[Milsurplus] Fw: Pi- Matching Network: When?

[DeWitt Clay]

Sounds like the Windom Antenna and Pi Coupler grew up together. 
I experimented with the Windom antenna and it worked pretty well for me. The tapped input impedance was given as around 500-600 Ohms and worked well into a pi network tank circuit for the transmitter I used on 40 meters. The single wire transmission line was also said to be 500-600 Ohms. 
The Windom antenna descriptions and calculations I remember were for single band use but Frank C. Jones' showed  it could be made into a multiband antenna by moving the tap from the usual recommended point and still get acceptable results. I haven't tried this multiband Jones setup so I can't say how well it works. Feeding it with a pi coupler/pi output network ought to reduce any potential harmonic radiation problems though, hi. 
I liked the single wire feedline setup. It was simple, inexpensive, and light weight. It is supposed to work against ground by capacitive return to the transmitter thru the earth and ground line to the rig. Some rf engineers have panned it because of this. But I don't remember if I grounded  my transmitter in my old station. It was a pretty basic setup.  Anyone know if it is really needed to get the system to work? 
The Windom's transmission line could also be tapped on to the final tank coil - adjustment being made until the proper loading was achieved. I also tried this setup and it worked (may be prone to harmonic radiation, hihi). Some of the older rig designs showed the pi coupler tapped on to the final tank as W7QHO pointed out. This makes for some interesting inital adjustments and tuneup, hi. 
73, DeWitt  N4QNX


________________________________
From: Mike Hanz <aaf-radio-1 at aafradio.org>
To: milsurplus List <milsurplus at mailman.qth.net>; Old Tube Radios <boatanchors at theporch.com>; Boatanchors-qth List <boatanchors at mailman.qth.net> 
Cc: David Stinson <arc5 at ix.netcom.com> 
Sent: Thursday, February 9, 2012 6:59 AM
Subject: Re: [Milsurplus] Pi- Matching Network: When?

On Feb 7, 2012, at 5:49 PM, David Stinson wrote:
>> Anyone have any idea when the Pi output matching
>> network appeared?

Looks like May 1931, Dave.  A quick google search brought out this 
article on the Windom antenna by John Nagle in the May 1978 issue of Ham 
Radio Magazine:

"William L. Everitt, as faculty advisor to the students who worked on 
the antenna, contributed much to its development.  Everitt began his 
amateur career in 1914 as 2ABI; in 1921 he became 8CRI. When he decided 
to go into communications professionally, he dropped amateur radio 
because he did not want to have the same vocation and avocation.  
Everitt was later to become a prominent author and educator.  He retired 
as Dean of Engineering at the University of Illinois and went on to 
become Dean Emeritus at that university.

Unfortunately, Dr. Everitt has been ill-treated by the amateur 
community.  His work on the off-center-fed antenna is largely unknown 
and certainly unrecognized.

Unhappily, the same thing happened to him a second time.  *Everitt was 
the first to describe the use of a pi network as a coupling device.*  He 
published this work in the Proceedings of the IRE in 1931 (12) and in 
Communications; (13) the pi network is also described in his book, 
Communication Engineering. (14)

Arthur Collins, W9CXX, of Cedar Rapids, Iowa, recognized the advantages 
of the pi network to couple the output stage of a transmitter to a 
transmission line, and used it in his transmitters. This application 
played an important part in establishing the reputation that Collins 
equipment will load up to "anything." Collins described the pi network 
to the amateur community in a QST article (15) and in a similar article 
in Radio, (16) and the network became known by old-timers as the 
"Collins Coupler" instead of, perhaps, the "Everitt Easy Loader." "

References:
12. W. L. Everitt, "Output Networks for Radio·Frequency Power 
Amplifiers," Proceedings of the IRE, May, 1931, page 725.
13. W. L. Everitt, "Coupling Networks," Communications, September, 1938
14. W. L. Everitt, Communication Engineering, McGraw-Hill, New York, 
1937, page 263
15. A. A. Collins, W9CXX, "A Universal Antenna Coupling System for 
Modern Transmitters," OST, February, 1934, page 15
16. A. A. Collins, W9CXX, "The Answers to the Flood of Inquiries 
Regarding the Collins Antenna System:' Radio, March, 1934, page 5

John J. Nagle, K4KJ (SK)
Herndon, Virginia
May 1978 in Ham Radio Magazine

So now you know...
73,
Mike  KC4TOS

______________________________________________________________
Milsurplus mailing list
Home: http://mailman.qth.net/mailman/listinfo/milsurplus
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Milsurplus at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html