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From: "James Moritz" <j.r.moritz@herts.ac.uk>
Organization: University of Hertfordshire
To: rsgb_lf_group@blacksheep.org
Date: Mon, 12 Mar 2001 18:25:29 +0000
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Subject: LF: Re: Active antennas at LF.
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<?color><?param 0100,0100,0100>Dear Andy, LF Group,<br><br>&gt;<?/color>The amp is specified as having a 50dBm third order intercept  &gt;point and by my reckoning could function as a power amp  &gt;delivering over 10W.   That's linear !!! Frequency response is  &gt;10kHz to 60MHz.   <?color><?param 0100,0100,0100><br><br>Sounds like the kind of thing I could do with - living near Brookmans  Park gives me MF field strengths of the order of 10V/m RMS, and  much higher than that on the peaks. I abandoned attempts to make  a wideband whip when I observed about 40v pk-pk RF on a 1m  antenna connected to a scope probe... <?/color> A tuned input certainly  makes life easier sometimes!<?color><?param 0100,0100,0100><br><br>I read somewhere that pre-WW2 naval receiving systems, using  basically long-wire antennas, were designed to operate with "up to  100V" unwanted signal on the antenna, with frequency separation  of 10% or more. This was achieved using passive preselectors.  The ob
jective was to allow simultaneous multi - transmitter  operation. When the war broke out, it was not found to be a big  issue, because radio transmission from ships was kept to an  absolute minimum to avoid direction-finding. <br><br>Cheers, Jim Moritz<br>73 de M0BMU<br><br>