To: | "RSGB LF Gp" <[email protected]> |
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Subject: | LF: Re: 136kHz ERP calculation |
From: | "Alan Melia" <[email protected]> |
Date: | Tue, 10 Aug 2010 23:39:44 +0100 |
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Hi Roger you can calibrate your loop first using DCF39 on 138.83. This has a field strength in our area of 1mV/m. Then you could work back your own ERP by comparison...... 1W ERP produces 300mV/m at 1km, 100mV/m at 10km (from memory ....I think that is correct....10dB per decade after 1km). Doing it that way removes as lot of the variables, and its a good thumbnail calculation. Alan G3NYK ----- Original Message ----- From: "Roger Lapthorn" <[email protected]> To: <[email protected]>; <[email protected]> Sent: Tuesday, August 10, 2010 7:09 PM Subject: LF: 136kHz ERP calculation > *My last post didn't appear, so this is a retry...* > > About a week ago I recorded my 136kHz QRP beacon (2W from PA, QRSS3, using > just 20m separated earth electrodes as the antenna) at 14.9km away from the > QTH using Spectran with a 30t, 80cm loop, Hi-Z matching into the FT817. > > I'm wondering if someone here is able to *work out the ERP* that I must be > achieving please. These are the numbers I have: > > Spectran signal level -42.5dB > Resolution 0.17Hz > Sampling rate 11025 > Distance (Rx from TX) 14.9km > > It surprises me that the signal can be seen so well at this distance with > such low power and with this "antenna" set-up. Thanks in advance for any > help and please excuse my ignorance. > > 73s > Roger G3XBM > > -- > http://g3xbm-qrp.blogspot.com/ > http://www.g3xbm.co.uk > http://www.youtube.com/user/g3xbm > G3XBM GQRP 1678 ISWL G11088 > |
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