[TowerTalk] Duo band 20/15 meter beam

[Jim Thomson]

Date: Mon, 7 Nov 2016 08:40:40 -0500
From: "StellarCAT" <rxdesign at ssvecnet.com>
To: <towertalk at contesting.com>
Subject: Re: [TowerTalk] Duo band 20/15 meter beam

hmm.... really? Don't hold a pattern? The testing I did on the 40M4LLDD 
showed quite good FB across the band with a measured ~15 db at the bottom, a 
peak around 30 at around 7.13 and still a good 15 db at the top at 7.3.... 
an Optibeam OB4-40 has similar numbers (after I increased the length of all 
the elements by 3.5"). I measured a good 20 db at 7011 and around 30 at 7.13 
... while still at least ~ 15 at the top of the band. The gain, although not 
great for the size of the antenna, is even less sensitive to where you are.

Both dual DE's.

Gary
K9RX

## 15 db  FB  at both ends of the band..and 30 in the middle is exactly what
Im talking about.  You would still get that, whether it had single or dual DE. 
The dual DE is just providing for a flatter swr.  They could have used relays
+ tapped coils in each leg of the feedpoint, and used a single DE, and got the
same results. But in terms of simplicity, just adding a 2nd DE is reliable..+ cheaper. 

##  I used 4 x  spdt  ceramic vac relays +  1 inch wide silver plated cu  strap coils,
with 1 coil in each leg. All inside the oem F12 ssb /cw nema relay box.  Then  I end up
with 4 x segments on 40M, = flat swr across the entire band.   But the relay box is on the
DE only of my  F12  340N.   I could have added boxes on the REF + DIR as well, for
improved FB, since it peaks at the lower end of the band, but chose not to.  I can easily get to the
DE, since its next to the mast.  Any problems with a box at each end of the boom, and the entire
yagi  would have to come down.   

##  In retrospect,  I could have used 2 x SPDT relays, and ended up with just 2 x segments,
which would have been plenty.   But I had loads of new gigavac  g2 relays, so used em. 

Jim   VE7RF