Topband: beverage lobes
k3bu at optonline.net
k3bu at optonline.net
Sun Jan 7 23:28:03 EST 2007
>> K3BU:
> > Staggered Beverages narrow the horizontal lobe, to get low
> > vertical lobes you need to go long beverages or long and
> > stagerred, and down hill if possible.
>W8JI:
> Not so. Staggered Beverages can place a null almost anywhere
> depending on stagger distance and phase. With 180 degree
> phase shift you can get a null straight up (and to the
> sides). Generally the stagger works best to control or
> improve F/B ratio or suppress high angle lobes. It actually
> doesn't do as much at all for lobe width.
>
IS So!
Using EZNEC file example of staggered Beverages from W8JI web site, they show 79.1 deg horizontal beamwidth at 35 deg elevation max angle, gain -14.9 dB F/B 15.6 dB
Removing one Beverage, the single one shows 94.8 deg horizontal beamwidth at 40 deg elevation angle, gain -13.15 dB F/B 6.49 dB
94.8 - 79.1 = 15.7 deg - that doesn't seem like "doesn't do as much".
> The high angle lobe generally doesn't contribute much noise.
> S/N is largely a function of directivity, and that is not
> impacted much by a few narrow spurious lobes.
>
> For Beverages in Echelon (stepped):
>
> http://www.w8ji.com/echelon-log_beverages.htm
>
> 73 Tom
Also statement on W8JI web site that "It is not necessary, nor does it do any good, to go beyond 1-1/2 or 2 WL." is not true. I have used 3.5 wave beverages and they kill other shorter Beverages when signal angles are low.
73 Yuri, K3BU
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