2016 events of the Dengie Hundred Amateur radio Society. (Incomplete)

Some information about previous events of the Dengie Hundred Amateur Radio Society (DHARS) may be found here. In many cases, clicking on an image will bring a higher resolution one.

Impedance measurements by Dr. David Kirkby G8WRB (25/01/2016)

David discussed various methods of measuring impedance, using commercial instruments, rather than ham-grade items, which claim to be instruments, but which rarely igve any specifications on their uncertainty. The model numbers linked are models for which David's company (Kirkby Microwave Ltd) owns. However, due to the size, weight, value etc, only the HP 8753ES was bought along to the talk. The methods discussed were

Roger Jones, one of the club members, bought along an unknown antenna for testing. Stephen Hedgecock (M0SHQ) bought along a homemade 2m/70cm antenna built for satellite work. The 2 m resonance was clear to see, but on 70 cm the resonate frequency was rather unstable. This instability is confirmed in computer models using MMANA-GAL, because one of the dimensions is very critical. Two elements are spaced about 16 mm apart, and slight changes causes significant deterioration of performance. A commercial antenna, which is sold as a log-periodic had somewhat better characteristics, although it looks nothing like a log periodic, and it is almost certainly mis-named.

Since David did not bring along a computer with a GPIB controller, those wanting data had to photograph the LCD screen of the HP 8753ES.

Virtual Computers by Dr. David Kirkby G8WRB (11/01/2016)

David gave a talk about the advantages of virtual computers, which are usually called virtual machines, which allow more than one operating system to simultaneously run on the one computer. There are various pieces of virtualization software available, but David Chose to install VirtualBox on his machine. David bought along his own computer, which is a Sun Ultra 27 running OpenSolaris. He showed how its possible to have other operating systems running at the same time, as any can be used with the click of a mouse. The machines are not dual-booted.

In the first screenshot

Host operating system

we see that the host computer is called "hawk", and the host operating system is running a 2010 copy of OpenSolaris. David is not one of those people that always wants to have the latest, and takes the attitude "if it is not broken, do not fix it". OpenSolaris is good for David's personal needs, as well as his business (Kirkby Microwave Ltd), but OpenSolaris incapable of running many programs that are sometimes needed.

In the second screenshot

VirtualBox installed

it can be seen that VirtualBox is installed. VirtualBox is available to run on a variety of operating systems. For this installation, a version for OpenSolaris needed to be installed. It can be seen there are 15 guest machines installed. These 15 machines run either one of 5 different guest operating systems

In principle all 15 guest machines could be run simultaneously, although even though the Sun Ultra 27 host has 24 GB of RAM, that would be incapable of running 15 machines well.

In the final screenshot VirtualBox installed it can be seen that the host system is still running OpenSolaris, but there is also a copy of Mint Linux running, as well as an XP installation which was allocated 2 GB of RAM and a Windows 7 installation which was allocated 4 GB of RAM. The amount of RAM a system uses is set before the system boots, so depending on what one intending doing with a particular virtual machine on a particular day, it could be increased. One of the Windows 7 or 64-bit XP machines might be increased up to about 18 GB, if it was the only system running. That would leave 24-18= 6 GB for the host system, which would be enough to run it comfortably.

David showed how a guest is installed, by starting an installation of XP, but since it takes some time to complete the installation, this was not completed as part of the talk.