Message-ID: <4E7095F2.8010209@iup.uni-heidelberg.de>
Date: Wed, 14 Sep 2011 13:54:26 +0200
From: =?UTF-8?B?U3RlZmFuIFNjaMOkZmVy?= <Stefan.Schaefer@iup.uni-heidelberg.de>
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:1.9.1.8) Gecko/20100227 Thunderbird/3.0.3
MIME-Version: 1.0
To: rsgb_lf_group@blacksheep.org
References: <E1R38sH-0004V1-00.rn3aus-mail-ru@f222.mail.ru> <4E6E44A0.4050000@iup.uni-heidelberg.de> <4E6E55A9.7030109@iup.uni-heidelberg.de> <E1R3Y17-00069M-00.rn3aus-mail-ru@f195.mail.ru>
In-Reply-To: <E1R3Y17-00069M-00.rn3aus-mail-ru@f195.mail.ru>
Subject: Re: LF: Re[2]: LF: DK7FC, DF6NM nr Moscow
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: quoted-printable
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
X-AOL-SCOLL-URL_COUNT: 0  
x-aol-sid: 3039ac1d61864e709634617b
X-AOL-IP: 195.171.43.25
X-AOL-SPF: domain : blacksheep.org SPF : none


Hi Alex,

Am 13.09.2011 20:47, schrieb Alex K:
> Hello Markus, Stefan, LF!
>
> My receiver is =EF=BB=BFon my workplace=EF=BB=BF, therefore at night I =
can't supervise its work directly. On screenshots I have noticed that wit=
h approximately 17:30 till 02:55 UTC quality of reception strongly worsen=
s.
This is probably just the opening band (DX) with its propagated QRN and=20
stronger levels of BCD stations that may cause some IM in your preamp or =
RX?

>   At first I thought that it, possibly joins any powerful device and cr=
eates a local QRN. To learn that this such, I have added in sheduled acti=
ons wave.record. In the morning, having come for work, I have analysed th=
is record. It has appeared that the entrance signal from the aerial incre=
ases at night almost in 10 times. The microphonic amplifier of my sound c=
ard strongly there were nonlinear distortions. I have switched off the mi=
crophonic amplifier and have reduced factor of strengthening of the recei=
ver=EF=BB=BF (receiver has no=EF=BB=BF AGC=EF=BB=BF); probably, it will a=
llow to have pure reception at night time.=EF=BB=BF
> So a continuous line=EF=BB=BF on 136172 Hz is  result of nonlinear dist=
ortions in the microphonic amplifier.
>   =20
What is your RX antenna, an E field probe, right?
You could run a wideband window (0...24 kHz or so) and check when and=20
where the overload occurs, if it is within the displayed band at all. If=20
the S/N in permits, you may lower the microphone gain or the preamp=20
gain. Otherwise a band filter should help. This does not need to have a=20
very high Q, depending on what makes the overload. 10 dB reduction=20
reduces the phantom traces by much more than 10 dB, if it is IM.

> =EF=BB=BF
> PS On screenshots each division of a scale of amplitudes is 10 dB
>   =20
OH! 10 dB ? I thought 5 dB. Then this reception must have been very well=20
;-) But the QSB is interesting too.


73, Stefan/DK7FC