[amsat-bb] Re: Relative merits power divider vs power divider/combiner

Scott Townley nx7u at cox.net
Tue Nov 21 06:58:23 PST 2006

As long as all ports are terminated properly, they both are reciprocal devices--they work the same on RX as they do on TX.
If ports are mismatched, different things happen between A and B (and that's true for both RX and TX)
Device A will show mismatched impedances at all other ports, and may no longer evenly divide power.
Device B will show no mismatch at the 3 input/output ports, but power will be dissipated in the port 4 load.
Note that a properly designed Device A will not be mismatched on RX at the split ports.

The main advantage of Device B is the relaxation of the requirements of precise impedance control.
Scott Townley NX7U
Gilbert, AZ  DM43di

---- Joop & Tineke Verdoes <joop.verdoes at nameplanet.com> wrote: 
> OM-s
> As I got so much truely valuable and usable feedback on my hybrid power
> divider/combiner questions, I now dare to ask the following.
> For making circulary polarised yagis one needs to split 'things' over
> two yagis
> There are basically two ways to split power
> A- use a 36 ohm power splitter, often a piece of waveguide with one
> connector on one end(for the TRX) and two connectors (for the Yagis) on
> the other end
> B- use a 70 (75) ohm hybrid power splitter/divider, which has 4 ports,
> one extra for a terminator. The TRX sees just 50Ohm.
> A- and B- are both fine for SPLITTING power. In both cases the TRX sees
> 50ohm, although there are two 50ohm connected in parallel and the other
> side of the divider. So both are fine for transmit.
> But......
> A- Is ONLY a power splitter seen from the transmitter's side, it does
> present a mis-match as seen from the yagi, so on receive things are less
> than optimal
> B- Does work both ways, it presents a nice 50ohm port to the yagi, but
> the RX signal is split between the RX and the other yagi, so the signal
> that goes to the RX is 3db down.
> Does anybody have a view on how "bad" A- is vs B-?
> Have fun
> Joop, PA1JAV
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