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From: "James Moritz" <james.moritz@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
References: <4E418609.6020500@iup.uni-heidelberg.de> <67A6F7BF45BF4A0193A3DCB53000A283@PcMinto> <008401cc56ce$2f1fb2c0$0401a8c0@xphd97xgq27nyf> <12C475F3F4C84B818461753F2E8A60A6@PcMinto> <4E41AECB.90808@iup.uni-heidelberg.de> <8D68749D37B94275855FDBA46A3F6C97@PcMinto> <op.vz0iyui5yzqh0k@pc-roelof> <8B4308E108A8499DAAAAD221713A676B@PcMinto>
In-Reply-To: <8B4308E108A8499DAAAAD221713A676B@PcMinto>
Date: Thu, 11 Aug 2011 10:39:16 +0100
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Subject: LF: Re: Re: HB9ASB...
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Dear Minto, LF Group,

I did a similar measurement around 1200utc yesterday with lower daytime 
noise levels - DCF39 was 870uV/m here, while the noise level was 
approximately 0.1uV/m in 1Hz. With 0.5Hz FFT noise bandwidth, SNR of DCF39 
would be 82dB, same as the night-time value - it seems that at night, 
ionospheric propagation enhances both DCF39 and noise by the same amount, at 
least at this QTH.

Noise floor measurements I did a few years ago at this QTH in quet 
winter-time conditions gave a lower value of about 0.07uV/m per sqrt(Hz), 
very similar to DF6NM's figure. So this would seem to be the limit on the 
maximum usable sensitivity of a 137kHz receiving system.

Cheers, Jim Moritz
73 de M0BMU