Re: Passive Relay's


Andy G4JNT
 


This assumes Line of Sight Tx to passive repeater, and from there to Rx
All antennas see terrestrial noise temperatures



On Tue, 19 May 2020 at 12:11, Andy Talbot <andy.g4jnt@...> wrote:
Correction:
If the repeater is exactly on the direct line from Tx to Rx,  MAXIMUM loss occurs if it is placed mid way
Better to have it close to one end or the other

Spreadsheet for a simplistic view will follow shortly



On Tue, 19 May 2020 at 11:29, Andy Talbot <andy.g4jnt@...> wrote:
I feel a spreadsheet coming on ..
Seem to recall doing this calculation back in the dim and distant past for work, and IIRC the mid point gave furthest range extension.   But that would have been for a naval scenario and no hills !



On Tue, 19 May 2020 at 10:58, Iain Young <g7iii@...> wrote:
Hi Nick,

On 19/05/20 10:24, Nick Gregory G0HIK via groups.io wrote:

> I have been told that you cant have the passive repeater anywhere near
> the middle of the link and has to be right at one end of it. Not sure
> how the logic works, as several of the communities fed by these are not
> that close to them, say up to 2 to 5 miles away.

I beg to differ. While this was done on 144MHz, and 433MHz, last time I
checked the rules of physics don't change at 1.2GHz and up,so here are
a couple of links tto a presentation that I did based on an experiment a
couple of years ago:

http://hal.g7iii.net/ppt/Passive_Repeater_Experiment.pdf
http://hal.g7iii.net/ppt/Passive_Repeater.pdf

Personally, I think it's all about overcoming the extra path loss, so
you need gain in the antennas. I must try it on 23cms and up sometime...


73s

Iain



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