102" problems again.
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Cain64
- Skipshooter
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102" problems again.
So my swr's were fine for a while and then i got a new ground strapping and put it straight to the frame, SWR is coming up at 2.5 and 2.8 hard to tell. now i had the same coax before and it was all fine so im not really sure what is going on any ideas.
Catching The Skip And Spitting The Grizz
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226 Got Them Ears On
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MoJo
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Texas Mobil 219
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cowboy 221
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How long are your straps? Make them as short as you can, no longer than three inches. If they are longer, they can make a di-pole antenna system per the AARL handbook. This may not be it but just so you are aware of this. 221
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Cain64
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Red Warrior
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Let me offer my experience with my 102. I placed the antenna on a marine foldover mount on the top of the side rail about two feet back from the cab. The antenna mount was suspended about 6 inches above the rail. The marine foldover mount had a 1 inch braid ground strap run through the bed directly to the frame. I hooked a MFJ up and the reactance was miserable. I attempted to tune the antenna and I couldn't even get close. If I walked up to the truck the reactance would change and the SWR would soar. I extended the antenna to 108" and the reactance did not change at all. I removed the marine mount and bolted the 102 directly to the bed rail and moved the ground strap to the base of the mount. The reactance immediately went to less than 5 ohms (very good). The antenna then tuned out and performs exactly as advertised. Reactance no longer changes based on proximity to other objects.
The lesson here is a mobile antenna wants to be mounted directly on the ground plane (metal mass). Using any form of standoff from the metal mass (such as mirror mounts, tire carriers etc.) will add a small counterpoise to the antenna system adding reactance. Adding reactance does not prevent you from tuning an antenna but it does make the antenna sensitive to nearby objects (such as your body). The antenna will seem to constantly change SWR based on surrounding objects.
Mount the base of your antenna directly to the largest available metal object on your vehicle and you will experience the best performance. All other mounting is a compromise.
The lesson here is a mobile antenna wants to be mounted directly on the ground plane (metal mass). Using any form of standoff from the metal mass (such as mirror mounts, tire carriers etc.) will add a small counterpoise to the antenna system adding reactance. Adding reactance does not prevent you from tuning an antenna but it does make the antenna sensitive to nearby objects (such as your body). The antenna will seem to constantly change SWR based on surrounding objects.
Mount the base of your antenna directly to the largest available metal object on your vehicle and you will experience the best performance. All other mounting is a compromise.
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sideways
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Is the mount hooked to the same side of the hinge as the ground strap? If not then I would add a small strap between the two sides of the hinge. Much like the door(s) etc to body and then body to frame suggestions always on here. Helped in my Van install. Hope this helps.
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Gummybear
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What would you guys recommend to use as ground straps? 8 gauge wire with terminal o-ring lugs? Or are you guys buying real ground straps from auto parts stores?
I read grounding 101 that is posted in beginners( or where ever) and it did not specify either so if someone could add that info to that post it would help future members.
I read grounding 101 that is posted in beginners( or where ever) and it did not specify either so if someone could add that info to that post it would help future members.
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sideways
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From all I've read there are two types of grounding. The elec. grounding, for the radio/amp/..... and this is the wire you ask about . Then there is the RF grounding, which is done with the straps, because the straps "defuse" the RF traveling on the "skin" of the wire. I think this would be where you are grounding the radio chassis etc. And if I condensed it too much I'm sure someone else will help.
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Morguerat
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Diesel546
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