high swr reading
04-21-2003, 04:46 PM
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high swr reading
hey guys
i got my rear bumper two days ago with my cb antenna mount on it. for some reason, when i put my cb antenna on the mount, the swr reading is unbelievably high. i tried to tune it, but nothing works..any suggestions?
i got my rear bumper two days ago with my cb antenna mount on it. for some reason, when i put my cb antenna on the mount, the swr reading is unbelievably high. i tried to tune it, but nothing works..any suggestions?
04-21-2003, 04:55 PM
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How high is unbelievably high? Where exactly on the rear bumper is the mount?
Some people use a rear bumper mount with no trouble, but others (for whatever reason) aren't so lucky. If your antenna coax isn't all tucked away, the first thing I'd try is moving around to other locations on the rig. If you get better SWR readings, then at least you know you have other options.
You may want to look at the Firestik web site for more info on tuning and mounts.
Some people use a rear bumper mount with no trouble, but others (for whatever reason) aren't so lucky. If your antenna coax isn't all tucked away, the first thing I'd try is moving around to other locations on the rig. If you get better SWR readings, then at least you know you have other options.
You may want to look at the Firestik web site for more info on tuning and mounts.
04-21-2003, 05:05 PM
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the reading is basically at 3 all the way around. i dont have any pictures, but, where the tire mounts to the tire swing...behind the tire.
this is hawkdog's rear bumper, but, basically the same set up.
before i got my rear bumper, i had my 4 ft antenna on my roof rack and it worked fine.go here to see what it looks like
this is hawkdog's rear bumper, but, basically the same set up.
before i got my rear bumper, i had my 4 ft antenna on my roof rack and it worked fine.go here to see what it looks like
Last edited by doink; 04-21-2003 at 05:07 PM.
04-21-2003, 05:21 PM
#4
Your ground wire coming out of the antenna coax sheath, is it grounded right on the mount, or run a ways away?
Also make sure that the main antenna lead is not accidentaly grounding to the rig.
Make sure you have the two rubber/plastic gaskets as seen here.
http://pnw4runners.net/tando/qd2.jpg
You can't see the bottom one, but it keeps your main antenna lead from grounding to the rig.
Here is my ground wire.
http://pnw4runners.net/tando/qd3.jpg
I could have drilled right through the clamp and into the round ARB bar, but I choose not to.
A high SWR reading like that suggests an improper ground.
Also make sure that the main antenna lead is not accidentaly grounding to the rig.
Make sure you have the two rubber/plastic gaskets as seen here.
http://pnw4runners.net/tando/qd2.jpg
You can't see the bottom one, but it keeps your main antenna lead from grounding to the rig.
Here is my ground wire.
http://pnw4runners.net/tando/qd3.jpg
I could have drilled right through the clamp and into the round ARB bar, but I choose not to.
A high SWR reading like that suggests an improper ground.
04-21-2003, 05:21 PM
#5
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Originally posted by doink
before i got my rear bumper, i had my 4 ft antenna on my roof rack and it worked fine.
go here to see what it looks like
before i got my rear bumper, i had my 4 ft antenna on my roof rack and it worked fine.
go here to see what it looks like
It looks like the firestik site has some good words. I hope you can find something that works for you. Any kind of distance you can get between the antenna and the rig will help.
If you still have the roof rack, that would actually be an ideal spot.
EDIT: Listen to Corey... I didn't even think about the ground issue. duh.
Good luck!
Mark
Last edited by midiwall; 04-21-2003 at 06:25 PM.
04-21-2003, 06:20 PM
#6
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Nothing to add, just curious to read as my CB should be coming in a week or so.
I tried to look at those pics and they didn't work on my end Corey, maybe problems on my end?
I tried to look at those pics and they didn't work on my end Corey, maybe problems on my end?
04-21-2003, 06:23 PM
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i can not find any so called ground wires comming out of my antennas..one of them is a 3ft firestik, i forgot what type the other is though.. oh, corey, i couldnt get the first link to work..
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04-21-2003, 06:34 PM
#8
Originally posted by Flygtenstein
I tried to look at those pics and they didn't work on my end Corey, maybe problems on my end?
I tried to look at those pics and they didn't work on my end Corey, maybe problems on my end?
www.featureprice.com
When they go down, it all goes down.
They might be doing an upgrade on their end right now, so all their servers are off line.
04-21-2003, 07:53 PM
#9
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Originally posted by Corey
Looks like my site is down, and also my host
www.featureprice.com
When they go down, it all goes down.
They might be doing an upgrade on their end right now, so all their servers are off line.
Looks like my site is down, and also my host
www.featureprice.com
When they go down, it all goes down.
They might be doing an upgrade on their end right now, so all their servers are off line.
Actually, it looks like there are a couple of problems...
Both pnw4runners.net and featureprice.com seem to have fallen out of DNS - that's producing the "can't resolve" errors that some folks are getting.
My local DNS happens to have a cached address for featureprice.com (64.38.96.100) and tracing against that stalls out after just 4 hops, just as it's leaving Genuity (GTE) and heading for the backbone on it's way to Florida where your ISP is.
In short... I don't think it's them specifically; it's something else along the way.
04-21-2003, 08:21 PM
#10
Hmmmm, about 10 minutes ago I tried pinging them at http://network-tools.com/ and it would not conenct.
Perhaps a 'gator from the Everglades took a big chomp out of the cable that runs into their server shack
So this means it culd effect serveral sites that mya be on the same DNS?
A Quake III server I use is also with Feature Price, and they are down.
http://www.dayentech.net/
Perhaps a 'gator from the Everglades took a big chomp out of the cable that runs into their server shack
So this means it culd effect serveral sites that mya be on the same DNS?
A Quake III server I use is also with Feature Price, and they are down.
http://www.dayentech.net/
04-21-2003, 08:33 PM
#11
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Originally posted by Corey
Hmmmm, about 10 minutes ago I tried pinging them at http://network-tools.com/ and it would not conenct.
Hmmmm, about 10 minutes ago I tried pinging them at http://network-tools.com/ and it would not conenct.
A Quake III server I use is also with Feature Price, and they are down.
http://www.dayentech.net/
http://www.dayentech.net/
So this means it culd effect serveral sites that mya be on the same DNS?
Unfortunately, the Internet isn't setup like the long distance phone network. When a route goes down, there's no real provision to automatically re-route around the failure.
There's a red light and a pager going off somewhere. Depending on just what's up, it'll be back "soon".
04-21-2003, 09:22 PM
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doink,
There won't be a ground wire on the antenna itself. The antenna is just an "extension" of the center conductor of the coax from your radio and is insulated from the mounting point by the plastic washers that Corey (I think) referred to. If you disconnect the coax from the radio, you could check the DC resistance between the center conductor of the coax connector to ground to see if there is low resistance which would be bad.
The outer shield of the coax is usually connected to the mounting bracket which should be well-grounded to the vehicle. You want that ground path to be as short as possible, ideally to a nice big horizontal metal surface with your antenna sticking up in the center above that. Your ground path looks like it is through the framework of the tire carrier, the carrier "hinge" or pivot, then the bumper, to the frame, and though some path to the body (not sure what gen you have, but I assume it is metal back there) that forms your ground plane. That makes a long path with quite a few places where the ground might be poor. Make sure you've got metal-metal contact for the coax shield first. If you check the resistance of the outside of the coax connector to ground with it disconnected from the radio it should be low. I wish I could give a precise definition of what is acceptable for "low". but I don't know. I'm mainly suggesting looking for gross errors like shorts or open circuits.
Even if you get a good DC ground, that doesn't mean you've got a good RF ground either, although other people have had success with this installation. You might experiment with a short wire from the tire carrier directly to the body to see if that changes anything.
I took a class many years ago from a guy who designed RF circuits. He used to say "Ground is not ground until proven otherwise."
Lots of strange things go on with radio frequencies, so it could be something besides the ground too as others have suggested.
From what I've read, and as has already been mentioned, mounting your antenna back there is never going to be ideal. If there isn't much antenna above the vehicle body, at the very least its going to distort the antenna pattern so you won't transmit or receive equally far in all directions.
There won't be a ground wire on the antenna itself. The antenna is just an "extension" of the center conductor of the coax from your radio and is insulated from the mounting point by the plastic washers that Corey (I think) referred to. If you disconnect the coax from the radio, you could check the DC resistance between the center conductor of the coax connector to ground to see if there is low resistance which would be bad.
The outer shield of the coax is usually connected to the mounting bracket which should be well-grounded to the vehicle. You want that ground path to be as short as possible, ideally to a nice big horizontal metal surface with your antenna sticking up in the center above that. Your ground path looks like it is through the framework of the tire carrier, the carrier "hinge" or pivot, then the bumper, to the frame, and though some path to the body (not sure what gen you have, but I assume it is metal back there) that forms your ground plane. That makes a long path with quite a few places where the ground might be poor. Make sure you've got metal-metal contact for the coax shield first. If you check the resistance of the outside of the coax connector to ground with it disconnected from the radio it should be low. I wish I could give a precise definition of what is acceptable for "low". but I don't know. I'm mainly suggesting looking for gross errors like shorts or open circuits.
Even if you get a good DC ground, that doesn't mean you've got a good RF ground either, although other people have had success with this installation. You might experiment with a short wire from the tire carrier directly to the body to see if that changes anything.
I took a class many years ago from a guy who designed RF circuits. He used to say "Ground is not ground until proven otherwise."
Lots of strange things go on with radio frequencies, so it could be something besides the ground too as others have suggested.
From what I've read, and as has already been mentioned, mounting your antenna back there is never going to be ideal. If there isn't much antenna above the vehicle body, at the very least its going to distort the antenna pattern so you won't transmit or receive equally far in all directions.
04-22-2003, 08:18 AM
#14
I hope this can explain it.
Just made this page.
http://www.pnw4runners.net/tando/cb_coax.htm
This is how mine is done, and shows you what must be isolated as to not get a ground to short condition.
Just made this page.
http://www.pnw4runners.net/tando/cb_coax.htm
This is how mine is done, and shows you what must be isolated as to not get a ground to short condition.
04-22-2003, 02:13 PM
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ahh, thats a killer info site man. thanks a lot. one question though, i dont see a ground wire comin from my firestik...is it inside somewhere?
04-22-2003, 02:22 PM
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There's not a ground wire on the antenna itself; I believe Corey was grounding the coax antenna wire on that page. All the antenna does is screw in to the top of the mount.
What coax are you using? When I installed mine, I purchased a Firestik "Mini Kit", which had a ring connector already on the mount-end of the coax. All I had to do was throw it on the mount.
If you areen't using a Firestik mini kit, then you'll have to open up the coax and connect it like Corey has.
What coax are you using? When I installed mine, I purchased a Firestik "Mini Kit", which had a ring connector already on the mount-end of the coax. All I had to do was throw it on the mount.
If you areen't using a Firestik mini kit, then you'll have to open up the coax and connect it like Corey has.
04-22-2003, 02:49 PM
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Originally posted by mertztr
There's not a ground wire on the antenna itself; I believe Corey was grounding the coax antenna wire on that page. All the antenna does is screw in to the top of the mount.
What coax are you using? When I installed mine, I purchased a Firestik "Mini Kit", which had a ring connector already on the mount-end of the coax. All I had to do was throw it on the mount.
If you areen't using a Firestik mini kit, then you'll have to open up the coax and connect it like Corey has.
There's not a ground wire on the antenna itself; I believe Corey was grounding the coax antenna wire on that page. All the antenna does is screw in to the top of the mount.
What coax are you using? When I installed mine, I purchased a Firestik "Mini Kit", which had a ring connector already on the mount-end of the coax. All I had to do was throw it on the mount.
If you areen't using a Firestik mini kit, then you'll have to open up the coax and connect it like Corey has.
04-22-2003, 02:59 PM
#18
Doink, should be two wires coming out of a sheath.
One wire is the ground, one is the one you put a connector on that goes under the bolt as seen in my picture.
That is the wire that must not touch any metal on your rig, and goes between the washer and bolt.
Worst case scenario, a CB shop will only charge you $20 to hook it up for you and do your SWR.
One wire is the ground, one is the one you put a connector on that goes under the bolt as seen in my picture.
That is the wire that must not touch any metal on your rig, and goes between the washer and bolt.
Worst case scenario, a CB shop will only charge you $20 to hook it up for you and do your SWR.
04-22-2003, 03:11 PM
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Doink,
No worries! Take a look at this pic:
All you need to do is open the end of the coax to expose the individual wires and throw some connectors on the coax as shown. The ring connector need to be isolated from the rest of the mount by using plastic washers. The ground wire just goes to the frame or good metal. Don't run it far though; it should only be a short distance from the mount, according to Firestik.
But yeah like Corey said, the worst thing is a few bucks for someone else to do it. That's not a bad idea at all, because they will do the tuning for you too.
No worries! Take a look at this pic:
All you need to do is open the end of the coax to expose the individual wires and throw some connectors on the coax as shown. The ring connector need to be isolated from the rest of the mount by using plastic washers. The ground wire just goes to the frame or good metal. Don't run it far though; it should only be a short distance from the mount, according to Firestik.
But yeah like Corey said, the worst thing is a few bucks for someone else to do it. That's not a bad idea at all, because they will do the tuning for you too.
Last edited by TDiddy; 04-22-2003 at 03:12 PM.
