From: Rik Strobbe <Rik.Strobbe@fys.kuleuven.be>
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
Date: Sun, 31 Oct 2010 10:42:10 +0100
Thread-Topic: LF: Re: SBL-3+
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Hello Stefan, Alan,

what about a CMOS analog switch mixer ? Cheap and easy to find.
I used a 74HC4053 as mixer in my 3.5MHz to 500kHz transverter.
Have a look at http://home4.swipnet.se/~w-41522/lfconv/lfconv.html (SM6LKM=
), wher Johan shows a LF to 4MHz converter with a 74HC4053 mixer. Just ada=
pt the LO and output circuitery for LF output.

73, Rik  ON7TD - OR7T

________________________________________
Van: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.or=
g] namens Stefan Sch=E4fer [schaefer@iup.uni-heidelberg.de]
Verzonden: zondag 31 oktober 2010 0:59
Aan: rsgb_lf_group@blacksheep.org
Onderwerp: Re: LF: Re: SBL-3+

Hi Alan,

I want to try an alternative to the BF981 which runs in my current LF
grabber RX. It downconverts 137 kHz to 12 kHz and feeds the soundcard
with this 12 kHz signal. It is running not too bad but i have some
problems with temperature drifting bandpass filters (since weeks) and
have thrown them out of the Drain-to-Plus path. So, now the setup is
running with a 2 stage RC LPF. I have had some problems with a to high
125 kHz level on the soundcard input and have applied a series LC
circuit for 125 kHz now which reasonably solved the problem. But the LF
noise is now just about 10 dB above the soundcard noise, in the
afternoon. There is still a lack of sensitivity. This RX QTH should be
very well for a grabber antenna but currently the setup is the problem.
So i want to try something different, like a DBM. I am not an expert
here and can/have to learn a lot, it seems ;-)

73, Stefan

Am 31.10.2010 00:41, schrieb Alan Melia:
> Hi Stefan why a difficult to get mixer?? the IF port on most DBMs is DC
> coupled so feed the siganl in there and (i presume) mix up ?? Or is the
> RF/LO response still too high on the easily available ones?
>
> Alan G3NYK
> ----- Original Message -----
> From: "Stefan Sch=E4fer"<schaefer@iup.uni-heidelberg.de>
> To:<rsgb_lf_group@blacksheep.org>
> Sent: Saturday, October 30, 2010 9:29 PM
> Subject: LF: SBL-3+
>
>
>
>> Dear LF,
>>
>> I want to try a LF converter using this mixer. Does anybody know a
>> (cheep!) distributor in Germany or EU for 1...3 pieces of it? I've just
>> found one where it costs about 40 Euro and this is to much!!
>>
>> 73, Stefan/DK7FC
>>
>>
>