[Elecraft] ½ λ dipoles

[riese-k3djc at juno.com]

early on the antenna would help define the operating frequency
spark made RF everywhere and the tank and antenna coupled
the RF to the operating frequency

Bob K3DJC




On Fri, 5 Aug 2016 18:41:57 -0400 "Charlie T, K3ICH" <pincon at erols.com>
writes:
> I'm curious as to when the concept of a ½ λ dipole became the norm?
> 
> In other words, the idea of the current distribution as exists on a 
> dipole.
> 
> Early pictures of typical ham antennas looked more like a set of 
> parallel
> clothesline wires.
> 
> What I gather from reading early articles,  it seemed that the more 
> wire you
> had in the air, the better it would "capture" (and radiate) the 
> signals.
> 
> Feel free to reply directly if you don't want to clutter the forum.
> 
> (k3ich at arrl dot net)
> 
> 73, Charlie k3ICH
> 
> 
> 
> -----Original Message-----
> From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf 
> Of Phil
> Wheeler
> Sent: Friday, August 05, 2016 10:58 AM
> To: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] OT:. G5RV's
> 
> Alas, the poor G5RV.  Now that its been flogged to death, maybe we 
> need a
> new target -- say the Windom?
> 
> Phil W7OX
> 
> On 8/4/16 10:22 PM, Wes Stewart wrote:
> > The tuner loss also depends on how it is adjusted. For example the 
> 
> > very popular high-pass Tee with three adjustable elements has an 
> > infinite number of possible combinations that will effect a match 
> on 
> > the same load Z.  One of them is the lowest loss solution, all of 
> the 
> > others aren't.
> >
> > As I said earlier, in a letter to Dean Straw dated February 2, 
> 1994 I 
> > offered an example where the SPC tuner, then current in the 
> handbooks, 
> > could be used to match an impedance of 4.34 +j46 to 50 ohm. (I 
> forget 
> > where this came from but it was a real possibility)  I assumed Qc 
> = 
> > 1000 and Ql = 300 (generous). I used Touchstone to calculate the 
> > minimum loss and maximum loss solutions The best case was 1.6 dB 
> and 
> > the worst case was 7.8 dB.
> >
> > With lower Q components, Qc = 500, Ql =200, the losses were 2.4 to 
> 9.5 
> > dB!
> >
> > Wes  N7WS
> >
> >
> >  On 8/4/2016 2:00 PM, Alan Bloom wrote:
> >> > It's a pity that too many newcomers, as well
> >> as many oldsters, are
> >> > enamored by this piece of wire.
> >>
> >> The G4RV is definitely a compromise antenna.  
> >> However its advantage is that is has low-enough SWR to be easily 
> >> matched by most tuners on a number of bands.
> >>
> >> > ... the horrific losses that could be
> >> incurred even
> >> > with high quality tuners,
> >>
> >> It's true that tuner losses are the
> >> manufacturers' dirty little secret. Loss is rarely specified, 
> partly 
> >> because it can be pretty bad, and partly because it is hard to 
> >> measure, but also because it is not constant - it depends on the 
> >> particular impedance being matched.
> >>
> >> One exception is the old Drake tuners.  Their Pi-L topology makes 
> the 
> >> loss almost independent of the load impedance.  If you can get it 
> to 
> >> match, you know that almost all the power is going into the feed 
> >> line. For example, the
> >> MN-2700 that I designed when I was at Drake was specified at 0.5 
> dB 
> >> maximum insertion loss and I did a lot of testing and tweaking to 
> 
> >> achieve that on all bands.
> >>
> >> Alan N1AL
> 
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