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From: John Rabson <john.rabson07@gmail.com>
In-Reply-To: <212280367.20180212164700@gmail.com>
Date: Mon, 12 Feb 2018 18:08:41 +0100
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 <5A81C025.13685.51C8EA38@mike.dennison.ntlworld.com>
 <212280367.20180212164700@gmail.com>
To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: Do I need an attenuator on LF RX??
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Possibly DCF39 and its companion? I believe they are used to control some sort of electricity grid.

John F5VLF

> On 12 Feb 2018, at 17:47, Chris Wilson <dead.fets@gmail.com> wrote:
> 
> 
> 
> Hello Mike, I just listened to what looks like the AM modulated bursts
> around 139 and 135.5 kHz and they sound like bursts of data, nothing
> intelligible whatsoever.
> 
> 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
> 
>