Hi Stefan.
I have resent this reply, I think the original with an attachment may have
been blocked
The answers to your questions are.
My RX is a Kenwood TS140S.
Antenna, 102ft doublet centre fed with 470 ladder feeder, strapped as a T
for 500 kHz working.
Because the antenna is never connected to any equipment when the station is
unattended there are only two GE diodes across the filter input.
The filter characteristics as follows, f0 = 501.87kHz.
3dB 495.71 kHz - 508.26 kHz
6dB 492.77 kHz - 511.29 kHz
12dB 486..89 kHz - 516.99 kHz
18dB 479.20 kHz - 523.83 kHz
24dB 468.43 kHz - 532.522 kHz
30dB 453.97 kHz - 543.25 kHz
It was the BC stations around 530 kHz which were causing the problems
73s,
Ken
M0KHW
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Stefan Schäfer
Sent: 17 September 2012 00:21
To: [email protected]
Subject: Re: LF: Re: RE: MF tonite
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
present
> for 500kHz I have a homebrew filter using two Toko transformers in between
> 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.
>
Yes, the input resistor value can be choosen in a very wide range. Yes,
you can use a input Xformer to get some gain.
73, Stefan/DK7FC
> Your thoughts please Stefan.
>
> 73.
>
> Ken
>
> M0KHW
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]] On Behalf Of Stefan Schäfer
> Sent: 15 September 2012 01:07
> To: [email protected]
> 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). Thus
> 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:
>
>> Hi Stefan.
>> Fully understand.
>>
>> 73.
>> Ken.
>> M0KHW
>>
>> -----Original Message-----
>> From: [email protected]
>> [mailto:[email protected]] On Behalf Of Stefan Schäfer
>> Sent: 13 September 2012 20:03
>> To: [email protected]
>> 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 affect
>> the matching, i would prefer that...
>>
>> 73, Stefan
>> Am 13.09.2012 20:43, schrieb Ken:
>>
>>
>>> Stefan.
>>> Thank you for the info, maybe sometime you will be able to post the
>>>
>>>
>> circuit?
>>
>>
>>> 73.
>>>
>>> Ken
>>>
>>> M0KHW
>>>
>>> -----Original Message-----
>>> From: [email protected]
>>> [mailto:[email protected]] On Behalf Of Stefan Schäfer
>>> Sent: 13 September 2012 12:26
>>> To: [email protected]
>>> Subject: Re: LF: Re: RE: MF tonite
>>>
>>> Ah yes, Thomas was faster, damn ;-)
>>>
>>> Another image from the experimental setup, using source followers
>>>
>>>
>>>
>>
>
https://dl.dropbox.com/u/19882028/MF/Mechanical_filter_with_source-followers
>
>>
>>
>>> .JPG
>>> The results have been very good last night!
>>>
>>> 73, Stefan/DK7FC
>>>
>>>
>>> Am 13.09.2012 13:12, schrieb Thomas Rosenkranz:
>>>
>>>
>>>
>>>> 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=Receiver
>>>>
>>>> 73
>>>> Thomas DM4TR
>>>>
>>>>
>>>> ----- Original Message ----- From: "Ken"<[email protected]>
>>>> To:<[email protected]>
>>>> 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: [email protected]
>>>> [mailto:[email protected]] On Behalf Of Stefan Schäfer
>>>> Sent: 12 September 2012 21:02
>>>> To: [email protected]
>>>> Subject: LF: MF tonite
>>>>
>>>> Christian,
>>>>
>>>> Are you QRV tonite? I would like to see or better hear the difference
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 the
>>>> passband ripple as low as possible. The afternoons tests have been very
>>>> promising, see https://dl.dropbox.com/u/19882028/MF/MF%20Filter.png
>>>> This is the frequency response:
>>>>
>>>>
>>>>
>>
https://dl.dropbox.com/u/19882028/MF/473%20kHz%20ZF%20Filter%2040%20dB.png
>>
>>
>>>>
>>>>
>>>
>>>
>>>> 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
>>>>
>>>>
>>>
>>>
>>
>>
>
>
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