[TowerTalk] Raibeam PART-2

[wa4dou@juno.com]

Hi Again,
  There are a variety of circumstances where front to back ratio is
important. There are also a variety of circumstances where a high F/B
ratio will guarantee you miss contacts. An example might be where one is
a contester and has only one tower and yagi. A high F/B ratio gives one a
sense of great directionality. Yet the antenna that produces that high
F/B has only 1-2 db more gain than a smaller yagi or quad. Look at the
yagi boom lengths for example. 2 element yagi requires a boom length of
.15-.2 wavelengths. 3 element yagi requires a boomlength of .3-.4
wavelengths. 4 and 5 element yagis require booms in the 1/2-3/4
wavelengths range. Beyond this is generally impractical in the 14-30 mhz.
range. Look how the weight and windloading grow as the boom and element
count grows. All for 1-3 or 4 db. Look how the cost of the tower and
antenna grows ,very disproportionately to the actual and real benefit of
the gain. 
  Example: Compare the gain figures for the Force 12 C3SS, C3, C3E,C3S.
Despite the boom length differences of 12 versus 18 ft. and the fact that
one antenna is linear loaded on 20 meters while another is full sized,
and while the c3E has 3 elements on one band and just 2 on both of the
others, these well designed, honestly rated antennas are essentially the
same in gain, front to back, etc. Actually the C3SS is probably the
better antenna by virtue of the fact that its already rated at 100 mph
wind rateing while the others are 80 mph. Now go on to compare these gain
and front to back ratio figures to the Force 12 C19XR, C31XR and C51XR. I
hope i recalled those model numbers accurately. Do you see any real
tangeable gain differences? No, because the law of diminishing returns is
already at work. Compare the gain and front to back ratios and the boom
lengths and the windloading and the weight and the tower requirements and
the costs and etc. , and its quite apparent that you'll pay heavily for
continuing to hold on to the idea that that great front to back
difference and gain difference is worth so much to you. Meanwhile
qrp'ers, with many db less sophistication in their stations, will
continue working lots of dx, and moving right on up to the honor roll. 
  Its time for hams to start learning the difference between reality and
illusion , fact and sales hype, db's and what they really mean and are
worth. When you are talking 2, 3, 4 db, you are not talking about a lot
of gain or signal strength difference. The same applies to other brands
of antennas and even comparing monoband yagis to multiband antennas. 
  My tower is built to withstand hurricane force wind, it cost me too
much to risk its failure by overloading it with double or triple the
windloading for the sake of 1-2 db. Propagation determines whether you
have a satisfactory path to dx. Not the extra db.The extra db affords you
the luxury of thinking you got something worthwhile for your gain
dollars. Yes, i know, races are won in hundredths of a second, but really
,who are you raceing with? I worked Clipperton with qrp on 3 bands, and 5
with 80 watts. I had excellent propagation. Without that, even 10-20 more
db would have been of little value. BTW, my C3SS is fed with Andrews !/2"
LDF Hardline. 
  73 Roy Lincoln WA4DOU
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