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Author Topic: How can I use the car stereo antenna on my car for  (Read 708 times)
KC8OBC
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Posts: 1




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« on: December 29, 2001, 10:05:54 PM »

Hello, I would like to use the existing car stereo antenna for 2 meters, I do not expect it to do double duty it will be just for ham radio. I have looked all around the web and have found little luck with this topic.  I did see some stuff about open wire matching with welding rods is this my best bet?  I would appreciate any info on this topic 73's

Frank Kc8obc
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KC8AXJ
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Posts: 303




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« Reply #1 on: December 30, 2001, 05:22:16 PM »

Frank- Modern radios are designed and work best when working into a 50 Ohm load. I’m not sure what the coax (wire) running to a car antenna is, but I doubt it is 50 Ohm. IF you can re-wire to the antenna with say RG-58 (50 Ohm coax) the rest is a breeze.
An element is an element!
Get a SWR meter, cut your antenna element to 19 and one half inches in length. This will most likely be a little long to start with, but play it safe.
Check SWR at 146.00 Mhz. If you are 1:5 to 1 or less, you’re in GOOD shape.  If not, check at 145.00 and then 147.990 and record SWR readings.  If  SWR is higher at the higher freq. (which  should be the result) you need to shorten the element. Only cut a sixteenth to one eighth  of an inch off at a time and keep checking it a 146. until you get 1:5 to 1 or lower. You’ll now have a ¼ wave vertical antenna for 2 meters .
73
Steve
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KC5JK
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Posts: 98


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« Reply #2 on: January 01, 2002, 02:52:02 PM »

The coaxial cable is typically RG-62/U and is the standard 93-ohms terminating with a Motorola plug.  While not ideal for two-way radio, it can be made to work.  Somebody back in the early 80s offered a matchbox with a splitter to feed both the VHF mobile rig and the Good Time radio simultaneously.  I'm sorry I've forgotten who (MFJ, Vocomm, B&W or somebody).  Antenna Specialists also offered a disguise antenna with a similar matcher and splitter, and I'm sure the latter part of the package (possibly available seperately or as a replacement part) could be used with your existing antenna.  Finally, it shouldn't be too hard to build a little matchbox/tuner.  Have you looked in any of the VHF mobile or antenna books?
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