I have written several articles recently on matters relating to Small Transmitting Loops (STL), or “Magnetic Loops” to hams ().
What of the Hertzian alternative, a small dipole. Continue reading Small Transmitting Dipole
Month: January 2015
Comparison of two small transmitting loops
At Efficiency and gain of Small Transmitting Loops (STL) I discussed the use of bandwidth measurement of a small transmitting loop (STL) for estimation of efficiency.
Paul Casper (K4HKX) has built a series of STL which he describes on his K4HKX QRZ page. Continue reading Comparison of two small transmitting loops
Loss of Wireman 553 windowed ladder line at MF/HF
Over a long time I have voiced concern at the likely performance at MF / low HF of the very popular windowed ladder lines that use CCS conductors.
A very popular form of commercial ladder line is that using #18 wire, comprised of 19 strands of #31 30% IACS conductivity copper clad steel. The copper cladding on such a conductor is about 14µm in thickness.
This article reports and analyses measurements of a length of Wireman 553 windowed ladder line. Continue reading Loss of Wireman 553 windowed ladder line at MF/HF
AIM 882 produces internally inconsistent results
I have had cause to validate the output produced by an AIMuhf measurement using AIM882 (current version, released about three months ago).
The test scenario is a pair of nominal 50+j0Ω loads on a Tee piece, connected to the AIMuhf by about 1m of RG58 coax and swept from 10 to 50MHz.
It is mental arithmetic that the VSWR should be very close to 2:1, and since the loss of the cable is quite low, VSWR should be almost uniform with frequency. Continue reading AIM 882 produces internally inconsistent results
BNC 75/50 compatibility
One sees perennial discussion in ham circles of compatibility of ordinary 50Ω and 75Ω versions of the BNC (Bayonet Neill–Concelman) connector, in particular the risk of damage in mating a 50Ω and 75Ω pair.
But are there incompatible connectors commonly in circulation.
These discussions often seize on the different dimensions 0.7mm and 0.9mm.
Above shows measurement of the centre pin diameter of a Kings BNC connector (for RG58), it is 1.339mm… nothing like 0.7mm or 0.9mm. (Amphenol Connex 2001) gives the centre pin diameter as 1.32-1.37mm. Continue reading BNC 75/50 compatibility
Low power Guanella 1:1 tuner balun using a pair of Fair-rite 2643625102 suppression sleeves
A reader of Low power Guanella 1:1 tuner balun using a pair of Jaycar LF1260 suppression sleeves asked whether there is an equivalent Fair-rite core for the project.
Fair-rite part 2643625102 (~$4 each from Element14) is of similar size and also medium µ, but slightly different characteristic to the LF1260. Continue reading Low power Guanella 1:1 tuner balun using a pair of Fair-rite 2643625102 suppression sleeves
Radcom review of Alpha Antenna microtune magnetic loop
Alpha antenna refers to the Radcom review of their microtune magnetic loop.
(Nichols 2014) describes the loop as 12.7×3.2mm aluminium flat section formed into an ellipse with average diameter 0.84m. The pictures show that it is close to circular and I will take it to be a circle of perimeter 2.64m.
The review offers some measurements of VSWR=3 bandwidth at the feed point on various bands, and an estimate of efficiency based on RJELOOP1. Continue reading Radcom review of Alpha Antenna microtune magnetic loop
LM386 audio power amplifiers
I tested a couple of LM386 audio power amplifier modules.
The larger one was a kit using the DIP package, the smaller came assembled and used a SO package. Both cost less than $2 each posted on eBay.
They both deliver close to 3Vpk into an 8Ω load at 1kHz when powered from 12.0V. That is close to 0.5W out, but the SO chip cannot withstand the associated dissipation of 0.5W continuous output.
Both handle broadcast program quite happily at 0.5W peak, the chip temperature rise is 15° and 25° respectively.
Another Osram e-ballast bites the dust
I wrote in the fraud of energy efficient lighting – e-ballasts of frustration with green measures forced on us, measures that have replaced tried and true reliable lighting solutions with high tech low reliability solutions in a false promise of net energy saving.
Typically, the cost of repair and replacement of this unreliable technology is much greater than their direct energy saving, indeed much greater than their energy consumption of the life of the equipment.
Above is a ballast removed from a light this morning after 4 years during which it was hardly ever used… perhaps 10 hours at most… so the original capital cost of $80 for luminaire and fitting for 10 hours service gives an average cost of $8/hr for capital and about $0.01/hr for energy. Continue reading Another Osram e-ballast bites the dust
Inexpensive utility rechargeable 9V battery pack for test instruments
There is often a need for a 9V battery for portable test equipment (NNA, Noise Bridge, Low R meter, Power Meter etc). A solution is a 8 cell NiMH pack.
Above, a battery pack made from two Hobbyking 4 low self discharge AA cells. The packs come with JR servo connectors, and the pins are rewired to use the -ve from one pack and +ve from the other pack to one of the JR connectors. The other wires are connected via a 3A Polyswitch for s/c protection. A short JR to 2.1mm DC connector is made from a JR extension cable and 2.1mm connector. Continue reading Inexpensive utility rechargeable 9V battery pack for test instruments