An Excellent Article Received via email on 8/31/2015 from Carter Rose, KD6GN

A Broadband Antenna System for 1.8 - 30MHz

by Carter Rose, KD6GN
Since publication of my 160m antenna article in the September 2001 issue of CQ amateur radio magazine I have experimented with several desktop impedence matching circuits for broadband operation of the antenna and feedline I described then.
These circuits have included the balanced-L  network using two expensive roller coils, a classical Johnson "matchbox", a single roller coil L-network, and now a fixed 'coil-stock'  L-network with a series reactance-cancelling capacitor.
The last circuit, which is presented here, has many advantages over other circuits which include:
-Low cost
-Quick frequency change
The antenna system described here is intentionally designed for 100 watts maximum of RF power and the use of one inductance value for each frequency range.
This system design uses only proven professional antenna engineering practices to maintain stability and high efficiency. Key references are given.
The ferrite chokes and choke balun in the system block diagram reduce RF currents flowing on AC and DC power lines and chassis surfaces to low values and thus protect the linear DC supply operational amplifier and keep the RF currents equal in the feedline wires. A switching DC supply is NOT recommended in this system because the pulse width modulator is too sensitive to RF,  even in recent designs.
Antenna construction
Surveying the space the wires and feedline will be in is the first step in building this system. Then determine where the apex support will be. Are the wires going to run straight?  If not, make sure the geometry of folding the wires into a smaller space  will be mostly symmetric. If 160 meters is not part of the operating plan then the antenna size can be halved and halved again if 80 and 75 meters is not of interest.
The wires can be #22 or larger. The L -network chart component values are for the 160 meter straight wire dimensions shown including the feedline length, apex height, and wire end height. Many other dimensions may be used while maintaining symmetry, but new chart values will have to be recorded.
I use straight #22 wires with an Everlast #70 pulley from Penn Plastics on one end. This pulley is available at Lowe's hardware. With 1/8 to 1/4" line and a 3 pound weight the wires stay mostly straight even in strong wind gusts.
Provisions for quickly removing the feedline from building entry in case of lightning is very important, especially in Tucson where I live part of the year and lightning can occur in any season.
I have made apex and end insulators from black abs plastic plumbing fittings and black poly flower pots. Black nylon ties may also be used.
The apex support I use is thirty feet high and made from galvanized steel TV mast and an upper 12'x 2"x2" fir pole. A smooth metal ring on top and nylon line lift the center insulator and feedline. There are also telescoping fiberglass masts now available at reasonable cost.
L-network construction
My network is made from junk box components mounted on an insulating wood base. C2 is an old 500pf per section, two section broadcast band receiver variable without trimmers with the two sections connected for 1000pf. C1 may be another old broadcast variable. Be sure to open or remove the trimmer capacitors so that capacity can be adjusted to a low minimum for the higher bands. Smaller variables may be used on the highest bands. Fixed capacitors may be used as indicated in the chart.
Some of you may be asking: Is this system like a G5RV antenna?  The answer is it is not. The critical difference is the choke balun and L - network, which keep the currents in the feedline and antenna wires balanced at all frequencies. In contrast, the currents at most frequencies in the G5RV system are not balanced. One recent key reference for this is the appendix page of John Belrose's article in the October 2004 issue of QST magazine.
Results and use
More than 95% of the transceiver RF power feeding the choke balun appears at the antenna apex. Part of the reason for this is the elimination of RF ground paths especially on 160 meters. The importance of this was discussed several times by Bill Orr, W6SAI in his Ham Radio magazine columns in the 1980s. One of these references is included.
Given reasonable propagation conditions my signal report experience with this system has been very favorable, even when I have reduced power output to less than 10 watts. QRP can definately be more fun with this system even on 160 meters.  I have always received strong signal reports on 40 meters, mainly because the apex begins to be almost one quarter wave above ground level on this band.
The radiant pattern of this antenna is basically hemispheric on 160 - 75 meters and then begins to diverge into complex symmetric lobed patterns on 60 meters and above.
This system is inherently portable and effective for field-day use.
This article is in memory of Clare Stadden, N7PXJ, formerly of Coos Bay, Oregon. Clare showed, by example, the importance of plane, simple, and effective HF wire antenna systems. Clare grew up with amateur radio and learned many of the old ways from his father who began transmitting in the early years of our hobby, in the 1920s. 
I have also learned much from:
-Walter Maxwell's clear discussions of the conjugate impedence match for maximum power transfer.
-John Belrose's many antenna articles written for radio amateurs by a professional radio scientist.
-Bill Orr's many articles and books on radio essentials.
-Heinrich Hertz's own descriptions of his 1880's experiments in his book Electric Waves which proved for the first time the existence of electromagnetic waves. Hertz was born 150 years ago on February, 22, 1857 in Hamburg, Germany.
Carter Rose has been continuously licensed since March 1957.
He graduated in electrical engineering from the University of Michigan in 1963.
Baird, B.  "Antenna Tuner with a New Twist"  Ham Radio,  June 1990 Belrose, J.  "On the Quest for an Ideal Antenna Tuner"  QST,  October 2004
Franke, E.  "Appreciating the L Matching Network"  Ham Radio,  September 1980
Hertz, H.    Electric Waves    translated by D. E. Jones,    MacMillan, London  1893
Maxwell, W.  "Reflections"  2nd edition  World Radio Publishing, 2001
Orr, B  "The Radio Ground on 160m"  Ham Radio   March 1988
Pattison, B.  "A Graphical Look at the L-network"  QST,  March 1979
Rose, C.  "A 160 meter Inverted-V Antenna"  CQ Amateur Radio magazine,  September 2001
Vissers, W.  "The L with it - an alternative to the variable inductor"  Seventy-three magazine,  March 1980
Antenna & Feedline:
Power:  100 watts  max.
Bandwidth:  160 -- 10 meters
SWR:   Quickly adjustable to 1:1
Feedline:  600, 450, or 300 ohm twinline or shielded twinline... length ~37.5' for straight wires and chart values given.
Apex:  30' minimum
Top wires:   Minimum  #22 copper  110'  long   for 160 meters lowest band of operation.
Top wire ends: ~6' high
Apex connector & end insulators:  Use black poly from 1 gallon or larger flower pot, or black abs plumbing fittings or black nylon ties.
Radiation pattern:  From 160 to 60 meters, mostly hemispheric, then varies widely as symmetric lobed patterns as frequency increases.
L1:  One form of this coil is #12 tinned wire, 2 1/2" ID, 5" long, 6tpi, 32 turns total. 21 turns has been the most used on 160, 80, and 75 meters. This larger coil allows much easier coil tapping with small clip leads.
C1:   Fixed values as shown in chart for 160, 80, 75, 60, 40, and 20 meters. Two section broadcast band variable , 0.015" spacing  for 30, 17,  15, 12, and 10 meters.
C2:   ~50 - 1000pf, 0.015" spacing.
1:1 Choke balun:
May be commercial unit or home made from tv flyback transformer core and ~8' of RG-58a/u coax or 30 turns of coax on a 4" paper or plastic tube.
Ferrite choke:
Any larger surplus ferrite cores from old speaker magnets, flyback transformer cores, cathode ray tube deflection cores etc. with AC power cord and DC cord wrapped around a few turns.