(Dunlavy 1967) sets out his description of a wide range tunable transmitting loop antenna and makes a broad efficiency claim of better than 30% (-5.3dB) for his system. Minimum efficiencies of 30 percent are attainable with practical designs having a diameter of only 5 feet for 3-15 Megahertz coverage. In a context where extravagant claims … Continue reading Review of Dunlavy’s STL patent gain claims
(N6PAA nd) describes several small transmitting loops (STL) and gives some meaningful performance measurements. It is rare to see such measurements and he is to be congratulated. This review focusses on his 40m STL. The loop is a circle of perimeter 3.83m which at 7.1MHz is 0.091λ which is at the top end of the … Continue reading Review of N6PAA’s 40m STL
(Roberts 2010) describes several small transmitting loop (STL) and gives some meaningful performance measurements. It is rare to see such measurements and he is to be congratulated. This review focusses on his 40m STL. The loop is a circle of perimeter 4.3m which at 7.1MHz is 0.102λ which is at the top end of the … Continue reading Review of KK5JY’s 40m STL
(Dodd 2010) describe a small transmitting loop (STL) and gave some meaningful performance measurements. It is rare to see such measurements and he is to be congratulated. The loop is an octagon of perimeter 4.7m which at 14.2MHz is 0.224λ so although many will consider it meets the requirements of an STL, the common formula … Continue reading Review of G3LDO STL (Radcom Sep 2010)
Over recent weeks, I have run literally hundreds of thousands of NEC models of small transmitting loops (STL) over real ground. The objective was to try to discover some simple methods for initial design of a STL, particularly an estimate of ground loss of STL mounted near natural ground. Last update: 23rd April, 2018, 8:23 … Continue reading A method for initial ground loss estimates for an STL
Small Transmitting Loops (STL) are loops of less than about 0.1λ in diameter or about 0.3λ in circumference. Below these limits, the current around the loop is almost uniform and this permits a simplified analysis. STL are commonly known by Hams as “magnetic loops”, but that term is rarely used in recognised antenna text books. … Continue reading Efficiency and gain of Small Transmitting Loops (STL)
Crystal substitute using si5351 – part 1 described the first part of a series on an inexpensive crystal replacement using a si5351-A / MS5351M PLL chip and an ATTiny controller. Above is an example pair of inexpensive modules, less than $10 for the pair (incl shipping). Both boards are powered from 5V, the left hand … Continue reading Crystal substitute using si5351 – part 2
An online expert talking about compensation capacitors and EFHW ferrite cored transformers opined: If the evaluation is done solely by the effect on measured SWR, whether it is measured with a standard reflectometer or a VNA, then it is just as likely the capacitor is changing the losses in the transformer rather than actually adjusting … Continue reading 1:49 EFHW transformer using a Jaycar LO1238 core – capacitor loss
Introduction There are several articles on this site describing EFHW transformers using the Jaycar LO1238 toroid, two particularly relevant ones are: End Fed Half Wave matching transformer – 80-20m – LO1238 variant; and Another small efficient matching transformer for an EFHW – LO1238 – VK3PY, VK3TU build and measurement. This article presents a design workup … Continue reading 1:49 EFHW transformer using a Jaycar LO1238 core – design workup
Barry, K3EUI, posted some interesting measurements of his MyAntennas EFHW which he described with some useful detail: I have been experimenting with a “MYANTENNA” 130 foot long “end-fed” with the 49:1 UNUN* I replaced their 130 ft antenna wire with a heavier gauge #12 stranded insulated wire (I had a few hundred feet).* This is … Continue reading K3EUI’s MyAntennas EFHW on 80m