A low Insertion VSWR high Zcm Guanella 1:1 balun for HF

This article describes a Guanella 1:1 current balun which has high common mode impedance (Zcm) and low Insertion VSWR. It is for application on antennas that have low VSWR(50) on at least some bands, especially if they would be used without an ATU on some bands. The purpose of the balun is to minimise common … Continue reading A low Insertion VSWR high Zcm Guanella 1:1 balun for HF

G3LNP balun with symmetric ‘matched’ load

My article G3LNP balun explored the operation of the G3LNP 4:1 balun on a 200Ω asymmetric load and found it exhibited extreme Insertion VSWR on what should have been an ideal impedance transformation but for the asymmetric element. The balun is in fact a Voltage Balun and cannot be expected to work properly on asymmetric … Continue reading G3LNP balun with symmetric ‘matched’ load

Inductance of sensorless brushless DC motors

A reader of A Demagnetisation Risk Index for a sensorless brushless DC drive asked whether the inductance of a sensorless brushless DC motor could be measured with one of the inexpensive LC meters available on eBay. Motor inductance line-line typically ranges from several µH up towards 100µH. Importantly, the fundamental frequency of flux change in … Continue reading Inductance of sensorless brushless DC motors

PD7MAA’s BN43-202 matching transformer for an EFHW – full measurement set

I have written some recent articles about or relevant to PD7MAA’s BN43-202 EFHW matching transformer. At about the same time a discussion started on and through that discussion, one ‘online extra expert’ stated that my analysis was bogus (dictionary meaning: not genuine, faked, a misrepresentation). This article presents detail that was not included in the … Continue reading PD7MAA’s BN43-202 matching transformer for an EFHW – full measurement set

PD7MAA’s BN43-202 matching transformer for an EFHW – measurement of a prototype

At PD7MAA’s BN43-202 matching transformer for an EFHW I gave an estimate of the core loss in PD7MAA’s transformer. This article reports measurement of a prototype built to his design.   Above is PD7MAA’s graphic for his transformer. It is a little confusing as an 11t wind will start and finish with ends as the … Continue reading PD7MAA’s BN43-202 matching transformer for an EFHW – measurement of a prototype

PD7MAA’s BN43-202 matching transformer for an EFHW

End Fed Half Waves have certainly captured the minds of QRP aficionados, and there is a steady stream of ‘designs’ appearing on the ‘net. A recent article by PD7MAA describes such a transformer using a BN43-202 balun core for up to 20W PEP from 7-29MHz. Above is PD7MAA’s graphic for his transformer. It is a … Continue reading PD7MAA’s BN43-202 matching transformer for an EFHW

Radio-Kits SWR meter – build and review

This article describes my build of a Radio-Kits SWR meter (v1.1) and post implementation review. Advertised features: HF coverage – 1.8-30MHz Displays VSWR, forward power, reverse power and supply voltage Peak reading power meter Bar graph or numerical format Reverse power alarm with adjustable threshold Auto turn on in presence of RF – sensitivity about … Continue reading Radio-Kits SWR meter – build and review