Mobile Antenna issues

[KD8PAV]

I run a very basic Cobra 19 in my Jeep for short range trail communications. I have 3 firesticks - 2 tuneable 4' and a 3' firestick II. One of the 4' tuneable antenna tunes beautifully - swr around 1.1-1.2. But on the same mount, same cable, same radio, the other two are off the chart, and no amount of tuning fixes the 4'. What am I missing? I would like to switch to a 3' antenna to fit in the garage, but want to identify my problem before I invest in another antenna.

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[W5LZ]

The shorter an antenna is the 'pickier' it will be to tune. If a shorter antenna would be more convenient for you, and if you're willing to put up with a little decrease in ability, it ought'a work fine for you.
- 'Doc

 

[hotrod]

I run a very basic Cobra 19 in my Jeep for short range trail communications. I have 3 firesticks - 2 tuneable 4' and a 3' firestick II. One of the 4' tuneable antenna tunes beautifully - swr around 1.1-1.2. But on the same mount, same cable, same radio, the other two are off the chart, and no amount of tuning fixes the 4'. What am I missing? I would like to switch to a 3' antenna to fit in the garage, but want to identify my problem before I invest in another antenna.

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3 antennas . 2 of them tune great. assuming the ones that are tunable tune great and the
one thats not tunable doesnt tune well. with a mobile antenna thats not tunable
then i wouldnt expect much from it. id run the 4 footer thats tunable

 

[9C1Driver]

Off hand I would say if ONE of the three works and tunes great and the other TWO are off the chart, something is wrong or broken in the TWO that don't tune. I would toss the two damaged ones in the trash and be done with it. You might consider looking for a K40 superflex, super little antenna's.

 

[Lil'Yeshua]

Does changing coax length change the swr the radio sees? Are you checking the swr at the antenna's feed point or at the radio?

 

[KD8PAV]

SWR was measured at the radio, not the antenna. I have not altered or swapped out the coax for different length, trying to get an antenna to tune on a Jeep can sometimes be a challenge and I don't want to mess up the good match I have with the one 4' antenna that I currently use. I am going to try swapping in a brand new 3' and see if it is the other two antennas, bit neither shows signs of excessive wear or damage.

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[CowboyCody]

Where is the antenna mounted? If part of the antenna is being "blocked" by the vehicle, it may explain why the shorter one won't tune. If A higher percentage of the overall antenna is being affected by the vehicle body.

 

[KD8PAV]

The Jeep is a soft top, so the antenna mount is attached to the left rear corner of the body tub. 1997-2006 Wranglers typically need a ground strap to the antenna mount, which I have already done. The 3' antenna projects 8-10" over the soft top, the two 4' antennas extend almost 2' over the top of the Jeep.

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[hotrod]

this is exactly why the 4 footer tunes better. cause more of the antenna is ABOVE
the vehicle. going shorter than 4 feet will raise your swr reguardless whos names on it

 

[CowboyCody]

Even if it is a soft top, there has to be some sort of steel support in the corner. I would blame that on your issues with the shorter antenna. The other 4' must be junk