AmateurRadio.com

Introduction:

• The earth moved in Texas, recently, which sends Richard down memory lane.

Announcements:

• Texoma Hamarama will held October 26-27, 2012 at the Ardmore Convention Center in Ardmore, Oklahoma. Pre-registration ends October 20th.
• The Augusta Hamfest will be Saturday, October 13, 2012 in Augusta, GA.
• Scott, N8VSI, was the LHS ambassador at the Ohio LinuxFest, September 28-30, 2012. We look forward to hearing a report from Scott in the near future.

Topics:

• Richard recounts his experience replacing a computer power supply. Moral? Don’t be afraid to try repairing a computer yourself. Swapping parts is easier than you might think. For power supplies, pay attention to the wattage required. (Ed. Note: When in doubt, it’s best to replace the bad supply with one that has the same or greater wattage rating.)
• Departing from our usual topics, Russ and Richard discuss a couple applications for producing slide shows and panoramic photographs:
  • Imagination is a lightweight and simple DVD slide show maker for Linux and FreeBSD that’s very easy to use, offers a wide variety of transitions, supports background music, and much more. Available in the Debian and Fedora repositories, and probably many others.
  • Hugin is a program that allows you to assemble a mosaic of photographs into a complete, immersive panorama, stitch together any series of overlapping pictures, and much more. It’s cross-platform and easy to use.
• Why Ham Radio? Richard talks about why you might wish to obtain an Amateur Radio License and how you can combine it with Linux, including:
  • Getting your ham license for our non ham listeners.
  • There are many modes of communication, including voice, Morse code, and many digital modes.
  • The ease of getting your license.
  • Why you should get your license.
  • How to get your license.
  • The Amateur Radio Relay League (ARRL) is a good source of information
  • Free practice tests are available at qrz.com
  • A list of certified Volunteer Examiner Coordinators is available at www.ncvec.org.
  • Test sessions can be found through the ARRL and many local radio clubs.
• Russ describes Universal Plug ‘n’ Play devices (UPnP). Many new devices offer the ability to play media from UPnP servers. It makes sharing your media very convenient and easy, but can also be a security risk.

Feedback:

• Pete, VE2XPL, sends a long email in response to episode 88, and covers such things as the Toonie, Alexandre Graham Bell, Brad Sucks, the wAVEgUIDES PodCast, SouthCARS, email addresses for LHS, and the MintCast.
• Ted, WA0EIR, asked if there is a problem with the LHS mailing list as his attempts to post a message there “bounced”. Yes, the mailing lists have been broken, but they’re fixed now.
• Larry Bushey of the Going Linux podcast says thanks for the great show, and admits they stole the LHS “badger” sound effect for use on their show. Episode 185 contains an example of their use of the Badger.
• LHS was mentioned in a comment to a post at hak5.org.

Contact Info:

• Contact Richard at [email protected], Russ at [email protected], or both at the same time at [email protected].
• Listen to the live stream every other Tuesday at 8:00pm Central time. Check the LHS web site for dates.
• Leave us a voice mail at 1-909-LHS-SHOW (1-909-547-7469), or record an introduction to the podcast.
• Sign up for the LHS mailing list.
• Sign up for the MAGNetcon mailing list.
• LHS merchandise is available at the Merch link on Web site. Check out the Badgerwear or buy one of the other LHS-branded items at PrintFection.com/lhs or Cafe Press. Thanks!
• Thanks to Dave from Gamma Leonis for the theme music.

Music:

• “You Are You” by Fall Walk Run from the album Throwing It All Away, courtesy of Jamendo.
• “Flash Back” by MattMigma from the album Phoenix, courtesy of Jamendo.

I’ve noticed a few spirited discussions regarding modifying computer power supplies for use with Amateur Radio equipment. On the surface it seems as though they supply the perfect solution: Inexpensive, high current, regulated 12V DC supplies for a fraction of the cost of specialized amateur equipment. Is it really is as straight forward as lopping off a molex connector and replacing it with an Anderson Powerpole?

By design PC power supplies are designed to output a fairly well regulated 3.3V & 5V to the PC motherboard and 12V to the motherboard, fans and hard-drive motors. Modern units are typically rated anywhere from 75W to 1200W which should be a measurement of the output power available from all the 3.3, 5 and 12 volts. Since this isn’t a lab grade power supply you can expect marketing hyperbole has perhaps inflated the power output figures.

Back when my job was to build PCs I had an issue with a server not being able to start its complete complement of disk drives. When I opened the case I found a 300W desktop supply board had been used in place of the 800W board … sometimes you don’t even get what you pay for!

Before you convert your first PC power supply there are two issues that may, or may not, cause a problem depending on your unit.

The first is load regulation or the ability of the power supply to maintain its rated voltage under load. If the output voltage drops too far your rig will shutdown, distort or fail to provide its rated output power.

The second issue is due to the high frequency switching circuits used in switch mode supplies. Depending on the individual power supply there can be adequate to no filtering to prevent radio frequency interference being broadcast to your receiver. Toroids on the input and output lines can help to reduce interference.

Because of construction differences between models and even between batch numbers for the same model you can never be certain how the power supply you purchase, or recycle, will perform. For the most part people’s experiences have been positive but I have heard of power supplies that were unusable because of RF interference or such poor load regulation that the 12V rail dropped to 11V under load.

Without a motherboard presenting a load and supplying the power-on signal there are a few changes that need to be made to the power supply. Modern power supplies will not enable the 12V output unless the power-on wire is grounded and a load should be placed on the 5V line to help with regulation. Additionally there is usually an adjustment that can be used to raise the voltage above 12V

The following links detail the steps required to convert a PC supply for use with amateur radio equipment. Whether this represents a good investment of your time will depend on your desire to do-it-yourself and the quality of the power supply you begin with. I’ve heard strong opinions either way but I’ll just say that, if luck favors you, you’ll save some money and learn a few new skills in this exercise.

Computer Power Supply Converted for Ham Use

CONVERTING COMPUTER POWER SUPPLIES (Advanced with theory)

Converting Computer Power Supplies to stabilized 13.8 V DC 20 A