Analog HF Antenna Analyser
#HF antenna
#VSWR meter
#amateur radio
#analog circuit
#antenna analyser
#radio frequency
#Break-In magazine
#signal measurement
Description: Results are displayed on an analog VSWR meter. The design was originally published in Break-In, New Zealand's amateur radio magazine in September/October 2005, and is republished here with the editor's permission. Note: Break-In is a term used in amateur radio to describe a system that allows another person's signal to be heard in the brief intervals between transmitted Morse Code symbols. Many amateur radio enthusiasts have experimented with antennas over the years. Much of this experimentation has been somewhat hit or miss, primarily relying on SWR meters and grid dip meters. The construction of an RF noise bridge provided significant advancements in impedance measurements but required a full coverage receiver and considerable analysis with a programmable calculator or PC to obtain useful information. Recent attempts to build a compact multi-band HF antenna necessitated more careful measurements of antenna impedance. Consideration was given to purchasing a commercial antenna analyzer, but upon reviewing the cost, the feasibility of building a similar device was contemplated. With some free time away from regular work, this analog antenna analyzer and a subsequent digital antenna analyzer were developed. An antenna analyzer is a device that measures the impedance of an antenna. The first device described in this article is entirely analog, without any microprocessor components. The second device, detailed elsewhere on the website, is a fully digital meter equipped with an LCD display. Both devices cover the full 3 to 30 MHz HF range. The analog analyzer is compact and powered by a recycled 6V NiCd battery. It comprises a signal generator, a simple three-digit LED frequency counter, an impedance bridge, and an automatic VSWR meter. A block diagram is included below. This instrument allows for quick antenna checks across the HF spectrum, enabling users to sweep through a chosen band or spot frequency and instantly read the VSWR on the meter. While it is possible to perform similar measurements with an HF transceiver and SWR meter, this approach can be inconvenient, requiring multiple trips between the antenna and transceiver for adjustments and meter settings. The use of a grid dip meter and antennascope has also been explored, but these methods can be inaccurate at higher frequencies and less effective at lower bands. The device described here addresses these issues effectively. Users can make adjustments to the antenna and immediately observe changes in the VSWR across various frequency ranges or at specific frequencies without concern for transceiver overheating or high VSWR issues. Accidental antenna short circuits or open circuits do not pose a problem for this analyzer. Multiple methods exist for measuring RF impedance and VSWR, and extensive experimentation has been conducted to develop these two analyzers. The chosen method for this analyzer is the bridge method, which is depicted in the accompanying diagram. The bridge consists of four components, three of which are 50-ohm resistors, as this instrument measures the VSWR.
The analog VSWR meter described serves as a practical tool for amateur radio operators, allowing for rapid and efficient evaluation of antenna performance. The device operates within the HF frequency range of 3 to 30 MHz, making it suitable for a wide variety of applications in amateur radio. The inclusion of a signal generator enables the user to emit a test signal, which the impedance bridge then analyzes. The use of a three-digit LED frequency counter allows for precise frequency selection, enhancing the accuracy of the measurements.
The bridge method employed in this analyzer is a well-established technique in RF measurement, utilizing resistive components to create a balanced network that can accurately reflect the impedance characteristics of the connected antenna. The three 50-ohm resistors form the backbone of this bridge, ensuring that the measurements are taken under standardized conditions, which is critical for reliable VSWR readings.
In practice, the user connects the analyzer to the antenna and selects the desired frequency or frequency range. As adjustments are made to the antenna, the VSWR reading can be monitored in real-time, allowing for immediate feedback on how these changes affect antenna performance. This is particularly advantageous for fine-tuning antennas to achieve optimal performance, which is essential for effective communication in amateur radio.
The compact design of the analyzer, powered by a rechargeable NiCd battery, enhances its portability, making it easy to transport to various locations for field testing. This feature is especially beneficial for operators who frequently adjust or experiment with different antenna configurations. Overall, this analog VSWR meter represents a significant advancement in antenna measurement technology, providing amateur radio enthusiasts with a reliable and user-friendly tool for optimizing their antenna systems.Results are shown on an analog VSWR meter. The design was originally published in `Break-In`, New Zealand`s amateur radio magazine in Sept/Oct 2005, and is republished here with the permission of the editor. Note: `Break-In` is a term used in amateur radio to describe a system which allows another person`s signal to be heard in the brief
intervals between transmitted Morse Code symbols. Like many hams, I`ve been playing with antennas for years. Much of that experimentation has been, in hindsight, somewhat hit and miss, relying mainly on SWR meters and grid dip meters. When I built an RF noise bridge (See Reference 1 - Note: All references are found at the bottom of this page), the resulting impedance measurements were a major advance, but it required a full coverage receiver and considerable analysis with a programmable calculator or PC before useful information was obtained.
Recent attempts to build a compact multi-band HF antenna required more careful measurements of antenna impedance. I briefly considered buying one of those commercial antenna analysers frequently advertised these days.
Glancing at the cost, I innocently thought Just how hard would it be to build something like that Casting wisdom to the winds, and with a little free time out from my regular jobthis, and a subsequent digital antenna analyser (described here ), were produced. An antenna analyzer is a device which measures the impedance of an antenna. The first, described in this article, is an all-analog device, with not a microprocessor in sight. The second, described elsewhere on this website, is a fully fledged digital meter complete with LCD display.
Both cover the full 3 30 MHz HF range. The analog analyzer, as you`ll see from the photograph, is quite small. Powered with a recycled NiCd 6V battery, it contains a signal generator and a simple three-digit LED frequency counter, an impedance bridge and an automatic VSWR meter. A block diagram is shown below. With this instrument in one hand, I can check an antenna literally in a matter of seconds, sweeping it from end to end of the HF spectrum, over a chosen band, or on a spot frequency, and instantly read the VSWR on the instrument`s meter.
Now, of course, it`s perfectly possible to do much the same measurement with an HF transceiver and SWR meter. In my case, I found that approach fairly inconvenient. I had to run back and forth between the antenna and my transceiver each time I made a minor adjustment to the antenna, switching between forward and reverse directions on the meter, setting the SWR meter forward power at full scale each time.
I`ve also used a combination of grid dip meter and an antennascope, the latter being described for several decades in the various amateur handbooks (See reference 2). Aside from the balancing act required with instruments in each hand, it tends to be wildly inaccurate at higher frequencies, and often pretty pathetic at lower bands too.
The device described on this webpage solved all that very quickly. Now, I can take it out by the antenna, make an adjustment to the antenna, sweep the analyser from one end to the other across each range, and see any change immediately. Or, I can simply adjust the antenna and watch the VSWR rise or fall on a spot frequency I have set the unit on.
I don`t have to worry about my transceiver overheating, or being affected by a high VSWR. Accidental antenna short circuits or open circuits are no problem for this analyser. There are a variety of ways to measure RF impedance, and thus VSWR I think I`ve tried them all in the process of developing these two analysers. The method chosen for this analyser is the bridge method. It`s shown in the diagram below. The bridge is made from four components; Three are 50 ohm resistors, since this instrument measures the VSWR aga
The analog VSWR meter described serves as a practical tool for amateur radio operators, allowing for rapid and efficient evaluation of antenna performance. The device operates within the HF frequency range of 3 to 30 MHz, making it suitable for a wide variety of applications in amateur radio. The inclusion of a signal generator enables the user to emit a test signal, which the impedance bridge then analyzes. The use of a three-digit LED frequency counter allows for precise frequency selection, enhancing the accuracy of the measurements.
The bridge method employed in this analyzer is a well-established technique in RF measurement, utilizing resistive components to create a balanced network that can accurately reflect the impedance characteristics of the connected antenna. The three 50-ohm resistors form the backbone of this bridge, ensuring that the measurements are taken under standardized conditions, which is critical for reliable VSWR readings.
In practice, the user connects the analyzer to the antenna and selects the desired frequency or frequency range. As adjustments are made to the antenna, the VSWR reading can be monitored in real-time, allowing for immediate feedback on how these changes affect antenna performance. This is particularly advantageous for fine-tuning antennas to achieve optimal performance, which is essential for effective communication in amateur radio.
The compact design of the analyzer, powered by a rechargeable NiCd battery, enhances its portability, making it easy to transport to various locations for field testing. This feature is especially beneficial for operators who frequently adjust or experiment with different antenna configurations. Overall, this analog VSWR meter represents a significant advancement in antenna measurement technology, providing amateur radio enthusiasts with a reliable and user-friendly tool for optimizing their antenna systems.Results are shown on an analog VSWR meter. The design was originally published in `Break-In`, New Zealand`s amateur radio magazine in Sept/Oct 2005, and is republished here with the permission of the editor. Note: `Break-In` is a term used in amateur radio to describe a system which allows another person`s signal to be heard in the brief
intervals between transmitted Morse Code symbols. Like many hams, I`ve been playing with antennas for years. Much of that experimentation has been, in hindsight, somewhat hit and miss, relying mainly on SWR meters and grid dip meters. When I built an RF noise bridge (See Reference 1 - Note: All references are found at the bottom of this page), the resulting impedance measurements were a major advance, but it required a full coverage receiver and considerable analysis with a programmable calculator or PC before useful information was obtained.
Recent attempts to build a compact multi-band HF antenna required more careful measurements of antenna impedance. I briefly considered buying one of those commercial antenna analysers frequently advertised these days.
Glancing at the cost, I innocently thought Just how hard would it be to build something like that Casting wisdom to the winds, and with a little free time out from my regular jobthis, and a subsequent digital antenna analyser (described here ), were produced. An antenna analyzer is a device which measures the impedance of an antenna. The first, described in this article, is an all-analog device, with not a microprocessor in sight. The second, described elsewhere on this website, is a fully fledged digital meter complete with LCD display.
Both cover the full 3 30 MHz HF range. The analog analyzer, as you`ll see from the photograph, is quite small. Powered with a recycled NiCd 6V battery, it contains a signal generator and a simple three-digit LED frequency counter, an impedance bridge and an automatic VSWR meter. A block diagram is shown below. With this instrument in one hand, I can check an antenna literally in a matter of seconds, sweeping it from end to end of the HF spectrum, over a chosen band, or on a spot frequency, and instantly read the VSWR on the instrument`s meter.
Now, of course, it`s perfectly possible to do much the same measurement with an HF transceiver and SWR meter. In my case, I found that approach fairly inconvenient. I had to run back and forth between the antenna and my transceiver each time I made a minor adjustment to the antenna, switching between forward and reverse directions on the meter, setting the SWR meter forward power at full scale each time.
I`ve also used a combination of grid dip meter and an antennascope, the latter being described for several decades in the various amateur handbooks (See reference 2). Aside from the balancing act required with instruments in each hand, it tends to be wildly inaccurate at higher frequencies, and often pretty pathetic at lower bands too.
The device described on this webpage solved all that very quickly. Now, I can take it out by the antenna, make an adjustment to the antenna, sweep the analyser from one end to the other across each range, and see any change immediately. Or, I can simply adjust the antenna and watch the VSWR rise or fall on a spot frequency I have set the unit on.
I don`t have to worry about my transceiver overheating, or being affected by a high VSWR. Accidental antenna short circuits or open circuits are no problem for this analyser. There are a variety of ways to measure RF impedance, and thus VSWR I think I`ve tried them all in the process of developing these two analysers. The method chosen for this analyser is the bridge method. It`s shown in the diagram below. The bridge is made from four components; Three are 50 ohm resistors, since this instrument measures the VSWR aga
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