Re: LF: Fieldstrength and radiated power

[Markus Vester <markusvester@aol.com>]

Hi Stefan, LF,

 

there is no peak-hold function, so your carrier has to be present at the grabber capture time. Allowing for a bit of clock uncertainty, you would want to transmit for say 20 seconds around any five minute multiple.

 

Here's an example for ERP calculation:

 E = 20 uV/m at R = 200 km distance would give

 EMRP = 26 + 46 + 4 - 49.5 = 26.5 dBm = 450 mW

 Dipole ERP = 0.82 W

To calculate the distance R to my receiver you could use

http://no.nonsense.ee/qthmap/?qth=JN59NJ69ES

 

Best regards,

Markus (DF6NM)

-----Ursprüngliche Mitteilung-----
Von: Stefan Schäfer <Stefan.Schaefer@iup.uni-heidelberg.de>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Di., 2. Aug. 2011, 23:46
Betreff: Re: LF: Fieldstrength and radiated power

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

 

 http://www.alice-dsl.net/df6nm/grabber/Grabber.htm

 

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)