wilson 5k issue

[hotrod]

my system hasnt been up to par as of late so i took my mfj 259 out to checkout my antenna see whats going on heres whayt ive found
271850 R=90 X=0 swr= 1.6
now imho R is way outta tune
now i did move the magnet all over the roof and seen no noticable change
and sliding the whip up and down only changed R 1-2 ohms once bottomed out.
now question is should i start trimming away at whip?on another note the whip
seems to have a rattle noise to it ??

 

[Robb]

Look for a flattened coax or a bad connector or connection.

 

[M0GVZ]

my system hasnt been up to par as of late so i took my mfj 259 out to checkout my antenna see whats going on heres whayt ive found
271850 R=90 X=0 swr= 1.6
now imho R is way outta tune
now i did move the magnet all over the roof and seen no noticable change
and sliding the whip up and down only changed R 1-2 ohms once bottomed out.
now question is should i start trimming away at whip?on another note the whip
seems to have a rattle noise to it ??

In the absence of crushed coax, when the value of R is not what you'd expect its usually because of a poor RF ground. You'll get low SWR but the efficiency is poor. There's no point trimming away on the whip because the antenna is resonant on 27.185MHz as indicated by the fact X=0. Trimming away on the whip may bring R down on that frequency but X will rise and the SWR will change because you're altering the frequency the antenna is tuned for. You will most likely find that the SWR will drop if you raise the frequency of the analyser above 27.185 and you'll find that the value of R may drop as well because the SWR dip usually follows on from the dip for reactance, X. However we still want to know the value of R at X=0 because that can give us an indication of how well the RF grounding is working or, in your case, not.

If you want to fix the above situation get a drill out, drill a hole in the roof, use a fixed mount, do some bonding of the hood, trunk and if its a truck, the cab to chassis and bed to chassis and bed to cab. You will find though that once you've done that you'll need to cut your antenna down a fair bit. I usually have to chop around 4 inches off every CB antenna I fit on my car due to how efficient the RF ground is. Whips tend to be supplied as new to cater for the lowest denominator of installation, a magmount.

 

[Robb]

If the antenna was working before and then had a problem; I doubt that the problem is the length of the whip.

Crushed or cut coax is something that can happen after the fact.

 

[hotrod]

sorry for long reply. i did find a piece of coax that was SLIGHTLY crushed ,but not slised or cut . i have since rerouted it. and recheched but still same results.
ive been looking online on how to check my coax for shorts

 

[222DBFL]

If the coax is crushed anywhere along the way, it will change the impedance and will skew your readings. Replace the coax. It's actually pretty easy to do on an Wilson antenna. JMHO. But I wouldn't trust the coax if it was deformed or crushed or pinched. It will and I mean will change the characteristics of the coax. Just some food for thought. Hope you get it resolved. Good day.

 

[Marconi]

Hotrod, before you get too excited about your Wilson, I have something for you to consider and you can test the idea using your analyzer.

Try moving your frequency around above, below, and through out CB, and if my model is close to right I think you might see what I use to see back in the day...using the Wilson mag mount.

It is very narrow banded antenna, but has a very wide useful band width at the same time. Check out this SWR bandwidth curve I got using Eznec as a follow up on your earlier idea to DB about a couple of mobile antennas you were considering.

I followed up on your idea after I told you I was having trouble modeling your Wilson...I did not have enough segments to work with on a mobile object that already had over 400 segments. I did not have a coil around here for a base load, so I used one from a Wilson T5000 Trucker with a 15" inch riser below it. I just took a guess it would work close to the base load.

I thought you got what you were looking for in deciding which antenna you were going to run...so I did not post any more, but I did continue to work on your idea none the less.

Here is an SWR curve my model shows and you will see it is rather strange looking. Back in the days when I ran a Wilson...I saw something similar as I change frequencies beyond CB. I did not understand it back then, but maybe that is the way this antenna works. Who knows what could have happened in your case...maybe the stinger came loose and moved.

 

[hotrod]

If the coax is crushed anywhere along the way, it will change the impedance and will skew your readings. Replace the coax. It's actually pretty easy to do on an Wilson antenna. JMHO. But I wouldn't trust the coax if it was deformed or crushed or pinched. It will and I mean will change the characteristics of the coax. Just some food for thought. Hope you get it resolved. Good day.

thank you. if it warm enough tomorrow gonna take and test coax for continuity