I know that, but why does it have to be 1/4 wave ?
I have made it so now, and added a pre-amp as well
Now we sit and wait for a satellite
---------------------------------------------------------------------------- Andrew Rich VK4TEC [email protected] mailto:[email protected] http://www.tech-software.net
-----Original Message----- From: [email protected] [mailto:[email protected]]On Behalf Of jonny 290 Sent: Saturday, 29 December 2007 11:29 AM To: [email protected] Subject: [SPAM] [amsat-bb] Re: 435 offset yagi phasing Importance: Low
The 1/4 wave sections transform the 50 ohm antenna impedances to 100 ohms at the end of the 75 ohm matching section. If you then use a tee to parallel the two antennas, the impedance follows the same rules as paralleled resistances, which means you have a 50 ohm system at the tee.
You can do it another way, too - just tee the 50 ohm lines and off the tee run a 1/4 wave section of 37 ohm cable, made with two runs of 75 ohm coax in parallel. This transforms the 25 ohm impedance at the tee back up to 50 ohms at the end of the matching section.
I don't know which is superior - you have your options, though.
Andrew Rich wrote:
Ok I have to ask the question.
With offset yagis, those antennae that introduce circular polarisation by means of offsetting the second yagi 90 degress, why would you cut your coax to a 1/4 wave length ?
You already have 90 degrees from the displacement of the yagis.
It should not matter what length the 75 ohm coax is ?
Would it not ?
--
Andrew Rich VK4TEC
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
_______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb