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Author Topic: AM/FM CAR ANTENNA  (Read 842 times)
VE7HHO
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Posts: 11




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« on: January 01, 2005, 06:46:55 PM »

Could someone please tell me the construction of a  am/fm car radio antenna?  It seems to me that it is just a metal rod.  Should it be more than that?  I want to make one so that I can use it with my old am/fm car radio indoor.
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KB1LKR
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Posts: 1898




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« Reply #1 on: January 01, 2005, 08:46:50 PM »

I believe the common fixed antennas on most cars is generally a plain 31" whip, though on some imports you also see telescoping power antennas, though of similar length when extended. The cable is coax and the connector is a "Motorola" to the best of my knowledge dating back to at least the 60's maybe 50's and unique to auto radio receivers.
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N3ZKP
Member

Posts: 2008




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« Reply #2 on: January 02, 2005, 11:19:54 AM »

Radio Shack carries a SO-239 to Motorola plug (commonly called a scanner connector).

Plug that into the radio and then plug a 40" or so wire into the SO-239.

Lon
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K7KBN
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Posts: 2817




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« Reply #3 on: January 03, 2005, 08:50:18 AM »

I salvaged an old analog-tuned AM/FM car radio from a junkyard, along with the antenna connector.  I have it in my garage for entertainment when I'm working out there, using just a random length of wire for an antenna.  Different stations require a different wire configuration, but since I only listen to a couple of stations, that's no problem.  Use a reasonably good pair of speakers - it won't be audiophile quality, but it'll be okay for this purpose.
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73
Pat K7KBN
CWO4 USNR Ret.
AA4PB
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Posts: 12907




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« Reply #4 on: January 04, 2005, 07:54:04 AM »

The coax is generally a special "high impedance" coax rather than the 50 ohm stuff you will find at Radio Shack. The AM performance will suffer greatly if you use 50 ohm coax on the antenna.
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KC4HGH
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Posts: 34




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« Reply #5 on: January 07, 2005, 06:48:19 PM »

I'm about to replace the radio in my '69 GMC truck with an original, plus I'll be adding a universal antenna from Advance Auto Parts (#AT-US23) that has a wire-wound coil in the center section for better AM reception, all for about $9.  Of course, it'll receive FM, but since I have a penchant for AM DXing, I wanted to try this antenna.  Heck, for $9, it's cheaper & simpler than trying to salvage something....
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VE6TXT
Member

Posts: 6




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« Reply #6 on: January 12, 2005, 09:50:26 AM »

I believe the "high impedance" coax for feeding auto antennas is usually RG62, around 93 ohms.
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K7KBN
Member

Posts: 2817




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« Reply #7 on: January 13, 2005, 07:17:13 AM »

KC4HGH - I think you'll find that antenna a lot less beneficial than you might expect.  That "center loading" feature actually gives the antenna more loss than a straight solid stainless rod.  It looks cool, but...

I admit I tried one, many years ago, expecting to be able to hear AMBC stations from a couple thousand miles away.  I was in Las Vegas at the time, and I heard KOMO in Seattle!  Wanting to make a comparison, I quickly reinstalled the factory antenna and found that I could hear KOMO MUCH better.  Switched quickly back to the center load - KOMO was there, but not nearly as clear and noise-free.

YMMV - just a heads-up.
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73
Pat K7KBN
CWO4 USNR Ret.
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