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Apr 18 2011

RFC Show Notes Episode 052

00:00 Opening Theme “Hand-Picked” by John Williams, from the album “Long Ride Home”
01:00 Introduction Due to the high volume of feedback, we’ll cover that in a future episode. 

The Resonant Frequency website has been updated, and the donation counter reset, but all donations are gratefully accepted. If an episode has helped you at all, it should be worth a dollar. Thanks.

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Visit the website often to see the latest articles and videos. Check out the Linux in the Ham Shack site, too.

Spring is here and storms are a frequent occurrence. Check out your local Skywarn group.

08:13 Song “Ain’t No Way” by Kirk Fletcher, from the album “My Turn”.
11:08 Topic Part 2 of the Mobile Installation series. This time, we’ll discuss routing power to the radio.
Wire gauge numbers decrease as the diameter of the wire increases. For example, #12 is smaller than #10. For mobile radio installations, bigger wire is better.
In general, stranded will be better than solid for this purpose. It is more flexible and less likely to fatigue and break as it moves.
Consider the voltage, current demand, and distance when choosing the power cable. One symptom of using too small a power wire is a “motor boat” sound on your transmission. The voltage will drop with distance, and that drop is greater on smaller wire than larger wire for the same distance.
Here’s a wire table to help choose the appropriate wire size for your installation.
An example might be:
A 100W HF radio that draws 20 amps, and a 50W dual-band VHF/UHF radio that draws 8.5 amps. The radios will both be 8 feet from the battery. Using the table above,
we can see that #8 wire will deliver up to 30 amps at 15 feet, so it would certainly do the job. It’s best to be a bit conservative. Since our run is only 8 feet, we might get by with #10.
If we were to run separate power leads to both radios, then #10 would certainly work for the HF rig, and #12 for the VHF/UFH radio. -Ed.
Most installations will use the nominal 12VDC power directly from the vehicle battery. It’s best to avoid plugging into the 12V accessory outlet (cigarette lighter) or under-dash fuse panel.
Examine the engine compartment carefully to determine the best route for the power wires. Avoid running the wire directly over the engine or exhaust manifold, as these get very hot and can melt the insulation.
Fasten the wires using cable ties, Velcro wraps, or spiral wrap suitable for vehicle use.
There will be access ports in the firewall to pass the cable into the passenger compartment. Some may have a rubber plug that you can pierce to pass the wire through. If you must drill through the metal firewall, use a grommet or other insulator to protect the wire from the sharp edges.
You may find cavities in the fenders and doors that will accept the power cable. Remember that the wire will vibrate and rub against surfaces and possibly wear through the insulation and cause a short, so take precautions.
Use standard connectors whenever possible, such as a Jones or Cinch plug, Molex, Anderson PowerPole or the like. (Note, PowerWerx.com is a good source for many of these. -Ed.)
Some prefer to solder the leads and shrink wrap or tape the connection.
If possible, crimp/solder ring lugs to the wires and attach them to the battery using the battery cable clamp screws.
Remember to fuse both the positive and negative leads! It’s best to have fuses at the battery AND at the radio ends.
Because the recommended wire is stranded, it can wick moisture into the cable and cause corrosion. Soldering the connection helps prevent this, as does electrical tape, heat shrink tubing, or liquid electrical tape.
Periodically inspect the wires in the engine compartment to catch potential problems early.
36:15 Song “Pearl River” by Mike Zito, from the album “Pearl River”.
41:05 Conclusion Next time, an all-feedback episode.
Check out the website, read the articles, leave a comment, look for a new video, make a donation to the podcast, use GoDaddy for your web hosting, and click the Amazon link for your purchases. Send your feedback! Check out Linux in the Ham Shack, too.
The hamfest season is upon us: Ham-Com, Ham Radio in the Park, and various hamfests. 

Email Richard at kb5jbv@gmail.com
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Closing theme “We Gotta Go” by David Henderson at Podsafe Audio.
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