Re: LF: AW: 8.97kHz - Near field and radiated signals?

[Roger Lapthorn <rogerlapthorn@gmail.com>]

Rick (et al),

I am confused by the near field attenuation rates quoted. Some quote 18dB for doubling distance which would mean an additional path loss of 56dB going from 0.4km to 3km. This makes a lot of difference to what may or may not be possible.

Which is the correct figure? Help!

73s
Roger G3XBM

On 26 May 2010 09:31, Rik Strobbe <Rik.Strobbe@fys.kuleuven.be> wrote:

Roger,

 

the near fiels signal drops with the 3rd power of the distance.

So 3km versus 0.4km = 422 times weaker = -26dB

Going from regular CW to QRSS30 will give you a 24dB benefit, so there is a fair chance to be copied at 3km in this mode. Of course the signal needs to be very frequency stable, it has to be better than an free running oscillator.

Moving up in frequency would also help.

And if you can lay your hands on an old stereo amp it would provide an extra 10dB TX power.

 

Even if your goal is regular CW over a 3km path, starting with QRSS will most likely give a visible signal at 3km and allow you to watch any progress.

 

73, Rik  ON7YD - OR7T

 

 - The best DX targets are quite modest: I would like to exceed 1km

 initially with the TX power I currently have (around 4W). If I could reach
 G6ALB in the next village 3kms away I would be delighted. If I got any
 further I would be both amazed and VERY happy!

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