Message-ID: <006b01cd13d1$2fbb5070$1502a8c0@Clemens04>
From: "Clemens  Paul" <cpaul@gmx.net>
To: <rsgb_lf_group@blacksheep.org>
References: <4F7DAA67.1000404@iup.uni-heidelberg.de>
Date: Fri, 6 Apr 2012 10:42:14 +0200
MIME-Version: 1.0
Subject: LF: Re: Audio transformer test
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Hi Stefan,

I have measured exactly this transformer about a year ago for a friend.
He tried it for a (meanwhile abandoned) soundcard based SDR- TRX project
for HF and failed due to lack of sensitivity.
I connected two of these XMFs back to back and measured in a 50 Ohm environment
with a VNA from 5-20kHz.
There was plenty of loss,IIRC something *around* 10dB per transformer.
That's not surprising after you have measured the DC resistance (high!).
This may or may not be of importance for your application depending on
your AF level and type of matching (power matching versus voltage matching).

73
Clemens
DL4RAJ


----- Original Message ----- 
From: "Stefan Schäfer" <Stefan.Schaefer@iup.uni-heidelberg.de>
To: <rsgb_lf_group@blacksheep.org>
Sent: Thursday, April 05, 2012 4:21 PM
Subject: VLF: Audio transformer test


> VLF,
>
> I just checked the amplitude and frequency respose of the audio transformer i 
> use to decouple my signals between soundcard and antenna. Just a simple test. 
> They are in use in various applications, are cheep and small.
> Type, Distributor and datasheet: 
> http://www.reichelt.de/Trenntrafos/NFU-1-4/index.html?;ACTION=3;LA=444;GROUP=C54;GROUPID=3320;ARTICLE=73039;START=0;SORT=artnr;OFFSET=16;SID=32fRwi5qwQASAAACIkJWk502917f27b61570f9f85c5c030e3f831#av_tabdata
>
> Looks they operate down to 5 Hz which is excellent: 
> http://dl.dropbox.com/u/19882028/VLF/Uebertragertest.png
> Also the wide range looks fine up to 20 kHz: 
> http://dl.dropbox.com/u/19882028/VLF/Uebertragertest_wide.png
>
> In the pictures, the upper SL instance is a frequency generator driving the 
> headphone output of the soundcard. The lower instance records signals coming 
> from the Mic input.
>
> As a conclusion i found that the transformer is even suitable for ZEVS 
> receiving at 82 Hz.
>
> 73, Stefan/DK7FC
>
>