Date: Mon, 12 Feb 2018 16:35:59 +0000
From: Chris Wilson <dead.fets@gmail.com>
Message-ID: <146589434.20180212163559@gmail.com>
To: rsgb_lf_group@blacksheep.org
In-Reply-To: <5A81C025.13685.51C8EA38@mike.dennison.ntlworld.com>
References: <1125097296.20180212141115@gmail.com> <5A81C025.13685.51C8EA38@mike.dennison.ntlworld.com>
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Subject: Re: LF: Do I need an attenuator on LF RX??
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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 as 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