group@blacksheep.org
>> [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Stefan Sch=E4=
fer
>> Sent: 13 September 2012 20:03
>> To: rsgb_lf_group@blacksheep.org
>> Subject: Re: LF: Re: RE: MF tonite
>>
>> Hi Ken,
>>
>> OK but later. I want to try some modifications, i.e. using the 500 Ohm
>> input and the 18 kOhm output, to have some gain. If this does not affe=
ct
>> the matching, i would prefer that...
>>
>> 73, Stefan
>> Am 13.09.2012 20:43, schrieb Ken:
>>
>>     =20
>>> Stefan.
>>> Thank you for the info, maybe sometime you will be able to post the
>>>
>>>       =20
>> circuit?
>>
>>     =20
>>> 73.
>>>
>>> Ken
>>>
>>> M0KHW
>>>
>>> -----Original Message-----
>>> From: owner-rsgb_lf_group@blacksheep.org
>>> [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Stefan Sch=E4=
fer
>>> Sent: 13 September 2012 12:26
>>> To: rsgb_lf_group@blacksheep.org
>>> Subject: Re: LF: Re: RE: MF tonite
>>>
>>> Ah yes, Thomas was faster, damn ;-)
>>>
>>> Another image from the experimental setup, using source followers
>>>
>>>
>>>       =20
>>     =20
> https://dl.dropbox.com/u/19882028/MF/Mechanical_filter_with_source-foll=
owers
>   =20
>>
>>     =20
>>> .JPG
>>> The results have been very good last night!
>>>
>>> 73, Stefan/DK7FC
>>>
>>>
>>> Am 13.09.2012 13:12, schrieb Thomas Rosenkranz:
>>>
>>>
>>>       =20
>>>> Hy Ken,
>>>>
>>>> the name of the mechanical filter is FZ02
>>>> http://www.oppermann-electronic.de/html/hf-spezialbauteile.html
>>>>
>>>> http://dm4tr.bplaced.net/index.php?section=3DReceiver
>>>>
>>>> 73
>>>> Thomas DM4TR
>>>>
>>>>
>>>> ----- Original Message ----- From: "Ken"<ken.h.wright@btinternet.com=
>
>>>> To:<rsgb_lf_group@blacksheep.org>
>>>> Sent: Thursday, September 13, 2012 10:28 AM
>>>> Subject: LF: RE: MF tonite
>>>>
>>>>
>>>> Hi Stefan.
>>>> What mechanical filter are you using?.
>>>> 73.
>>>> Ken
>>>> M0KHW
>>>>
>>>> -----Original Message-----
>>>> From: owner-rsgb_lf_group@blacksheep.org
>>>> [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Stefan Sch=E4=
fer
>>>> Sent: 12 September 2012 21:02
>>>> To: rsgb_lf_group@blacksheep.org
>>>> Subject: LF: MF tonite
>>>>
>>>> Christian,
>>>>
>>>> Are you QRV tonite? I would like to see or better hear the differenc=
e of
>>>> my RX performance when using my band filter i was testing in the
>>>> afternoon.
>>>>
>>>> It is the mechanical filter which uses source followers at the input=
 and
>>>> output, to provide a constant accurate impedance matching to keep th=
e
>>>> passband ripple as low as possible. The afternoons tests have been v=
ery
>>>> promising, see https://dl.dropbox.com/u/19882028/MF/MF%20Filter.png
>>>> This is the frequency response:
>>>>
>>>>
>>>>         =20
>> https://dl.dropbox.com/u/19882028/MF/473%20kHz%20ZF%20Filter%2040%20dB=
.png
>>
>>     =20
>>>>
>>>>         =20
>>>
>>>       =20
>>>> There should be a much better image rejection now and so maybe a few
>>>> more dB SNR... Unfortunately the filter does not cover the 502 kHz
>>>> region. But this problem will be gone in some months...
>>>>
>>>> Will be on 472.5 kHz soon.
>>>>
>>>> 73, Stefan/DK7FC
>>>>
>>>>         =20
>>>
>>>       =20
>>
>>     =20
>
>   =20