An online expert held forth on the design of ferrite chokes and transformers, and to quote one paragraph: Equally selfevidently we don’t want ANY real part of the reactance in a transformer and, for a practical transformer, we want the self inductance on each side (primary and secondary) to be at least j10*R(Load or Source) … Continue reading Selfevidently
A recent online posting offered measurement of an ATU balun in a Heathkit SA-2060A and sought advice on the ferrite core type, losses etc. Above is a diagram from the manual. It is a pair of cores stacked, each core is wrapped in self adhesive glass fibre tape. Last update: 26th February, 2022, 11:26 AM
Over more than 50 years, I have measured literally thousands of RF inductors and transformers. This article gives some hints and techniques for making / preparing prototypes for measurement, and measurement. RF inductors and transformers will often use enameled copper wire (ECW) or some form of insulated wire or coax. Solid core LAN cables are … Continue reading Tips and techniques for measuring small RF inductors and transformers
The article Another small efficient matching transformer for an EFHW – 2643251002 described a correspondent’s , Luis, CT2FZI, implementation of the transformer. I have also had lengthy discussions with Faraaz, VK4JJ, who is experimenting with a similar transformer. This article describes my own design workup and measurements using a Fair-rite suppression core, 2643251002. The cores … Continue reading Another small efficient matching transformer for an EFHW – 2643251002 – #1 – design workup
It seems that lots of hams find measuring the impedance of a common mode choke a challenge… perhaps a result of online expert’s guidance? The example for explanation is a common and inexpensive 5943003801 (FT240-43) ferrite core. Expectation It helps to understand what we expect to measure. See A method for estimating the impedance of … Continue reading nanoVNA – measure common mode choke – it is not all that hard!
This article describes a Simsmith model for an EFHW transformer using a popular design as an example. This article models the transformer on a nominal load, being . Real EFHW antennas operated at their fundamental resonance and harmonics are not that simple, so keep in mind that this level of design is but a pre-cursor … Continue reading A simple Simsmith model for exploration of a common EFHW transformer design – 2t:14t
This article describes a Simsmith model for an EFHW transformer using a popular design as an example. This article models the transformer on a nominal load, being . Real EFHW antennas operated at their fundamental resonance and harmonics are not that simple, so keep in mind that this level of design is but a pre-cursor … Continue reading A simple Simsmith model for exploration of a common EFHW transformer design – 2t:16t
A recent online discussion tried to advise on the need of a common mode choke on a UHF Yagi. Above is the subject M2 440-6SS, 420-450 MHz Yagi deployed in vertical polarisation (using the other pair of holes for the U bolt). Last update: 9th October, 2021, 7:10 PM
A question was asked recently online: I am about to measure a 1/4 wave of 450 ohm windowed twinlead for the 2m band using my NanoVNA. My question is, since I will be making an unbalanced to balanced connection, should I use a common mode choke, balun or add ferrites to the coax side to … Continue reading Measuring a 1/4 wave balanced line – nanoVNA
This article offers a simple Simsmith model for the Small efficient matching transformer for an EFHW. Above is the model topology. D1 is a daemon block which essentially, calculates key values for the other blocks based on exposed parameters and the named ferrite material complex permeability data file. The prototype used a Fair-rite 2643625002 (#43) … Continue reading Small efficient matching transformer for an EFHW – a Simsmith model