[TowerTalk] Cage dipole revisited.

[Rick Stealey]

Today I did a little modeling with 4NEC2 on 80 meters.  First a regular dipole showed a bandwidth of 200 KHz at the SWR=2:1 points.
Then I decided to see how close to a real cage a pair of dipoles has to be to get the same benefit.  So I added another dipole, fan style, to it and got 320 KHz bandwidth.  I varied the length of the second dipole all over the place.  I was modeling on 80 meters, and made the 2nd dipole small (like the length of a 40 m dipole) and could see SWR dips in the 80m and 40m bands when I did a frequency sweep.  Then I lengthend the small dipole and watched the 2nd dip drop in frequency till it got close to the 80 m band and the bandwidth began increasing.  But I was never able to get a "double hump" inside the 80m band as I had hoped.
But 320 KHz bandwidth was easily obtained.
Now the question is, how different is a pair of dipoles (with 10-20 degrees angle between them)from a real cage dipole ?  So to do this I modeled three dipoles, parallel to each other and separated a few feet apart.  The bandwidth was the same as the fan, indicating to me that very likely a simple two dipole fan antenna (both elements can be the same length) will give good swr performance compared to a dipole and might be worth the effort.  Sure would be simple to build compared to a cage

Rick  K2XT

_________________________________________________________________
Rediscover Hotmail®: Get quick friend updates right in your inbox. 
http://windowslive.com/RediscoverHotmail?ocid=TXT_TAGLM_WL_HM_Rediscover_Updates1_042009