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References and further reading for Chapter 5.
| Further Reading: |
 The ARRL
Antenna Book, 19th edition, ARRL publ, 2000. ISBN: 0-87259-804-7.Ch 25: Coupling the Transmitter to the Line. Discussion of harmonic attenuation in antenna tuners [pointing out that it is not reliable!], and the problem with trapped antennas. Matching circuits: Inductive coupling, L-network, p-network, T-network. The 'Analyze Antenna Tuner' Program (supplied on CD-ROM with the book). Practical antenna tuners: Link-coupled, High-power T-network with input-side balun). CD ROM: AAT (Analyze antenna tuner program), etc. The ARRL
Handbook 2000, 77th edition. ARRL publ. 1999, ISBN: 0-87259-183-2.Ch 13: RF Power Amplifiers Ch 22: Station Setup and Accessory Projects. High-Power T-match Antenna Tuner with TX-side balun, p56-59.) "Graphical
solution of impedance matching problems" I L McNally
W1NCK and Henry S Keen W2CTK, Ham Radio Dec 1969 p. Reprinted
Mar 1978 p82-89. " ",
Elmer Wingfield, W5FD, QST, Aug 1983, "A Note
on Pi-L Networks" Elmer Wingfield, W5FD, QEX, Dec 1983
p5-9 "Analyzing
Simple Matching Networks", Mark Bacon, KZ9J, QEX, Feb.
1987, p3-6, contd, p13. "Selectivity
of Single-Resonator Coupling Networks", William E Sabin
W0IYH, QEX July/Aug 2001 p43-47. "Antenna
matching", Tech Topics, Rad Com, Sept 1981, p818-819.Arthur collins, W0CXX, in the mid 1930s, popularised the 'Collins Universal Coupler' (p-network), on the basis that any TX could work successfully with any length of antenna. W2DK pointed out that when an antenna element presents to a transmission line an impedance other than R0, the impedance offered to the TX at the other end of the line may be quite different. The feeder acts as an impedance transformer. Unless a matching unit is interposed between the transmitter and the transmission line, the impedance may be of a value with which the TX output circuit cannot cope. An ATU must ideally cope with a very large range of impedances. Only one capacitor and one inductor is required to do this, but values and voltage ratings may become unwieldy. Most ATUs represent configurations aimed at reducing component sizes to manageable proportions. Dr M. J. Underhill, G3LHZ, presented a paper at a Leeds conference, showing that wide range matching can be achieved based on a two-stage approach, involving a pre-match unit (PMU) at the antenna junction, and a final-match unit (FMU) at the transceiver. The PMU may be, for example, a coaxial balun. An FMU design offering switchable p-network configurations to keep voltages within reasonable limits is given [see erratum, TT Nov 1981, next ref.]. The series variable capacitance and tapped inductor is suggested as an alternative to the roller-coaster coil. "Antenna
matching for amateur bands", Tech Topics, Rad Com, Nov
1981, p1034.Variable capacitor marked 220pF in previous article should have been 2200pF. G3LHZ FMU circuit is reprinted with C1=1600pF (not 2200pF), since amateurs require only 1.8-30MHz, not 1.5-30MHz. "The transmitter
/ antenna Interface" Tech Topics, Rad Com, Dec 1984,
p1054-5.Brief review of antenna coupling practices from early techniques onwards: The widespread introduction of VHF TV after the end of World War II brought about renewed interest in the p-network on accountof its low-pass characteristic. The need for better harmonic suppression however soon led to the fixed-impedance low-pass filter, which meant that transmitters were designed to work into a 50W load in order to terminate the LPF correctly. The output of the LPF was connected directly to the coax feedline of a resonant antenna. ATUs were relegated for use by those who used end-fed wires, open-wire feeders, or wanted extra harmonic suppression. The situation changed however with the introduction of solid-state transmitters with protection circuits, which do not give full output with high SWR. Few practical antennas provide sufficiently low SWR over entire amateur bands without the intervention of a matching unit. Consequently, the ATU came back into vogue. G3VA reminds us that a resonant antenna does not radiate any better than a non-resonant one. The new WARC bands make it necessary to be able to cope with a wide range of resistive and reactive load impedances. Repeats information on the G3LHZ PMU-FMU approach for those who did not see the 1981 articles (above). Also repeats circuit and information on the G3LHZ wide-range FMU. "The PA0SE
Comudipole Multiband HF Antenna", Tech Topics, Rad Com,
May 1993, p54-55.Dick Rollema, PA0SE, notes that it is not always convenient to bring the open-wire line into the transmitter room, and recommends a variation of the PMU-FMU scheme devised by Mike Underhill, G3LHZ (see "Antenna matching" TT sept. and Nov.1981, and "The Transmitter / Antenna Interface" Dec 1984, above). The G3LHZ information is repeated for those who did not see the 1981 and 1984 articles, giving construction details of a 4:1 air-cored coax balun (PMU) for connection via 50W coax (SWR <20:1) to a switch-configurable variable matching network (FMU). PA0SE considers the G3LHZ FMU over-complicated and adopts a simple switchabe L-network. Describes an installation with a 38m long inverted V dipole using 4:1 coax balun PMU at the antenna, 30m of RG213, and an L-network FMU. Perfect matching is obtained on 10 bands from 1.8 - 50MHz, but with low efficiency on 1.8MHz. Coax losses may be a few dB on some bands, "but this is a small price to pay for the convenience of a simple all band antenna without traps". "The advantage of [the coax] balun over those using ferrite or powdered iron toroids is that there is no danger of saturating the core [for advice based on actual research, see "Building and Using Baluns and Ununs" by W2FMI] ... additionally, toroidal baluns are not really suitable with reactive loads" [MFJ transmatch owners might be inclined to disagree]. "Ultimate
Transmatch Improved" Doug DeMaw W1FB, Technical Correspondance,
QST July 1980 p39.W1FB states [incorrectly] that the original circuit was developed by the James Millen Co. and was popularised in QST by W1ICP as the "Ultimate" transmatch. Goes on to point out that the input-side parallel capacitor is redundant and the circuit is effectively an expensive T-match. The problem with the T-match is that under some circumstances it degenerates into a high-pass filter. Introduces the SPC circuit, which gives better harmonic attenuation and extends the low-frequency limit. "Set the
Record Straight" Lew McCoy W1ICP, Correspondance, QST
March 1981 p56. "The Ultimate
vs the SPC Transmatch", Walt Maxwell W2DU, Technical
Correspondance, QST Aug 1981 p42-43. "Ultimate
vs SPC Transmatch" Tech Topics, Rad Com, Sept 1984,
p771.G3KSU points out that the 'Ultimate' transmatch is still being advocated in books and journals, despite the shortcomings documented in the technical correspondance columns of QST in July 1980, March 1981, and August 1981. Essentially, the extra shunt capacitance across the TX terminals is useless and causes a reduction in efficiency. The drawback of the Ultimate was overcome by the 'SPC' (Series-Parallel Capacitance) configuration devised by Doug De Maw, W1FB, which offers improved harmonic attenuation [but reduced efficiency] compared to a straight T-network [the SPC configuration was also dropped by the ARRL Antenna Book by the 19th edition]. "The ATU
Debate Continues" Tech Topics, Rad Com, Dec 1984, p1055-6."It would be a brave or foolhardy writer who claimed categorically that any one network was clearly superior to all others". Peter Chadwick, G3RZP, finds the SPC transmatch less eficient than a 4:1 transmission-line transformer and a series capacitor for matching an impedance of 12.5+j22W. The problem is that of excessive loaded Q. He prefers a parallel-tuned auto-transformer, adjusting the working Q by selecting the input and output taps and the L:C ratio, and canceling inductive reactance by means of a series capacitor in the output line. Admits that such tuners require elaborate switching and are not easy to set up. Discusses problem of arcing in un-shorted overwinds, and eddy currents in shorted overwinds. Rejects the idea of trying to get harmonic attenuation from an ATU, preferring the efficiency gain from operating the matching network with low working Q. Ivan James, G5IJ, favours the 'Ultimate' transmatch for voltage fed antennas, since the configuration reduces the required voltage rating of the ganged capacitors. Rejects the harmonic attenuation argument and recommends a multi-section LPF between the TX and the ATU. Also objects to the 1980 QST harmonic reduction tests, which used a 1000W test load for fundamental, 2nd, and 3rd harmonics, pointing out that the antenna impedance is hardly likely to be the same on all three frequencies. "the arguments about harmonic reduction depend so much on the actual antenna impedance that no definite conclusions can be drawn from such tests". Frank Rogers, G3BFR, converted a T-match to an SPC and found it extended the low-frequency limit. The Coil was 27mH, but C values are not given. Also, some material by Rob Gurr, VK5RG, on the Z-match, is reprinted. "A Versatile
ATU", Tony Smith G4FAI, Practical Wireless, April 1983,
p20-21. Constructional article for a tapped-inductor version of the W1ICP "Ultimate" transmatch. "Which
Transmatch?" Tony Smith G4FAI, Practical Wireless, Aug
1985, p22-23.G4FAI Modifies his 'Ultimate' to make it into an SPC. Also briefly discusses the history of the two networks: Lew McCoy W1ICP introduced the 'Ultimate' transmatch in a QST article in [July] 1961 [actually July 1970], several versions appeared in subsequent issues of the ARRL handbook, and commercial versions were produced. The SPC transmatch by Doug DeMaw W1FB appeared in the 1981 ARRL handbook. DeMaw had written to QST in July 1980 pointing out that the T-match would function as a HPF under some conditions, and a LPF between TX and transmatch was required. The SPC was developed in an effort to maintain a band-pass response under all load conditions. He claimed better harmonic attenuation and wider range compared to the 'Ultimate', and included details of tests carried out using a spectrum analyser. McCoy responded in March 1981 claiming that the extra 10dB of harmonic attenuation given by the 'Ultimate' was sufficient. In August 1981, Walt Maxwell, W2DU, produced a detailed analysis of both circuits, observing that the input shunting capacitor of the 'Ultimate' was useless for impedance matching and reduced efficiency, but that the circuit did attenuate harmonics slightly. The harmonic attenuation of the SPC was substantially better. The 1983 ARRL handbook observed that harmonic attenuation with the 'Ultimate' can be as low as 3dB under some load conditions; whereas the SPC maintains a band-pass response with loads of <25 to >1000 W, this being due to the capacitance in parallel with the inductor. "A General-Purpose
Antenna Matching Unit", M J Grierson, G3TSO. Rad Com,
Jan 1987, p18-22. Reprinted in "HF Antenna Collection"
Ed. David Erwin G4LQI, RSGB publ 1991 ISBN 1-872-309-089. p119-124.Constructional article describing T-match tuner with integral SWR meter and output-side balun. Author considers SPC and differential capacitor configurations but rejects them on grounds that harmonic suppression is provided by modern TX. Balun is voltage type 1:1 - 4:1 switched, with powdered iron toroidal core [and should be updated in view of W2FMI work]. Suggested tuning procedure involves beginning with both capacitors set half-way. Observes "it is not uncommon ... for one capacitor to be very sharp ... while the other is flat and unresponsive". "A differential
T-match antenna tuner", Mike Grierson, G3TSO, Rad Com,
Sept 1990, p48-49.Constructional article. The differential T-match is capable of matching a similar range of impedances to the traditional T-match. Efficiency is not discussed. MFJ-986 Differential-TÔ Antenna Tuner. Advertisement
2001."Replacing two variable capacitors with a single differential capacitor gives a wide-range T-network tuner with on;y two controls. .. You get minimum SWR at only one setting and a broadband response that ends constant re-tuning". "Estimating
T-network Losses at 80 and 160 Meters", Kelvin Schmidt,
W9CF, QEX, July 1996 p16-20(see refs of this article- QST Jan, April, May 1995, ) [nn] "Understanding the T-tuner (C-L-C) Transmatch" William E Sabin, W0IYH, QEX, Dec. 1997, p13-21. Suggests that shorting out C1 and C2 will improve efficiency in some situations. States that efficiency increases as L is reduced. (Need to investigate this assertion). "Save
Your Tuner for Two Pence", Tony Preedy, G3LNP, Rad Com,
May 2000, p20-25.The "two pence" in question are copper cams used to make shorting switches for the capacitors in a commercial T-match tuner. Article contains much useful information on ATU design and coil losses, with graphs of Q vs frequency for various roller inductors [unfortunately, working out which graph corresponds to which coil is left as a puzzle for the reader, but the solution appears to be a=1, b=2, e=5. If this is correct, graph e is for the inductor from an MFJ 989C tuner, and shows a rather poor Q (~100 at 4MHz, ~40 at 29MHz)]. Author demonstrates that lowest losses occur in the T-match when one capacitor is set to its maximum value, and consequently gives correct procedure for adjustment. Goes on to describe shorting-switch modification, noting that in addition to reducing losses, it permits higher power on higher frequencies, and extends the upper frequency tuning limit for a given range of load impedances. In practice, notes that there is sometimes insufficient capacitance (in the commercial tuners modified) to effect a match with the L-configuration at lower frequencies, and the intermediate transformation (T-network) is required. "The E-Z
Tuner", James C Garland W8ZR, QST Apr 2002 p40-43. May
2002 p28-34, Jun 2002 p33-36.Reduces the number of coil tappings required for a T-network tuner on the basis of constant SWR curves and power loss curves [appears to consider only resistive loads in the design procedure. Suspect that efficiency considerations will not hold up when a reactance cancelling requirement is introduced - warrants detailed analysis]. "PicATUne
- the Intelligent ATU." Peter Rhodes, G3XJP, Rad Com,
Sep 2000 p16-20, Oct 2000 p21-25, Nov 2000 p20-24, Dec 2000 p24-31,
Jan 2001 p21-24 cont p29-30.Summary: Series of 5 articles describing an automatic ATU using only SWR and a search algorithm. L-match configuration with high Z - low Z switching is used on the basis of efficiency calculations. Efficiency graphs are given in part 1 (erratum part 4, p31). Design includes well-linearised tapped 30mH solenoid (graph in part 5 p24). Directional coupler is Sontheimer-Fredrick type [US pat. 3426298 fig. 9, incorrectly attributed] used with dummy load on through port and antenna system on reverse port for quiet tuning (citing Underhill & Lewis, Electronic Letters, 4th Jan 1979). "Beyond
the Z-Match. The IBZ coupler", Charles A Lofgrenn W6JJZ,
Communications Quarterly, Winter (Jan) 1995 p27-32. " "
Lew McCoy W1ICP, QST, March 1959 p11-15. " "
Lew McCoy W1ICP, QST, Nov 1961 p " "
Lew McCoy W1ICP, QST, Oct 1966 p " "
Lance Johnson K1MET, QST 1966L-C-L T-network " "
QST Oct 1967 pDrake MN-4 pi-network. "Ultimate
Transmatch" Lew McCoy W1ICP, QST July 1970 p ~24 "Appreciating
the L Matching Network", Ernie Franke WA2EWT, Ham Radio,
Sept 1980 p26-30.Theory and applications. |
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"Impedance
Matching: a brief review", Chris Bowick WD4C, Ham Radio,
Jun 1984, p49-50, 53-56. Maximum power-transfer theorem. The conjugate match. Design of L-networks. "Examining
the Mechancics of Wave Interference in Impedance Matching",
Walter Maxwell W2DU, QEX Mar/Apr 1998, p17-24. "VSWR,
Reflections, and the "Conjugate" Impedance Match",
Dr Steven R Best VE9SRB, Communications Quarterly, Winter (Jan)
1999, p9-19. "Impedance
Matching: Interpreting the Virtual Short Circuit", Dr
Steven R Best VE9SRB [Cushcraft], Communications Quarterly, Fall
(Oct) 1999, p31-56.The virtual short-circuit idea is wrong. Reflections from the input to the ATU are eliminated by a cancellation process. "Impedance
Matching: Interpreting the Virtual Short Circuit (re: Communications
Quarterly, Fall 1999): QEX (Letters to the Editor) Sept/Oct 2000,
p60-62Walter Maxwell W2DU. Dr Steven R Best VE9SRB. "Wave
Mechanics of Transmission Lines, Part 1: Equivalence of Wave
Reflection Analysis and the Transmission-Line Equation",
Dr Steven R Best, VE9SRB, QEX Jan/Feb 2001, p3-8."Wave Mechanics of Transmission Lines, Pt 2: Where Does Reflected Power Go", Dr Steven R Best, VE9SRB, QEX July/Aug 2001, p34-42. "Wave Mechanics of Transmission Lines, Part 3: Power Delivery and Impedance Matching", Dr Steven R Best, VE9SRB, QEX Nov/Dec 2001, p43-50. Correspondence, Lincoln Kraeuter KB1EYQ, QEX July/Aug 2002, p61. |
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Lowpass and bandpass filters: "Clean
Up Your Signals with Band-Pass Filters" Ed Wetherhold
W3NQN, QST May 1998 p44-48, June 1998 p39-42. Three-resonator bandpass filters for 160, 80, 40, 20, 15, and 10m, using Micrometals (same as Amidon) powdered-iron and phenolic toroidal cores and high-voltage NPO ceramic capacitors (200W throughput, 50W termination). Design information and return loss measurements. Filters prevent radiation of spurious signals, and prevent receiver blocking and damage due to strong out-of-band signals (i.e., for multiple HF transceivers and antenna systems operating on the same site). |
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p-networks for power amplifiers: "Pi-network
design for high-frequency power amplifiers" Irvin M
Hoff W6FFC, Ham Radio, Sept. 1972 . Reprinted June 1978
p52-64 "Pi Network
Design and Analysis", Earl W Whyman W2HB, Ham Radio,
Sept 1977, p30- "Pi Network
Design", Leonard H Anderson, Ham Radio, March 1978
p36-40. p-networks for transmitter output stages. "Transmitter
Matching Networks" Irvin M Hoff W6FFC, Ham Radio, March
1978 p42-46.Networks for matching an exciter to the input impedance of a linear amplifier. "Optimum
pi-network design", Ulrich Fleischmann DL9LX, and Leonard
H Anderson, Ham Radio Sept 1980, p50-56.Methods for optimising bandwidth without using the Q factor. Use of Z-plane diagram to illustrate the transformation process. "Pi-Network
Formulas", Elmer Wingfield W5FD, (Correspondence) QEX
Sept 1982, p2.Comments on defective p-network design formulae published in various amateur radio books and journals. "More
on Pi-Network Formulas", Mason A Logan, K4MT, (Correspondence)
QEX Dec 1982, p2.Corrections to the above. Series-parallel and parallel series transformations. "New and
Improved Formulas for the Design of Pi and Pi-L Networks",
Elmer A Wingfield W5FD, QST Aug 1983 p23- "Impedance
Matching - A Brief Review", Chris Bowick W4DC, Ham Radio,
June 1984, p48- Walt Maxwell W2DU,
Technical Correspondence, QST, Mar 1985, p45-. "Design
a toroidal tank circuit for your vacuum tube amplifier",
Robert E Bloom W6YUY, Ham Radio, Aug 1985, p29-31, 33-36.Full design procedure for amplifiers up to 2KW. "Pi Network
Capacitor Equations", Mason A Logan, K4MT, Ham Radio,
Oct 1988, p109-110. "A Concise
Calculation Method for Pi-L Networks", Karl Gerhard
Lickfeld, DL3FM, QEX Sept/Oct 1998 p47-49. "A Concise
Calculation Method for Pi-L Networks" William H Sayer
WA6BAN, Doug Smith KF6DX (Editor), (Correspondence) QEX March/April
1999, p59-60.Errors in Lickfield's article. "A Concise
Calculation Method for Pi-L Networks" Vince Bartell
W0MFK (Correspondence) QEX, May/June 1999, p61.Lickfield's method is flawed. |
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© D W Knight 2007.
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