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*Subject*: RE: [amsat-bb] Power divider for X-yagis*From*: "Howard Long" <howard@xxxxxxxxxxxxxx>*Date*: Fri, 26 May 2006 16:17:03 +0100*In-Reply-To*: <006101c680cd$21b07020$0201a8c0@tin.it>*Thread-Index*: AcaA0GVv7cVuHPv5S2G+BGMsCxpmZwABZzyw

Folks > If you look at the Microwave Handbook Volume 2 of the RSGB edited > by M.W.Dixon, G3PRF page 13.11 you will find that for a square tube > with air as dielectric and equal sides with inside dimension (D) and a > round inner conductor of outside diameter ( d ) the characteristic impedance > Zo can be computed using the following formula where (D) and (d) are > expressed in millimeters. > > 1.178 D > Zo= 138 log ( ----------- ) > 10 d I was going to wait until I got home to discuss this, but as it's come out now I believe that there has some disagreement over the validity of this formula. It's widely quoted in lots of RSGB literature, but the correct version is, for D/d > 1.5, Z0 = 138 * log10 ( 1.08 * D / d ) A treatise online on this subject is covered here: http://fermi.la.asu.edu/w9cf/articles/square and here http://hjem.get2net.dk/ole_nykjaer/oz2oe/combiner/combiner.html True, the differences around 50 ohms are only of the order of 10%, but I guess if you're scratching your head wondering why things ain't working like they should be this is one more concern to consider. 73, Howard G6LVB ---- Sent via amsat-bb@amsat.org. Opinions expressed are those of the author. Not an AMSAT member? Join now to support the amateur satellite program! To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org

**References**:**Re: Power divider for X-yagis***From:*i8cvs

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