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3 foot firestik failure...
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=45&t=11704		 Page 1 of 2
Author:  Se7enLC [ Thu Aug 24, 2006 8:57 am ]
Post subject:  3 foot firestik failure...
Ok, so I currently have a 4 foot firestik which works great. I decided to replace it with a 3 foot firestik, figured it would help my clearance getting into garages, and since the 4 foot was so good, 3 foot shouldn't be too much worse, right? WRONG.

My 4 foot firestick is tuned to an SWR around 0.2 or so. It kicks some serious @$$. I change nothing else except removing the 4 foot firestick and screwing in the 3 foot firestik.

It pings a TEN. If I adjust the tuning screw all the way down and remove the spring, I can get it to a 1.5, but only on channel 1, and as soon as I put the end cap on, it's back to at least a 4. Everywhere else in the full tuning range is between a 5 and 10 SWR. For now I guess I will stick with the 4 foot ugly white antenna, but this is a little ridiculous. Has anyone else out there tried a 3 foot with any success?
Author:  swyszomirski [ Thu Aug 24, 2006 12:10 pm ]
Post subject: 
maybe your 3 footer has a bad wire coil? Get it replaced.
Author:  Se7enLC [ Thu Aug 24, 2006 12:43 pm ]
Post subject: 
swyszomirski wrote:
maybe your 3 footer has a bad wire coil? Get it replaced.


Unfortunately, there's no Firestik dealer anywhere within 500 miles or so of here. To get it replaced I'd have to ship it back and have a new one shipped out to me. I'd like to find some way to see if that really is the problem before going through that hassle.

Can anyone think of a good way to test an antenna like that? Maybe I could try to temp-mount it somewhere else on the jeep to see what it does?
Author:  Gris [ Thu Aug 24, 2006 1:07 pm ]
Post subject: 
Your entire jeep comes into play with a CB antenna. WIth the 4', you were sticking a good bit above the roof of the jeep, meaning the tip was clearing of most of the metal. WIth a 3', you are a lot closer to the roof, which will now start absorbing some of the signal intended for the antenna.
Author:  dirtykj [ Thu Aug 24, 2006 2:24 pm ]
Post subject: 
I used to use a 3" firestik and it worked fine for me. Keep in mind the tuning must be done in the environment you expect to use it, e.g., tip on, window up, measure. Get out, tune, vinyl tip on, get in, measure. Repeat.

The tip is vinyl, which is dielectric, and you will get different SWR readings with it on and off.
Author:  Se7enLC [ Thu Aug 24, 2006 3:31 pm ]
Post subject: 
dirtykj wrote:
I used to use a 3" firestik and it worked fine for me. Keep in mind the tuning must be done in the environment you expect to use it, e.g., tip on, window up, measure. Get out, tune, vinyl tip on, get in, measure. Repeat.

The tip is vinyl, which is dielectric, and you will get different SWR readings with it on and off.


Yup. I tried it both ways and in many different combinations of doors open, windows open/closed, etc, I couldn't get any of them even close to correct. If it were around 1.5 or 2 and I were adjusting and making any difference, I'd keep at it, but only time I can even get down to 1.5 is only on channel 1, only when the tuning screw is all the way down. Any other adjustment and it jumps up to 5 ot 10.

Quote:
Your entire jeep comes into play with a CB antenna. WIth the 4', you were sticking a good bit above the roof of the jeep, meaning the tip was clearing of most of the metal. WIth a 3', you are a lot closer to the roof, which will now start absorbing some of the signal intended for the antenna.


I think that may well be the case. Not because of absorption, but because of reflection. It's not range + power I have a problem with, it's just that pesky reflected signal. It's actually sort of impressive that just a big roof could end up reflecting back 10 times more power than is being transmitted.
Author:  raceinfan [ Thu Aug 24, 2006 4:18 pm ]
Post subject: 
The roof interfering sounds logical, but I had issues with my 4ft come to find out it was the coax cable been fine ever since
Author:  Gris [ Thu Aug 24, 2006 4:30 pm ]
Post subject: 
another thing to check is the mount/cable situation. Make sure nothing that you changed could have caused a ground-out condition. I know you only changed the stick, which is screw-off/screw-on, but who knows.

I'd still check the roof issue. throw a big blanket over the roof to help insulate it a bit and try again.

P.S. what did you do with your 4'? I have a 3 foot and would love to see how a 4' looks/acts.

***Edit to add***

I just looked at your pics...

Make sure you didn't loose one of the insulating washers from the firestick's cable. If the washers are damaged or missing, it might be causing a ground-out.
Author:  Se7enLC [ Thu Aug 24, 2006 4:53 pm ]
Post subject: 
Gris wrote:
another thing to check is the mount/cable situation. Make sure nothing that you changed could have caused a ground-out condition. I know you only changed the stick, which is screw-off/screw-on, but who knows.

I'd still check the roof issue. throw a big blanket over the roof to help insulate it a bit and try again.

P.S. what did you do with your 4'? I have a 3 foot and would love to see how a 4' looks/acts.

***Edit to add***

I just looked at your pics...

Make sure you didn't loose one of the insulating washers from the firestick's cable. If the washers are damaged or missing, it might be causing a ground-out.


To clarify pretty much all of those questions, I went back and forth between the 4 foot and 3 foot antennas. The 3 foot was consistently pegging a 10, the 4 foot was only coming up at a 0.2. I did disaessemble the entire mount and pulled cable out, fed it back in and retested, got the same results. Tested continuity of all the parts with a meter, made sure that it was properly grounded. The fact that I have the 4 foot back on there and working fine with a low SWR tells me that the mount and cable are fine.

Right now the 4 foot is back on the jeep, and I probably won't be getting rid of it until I get a 3 foot working properly (or worst case, I'm going to buy another 4 foot antenna in black so people stop making fun of how ugly the white one is :-P)

I'll try the blanket thing, that's a good idea. I may also try pulling off the bike rack and other metal things from the roof to see if they were somehow causing it.
Author:  dirtykj [ Thu Aug 24, 2006 5:04 pm ]
Post subject: 
Se7enLC wrote:
I think that may well be the case. Not because of absorption, but because of reflection. It's not range + power I have a problem with, it's just that pesky reflected signal. It's actually sort of impressive that just a big roof could end up reflecting back 10 times more power than is being transmitted.


I'm not convinced it's the roof, yet. If you look at my avatar, you'll see that the antenna did NOT quite clear the roof rack (OK, so it cleared the roof a little bit but there's the rack in the way). With this setup I still get satisfactory SWR measurement.

Try checking the coax cable first ... check to make sure you have the vinyl washer between the mount and the coax attachment.
Author:  dirtykj [ Thu Aug 24, 2006 5:06 pm ]
Post subject: 
Se7enLC wrote:
Tested continuity of all the parts with a meter, made sure that it was properly grounded.


Did you intend to ground it?
Author:  Gris [ Thu Aug 24, 2006 5:40 pm ]
Post subject: 
Does the new 3' antenna have a grounding cable on it or just the screw on the bottom? The 3' FireStik FireFly I chose has no ground strap. IT'S GROUNDLESS!
Author:  gopherbeats [ Thu Aug 24, 2006 8:45 pm ]
Post subject: 
yea.. why would you buy a white one? heheheh

There has to be a truck stop some where in the vacinity where you live.. In my area there is no where to buy antennas except the truck stops off of the hiway, or on line.
Author:  Se7enLC [ Thu Aug 24, 2006 10:00 pm ]
Post subject: 
dirtykj wrote:
Try checking the coax cable first ... check to make sure you have the vinyl washer between the mount and the coax attachment.


The coax is fine, the 4 foot antenna gets a 0.2 and works great. I've tested it numerous times, it's all done right.
Author:  Se7enLC [ Thu Aug 24, 2006 10:01 pm ]
Post subject: 
dirtykj wrote:
Se7enLC wrote:
Tested continuity of all the parts with a meter, made sure that it was properly grounded.


Did you intend to ground it?


The mount is properly grounded to the sheild of the cable, the antenna is properly connected to the center pin of the coax, the shield has no connectivity to the center pin. All intended, all working fine with the 4 foot, not working fine with the 3 foot.
Author:  Se7enLC [ Thu Aug 24, 2006 10:02 pm ]
Post subject: 
Gris wrote:
Does the new 3' antenna have a grounding cable on it or just the screw on the bottom? The 3' FireStik FireFly I chose has no ground strap. IT'S GROUNDLESS!


Just the screw on the bottom. It's screwed into the mount, the mount is grounded. The antenna itself isn't grounded, though, the nylon washer is doing just what it's supposed to.
Author:  Se7enLC [ Thu Aug 24, 2006 10:06 pm ]
Post subject: 
gopherbeats wrote:
yea.. why would you buy a white one? heheheh

There has to be a truck stop some where in the vacinity where you live.. In my area there is no where to buy antennas except the truck stops off of the hiway, or on line.


I got the white one because wayne was selling it for $12, and it was really convenient. It would have cost about $30 including shipping to get a black one. I thought the white would be nice since it's visible like a flag. But no, it's hideous.

There are some places to buy antennas, and even a great little electronics store that has a whole lot of CB stuff. But none of the CB antennas are screw-tunable, only end-clip and unravel tunable.
Author:  W3CSX [ Thu Aug 24, 2006 10:36 pm ]
Post subject: 
First, the idea of SWR being affected by the size of the antenna vs. proximity to the vehicle is not true. SWR is a measurement of power from the radio and how much of that power is reflected back into transmitter. Yes, how / where the antenna is mounted as a direct relation to how the signal pushed thru it is propagated. But, this will not affect your SWR reading.

If your new antenna is pegging over 8. Usually there is a grounding issue. I am assuming you are using the same mount for both just swapping the radials. If the 4' will tune and the 3 won’t. I would suspect the problem is within the three footer. To check, remount the 3' an Remove the antenna cable from the back of the radio. Use a multi-tester and check the cable for continuity. If the circuit is open (the meter will still read 1.00) it’s ok. If it is closed (Probably reading .001) there is a short. Retest with the longer antenna if it shows open and the 3' is closed. The problem is in your shorter whip.

You said you remove the spring to mount the 3' antenna. Make sure there isn't a nylon washer stuck to the bottom when you are removing it. With out it, if the screw on the antenna is touching the metal on the mount this is your problem.

Let us know what you find. I can help you from there.

Jason
Author:  unixxx [ Thu Aug 24, 2006 10:48 pm ]
Post subject: 
The CB expert has posted ;) Jason, you're always troubleshooting CB radios :lol:
Author:  Se7enLC [ Fri Aug 25, 2006 10:30 am ]
Post subject: 
W3CSX wrote:
First, the idea of SWR being affected by the size of the antenna vs. proximity to the vehicle is not true. SWR is a measurement of power from the radio and how much of that power is reflected back into transmitter. Yes, how / where the antenna is mounted as a direct relation to how the signal pushed thru it is propagated. But, this will not affect your SWR reading.

If your new antenna is pegging over 8. Usually there is a grounding issue. I am assuming you are using the same mount for both just swapping the radials. If the 4' will tune and the 3 won’t. I would suspect the problem is within the three footer. To check, remount the 3' an Remove the antenna cable from the back of the radio. Use a multi-tester and check the cable for continuity. If the circuit is open (the meter will still read 1.00) it’s ok. If it is closed (Probably reading .001) there is a short. Retest with the longer antenna if it shows open and the 3' is closed. The problem is in your shorter whip.

You said you remove the spring to mount the 3' antenna. Make sure there isn't a nylon washer stuck to the bottom when you are removing it. With out it, if the screw on the antenna is touching the metal on the mount this is your problem.

Let us know what you find. I can help you from there.

Jason


Ahh, finally! Somebody actually *read* what I posted! Even firestik gave me the packaged response of "Make sure you check SWR with the end cap ON" as if that was going to magically fix the problem (and I had told them that I checked it both on and off).

I'll try that continuity test tonight. So I should be testing from the center pin on the radio end of the coax to the tip of the antenna and checking to see what the resistance is for each antenna?

I removed the spring as another possibility for getting it to tune, I only did that after changing just the antenna didn't work. I've tried it both with the spring on and off, and I have gone back and forth changing nothing but the actual antenna and it's clear that it's the antenna that is the problem. The continuity test sounds like the best bet so far, I'll let you know what I get for measurements. Thanks!

I do disagree with your saying that SWR is not affected by antenna placement, though. Signal which either can't propogate or is reflected back to the antenna ends up reflecting back to the radio, thus the standing wave. I still think the problem is the antenna and not the length, but we shall see!
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