Sorry about the previous blank post.
In a best of the world situation, you can hope for about
2.8 dB loss through a Cavity system.
Through a hybrid combiner system you can hope for
about a 3.5 dB (best) loss.
Hybrids only if you must... otherwise you end up with
a room full of space heaters fighting the AC.
cheers,
skipp
> Doug Bade <[EMAIL PROTECTED]> wrote:
> It should also be clarified that this is the major difference
> between a hybrid ferrite combiner and a cavity combiner. The hybrid
can be
> used with any freq's in the specified band, no matter how close
spaced (
> technically 2 transmitters on the same freq is ok) , but at the cost of
> major power insertion with large channel capacity... Cavity
combiners are
> substantially less loss however the freq spacing needs to exceed 150khz
> between channels to get reasonably better performance....even then
cavity
> versions are going to be on the order of 5-6db IL on channels in a 10
> channel config. ( Theory vs real world performance)
>
> Real power loss on a hybrid combiner is more like 4db per 2
port/channel
> coupling, as opposed to 3db, so IL is going to be higher than the
> theoretical losses.
>
> Doug
> KD8B
>
>
>
> At 10:48 AM 8/5/2005, you wrote:
> >Tom Saunders wrote:
> >
> > >>about 55% of each transmitter's
> > >>output gets burned up in a dummy load, each time two signals are
> > >>combined. Thus, eight 100 watt repeaters combined into one
antenna will
> > >>have about 11 watts at the antenna.
> > >
> > >
> > > While it is true that aprox. 50% of the power from each
transmitter is
> > > lost in the combiner, the remaining 50% gets thru. So a 100 watt
> > > transmitter will send 50 watts out to the transmission line. 50
* 8 =
> > > 400w total.
> >
> >No-doesn't work like that. For every two transmitters you combine, you
> >have ~3dB loss. So for 4 tx's, you have 6 dB loss, and for 8 tx's, you
> >have 9 dB loss. (Barring of course hardware differences that will move
> >those maybe a dB either way.)
> >So for 8 100W tx's, the theory gives you 12.5 W to the bottom of the
> >coax per channel. And other factors will likely add up to yield the 11W
> >that was mentioned.
> >--
> >Jim Barbour
> >WD8CHL
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