To: | [email protected] |
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Subject: | Re: LF: Loop TX antennas at VLF? |
From: | Roger Lapthorn <[email protected]> |
Date: | Fri, 18 Mar 2011 21:39:20 +0000 |
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Hi All Just run Andy's spreadsheet for magnetic loops to see the sort of figures we get at 8.9kHz. Assuming 100W and a loop diameter of 10m with 3mm wire the efficiency works out at -87.4dB and the ERP -67.4dBW (0.2uW). There is also the matter of the low loss 6211.7nF capacitor. With larger loop diameters, thicker wire (or multiple paralleled wires) and maybe 200W then the ERPs are starting to get more useful. The Marconi does seem a better bet, even with all the issues with losses in the huge loading coil, but a VLF TX loop doesn't look a total "no-hope" approach. Larger loops, with improved efficiencies, may be easier than kite or balloon supported ones in a /P location. And then there is the widely spaced earthed electrode antenna..... but I won't start a discussion on the merits or otherwise of this as I am about to go on holiday this weekend and will not be able to respond to emails next week. We know from work by DK7FC (and VLF professionals) that this does work as a radiating structure. 73s Roger G3XBM On 18 March 2011 14:09, Roger Lapthorn <[email protected]> wrote: Just wondering if anyone has done the maths to work out what sort of ERP could be expected at 8.97kHz with, say, 100W to a smallish loop antenna in the garden? -- http://g3xbm-qrp.blogspot.com/ http://www.g3xbm.co.uk http://www.youtube.com/user/g3xbm https://sites.google.com/site/sub9khz/ G3XBM GQRP 1678 ISWL G11088
8pt9khz_loopcalc.jpg |
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