cb antenna.
08-08-2008, 04:35 PM
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cb antenna.
ok so here's the plan tonight i am ordering a door jam cb antenna mount and 18 foot cable package (http://www.wearecb.com/store/firesti...it-p-1646.html) and i am going to be mounting it in the back tailgate jam. I would like a 3 foot firestick antenna i have a 19 DX IV Compact CB Radio (http://www.cobra.com/index.cfm?fusea...category_ID=30) and I was wondering if anybody that has this radio what size antenna works the best. I'm not the best with electronics so I didn't know if a tunable antenna or non tunable or even size makes a difference. So some help would be much appreciated! Thanks 
08-08-2008, 04:47 PM
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Tunable antenna would be better, I'm told since it allows a more precise matching to the radio. A non-tunable is set at the factory to a more or less middle of the road setting which may or may not work well with the radio you choose. As for location you want to mount it as high as you can to get the best radiation. A 3' antenna mounted down near the bumper on one side would be partially shielded by the body of the vehicle which would cost you tx/rx range but if you're only using it for close in trail comms you probably won't notice too much of a difference.
Several members here are far more into CBs and can give you much better advice than me but I hope this helped you a bit anyways. Aviator
Several members here are far more into CBs and can give you much better advice than me but I hope this helped you a bit anyways. Aviator
08-08-2008, 04:48 PM
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Make Sure All Your Ground Connections Are Good, Secure And Clean. A Bad Ground On A Cb Antenna Will Make It Very Hard To Transmit And Receive. Happy Squelching.
08-08-2008, 05:06 PM
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you won't notice a big difference between the 3, 4, 5 or 6 foot firestiks. the primary difference other than size is how much transmit power they handle- the longer ones handle more power. if you are not using a linear amplifier, then any one is acceptable.
as for tunability, firestik antennae are allegedly tuned in the factory but if you're using the upper channels exclusively, you can clip the firestiks down to better tune them to the upper channels. if you're using the lower channels most often, the firestik works well (and can't be tuned to optimize the lower channels anyways). most tunable fiberglass whips only adjust the impedance of the antenna to better match it to the radio than to the improving transmit performance. tunable steel whips are tuned by sliding the element in or out, effectively changing the length of the antenna and tuning it to the different frequencies.
if you install one of the spring loaded mounts that let's the antenna flex at the mount, the antenna should be tuned since the antenna is now longer. and you'll need a VSWR meter (voltage standing wave ratio) to do so.
now, more important is where the antenna is mounted. if you're mounting it to the side of the tailgate, the metal of the body will direct the signal (it's called 'ground plane effect'), so if it's say on the driver's side of the gate, the transmit and receive signals will be slightly stronger in the direction of the passenger side. if it were directly on the corner, next to the taillight, the signal will be stronger along the side of the truck and along the back- any signal coming from the opposite corner of the truck.
this is why most truckers put an antenna on each side cause the cab and trailer direct the signal front and rear and partially blocks the signal from the opposite side [through the body] draw a line down the center of the cab and draw a half-circle on one side of the cab and you can get an idea of where the antenna's sensitivity is greatest. the second antenna is matched to the other antenna and picks up signals on the other half of the truck. this technique is called co-phasing and when done properly works as well as one antenna in the middle of the roof.
which brings me to the optimal location to mount a single antenna- as high as possible and centered, meaning the middle of the metal part of the roof. probably not an option for your truck though since it is already fairly tall.
if it were me, I would do two 7' 3/4 wave firestiks, one on each side just in front of the taillights, with a cophasing harness. the signal would be strongest to the front of the truck, but not appreciably lower to the rear.
something that may help you visualize what I'm describing about antennas would be to imagine that the antenna is a very bright lightbulb. imagine how the light would shine and reflect off the body of the truck, and where the body of the truck would cast shadows.
*edit- sorry for the dissertation...
10-8, 10-10
as for tunability, firestik antennae are allegedly tuned in the factory but if you're using the upper channels exclusively, you can clip the firestiks down to better tune them to the upper channels. if you're using the lower channels most often, the firestik works well (and can't be tuned to optimize the lower channels anyways). most tunable fiberglass whips only adjust the impedance of the antenna to better match it to the radio than to the improving transmit performance. tunable steel whips are tuned by sliding the element in or out, effectively changing the length of the antenna and tuning it to the different frequencies.
if you install one of the spring loaded mounts that let's the antenna flex at the mount, the antenna should be tuned since the antenna is now longer. and you'll need a VSWR meter (voltage standing wave ratio) to do so.
now, more important is where the antenna is mounted. if you're mounting it to the side of the tailgate, the metal of the body will direct the signal (it's called 'ground plane effect'), so if it's say on the driver's side of the gate, the transmit and receive signals will be slightly stronger in the direction of the passenger side. if it were directly on the corner, next to the taillight, the signal will be stronger along the side of the truck and along the back- any signal coming from the opposite corner of the truck.
this is why most truckers put an antenna on each side cause the cab and trailer direct the signal front and rear and partially blocks the signal from the opposite side [through the body] draw a line down the center of the cab and draw a half-circle on one side of the cab and you can get an idea of where the antenna's sensitivity is greatest. the second antenna is matched to the other antenna and picks up signals on the other half of the truck. this technique is called co-phasing and when done properly works as well as one antenna in the middle of the roof.
which brings me to the optimal location to mount a single antenna- as high as possible and centered, meaning the middle of the metal part of the roof. probably not an option for your truck though since it is already fairly tall.
if it were me, I would do two 7' 3/4 wave firestiks, one on each side just in front of the taillights, with a cophasing harness. the signal would be strongest to the front of the truck, but not appreciably lower to the rear.
something that may help you visualize what I'm describing about antennas would be to imagine that the antenna is a very bright lightbulb. imagine how the light would shine and reflect off the body of the truck, and where the body of the truck would cast shadows.
*edit- sorry for the dissertation...
10-8, 10-10
Last edited by abecedarian; 08-08-2008 at 05:08 PM.
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08-08-2008, 05:33 PM
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you'll be fine with the 3' firestick. expect about 4 miles range on flat open ground, maybe 1/4 that in mountainous territory. but basically, if you can see each other, you will be able to talk.
08-08-2008, 06:02 PM
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ok so i read earlier that you said you would to tune it if i got a spring for the base. well if i go to a 4 or 5 foot antenna will i need to tune it just for what i'm doing? thanks by the way for awnsering all my questions
08-08-2008, 06:21 PM
#16
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I won't be any help with the antenna question so this is a little hijack.
Where did you mount the CB? I'm trying to find a place to mount a Cobra 29 and it's so dang big I just can't find a spot to put it.
Where did you mount the CB? I'm trying to find a place to mount a Cobra 29 and it's so dang big I just can't find a spot to put it.
08-08-2008, 06:31 PM
#18
Get a tuneable antenna, the FireStik-II is great, they are very rugged and hold up to lots of abuse. I used to run a 4' then switched to 2' on the back corner of my 4Runner:
http://www.4crawler.com/4x4/CheapTricks/CBantenna.shtml
Pop for an SWR meter if the local CB shop does not have one to tune your antenna with, I got mine at Radio Shack for like $15. And don't think of tuning as a one time deal. Good idea to check it periodically, coax cables age, ground connections can go bad and I even once had an SWR problem after wheeling at the ocean beach. I guess the coating of salt spray and dust on the antenna changed its impedance (salt is conductive).
BTW, I do have a cheapie fiberglass whip from Radio Shack on my daily driver. One thing I found with it is do not touch it with bare hands after a few years of use as those glass fibers are like fine cactus stickers, BTDT! The FireStiks have a heavy shrink wrap covering and it will stand up to scraping on parking garage roofs, tree branches, etc. without damage.
http://www.4crawler.com/4x4/CheapTricks/CBantenna.shtml
Pop for an SWR meter if the local CB shop does not have one to tune your antenna with, I got mine at Radio Shack for like $15. And don't think of tuning as a one time deal. Good idea to check it periodically, coax cables age, ground connections can go bad and I even once had an SWR problem after wheeling at the ocean beach. I guess the coating of salt spray and dust on the antenna changed its impedance (salt is conductive).
BTW, I do have a cheapie fiberglass whip from Radio Shack on my daily driver. One thing I found with it is do not touch it with bare hands after a few years of use as those glass fibers are like fine cactus stickers, BTDT! The FireStiks have a heavy shrink wrap covering and it will stand up to scraping on parking garage roofs, tree branches, etc. without damage.
08-11-2008, 07:20 AM
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Honestly The firestick is a good antenna but the radio is a less than desirable one (but it fits in a small truck). Move the anntenna closer to the radio and use the shortest coax possible (less coax = lower resistance = Lower SWR).
Buy a SWR meter and 6" piece of coax to test the SWR. If it exceeds 2 then you are not going to get out very well. Magnet mount antennas are problematic and fiberglass whips are the most economical solution (but I've had great luck in the past with the "K40 Gold Series" Steel Whips).
BTW where do you mount a full size radio in one of these trucks, on the glovebox, only place where mine would fit, not enough room under the AM/FM radio, no room on the dash where It wasnt in the way, tranny tunnel was too shallow, and no roof bows where it could be mounted
My setup is a "Peaked and Tuned" Uniden 68 LT with a 40"x3/8" Radio Shack Brand Fiberglass whip (same as found on most International OTR trucks) mounted at the very front of the bed on a custom bracket (its a 1"x5"x1/16" piece of angle with a 1/2" hole in it). (whole setup was approx $300-400).
Buy a SWR meter and 6" piece of coax to test the SWR. If it exceeds 2 then you are not going to get out very well. Magnet mount antennas are problematic and fiberglass whips are the most economical solution (but I've had great luck in the past with the "K40 Gold Series" Steel Whips).
BTW where do you mount a full size radio in one of these trucks, on the glovebox, only place where mine would fit, not enough room under the AM/FM radio, no room on the dash where It wasnt in the way, tranny tunnel was too shallow, and no roof bows where it could be mounted
My setup is a "Peaked and Tuned" Uniden 68 LT with a 40"x3/8" Radio Shack Brand Fiberglass whip (same as found on most International OTR trucks) mounted at the very front of the bed on a custom bracket (its a 1"x5"x1/16" piece of angle with a 1/2" hole in it). (whole setup was approx $300-400).
