Voltage baluns are making a comeback for HF antennas discussed the application of a common Ruthroff 1:4 (voltage) balun design to a slightly unbalanced theoretical scenario.
This article applies the same analysis to two reported measured dipole cases at 3.6MHz.
(Hunt 2015) reported measurements of his dipole antenna system at 3.6MHz. Continue reading Voltage baluns are making a comeback for HF antennas – some real antenna measurements
I planned this article to be a Youtube video, but recent behaviors of Google / Youtube give me pause to consider whether or how I use Youtube in the future. So, this article is a simpler presentation of the underlying concepts.
For most purposes, users of HF antennas would like the feed line to perform that function alone, ie to not participate as radiating or pickup conductors.
For that end, we want the common mode component of feed line current to be very very low.
Discussion of antennas tends to represent them as two terminal devices in free space, ie ignoring the presence of ground in close proximity. This applies whether the feed line is coax or two wire line.
A more complete representation (or model) is a three terminal network that includes a terminal to permit current to flow to ground. Above is a Wye or Delta equivalent circuit, and that can be transformed to an equivalent Tee circuit. Continue reading Voltage baluns are making a comeback for HF antennas?
I have a GPSmap 76 which has not been used for perhaps 12 years, stored without batteries.
The GPSmap 76 appears to use an internal battery for non-volatile memory and clock, likely to be a MC621 rechargeable LiIon (MnO2) button cell of about 3mAh capacity. Continue reading Reviving a Garmin GPSmap 76 (GPSmap76)