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

kc6uqh kc6uqh at cox.net
Tue Nov 21 18:45:39 PST 2006

If you yous two 75 Ohm 1/4 wavelength sections to make the power divide and 
another 50 Ohm 1/4 wave section on one antenna to give the 90 degree phase 
shift it should work just fine. The antennas are 50 ohm.
Another solution is to offset one antenna a 1/4 wavelength on the boom from 
the other when mounting two antennas crossed on the same boom. Hybred is 
also a solution but be careful of losses on the broad band devices.

----- Original Message ----- 
From: "Joop & Tineke Verdoes" <joop.verdoes at nameplanet.com>
To: <amsat-bb at amsat.org>
Sent: Tuesday, November 21, 2006 4:33 AM
Subject: [amsat-bb] Relative merits power divider vs power divider/combiner

> 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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