Antenna light issue on cobra 29

was this a new wilson or one you used before. Make sure that the insulator is on the top of the mount and that the coax is good.. I can't say at this moment what it is but I'm leaning twards a mount or broken coax ground or bad connection but it will be with the antenna or coax or mount or multiples or those issues.

 

More likely an untuned antenna and/or poor ground. High SWR measurement as well as the light indicate power reflecting back in. Tune the antenna. Also common for the light to come on especially on voice peaks even with good SWR's if the radio is peaked but the light was not readjusted for the higher power level. However in your case you know for sure the light has a valid reason for coming on. Holding the coil shunts RF into your body, lowering the reflected power. So you see lower SWR but you are merely faking yourself out. It means nothing to see the SWR drop by grabbing the coil other than you are loading the system with your body and irradiating yourself.

 

I agree w/ Outlaw CB. Everything he stated is top notch advice.
Ground your radio to the frame.
Check to make sure the ground stud ( if this is where you are attaching the radio's ground? ) is connected to your truck's ground.
Some of these studs were never connected by the manufacturer. And follow the antenna's instructions found on their packaging.
You may have to cut the antenna's whip to get the correct swr ( standing wave ratio )?
Jimbowilly

 

Ok I don't know Outlaw But He isn't correct as to how loaded antennas really work. Is it possible that your antenna is mistuned of course it's possible but after having installed thousands of Wilsons on trucks it's truly rare to find one that is so far off the scale as you say this one is and have it just be a tuning issue. I have seen some strange things with antennas on Trucks, pickups, cars busses even trains and I have instsalled antennas on all of them.

Now, putting your hand on the COIL and seeing a drastic change in the match is actually a good thing if you understand why that happens. For one thing it most likely means the coil is functioning as it was designed. It's an inductor and they are very sensitive to being close to anything metal or anything that has the abiltity to change it's properties. When you put your hand on the coil are causing it to be detuned at a different Q Factor it has little to do with shunting all the RF through you Body and everything to do with becoming detuned, If you wrapped the Coil with Tinfoil you would see the same kind of response on the SWR meter but the Coil is simply being detuned. Is it possible some RF is being shunted through the body of course it is but, it didn't drain all the RF through your body it just created a load that appeared to the swr meter to be a good match.

The first thing you always do is establish that all the things involved in the antenna system are known to be in perfect order otherwise you could be pissing in the wind trying to tune the antenna. I can't tell you how many times a driver came in the shop after trying to tune his antenna because somebody told him to and he ends up cutting 8 or 10 inches off and never got close to a good match only to find out his coax was at fault or even worse his mount was not assembled correctly..

I assumed from reading your Post you claim to have already grounded everything do I know if all those things you done were done the way they should have been done NO I DONT. But you said you did them so I believe you. If you are not certain that the grounding methods you used are done the way they should be, Well then we need to address that as well.

My point is this you must establish first that your antenna is NEW or USED this is important

Then you must establish your coax is of the highest quality and in perfect condition

Then you establish the fact that your mount is properly assembled. I can't tell you how many times I had complaints exactly like yours only to find out the mount was not assembled properly.

Once you make sure all those things are correct you then have something to work with because you have eliminated the from the equation the possibility that your mounts, antenna or coax are part of the problem you can then proceed on to more advanced troubleshooting ideas.

 

cb hot/ground to battery= ok, antenna to battery ground= not good, the antenna mount needs a ground plane/ rf ground, ie= ground to frame. what kind of truck, where is antenna mounted, what kind/type of mount, is antenna new or used, has the whip been adjusted, etc,

 

stock coax and mount on the pete, also how much have you trimmed off the whip so far? if so you probably need a new stud and coax, the mount itself on the 379 should not need a frame ground as the 379 generally provides a good ground plane as it is steel/aluminum body/doors/etc but anything is possible. I would take the ground off the antenna mount, if it is old/factory coax, change it and then re check swr's.

 

Vintech "Ok I don't know Outlaw But He isn't correct as to how loaded antennas really work." "Now, putting your hand on the COIL and seeing a drastic change in the match is actually a good thing if you understand why that happens. For one thing it most likely means the coil is functioning as it was designed. It's an inductor and they are very sensitive to being close to anything metal or anything that has the ability to change it's properties. When you put your hand on the coil are causing it to be detuned at a different Q Factor it has little to do with shunting all the RF through you Body and everything to do with becoming detuned, If you wrapped the Coil with Tinfoil you would see the same kind of response on the SWR meter but the Coil is simply being detuned. Is it possible some RF is being shunted through the body of course it is but, it didn't drain all the RF through your body it just created a load that appeared to the SWR meter to be a good match."


I can see physics is not your strong point. No you don't know me nor how many years I have worked in RF. The main de-tuning is due to capacitive loading when his hand is around the coil. His body is not significantly having any effect on the magnetic field around the coil. No mystery, I have never met people who can stick magnets to their forehead. Read about them in tinfoil hat magazine, just never met them. If people were attracted to magnetic fields having a CAT scan would be a horribly life ending experience. In short his body is not ferromagnetic therefore he cannot significantly affect the magnetic field around the coil. He is at best dragging the resonant frequency down 30 or 40 channels due to his body adding capacitive loading to the antenna, but it is already two or three times below the middle of his frequency range anyway. He can only calibrate somewhere within the 40 channels of the radio. Meaning while he could alter the resonant frequency from capacitive loading, only downwards and he is already thrice downwards in resonant frequency to begin with. Therefore the meter will not show a much lower SWR from his capacitive loading, it is mainly caused by a shift in reflected power. Only makes sense if one considers the definition of lower SWR is less reflected power. However the bulk of the 'less reflected power' is due mainly to dissipation. This leaves only energy dissipation to explain the drop. This dissipation effect will be greatest at a nodal point of voltage along the length of the antenna.

Since you are bold enough to state I am wrong in my analysis while using invalid science to back you up I think I am justified in setting you straight. Just to be nice I will give you a way to prove energy dissipation effects from what he was doing. Have someone repeat exactly his circumstances and actions while you are 20 feet away holding a field strength meter very still. You will see the drop in radiated field intensity. Not magic, science. Since he most likely just dropped the stinger in without tuning a new Wilson it is probably around 3 inches too long. As He is using a 40 channel radio, not an export or an analyzer where he can move down 150 channels, no matter where in the 40 channels he was when he calibrated the forward power the SWR is buried far outside of his ability to calibrate anywhere near the actual resonant frequency of the antenna. Since the reading he was seeing was based upon the forward calibration he did before he grabbed the antenna, the meter would see less RF returning. Therefore a reading of lower SWR based upon his previous power calibration reference. Another proof is have a third person in the vehicle to recalibrate the forward power reference while he is holding the antenna in TX. While still holding it in exactly the same position next measure reflected. If your meter is of high accuracy you will see the change based only upon the resonant frequency drop caused by the capacitive body loading since both calibration and measurement was done under the same loaded condition. I don't recommend he have an amplifier on at the time of course. Around 25 volts P-P is plenty to hold onto, 200 P-P not so good.

This is 8th grade physics. I will say to you what I say to anyone. If you want to shoot me down always bring a loaded weapon.

skywalking 44 you need to provide precise information since no one online can see your setup nor look at meters. How much did you cut the stinger and did you drop it all the way down before tightening the set screw. You never answered vintech about the proper antenna hardware configuration, and poor ground could be adding to your problems. Poor ground at the coax termination at the feedpoint will increase the effect of loading the antenna by grabbing it. By the way this indicates the coax cannot be very bad if at all, as you would see less change or no change when grabbing the antenna if the coax was not completing the circuit between radio and antenna. No one can see therefore you have to provide information if you wish help. What is the shaft length? If 10 inches the stinger length should be near 49.5 inches. You are not giving enough data. You stated the antenna is grounded to the battery. I do not think this is ever a good idea, RF is looking for a geometric ground not DC, meaning large surface area low inductance. Exactly, precisely, where on the antenna is the ground connected? We have no way to know unless you inform.

The following link may help.

http://www.wilsonantenna.com/cutting.php