Message-ID: <11108.200102011452@gemini>
From: "James Moritz" <j.r.moritz@herts.ac.uk>
Organization: University of Hertfordshire
To: rsgb_lf_group@blacksheep.org
Date: Thu, 1 Feb 2001 14:56:38 +0000
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Subject: LF: Beacon sigs / Ferrite grades
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Reply-To: rsgb_lf_group@blacksheep.org
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Dear LF group,

Transmitted the usual beacon signal on 135.923kHz from 2000 until 
0305 last night, apart from a period from 2205 - 2220 when I was 
making an adjustment to the antenna.

For the record, my 136kHz rig details for these tests are:

TX output - 1200W, 6A antenna current.
Antenna - inverted 'V' single wire, fed at one end. Total length of 
wire 50m, about 16m high in the middle and 9m at the ends.
ERP -  (estimate based on old measurements - antenna changed 
slightly since then) approx. 1W.
Location - IO91VR; near Hatfield, about 25km north of london, 
adjacent to the Brookmans Park BBC MF transmission site.

I also monitored VA3LK's frequency from 0310 - 0900, but only 
saw a single 'K' at about 0720. The noise level dropped abruptly at 
0600. I don't think the street lights switch off this early, anyway 
there aren't any down my road. It would certainly be interesting if 
VE1ZZ could run some signals in the early morning; I don't recall 
him ever being QRV at this time of day, and VA3LK's signal is on 
the whole best at this time.

3C85 ferrite has an initial permeability around 2200 as I recall - 
this is typical for a 'power' grade ferrite. The very high permeability 
ferrites are intended for small-signal, wide band transformer 
applications usually. Lower permeability ferrites such as 4C65 (mu 
= 125) are well suited to HF transformer applications. Iron dust 
cores, like the Micrometals -2 and -6 grades have much lower 
permeability, and are intended for 'energy storage' applications 
(resonant circuits and filter components in this context). Philips 
seems to have sold it's ferrite components buisness to a 
Taiwanese company called Yageo - oh dear..... But fortunately, 
Ferroxcube seem to have reappeared in the meantime - 
http://www.ferroxcube.com/ has data sheets.

Cheers, Jim Moritz
73 de M0BMU