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Re: LF: Fieldstrength and radiated power

To: [email protected]
Subject: Re: LF: Fieldstrength and radiated power
From: Stefan Schäfer <[email protected]>
Date: Tue, 02 Aug 2011 23:42:09 +0200
In-reply-to: <[email protected]>
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Thanks Markus,

Will try now if it works and see what my level will be ;-) Good for PA adjustments, at least in times without a skywave component. Anyway...

So, do we have to send a longer dash or acidentally transmit to the right time? :-)

73, Stefan/DK7FC

Am 02.08.2011 18:26, schrieb Markus Vester:
Dear LF,
 
to support estimates of radiated power, I have added a fieldstrength readout on my LF grabber
 
 
It simply displays the peak frequency and amplitude within the QRSS subband at the time of the capture (ie. every five minutes). Due to different calibration issues, the readout will be accurate only to within about 3 dB. There may also be considerable day-to-day variation, for example from switching between different receive antennas.
 
In the region of groundwave dominance (up to 400 km daytime, 200 km in darkness), radiated power in dBm or milliwatts can be roughly estimated based on distance R using
 
 EMRP[dBm] = 20 log E[uV/m] + 20 log R[km] + 0.02 R[km] - 49.5
 EMRP[mW] = 10^(EMRP[dBm]/10)
 
To convert to halfwave-dipole ERP or EIRP, you would have to apply the usual factor of 1.83 or 3.
 
Hope this may be useful...
 
Best 73,
Markus (DF6NM)


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