This article uses a report of an experimental small transmitting loop (STL) for 20m to demonstrate application of the calculator Calculate small transmitting loop gain from bandwidth measurement to predict efficiency and gain of the circular STL from the loop radius, conductor radius and measured half power bandwidth. Last update: 17th April, 2015, 7:07 AM
The recent release 11.2 of BLHeli supports some popular Atmel based ESCs. This article is a review of HK_UBEC_40A_MULTI_REV11_2 on that ESC (http://www.hobbyking.com/hobbyking/s…arehouse_.html) at 4S with a Hobbyking 4822-690Kv 22 pole motor and 1045 SF propeller. This ESC was chosen as it is an inexpensive ESC that rates well in features (fast N FETs, support … Continue reading BLHeli on Hobbyking 40A ESC 4A UBEC 9261000003
A correspondent is designing a high performance transverter from 144MHz to 28MHz to be used with a Elecraft K3 transceiver. A question that arises is just how good should the performance of the transverter be, what Noise Figure and Gain should it have without having performance that cannot be fully realised due to external noise. … Continue reading High performance 144MHz transverter design workup – noise and gain analysis
Balun designs has a warning to users of baluns on a full wave dipole. ***ONE EXCEPTION!*** It must be pointed out that a 1:1 balun should never be used on the second harmonic of a half-wave center-fed dipole fed with coax (like an 80 meter dipole being used on 40 meters). The impedance can be … Continue reading Feed point voltage – full wave dipole
Bringing it all together This part explains how to build a model of the entire receive system to calculate G/T. Firstly, make an inventory of all of the system elements that you intend to model. A model needs to be no more detailed than is necessary to provide adequate accuracy for the purpose at hand. … Continue reading Designing high performance VHF/UHF receive systems – Part 5
I made a measurement of ambient noise on 144MHz this morning using the technique described at (Duffy 2009). First step is to recheck the NF of the receiver. The TS2000 is getting a little tired, NF=8.3dB. The technique calculates ambient noise from the variation in receiver output noise of a receiver of known Noise … Continue reading VK2OMD ambient noise measurement 144MHz – 20140217
From time to time, correspondents have asked how the Cobwebb antenna works, and particularly how the impedance matching scheme works. Firstly, what is the Cobwebb? It is an innovative antenna for small spaces, quite compact and as I recall originally intended to cover five amateur bands from 20-10m. Last update: 16th February, 2014, 7:53 PM
An antenna feed line is intended to convey energy from the transmitter to the antenna, and usually without giving rise to radiation itself. The term “common mode” comes from consideration of the currents on an open two wire line, and it refers to the net or unbalance current, ie the current that would give rise … Continue reading Common mode current and coaxial feed lines
As a prelude to this discussion, let us visit the meanings of maker and ham radio or Amateur Radio as it is more formally known. What is ‘maker’ Wikepedia offers: The maker culture is a contemporary culture or subculture representing a technology-based extension of DIY culture. Typical interests enjoyed by the maker culture include engineering-oriented … Continue reading Are radio hams ‘makers’
A sensorless brushless DC motor senses motor position for the purpose of commutation timing by using the voltage induced in the unused winding at the time. Reliably sensing the motor position for a range of motor constructions and speeds proves a challenge. Last update: 16th February, 2014, 8:06 PM