Re: LF: Link budget calculation or estimation of dist for given power on WSPR

[Andy Talbot <andy.g4jnt@googlemail.com>]

That spreadsheet is for calculating the free space path loss between two stations - given by L = 32.4 + 20.LOG(F.d)   F in MHz, d in km

 

Totally inappropriate for LF ionospheric,  groundwave , microwave ducting and even  tropospheric propagation.

 

In fact, only really applicable to satellites and hilltop to hilltop links

Andy
www.g4jnt.com

This email has been scanned for damaging side-effects by the health and safety police, is guaranteed to contain no substances hazardous to health, but may contribute to dissolving the nether and polar regions

2010/1/10 James Cowburn <james.cowburn@virgin.net>

Dear All

 

I have been inputting some numbers into the calculator from the link below, clearly some assumptions need to be made as well as guesstimates but this may be able to give an idea of the range expected at a given power, and assuming x hops etc.

 

 

http://www.aubraux.com/design/rf-link-budget-calculator.php

 

Putting in Roger’s power of 1mW and a distance of 990km (his best and reception report of -20dB) then it gives for a -20dB signal a “gain factor” for WSPR of 65dB.

 

This seems rather implausibly high so I’m obviously missing a trick somewhere.

 

 

 

 

 

RF Link Budget Calculator

RF Link Budget Calculator: To calculate power at the receiver input, enter values in the empty boxes below.

 

Transmitter Power		W
Transmitter Center Frequency		Hz
Transmit Antenna Gain		dB
Distance Between Antennas		km
Receive Antenna Gain		dB
Other Losses		dB

 

Results

 

EIRP	=	-28.20	dBW
Wavelength	=	596.42	m
Free Space Loss	=	86.39	dB
Received Power	=	-49.59	dBW
	=	1.10E-5	W
	=	-19.59	dBm
	=	1.10E-2	mW

 

 

With best regards

 

 

Jim

 

 

Dr. James Cowburn

 

From: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Roger Lapthorn
Sent: 10 January 2010 19:55

To: rsgb_lf_group@blacksheep.org

Subject: Re: LF: Link budget calculation or estimation of dist for given power on WSPR

 

Do we know how many dB loss (over land and over sea) for a single hop Rik?

73s
Roger G3XBM

2010/1/10 Rik Strobbe <Rik.Strobbe@fys.kuleuven.be>

Jim,

if ionoshperic propagation is involved signal strength (and thus SNR) depends more of the number of hops involved than the absolute distance.
And each hop "costs" a number of dB's in signal strength.

73, Rik  ON7YD - OR7T

Quoting James Cowburn <james.cowburn@virgin.net>:

 Dear LF,
Has anyone any ideas or suggestions on a resource for calculation of  a link budget for WSPR over a set distance?
As it seems I can get up to GM4SLV reasonably consistently on my  current antenna/power setting with a SNR of around -22dB and the  limit for WSPR is around -30dB then is there a means for roughly  estimating or indeed accurately calculating the Expected Max Range  (EMR) at that power setting and antenna configuration?
Clearly, there are differences between separate Rx stations but if  one knows the ratio between two or more Rx stations then it should  be possible to pro-rate or estimate at least the signal strength at  a given Rx based on its performance with other known signals.
If I can do 916km with an SNR of say -22dB then how much further  would the remaining  8dB or so of WSPR detection get me, assuming  the other Rx has the same capability as GM4SLV and if their  capability is different, then is it fine to factor for the dB  difference over known paths/signals?
Thanks in advance for any answers or pointers and best wishes to all  for a great 2010
With best regards


Jim


Dr. James Cowburn G7NKS

E james.cowburn@virgin.net<blocked::mailto:james.cowburn@virgin.net>

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