Tom Osborne wrote:
>
>
>Hi Gang
>
>I've been wondering about some things. Say 2 3 element
>monobanders are stacked, the gain goes up 3 db (at least that's
>what I think). If there is 100 watts going to the antennas, when
>it reaches the splitter does 50 watts go to each antenna or does
>the full 100 watts reach each antenna. If only 50 watts, it
>doesn't seem like there is actually any gain in stacking antennas
>as the gain goes up but the ERP is the same as with one antenna.
No, the ERP is doubled:
same total power radiated * twice the gain (3dB) = twice the ERP.
What happens is that the voltages received from each antenna add in
phase (in the optimum direction) which actually gives an increase of
(2*voltage) = (4*power) = 6dB. But you divided the available power
between the two antennas, so you lose 3dB, giving a net stacking gain of
3dB.
73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.demon.co.uk/g3sek
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|