Message-ID: <4FDE8631.8010002@iup.uni-heidelberg.de>
Date: Mon, 18 Jun 2012 03:36:49 +0200
From: =?ISO-8859-15?Q?Stefan_Sch=E4fer?= <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: <4FDDE3C9.8080505@iup.uni-heidelberg.de> <15B9C0CD09D4429B83AB1E02595502AD@JimPC>
In-Reply-To: <15B9C0CD09D4429B83AB1E02595502AD@JimPC>
Subject: Re: LF: Re: Further MF impressions
Content-Type: text/plain; charset=ISO-8859-15; format=flowed
Content-Transfer-Encoding: 7bit
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: 3039ac1d40c94fde86d71071
X-AOL-IP: 195.171.43.25
X-AOL-SPF: domain : blacksheep.org SPF : none


Hello Jim, Alan, G.., Laurence, Roelof, MF,

Thanks for the discussion and detailed informations. Many interesting 
things to learn. That sounds all very exciting and confirms many of my 
assumptions.
Hope to meet you soon on the band.

73, Stefan/DK7FC

Am 17.06.2012 22:06, schrieb James Moritz:
> Dear Stefan, LF Group,
>
>> I just thought my receiver isn't working correctly. I thought the 
>> xtal does not start to oscillate due to the higher ambient 
>> temperatures in the afternoon. But later i found that the band noise 
>> on MF is significantly lower than in the evening, at least 20 dB.
>
> As well as the natural band noise being lower at MF (I estimate the 
> noise FS is about 10dB lower), there is also not the constant presence 
> of man-made noise, such as Loran and DCF39 sidebands. So the spectrum 
> around 500kHz does sound much quieter, especially during daytime.
>>
>> What do others know about the ground wave range in summer and in the 
>> afternoon? When does the band open? Similar to LF?
>
> As others have said, broadly similar to LF - sky wave is very weak 
> until darkness has arrived, so ground wave dominates daytime 
> communication. Ground wave signal levels seem to depend greatly on the 
> type of ground at distances more than 100km or so. For example I can 
> easily hear G3KEV during the daytime here,  and the path from Hatfield 
> to Scarborough is over flat, high-conductivity ground down the east of 
> England. But G4WGT and G0NBD, and stations in Wales, are extremely 
> weak in daylight at similar distances, although they are quite strong 
> after dark The ground path to these stations is over hilly, lower 
> conductivity ground.
>
> Sky wave signals over fairly long distances show very deep fading over 
> periods of a few minutes - signal levels are usually constantly 
> changing, and I have often seen variation of over 30dB in one minute 
> on beacon signals. This can make QSOs difficult, with a signal that 
> was R5 suddenly disappearing completely and not even visible on the 
> spectrogram. Over very long distances, trans-atlantic for example, the 
> fading seems less severe although signals are usually quite weak and 
> propagation is very variable.
>
> For contacts around Europe, I would say 136k actually gives more 
> reliable signal levels, but for many stations 500k is easier because 
> higher ERP can be achieved with a small antenna, and noise levels are 
> often lower.
>
> Cheers, Jim Moritz
> 73 de M0BMU