[Elecraft] Subject: The G5RV trivia

[Don Wilhelm]

I was also 16 in 1956, and do remember trying a few antennas.  I had a 3 
half waves in phase antenna for 40 meters, and it did the job nicely, 
but my first antenna was a 40 meter dipole fed with 75 ohm parallel 
feedline.  It worked fine with my homebrew 75 watt 6146 transmitter with 
a Pi-Network output.  The Pi-Network had a sufficient range to match it. 
  I did not have an SWR meter at the time, so that is all I can say.
The 3 half-waves in phase was fed in the center with true ladder line 
and the Pi-Network matched it too.

Since modern transceivers want to see a 50 ohm load, the ATU takes the 
brunt of matching to the antenna and the task of achieving a good match 
is no longer by tuning to resonance (plate dip) and then loading for the 
desired amount of plate current.  Those old days are gone.

We could get radiation out in those old days just by looking at our 
meters and know that we had tuned up correctly.  Such is not true 
anymore - there is just no proper comparison.  You must tune the 
antenna/feedline to produce a 50 ohm load by use of antenna/feedline 
lengths and/or relying on a good ATU to bring the antenna load to near a 
50 ohm match.  An antenna analyzer is a great tool to use when working 
with antennas.

A good link coupled antenna tuning unit can cover a large range (Johnson 
Matchbox is one example), and has many benefits that can be used today, 
but few know how to use it to advantage.

73,
Don W3FPR

On 3/23/2020 10:18 PM, Fred Jensen wrote:
> Bob:  My memory from 1956 is a bit thin, I was 16 then, but I don't 
> remember RF inductors wound on "cores", unless you count a plastic coil 
> form with a 5-pin base to be a "core."  Not sure ferrite had been 
> invented.  [:-)  The Pi-network was a big deal then, those of us who 
> couldn't afford the two capacitors used parallel resonant tanks with one 
> capacitor with link coupling.  Interestingly, it did harmonic 
> suppression and also matched whatever impedance was at the shack end of 
> the feedline to the plate impedance of the PA.  I don't recall anyone 
> talking about SWR.