Using car radio antenna?

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mrsvensven

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Has anyone ever tried cutting their car's FM radio antenna down to transmit in the 2M ham band? I am pretty sure it should work as long as it has a good enough ground plane, I'm just wondering if anyone has tried it.

I assume the FM radio antenna is fed with 75 ohm coax?
 
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fineshot1

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Waste of time & effert. A 2 meter 1/4 wave antenna is pretty cheap these days. As you said the 75 ohm coax of the car antenna is gonna make it a PITA. Not worth the trouble since the availability of whats out there now.
 

jhooten

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Buy the Stico undercover antenna that replaces the good time radio antenna. The coax is much better quality, maintains the stock apperance, and is tunable
 

prcguy

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A stock AM/FM whip works surprisingly well and is easy if you use the cheap adapters specifically made for scanner use. I tried this with an $11.95 Ebay unit and will probably use one on my next new vehicle. Its obviously not going to perform as well as a dedicated roof mount antenna but it can work better on VHF lo band than lets say, a Larsen VHF/UHF tri band. I've done some studies and field testing using a stock AM/FM antenna for covert military use in the 30-90MHzband and it really surprised me how good it works for something that was never intended for this. The stock AM/FM antenna does not use 75ohm coax, its higher impedance to better match the short whip on AM broadcast band and it actually helps when using the antenna over a large frequency range.
prcguy
 

ScanDaBands

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prcguy said:
A stock AM/FM whip works surprisingly well and is easy if you use the cheap adapters specifically made for scanner use. I tried this with an $11.95 Ebay unit and will probably use one on my next new vehicle. Its obviously not going to perform as well as a dedicated roof mount antenna but it can work better on VHF lo band than lets say, a Larsen VHF/UHF tri band. I've done some studies and field testing using a stock AM/FM antenna for covert military use in the 30-90MHzband and it really surprised me how good it works for something that was never intended for this. The stock AM/FM antenna does not use 75ohm coax, its higher impedance to better match the short whip on AM broadcast band and it actually helps when using the antenna over a large frequency range.
prcguy
Most Excellent Information prc - appreciate it !!! :)

(this is the reason I absolutley love this board - facts are good)
 

af5rn

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Yeah, I've had decent results with an am/fm/scanner splitter on my stock antenna (telescopic, even!) on VHF-Hi band, which is roughly the same as 2m. 2m should do even better, being closer to the FM broadcast band. Of course, that was just receiving, not transmitting. But at least you know that you'll hear okay!

If you are transmitting, you will definitely want to make sure you're using 50ohm coax.
 

mrsvensven

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af5rn said:
Yeah, I've had decent results with an am/fm/scanner splitter on my stock antenna (telescopic, even!) on VHF-Hi band, which is roughly the same as 2m. 2m should do even better, being closer to the FM broadcast band. Of course, that was just receiving, not transmitting. But at least you know that you'll hear okay!

If you are transmitting, you will definitely want to make sure you're using 50ohm coax.
I don't actually need the antenna for my radio, so I am hoping to but it down to make it work even better.
 

af5rn

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Just don't try to wing it by screwing it in and seeing what happens. When you use an antenna that is not tuned to your specific band, you risk a mismatch that can burn up your radio when you transmit. Either do it right, getting a matching transformer made for converting that antenna to 2m, and check it on an SWR meter, or don't do it at all.
 
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