[TowerTalk] 6M yagi

[Brian Beezley]

AB7E wrote:

"I can't think of any reason why an antenna would be "quieter" other 
than it having a tighter pattern, either horizontally or vertically, and 
therefore discriminates against background noise better.  If it is 
noticeably quieter, that suggests to me that it is hands down a better 
design."

Everything else equal, yes. But it never is.

Yagi optimization is a trade-off between forward gain, the radiation 
pattern, and SWR bandwidth. If the design is optimal, you can't improve 
one objective without degrading another. Constraining the elevation 
pattern to reject local noise will necessarily lower forward gain or 
worsen SWR bandwidth. It may degrade the azimuth pattern as well.

I used to think that the term "low noise" Yagi was just marketing BS. 
But I can see how constraining lobes that point toward ground ought to 
reduce the level from noise sources there. The question is, how much 
gain does it cost? How much do SWR bandwidth and the azimuth pattern worsen?

It may well be that for a noisy location the receive improvement is 
worth the cost in gain and SWR bandwidth. But be clear-headed about it. 
It won't come for free.

Brian