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30/40m. Interlaced 3el. Yagi


30/40m. Interlaced 3el. Yagi

During the night between 18 to 19 Febbruary 2004 just lost my 2 el. Quad for 40 and 30 m. by a big snow-storm, now i decided to replace my 40/30 m. Quads with two 3 el. Yagi for 40 and 30m. experimenting both antennas interlaced in a 57 foot double boom, 2 inches each in diameter, the two booms Quad and Yagis are joined toghether so to strengthen the whole system, I don't know if the project will work OK, the antenna elements are from PKW , the 40m elements are loaded, the 30m elements are full sized, just now july 04 I'm assembling all the elements.

17 Aug 2004 added comments

I spent some days to proper find right positions of the 3 el. 40m. and 30m. Yagis across the boom due to little interaction with 20/17/15/12/10m.( particulary on 15/17m. no interaction at all on 6m. ) simply I lenghethen both sides of the double Yagis boom to a total of 57 feet in order to have the opportuniy to move rigth left the 30 and 40m. Yagis elements finding right position and keeping them so far away as possible from the 5 elements six band Quad still keeping theirs right spacing design , note that 30 and 40m Yagis seems not suffer interactions each other, anyway on 15/17m. Quad the SWR at the feed point still was around 1.1,5, to cure the problem I had to retune a little the 15/17m. gamma matchs, to brigs down SWR to normal value 1. 1,1 on middle of these bands,
the mechanical balance of the entire system after I put the two yagi antennas for 30 and 40m, it was not so perfect, as not having to move around the system on the mast, ( it would be a heavy job ), I put a counterweight to the end where needed, by entering and staring at the end of the boom, a weight of lead.. in few days I will raise the eight bands antenna system at 85 feet natural position and will test particulary the 30 40m. Yagis.

Performances : Yagi 3 elements 30m. gain over dipole 7.5 DB - F/B 18 DB - F/S 35 DB, Yagi 3 elements 40m. gain over dipole 7.5 DB - F/B 18 DB - F/S 35 DB.

Here a photo slideshow on the assembly of a interlaced 30/40m. 3el. Yagi on a pre-existent boom wich support 6 band Cubical Quad.

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