The gain loss is NOT due to the classic feed (actually a
clever idea). The gain loss in SPLIT DIPOLE FED antennas
comes from *detuning* the parasitic elements enough to raise
the feed impedance to 50 ohms.
Tuning the parasitic elements for maximum gain usually results
in much lower DE impedances (say 10 to 30 ohms) which then
requires a matching system such as a Beta Match, Gamma Match,
Omega Match, TEE Match, etc to transform the DE impedance
up to 50 ohms.
Tom N4KG
On Sat, 13 Jul 2002 Mark <aa6dx@pacbell.net> writes:
> Lots of folks have a problem with the Classic beams having a longer
> driven
> element VS the reflector .. due to the feed via coax inserted into
> the
> driven element. I do not see a REAL loss of gain via this method ..
> in the
> "real world" ... Loved my 5 el mono 20M, 46` boom .. which, I had to
> leave
> in Alaska .. became a true sourdough. Soured on Alaska, no dough
> to get
> out!
> 73 ---- Mark 6dx
> ----- Original Message -----
> From: <n4kg@juno.com>
> To: <TOWERTALK@contesting.com>; <kk9a@arrl.net>
> Sent: Saturday, July 13, 2002 10:03 AM
> Subject: Re: [Towertalk] OWA Yagis
>
>
> > Generally speaking, the higher the gain, the lower the
> > Feed Impedance for a split dipole feed. When antennas
> > are tuned to produce a 50 Ohm feed, they give up some
> > gain. The TA33 is a 'classic' example of this. That's why
> > all the HyGain beams have Beta Matches, to step up the
> > low feed impedance to 50 ohms.
> >
> > Tom N4KG
> >
> > On Sat, 13 Jul 2002 <kk9a@arrl.net> writes:
> > > Does anyone have any experience with the OWA design yagis. Is
> there
> > > any advantage other than low SWR and direct 50 ohm feed? I
> modeled the
> >
> > > 15m 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 band.
> > > Are there losses in the DX Eng. hair pin match or higher SWR
> that
> > > would make the OWA come out on top?
> > >
> > > 73,
> > > John
> > >
> > >
>
>
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