Joop, 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.
Art, KC6UQH ----- Original Message ----- From: "Joop & Tineke Verdoes" joop.verdoes@nameplanet.com To: amsat-bb@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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