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

["James Cowburn" <james.cowburn@virgin.net>]

Hi Roger

 

I have managed 1020km  D?RAJ on my old Tx before it expired.   TF3 would be great though.

 

73s

 

Jim

 

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From: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Roger Lapthorn
Sent: 10 January 2010 19:03
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: Link budget calculation or estimation of dist for given power on WSPR

 

Certainly GM4SLV has a much lower noise floor than most stations on 500kHz Jim. I think he estimated about 10dB lower, so it may be easier for him to hear very weak signals than many others.

For what it's worth, my 1mW ERP has been received at -18dB S/N at 990kms range in S.Germany (and at around -23dB a few times), so assuming another 10-12dB in hand, that must be good for another skywave "hop" under favourable conditions. I am still hopeful that TF3HZ might just spot me on a good night. The magic 1000kms barrier is tantalisingly close. RN3AGC says he might just have seen a "whisper" of a trace from me the other night and he is 2400kms away, but if it was me it was far too weak to decode.

It will be interesting to see what people say is possible based on the propagation theory etc.

73s
Roger G3XBM

2010/1/10 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

 

 

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