[Towertalk] Re: [Towertalk] OWA Yagis

[i4jmy@iol.it]

As everyone knows it's almost impossible to set all parameters at best 
in a single yagi antenna.

In my experience, the difference in gain between an optimized yagi with 
good F/B over a stated boom and an OWA is within half dB.
Taking in account for matching losses when the impedance is low, 
probably the half db advantage for the non OWA design further reduces 
or even inverts, expecially if the peak gain of the yagi doesn't drop 
where predicted, a good SWR is not a gain indicator.

Along an HF band the OWA is a very good solution to insure stable 
performances within an entire band at the price of a small gain 
reduction compared to the peak one of the classic yagi, but probably 
giving more in terms of gain/BW and F/B, not counting the semplicity 
and safe power handling of a symple 50 OHms feed compared to matching 
devices that might have problems and further reduce BW.

On the other hand, when the required BW is a smaller percentage than Cf 
the OWA is loosing something in pure gain, at least in theory.

One can always decide if to give up 0.3 db gain and beeing almost sure 
about the obtained gain or trust narrow BW design and to obtain the 
peaked gain just where it serves.

Is a mistery why hams put always so great attention to fractional 
antenna gain, prone to pay for that (promised) extra, while they have 
the tendency to spare money with lines where gain is frequently lost in 
larger amounts.

73,
Mauri I4JMY

 

> Does anyone have any experience with the OWA design yagis.  Is there a
ny
> advantage other than low SWR and direct 50 ohm feed?  I modeled the 15
m 6el
> X 36' boom and compared it to my DX Engineering 15DX-
6 with the same boom
> length and the DX Engineering had more gain throughout most of the ban
d.
> Are there losses in the DX Eng. hair pin match or higher SWR that woul
d make
> the OWA come out on top?
> 
> 73,
> John
> 
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