Windows 10 Preview on Linux Virtual Machine

Click above for a larger view.

Here is a screen shot of the Windows 10 Technical Preview running as a guest OS in a virtual machine in Ubuntu 14.04. Windows 10 is in the smaller window (1024 x 768) in the center of the wide screen (1920 x 1080) Linux display. It can also be run in full screen mode.

The Kernel-based Virtual Machine is configured to use one CPU core, 2 GB RAM and 12 GB disk space.  The Windows 10 setup asked for 11.1 GB of disk space. After install there was 2.64 GB of free disk space. A bunch of apps were downloaded and installed automatically after the basic Windows 10 installation completed.


At the far left of the Linux screen is the standard Ubuntu Unity launcher (dock). At the far right is the Conky Seamod widget that shows various aspects of resource usage on the host PC.

My reference for setting up the virtual machine was this article. Performance of Windows 10 is quite good under this configuration, and gives a good opportunity to try out the preview version.

Password Management

Below are my notes about several methods and tools for password management. Individual needs and preferences will always help to determine the best approach. 

For a collection of articles that review various password management programs, scroll down to the section labeled  "Reviews".

Paper Records

• easy to use, but requires manual keyboard entry of login data
• storage is offline
• must be stored and transported securely
• may not be with you when you need it
• no electrical power needed to access
• frequent updates can get messy

Web Browser Password Storage

• built into popular web browsers
• convenient for most web sites
• storage by web browser on your device is not highly secure
• password data can be lost if not backed up
• must synchronize among multiple devices
• master password strongly recommended for user access

Spreadsheet Password Storage

• convenient for most web sites
• storage by spreadsheet file on your device is not highly secure
• password data can be lost if not backed up
• must synchronize among multiple devices
• master password strongly recommended for user access

Cloud-based Password Managers

• encrypted password data is shared among all of your registered devices via cloud storage
• all encryption / decryption is done on your device
• software must be installed on each device
• can augment security with a hardware multifactor authentication device
• able to capture login information during initial login creation on a web page
• automatically enters login information on subsequent logins
• easy to create new login information and updated passwords
• can generate strong random passwords that meet web site requirements
• can securely store content other than logins
• a master password is required

Local Computer-based Password Managers

• encrypted password data is stored on your device (computer, phone, flash drive / removable media)
• data file must be backed up
• if removable media used for storage, must transport between devices
• all encryption / decryption is done on your device
• software must be installed on each device
• some can augment security with a hardware multifactor authentication device
• data can be shared among all of your devices via manual copy process, local server or cloud
• easy to create new login information and updated passwords
• can use copy / paste or auto-text to apply login data to a web page
• can generate strong random passwords that meet web site requirements
• can securely store content other than logins
• a master password is required

Reviews

Many articles are published that review and compare password manager programs. Here are a few for information. The first article does a very good job of explaining the big picture and the specifics of various approaches.

Password managers: Are they safe? Which is the best?
The Best Password Managers
Lifehacker Faceoff: The Best Password Managers, Compared 

Take control of password chaos with these six password managers

Web Browser Based Password Managers  -- See page 5

Top 10 password managers

80 m Dipole Bandwidth

Some recent conversation in our morning group touched upon the bandwidth of an 80 m dipole. We know that the commonly used wire diameters do not allow low-SWR coverage of the entire 500 kHz of bandwidth. Here are model results showing the bandwidth of a theoretical dipole that is fed with a 73-ohm source.

126 ft dipole; no feedline

 This first figure shows the SWR vs frequency for a 126 ft dipole at 50 ft above ground. The source (transmitter) is connected directly to the center of the dipole. Choosing the data points close to the SWR=2 line gives a bandwidth of about 230 kHz (marked in green). At SWR=3 the bandwidth is about 380 kHz (marked in orange).

The next figure is for the same dipole with a feedline having 73-ohm characteristic impedance and fed with a 73-ohm source.

125 ft dipole; 73 ft feedline

The bandwidth for this case at SWR=3 is about 360 kHz -- slightly less that the first case. Additional data points would be needed to more precisely locate the frequencies where SWR exactly equals 3.

An additional model case for feedline of 70.3 ft yielded very close to the same results as for 73 ft. There is little effect from changing the feedline length when operating with feedline characteristic impedance and source impedance close to the impedance of the dipole near resonance.

UPDATE:  I changed the feedline and source (transmitter) impedance to 50 ohms, leaving the other parameters unchanged. The model gave:

• SWR less than 3: bandwidth 280 kHz
• SWR less than 2: bandwidth 150 kHz
• minimum SWR = 1.37

For the cases of 300-ohm or 450-ohm feedline, the SWR is greater than 3 across the entire range of 3.5 to 4.0 MHz, requiring the use of an antenna tuner or other impedance matching methods to operate with a 50-ohm transmitter.


A dipole that is longer or shorter than 1/2 electrical wavelength at the operating frequency will have considerably different SWR than the above ideal cases. Likewise, using a feedline that is much different than the dipole's resonant impedance will affect the SWR significantly. Under these conditions a different definition of bandwidth is needed and relates more to the impedance range that an antenna tuner can accommodate, since the antenna will present a much higher SWR on its own.

WA5MLF

Static Crashes on 3740

Here is an annotated screen shot of the waterfall display showing the static crashes as pale or brighter horizontal strips. The time scale is about 47 seconds from top to bottom.

QRM on 60 m

Here is a screen shot of waterfall display during KE4ID's turn on 60 m. Some Spanish speakers were operating 2 kHz above -- at 5405.5 kHz at 0734 CST.

80 m Loop Feedline Analysis

Recently I used NEC antenna modeling software to analyze the effects of different feedline lengths on SWR for an 80 m horizontal loop at 40 ft height above the "medium hills and forest terrain" ground model. The goal was to see the effects of various feedline lengths that either conformed with or departed from the lengths recommended by W8JI in his article Choosing the Correct Balun in table  3.

I collected the model's data output in increments of 0.2 MHz from 3 MHz to 29 MHz. (The modeling software permits a maximum of 256 data points.) The data were collected for the following lengths of 450-ohm feedline:  384, 400, 418, 467, 512 ft.

The graph below presents the calculated SWR at nine selected frequencies. All feedline cases show a high SWR peak in the 60 m band.  (Click on the image for a larger view.)

 All lengths have similar SWR values at the lower frequencies, and more variation at the higher frequencies. The recommended lengths of 384 and 512 ft (multiples of 127.9 ft) seem to have a bit less variation in SWR at the high frequencies, although 418 ft behaves pretty well. 400 and 467 ft look less favorable.  In the real world, experimentation will lead to an optimal or an acceptable feedline length.  Naturally, it is best to avoid combinations that give very high SWR in a frequency range of interest, since the high SWR will require the antenna tuner to compensate more and the overall antenna efficiency is reduced.

Below are the full calculated SWR plots from the modeling program for each of the feedline lengths. No other antenna parameters were changed. (Click on each image for a larger view. These are reduced-resolution copies, but should suffice for overall impressions.) I found that shorter feedlines, especially 128 and 256 ft (not presented here), gave smoother curves, but I don't have an explanation.  The plots start at 3 MHz, for nicer scaling on the frequency axis, but the antenna is designed for about 3.5 MHz, so the SWR is high at 3 MHz. 

384 ft feedline

400 ft feedline

418 ft feedline

467 ft feedline

512 ft feedline

The program's output numeric data files provide SWR, reflection coefficient, resistance, reactance impedance and phase for every frequency.  Radiation pattern data are also available and can be displayed graphically. For this analysis, the radiation patterns are all identical, since the model's transmission line element is specialized, compared with the wire elements, and does not contribute to the radiation pattern. If the radiation effects of a feedline must be considered in a model, then it must be included in the model as a pair of parallel wires.  For more information on this topic, see part 4 of the QST article series "A Beginner's Guide to Modeling with NEC" by L. B. Cebik.

75 m spectral view at 0738 CDT

Here's a view of 75 m showing low signal levels for this time of day.