Tech Net Notes December 17, 2008

1. ke5omv, Don asks, "How do I splice two pieces of coax together? Should I use 2 PL259s and a coupler, or something else?”

Kd5cny, Tom says, “Barrel connector, “N” connector is a little better but harder to put on. I would suggest a PL 259, a little more loss, but probably not enough that you would notice.

Ke5lnn, Dave, “Purist would advise you not to splice together like that because of the loss.” Tom says, “1/10th of a db loss on each connector”. Ray says, “Put waterproof tape around the connector. I had a little higher SWR when I used a splice with a barrel connectors.

Kd5cny, Tom asks, “At what frequencies will you be running through the coax?” Answer: “70 cm & 2-meter”. Tom says, “If running 440 I strongly suggest not using three pieces of cable”.


2. ke5lnn, Dave asks, "When I have my mobile radio on scan mode and engage my automobile cruise control, the radio scan is interrupted. How do I fix it?"

Ke5lnn adds, Dave says that ferrite RF chokes have not helped any. He thinks he may have to do something with the cruise control. The hot line goes to the battery. Ground goes to the chassis.

From another ham: The cruise control module is located either under the dash or under the hood. If you run your wiring anywhere close to the cruise control module, you may be picking up interference. You may want to try rewiring the power along a different route. You might try moving your ground and your power cord to a different location.

Jeff asks, “What does the cruise control module look like?” Ray, kc5wsi, “What is the year and Make of the vehicle?” If it’s a Chrysler product, they have been known to have cruise control units that affect other vehicle electronics. Dave says, “It’s a 2001 Toyota Tacoma.” Ray says, “The unit is probably going to be under the dash with four to 5 wires 1” x 3” x 5”. It should have a back plug on one end. I will try to find out specifically what it looks like and its location and get back with you next week.”

Kc5bgf, David says, “You might try a coax line for your power feed line. Older coax is often heavier and some is double shielded and makes a better conductor.”

Kd5cny, Tom, “Fuel pump noise in today’s cars is often a problem for interference.”