Date: Mon, 12 Feb 2018 17:20:18 +0000
From: "mike.dennison" <mike.dennison@ntlworld.com>
To: =?utf-8?Q?rsgb=5Flf=5Fgroup?= <rsgb_lf_group@blacksheep.org>
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Subject: Re: Re: LF: Do I need an attenuator on LF RX??
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Chris. Isn't the 'noise hump' due to the resonance of your antenna?  
 
Mike
 
=====
 
 
>  
> On 12 Feb 2018 at 16:35,  <Chris Wilson>  wrote:
>  
>  
>  Hello Mike, Thanks for the reply, it actually has 2 (in series) N1BUG band pass filters in front of it! I have always had this "noise hump" around the band, I once thought the filter (one...) had cured it, but next time I looked it was back. MF is lovely and quiet in comparison. i see exactly the same with a Softrock with or without a BPF. http://blog.n1bug.com/2017/02/01/2200-meter-softrock-lite-ii/ Monday, February 12, 2018, 4:26:13 PM, you wrote:  >  Chris,  >  It looks like you have a broadcast station where it shouldn't be (at  >  132.65kHz) and several other spurious stations in that area, so you  >  may well have unwanted signals within the 136kHz band, especially at  >  night (your recording seems to have been done during the middle of  >  the day). You might improve things by by-passing the pre-amp. It  >  would do no harm just by experimenting with an attenuator but why  >  attenuate and amplify at the same time unless the preamp also  >  provides another function such a
s matching? It seems the only  >  front-end selectivity on that receiver is a narrow bandpass so you  >  would really benefit from some additional wider filtering, eg an LPF  >  with a cut-off just below the LW BC band.  >  Mike, G3XDV  >  ========== -- Best regards, Chris mailto:dead.fets@gmail.com 
>  
     
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<div id=3D=22edo-message=22><div>Chris. Isn't the 'noise hump' due to the=
 resonance of your antenna=3F&nbsp;</div><div>Mike</div><div>=3D=3D=3D=3D=
=3D<br><br><br><div id=3D=22edo-signature=22></div></div></div><div id=3D=
=22edo-original=22><div><blockquote type=3D=22cite=22><div id=3D=22edo-me=
ta=22>On 12 =46eb 2018 at 16:35, &lt;<a href=3D=22mailto:dead.fets=40gmai=
l.com=22>Chris Wilson</a>&gt; wrote: <br><br></div><pre>
Hello Mike,

Thanks  for  the  reply, it actually has 2 (in series) N1BUG band pass
filters in front of it=21 I have always had this =22noise hump=22 around =
the
band, I once thought the filter (one...) had cured it, but next time I
looked  it  was  back.   M=46  is  lovely and quiet in comparison. i see
exactly the same with a Softrock with or without a BP=46.

http://blog.n1bug.com/2017/02/01/2200-meter-softrock-lite-ii/

Monday, =46ebruary 12, 2018, 4:26:13 PM, you wrote:

&gt; Chris,

&gt; It looks like you have a broadcast station where it shouldn't be (at=
 =20
&gt; 132.65kHz) and several other spurious stations in that area, so you =
=20
&gt; may well have unwanted signals within the 136kHz band, especially at=
 =20
&gt; night (your recording seems to have been done during the middle of =20
&gt; the day). You might improve things by by-passing the pre-amp. It =20
&gt; would do no harm just by experimenting with an attenuator but why =20
&gt; attenuate and amplify at the same time unless the preamp also =20
&gt; provides another function such as matching=3F It seems the only =20
&gt; front-end selectivity on that receiver is a narrow bandpass so you =20
&gt; would really benefit from some additional wider filtering, eg an LP=46=
 =20
&gt; with a cut-off just below the LW BC band.

&gt; Mike, G3XDV
&gt; =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D


-- =20
Best regards,
 Chris                            mailto:dead.fets=40gmail.com


</pre> =20
 <br> </blockquote></div></div>
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