An issue that often arises in online discussions inability to reconcile the VSWR indicated by a transceiver (or possibly an inline VSWR meter) and an antenna analyser.
Is this Segal’s law at play?
There are several common contributors including:
Continue reading Disturbing the thing being measured – coax line
I have set out an initial design method for RF inductors and transformers using toroidal ferrite cores and over time I get correspondence drawing my attention to Amidon’s advice, specifically sections 1-35 and 1-36.
Section 1-36 states explicitly that it is applicable to Iron Powder and Ferrite, which is interesting because they are very different materials from a loss point of view.
Basically, their method depends on a maximum safe value for peak flux density.
They give an expression for peak flux density \(B_{max}=\frac{10^8E }{4.44 A_e N F}\) and the following table of design limits for Bmax.
Note that the table and formula are independent of ferrite mix type (though they do mention that “these figures may vary slightly according to the type of material being used.” Continue reading Amidon’s method of rating ferrite inductors and transformers
I see online discussions struggling to try to work out if a receiving system is sufficiently good for a certain application.
Let’s work an example using Simsmith to do some of the calculations.
Scenario:
An NEC-4.2 model of the antenna gives a feed point impedance of 146-j4714Ω and radiation efficiency of 0.043%, so radiation resistance \(Rr=146 \cdot 0.00043=0.0063\).
Above, the NEC antenna model summary. Continue reading Quantifying performance of a simple broadcast receive system on MF
This article is demonstration of measurement of Transmission Loss in a section of coaxial transmission line. The scenario is chosen to expose the experiment to some of the things that complicate such measurements.
The very popular nanoVNA-H will be used to make the measurements.
The scenario:
Above is a block diagram of the test configuration. nanoVNA measurements are wrt 50Ω, so \(P=\frac{V^2}{50}\) and \(V=\sqrt{50P}\). Continue reading nanoVNA – measure Transmission Loss – example 4
KL7AJ on the Conjugate Match Theorem asked the question Should we have expected this outcome?
Let us solve a very similar problem analytically where measurement errors do not contribute to the outcome.
Taking the load impedance to be the same 10.1+j0.2Ω, and calculating for a T match similar to the MFJ-949E (assuming L=26µH, QL=200, and ideal capacitors) with Simsmith we can find a near perfect match.
The capacitors are 177.2 and 92.9pF for the match. Continue reading KL7AJ on the Conjugate Match Theorem – analytical solution – Simsmith
This article is demonstration of measurement of Transmission Loss in a section of coaxial transmission line. The scenario is chosen to expose the experiment to some of the things that complicate such measurements.
The very popular nanoVNA-H will be used to make the measurements.
The scenario:
Above is a block diagram of the test configuration. nanoVNA measurements are wrt 50Ω, so \(P=\frac{V^2}{50}\) and \(V=\sqrt{50P}\). Continue reading nanoVNA – measure Transmission Loss – example 3
This article is demonstration of measurement of Transmission Loss in a section of coaxial transmission line. The scenario is chosen to expose the experiment to some of the things that complicate such measurements.
The very popular nanoVNA-H will be used to make the measurements.
The scenario:
The transmission line load is four 50Ω loads in parallel, one of them being VNA Port 2. Only one quarter of the output power is captured by the VNA, so there is effectively a loss of 6.02dB in that configuration. It also delivers a 12.5+j0Ω load the the transmission lines, VSWR is about 6. Note this power division is based on the assumption that Zin of Port 2 is 50+j0Ω, and error in Zin flows into the result. A 10dB attenuator is fitted to Port 2 prior to calibration to improve accuracy of Zin.
Above is a block diagram of the test configuration. nanoVNA measurements are wrt 50Ω, so \(P=\frac{V^2}{50}\) and \(V=\sqrt{50P}\). Continue reading nanoVNA – measure Transmission Loss – example 2
This article is demonstration of measurement of Transmission Loss in a section of coaxial transmission line. The scenario is chosen to expose the experiment to some of the things that complicate such measurements.
The very popular nanoVNA-H will be used to make the measurements.
The scenario:
Above is a block diagram of the test configuration. nanoVNA measurements are wrt 50Ω, so \(P=\frac{V^2}{50}\) and \(V=\sqrt{50P}\). Continue reading nanoVNA – measure Transmission Loss – example 1
The discussion at Magnitude and phase of I2/V1 for a 90° transmission line raises the question whether something special happens for a 180° line section.
This article discusses the quantity V2/V1 for a special case, a 180° transmission line section.
180° transmission line sections are often used as part of a balun for VHF/UHF antennas.
Above is an application of a 180° line, a ‘half wave balun’, the U shaped section is 180° in electrical length. Continue reading Magnitude and phase of V2/V1 for a 180° transmission line section
Magnitude and phase of V2/V1 for a transmission line section ended with:
The quantities I2/V1 and V2/I1 can be more interesting in some applications.
This article discusses the quantity I2/V1 for a special case, a 90° transmission line section.
90° transmission line sections are often used as a splitter / combiner / impedance transformer for two nearly identical antennas. I say “nearly” because no two antennas are likely to be exactly identical. They are sometimes called phasing harnesses.
Above, an example. Continue reading Magnitude and phase of I2/V1 for a 90° transmission line section