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Old 02-22-2014, 09:32 PM
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CO Hunter CO Hunter is offline
Join Date: May 2010
Location: Colorado Springs
Posts: 133

Originally Posted by DaveInDenver View Post
..What bugs me is the extra 1/2" or so I have to trim to hit resonance. I can't figure out where it comes from. I have a decent transmission line model so I'm assuming it's in the PL259 or in the NMO on 70cm, even though they are supposed to be impedance matched to 1GHz I just don't buy it.
This is why it must be so nice to have an antenna analyzer.

Originally Posted by DaveInDenver View Post
On your other issue, this is something I preach, lip and fender mounts distort your signal patterns, especially with 1/4λ and 5/8λ antennas. You lose about 3dB compared to the center of a roof in the plane direction and will have very little signal to the non-plane side.
That is exactly why I have the center roof mount! Those are some good references, one I had not seen before.

I did some testing with a 1/4 wave mini mag mount located between the sunroof and the windshield. At 5w I was full quieting into the Pikes Peak repeater, with any vehicle orientation with rear facing having slightly more static. Here are a few pics of the various setups. Obviously the 5/8 wave struggled MUCH more with the limited metal in the immediate surroundings. A correction to the location for the 5/8 wave, it was over the sunroof opening. I was really surprised by these differences in performance, especially how poorly the 5/8 wave was in this configuration.

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5/8 wave bar mounted over sunroof and fed into NMO roof mount. I am guessing this will be the location with the RTT.

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NMO roof mount adapters

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NMO roof mount adapters

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MFJ 1/4 wave mini mag mount into fed into NMO roof mount. Located just in front of load bar, between sunroof and windshield. I am very surprised this location worked so well in the forward direction.

I wish I could see RF. Maybe I need to get a pair of those Geordi La Forge visors...Anyhow, I need to think about this a bit more.
1996 LX 450 OME heavy front/med rears, factory e-lockers, 285/75-16 Discoverer STT, home made t-case skid plate, ARB front bumper, XD9000i, Redline sliders, HID off road lights, Kenwood TM-D710

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