OCF dipole covers 40 – 6 meters
I don’t usually plug products here, but I thought that this M0CVO off-center fed dipole was a clever design. Not only that, it can be easily built by the homebrewer. According to M0CVO,
The HW-42HP is an Off Centre Fed Dipole with a difference. Designed to operate on all bands from 40m (7MHz) – 6m (50MHz). It will operate on 40, 30, 20, 17, 15, 12 and 10m without an ATU (SWR <3) plus 6m with an ATU. It is also possible to operate on both 80m (3.5MHz) and 60m (5MHz) via a good ATU. This will handle 400W key down or 500W PEP.
Having a feedpoint 1/3 of the way along gives a feedpoint impedance of 200ohms. This is not ideal for modern day transceivers requiring an antenna with a 50ohm impedance. Therefore, a 4:1 balun is added at the feedpoint to alter the impedance to something closer to the 50ohms required. This then allows the antenna to be fed using standard 50ohm coaxial cable such as RG8 or RG213.
The overall length of the antenna is 20.28m or 66ft. It may be mounted horizontally, as a sloper or as an inverted vee. If space is at a premium it may also be ‘bent’ to fit in with no loss in performance.
Generate your own azimuthal map
NS6T has made available an online azimuthal map generator, and it’s very cool. Here’s an azimuthal map centered on my location in Ann Arbor, MI.
To generate a map, all you have to do is to input your grid square or latitude and longitude, but wait, there’s more! You can also specify a distance from your location to get a smaller map, and have it include grid squares.
Build an all-band receiver with an Arduino (and an Si4735)
Here’s an interesting project that looks relatively simple to build. It uses an Arduino to control an Si4735, which is a fully-integrated, 100% CMOS AM/FM/SW/LW radio receiver on a chip. DigiKey has them for $18. You could probably build a complete receiver for less than $50.
This video shows some enhancements that Mirko has added to the software, but there are links to oprevious videos describing the original project.
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