cb antenna help

Elbo

Elbo

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Joined
Dec 11, 2015
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21
Location
Pendleton, Or.
I have tried everything I can think of and the antenna will not match. High SWR tried moving it to different spots acts like the ground is bad. I even tried a different radio same results. Could the antenna be bad? It is a firestik but one that is not adjustable in fact it has a white plug on the top don't see how to tune it.
 
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Your high SWR is likely caused by the mount having been misassembled so it isn't insulating the antenna from the mount and Jeep. When the mount is misassembled, like if the white nylon insulating shoulder washer isn't present or it's in the wrong position, the antenna will be shorted to ground and cause a high SWR. Take a good sharp close-up well-lit photo of your mount, top and bottom, and post the photo here.

This also depends on the type of mount you are using so seeing the mount will be important to troubleshooting the problem.

If you have the type of mount shown below, take particular care that its Insulated Shoulder Washer is present, installed exactly (!) as shown, and that it is centered in the hole. If it's not, the antenna will have a dead short to ground.

Also, certain parts of the mount must be well grounded. Like where it bolts to the Jeep, and where the top of the SO-239 Coax Connector touches the mount... the powder coating must be removed from the bottom of the bracket as shown so those two parts have a good solid electrical connection. Don't remove the powdercoating inside the hole.

ant-mount grind away location.JPG
 
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Jerry Bransford said:
Your high SWR is likely caused by the mount having been misassembled so it isn't insulating the antenna from the mount and Jeep. When the mount is misassembled, like if the white nylon insulating shoulder washer isn't present or it's in the wrong position, the antenna will be shorted to ground and cause a high SWR. Take a good sharp close-up well-lit photo of your mount, top and bottom, and post the photo here.

This also depends on the type of mount you are using so seeing the mount will be important to troubleshooting the problem.

If you have the type of mount shown below, take particular care that its Insulated Shoulder Washer is present, installed exactly (!) as shown, and that it is centered in the hole. If it's not, the antenna will have a dead short to ground.

Also, certain parts of the mount must be well grounded. Like where it bolts to the Jeep, and where the top of the SO-239 Coax Connector touches the mount... the powder coating must be removed from the bottom of the bracket as shown so those two parts have a good solid electrical connection. Don't remove the powdercoating inside the hole.

View attachment 3704
Click to expand...
Here is pic of my mount
20160314_144628.jpg
20160314_144621.jpg
 
It appears to be assembled properly. Did you grind the powder coating away from the mount so the it is properly grounded where it is attached to the Jeep and also underneath the mount where the top of the bottom-half of the antenna mount touches it so it is properly grounded? No ground will cause a high SWR too.
 
Jerry Bransford said:
It appears to be assembled properly. Did you grind the powder coating away from the mount so the it is properly grounded where it is attached to the Jeep and also underneath the mount where the top of the bottom-half of the antenna mount touches it so it is properly grounded? No ground will cause a high SWR too.
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yes I did and checked it with a multimeter and added a extra ground to the tub and it shows a ground.
 
It's not making sense if you ground sufficient powder coating away from under the mount all the way around where the SO-239 touches, and where the mount is bolted in place... there has to be a large bare metal connection there too.

Understand the RF type of ground an antenna needs is far more demanding than a simple DC ground like a multimeter tests for. The simple type of ground that works for a light bulb or amplifier will not usually be good enough to serve as the RF ground an antenna requires.

Assuming you have a tunable tip on top of that antenna... are you making very small adjustments each to the brass tuning tip, like no more than about a half-turn each check of the SWR? It's easy to spin that tip right past the point the SWR drops if you turn it too far between SWR checks.
 
Jerry Bransford said:
It's not making sense if you ground sufficient powder coating away from under the mount all the way around where the SO-239 touches, and where the mount is bolted in place... there has to be a large bare metal connection there too.

Understand the RF type of ground an antenna needs is far more demanding than a simple DC ground like a multimeter tests for. Assuming you have a tunable tip on top of that antenna... are you making very small adjustments each to the brass tuning tip, like no more than about a half-turn each check of the SWR? It's easy to spin that tip right past the point the SWR drops if you turn it too far between SWR checks.
Click to expand...
It does not have a tunable tip. I've never have got it close enough to try to tune it. Is the ground shown in the picture sufficient? The mount is one that I made
 
The wire itself is probably adequate for a ground but I dunno how it is attached to the mount or Jeep. Tailgates are seldom well grounded so if that's your ground, odds are it's inadequate.

I've never seen a FIrestik with a white cap on it but for non-tunable tip Firesticks, they are usually tuned by pulling a wire out of the top of the antenna and snipping short lengths off between SWR checks. Don't snip off too much at a time... which is why I always recommend the FS series of Firestick antennas which have an easily tunable threaded brass tuning tip.
 
Jerry Bransford said:
The wire itself is probably adequate for a ground but I dunno how it is attached to the mount or Jeep. Tailgates are seldom well grounded so if that's your ground, odds are it's inadequate.

I've never seen a FIrestik with a white cap on it but for non-tunable tip Firesticks, they are usually tuned by pulling a wire out of the top of the antenna and snipping short lengths off between SWR checks. Don't snip off too much at a time... which is why I always recommend the FS series of Firestick antennas which have an easily tunable threaded brass tuning tip.
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Could the antenna itself be bad? I thinking on getting one that is easily tunable anyway. Is a 3 or 4 foot the best?
 
3 feet is all you need. Like Jerry said though, I highly, highly doubt the antenna itself is bad. Not really much to go bad there.

What happens when you turn on the CB, can you get any reception at all? When I first set mine up I could hear people talking but it was fuzzy. I tuned the tip and got it to sound much better!
 
Chris said:
3 feet is all you need. Like Jerry said though, I highly, highly doubt the antenna itself is bad. Not really much to go bad there.

What happens when you turn on the CB, can you get any reception at all? When I first set mine up I could hear people talking but it was fuzzy. I tuned the tip and got it to sound much better!
Click to expand...

Nope. Don't even have to turn up squelch. When I try to tune it it won't get below 4.
 
I finally got it matched. Added a ground to the tub and got a FIrestik ll and Eureka got it. Thanks for the help Chris and Jerry.
 
Elbo said:
I finally got it matched. Added a ground to the tub and got a FIrestik ll and Eureka got it. Thanks for the help Chris and Jerry.
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Glad you got it figured out, the problem sure did sound like a grounding issue from day one.

Bamacon said:
I'm sorry for this dumb question but what is high "SWR"o_O
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SWR stands for standing wave ratio. The quick explanation is this... a perfectly tuned antenna sends all the signal out that is given to it by the transmitter. An untuned antenna reflects back part of that power like a mirror. So a poorly tuned antenna may be receiving 4 watts of power, reflecting back 2 watts, and only radiating 2 watts. Not good.

A high SWR like 1.8:1, 2:1, or even 3:1 means the antenna is reflecting power back to the transmitter. A perfect SWR is 1:1 which means it is transmitting everything it's getting and reflecting nothing back.

Tuning an antenna for the lowest possible SWR means adjusting its length using an SWR meter so it reflects back the lowest power possible. The lower the SWR shown by the SWR meter, the better. :)
 
Jerry Bransford said:
Glad you got it figured out, the problem sure did sound like a grounding issue from day one.

SWR stands for standing wave ratio. The quick explanation is this... a perfectly tuned antenna sends all the signal out that is given to it by the transmitter. An untuned antenna reflects back part of that power like a mirror. So a poorly tuned antenna may be receiving 4 watts of power, reflecting back 2 watts, and only radiating 2 watts. Not good.

A high SWR like 1.8:1, 2:1, or even 3:1 means the antenna is reflecting power back to the transmitter. A perfect SWR is 1:1 which means it is transmitting everything it's getting and reflecting nothing back.

Tuning an antenna for the lowest possible SWR means adjusting its length using an SWR meter so it reflects back the lowest power possible. The lower the SWR shown by the SWR meter, the better. :)
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Thanks Jerry
 
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