swr trouble

This forum provides help with antenna installation, as well as guidance on selecting the right antenna for your radio or mobile setup.
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crazymikey555

swr trouble

#28069

Post by crazymikey555 »

Well i got a dual antenna set up fire stiks stock radio the radio swr says 1.5 and my buddies swr meter said 8 or some thing like that so i hooked it up to one and got 2.8 than i hooked up the other on and got 3 so i set them together and got 8 or 5 some thing big like that.
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231

#28072

Post by 231 »

Welp, the antennas need to be at least 8' (closer to 9') apart in order for a cophased set up to work properly. What kind of rig do you have it mounted on and how far apart are they spaced?

Next is the coax. Did you use a 75ohm cophased coax set up?

Finally, each antenna should be tuned individually for minimum SWR using 50ohm coax. Did you guys do that?

More info' please.

;)
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crazymikey555

#28076

Post by crazymikey555 »

well there about 6 and we did use 50 ohm and 75 ohm and i have them well ground there on the mirrors and i ran a ground wire from them to the body.
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Phaze91460

#28085

Post by Phaze91460 »

Is there an adjustment on those firestix ?
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crazymikey555

#28102

Post by crazymikey555 »

yes indeed screws in the top.
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Rex_foxhound

#28118

Post by Rex_foxhound »

How far apart are your mirrors?

Make sure your coax isn't coiled up. That will increase your swr.
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231

#28142

Post by 231 »

crazymikey555 wrote:well there about 6 and we did use 50 ohm and 75 ohm and i have them well ground there on the mirrors and i ran a ground wire from them to the body.
6' apart they'll fight each other. That is part of the problem.

And an electrical ground isn't the same as an RF ground. RF travels on the "skin" of the wire, unlike electrical electrons...and is more difficult to achieve. Where is your ground point and specifically how did you ground it?

Some simply like the looks of a cophased set up. If that is the case, I'd highly recommend making one a "dummy" antenna or even a back up antenna. If you can't space them properly, you'll be spinning your wheels...no two ways about it. They work great with big rigs because 99% of the time they are mounted on the mirrors, with more than enough spacing. But often even then the guys fight to get the SWR's down and an effective performer over a single antenna.

I smile whenever I see someone with a cophased antenna set up that isn't anywhere close enough to being spaced properly. I hear from them, "yea it works great." Then I ask if they've ever run a single antenna (of decent quality) and 99% of the time the answer is "no." So really they have nothing to compare it to.

I'm no 'guru' on the subject, but have seen it time and time again where a single antenna properly placed (sometimes even improperly placed) out performed hands down a cophased set up. Follow your own conscience on this, but I personally feel you have more than any one thing working against you.

Hope that helps a little.
;)
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