Firestik CB and Radio Antenna Cowl Set Up

B

Bernie

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Good choice on the radio. The Cobra 29 is a good, dependable rig.

Firestick also makes a darn good antenna, but we need to talk some about your choice of mounting it. First, with antennas in general, longer is better (with some exceptions that mostly don't apply to CB anyway) but don't just go by the physical length, also look at the electrical length. The electrical length will usually be expressed in a fraction of a wavelength and, bigger is generally better.

So, take two 36" antennas, both fiberglass wirewound, and one is 1/2 wave while the other is 5/8 wave. The 5/8 wave will be marginally better, but every little bit helps when you're working, as we hams call it, "QRP" (ie: low power).

Now, mounting location...

First off, a CB antenna is not going to function very well as an AM/FM receiver antenna. It will work, just as a coat hanger will work, but the reception will be less than ideal. Second, those "all-in-one" antennas, while they do work, are again, a poor compromise and will be less than ideal for all functions.

(I'll continue this in a few - gotta get the door)
 
B

Bernie

Guest
Okay, continuing about antennas... Just as in real estate, it comes down to location, location, location!

Ideally, for a single CB antenna, you want it as high on the vehicle as you can get it, and as close to the center as possible. The vehicle itself acts as half the antenna system (the "ground plane") and plays a big part in what your radiation pattern is going to look like. Located as I said above, in the center of the vehicle, you'll get a sort of oval pattern, longer towards the front & back, narrower towards the sides. With a CB in flat terrain and good conditions that'll give you a forward and backwards range of about 15-25 miles, and about 5-15 miles to the sides. Moving the antenna adjusts that pattern in such a way that the closer the antenna gets to an "edge" of the vehicle, the shorter the range will be in that direction, and the longer the range will be in the opposite direction. For example, mount it in the center of the tailgate and you'll greatly increase your forward range (probably to about 30-40 miles on flat terrain and in good conditions), greatly shorten you range to the rear (about 3-5 miles) and hardly change to the sides (though the pattern, seen from above, will look somewhat fan shaped, giving the best signal to the sides at about a 45 degree angle left & right of the front of the vehicle). Move it to the front of the hood and the opposite happens. This is why a good setup for highway use is to mount it on the right rear fender. That puts most of your signal ahead and to your left (towards traffic coming the other way, allowing you longer range notice of road conditions ahead) while still giving halfway decent coverage behind you.

Dual (co-phased) CB antennas are a whole different ballgame, and would require a bigger vehicle than what you have. (Needs a minimum of 8' of separation between them)

My advice? Cab mount (either permanent NMO style mount or a magnetic mount) a single antenna and you'll be good to go.

Other thoughts:

  • No CB antenna is going to survive repeated whacks on tree branches at anything over 20 mph for very long, especially not fiberglass antennas. They tend to snap right off at the base. (I have several here like that if you want to see what I mean)
  • A spring mount will help greatly if you do hit something, but only up to about 35-40 mph
  • A quick disconnect mount, or "foldover" mount (some antennas have it built in) makes car washes and low garages easier to deal with. But for car washes with brushes or anything but "touchless", remove it or lose it, so I strongly recommend either the quick disconnect or a mag mount.
  • That Cobra 29 also receives NOAA weather radio, so you'll need to find a CB antenna that also can receive those frequencies. Not all can. Look for one that says it will receive NOAA or WX frequencies and you'll be okay.
 
B

Bernie

Guest
So I'm kicking around getting a CB for the truck "just because". I'm most likely going with this:

http://www.walcottcb.com/cobra-29-lx-multicolor-faceplate-radio-p-2074.html.

I will be mounting it in place of the factory aux tape deck after modifying the opening. Giving it a "factory installed" look.

Rather then running a splitter and one antenna I was thinking of a pair of these:

http://www.firestik.com/CatalogFrame.htm

One mounted where the factory radio antenna is and the other symmetrically opposite with a set of these (probably the Model K-154A) :

http://www.firestik.com/CatalogFrame.htm

and running grounding straps to the frame.

Is anyone running this set up the same way? Would Ya'll go with a pair of 36"s or would 24"s be sufficent?:dunno: Are theses antennas flexible enough they can with stand getting smacked around by a car wash, branches etc. mounting them on the cowl?

Thanks in advance for Ya'lls input.:cheers:

Firesticks are good antennas...
Use the longest one you can get and still be practical.

The firestick "SCREWS" into the mount.
Carry a little open end or a small Cresent wrench in your console.

When going to the carwash... it takes about 10 seconds to unscrew them and lay them in the floorboard.

About 12 seconds to put them back on...
:lol:
That way nothing gets broke and you don't get gray hairs worrying about them...:lol: :thumbs:

A quick disconnect (bayonet) mount takes even less time, and doesn't even need tools. Several of the antennas on my truck are mounted that way, and I can (and have) swapped antennas without even getting out of the truck, just roll down the window, pop the antenna off, pop the new one on, roll up the window again.

Something like this is very good: http://www.universal-radio.com/catalog/hamantm/0696.html

But these are the style I use:
1213.jpg
 
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bubbatrucklover

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Fwonk me Bernie :eek: Let me quote myself:

When it comes to communications Bernie DEFINITELY knows his shit.:thumbs:

Thank you SOOOOOO much for that VERY descriptive detailed explanation. :cheers:

I heard the term "ground plane", but was unclear as to the specific definition.:dunno:

and the NOAA frequency compatibility didn't even occur to me. I would have been pissed and confused had I got an antenna that didn't receive those frequencies properly.

To tap your knowledge a little further, the 2 Firestiks (for example) one (the 2 Ft 5/8 wave) is rated @ 100 watts) and the other (3 Ft 5/8 wave) is Rated @ 300 watts.

What exactly is the 100 and 300 watts referring to.:confused:

Thanks again Bernie. :cheers: Based on your advice I now have to decide if I want to have an antenna on my roof or back fender.

If not I can expect less then optimal signal or just not go with a CB all together.
 

dirtyoldman

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Don't give up on a CB,they're very usefull when traveling in a group,especially when off-roading.

I bought a cheapy Cobra last year and mounted it where the tape deck was..I already had a magnetic antenna so I mounted it on the roof above the rear doors and ran the wire down the rear door jamb under the rubber door seal,then under the driver's seat and up under the dash.I don't really know the range of the signal but when in a close group it doesn't really matter.

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No cutting or drilling :thumbs:
 

bubbatrucklover

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Looks good gramps. :thumbs: I'm not giving up yet. "Back in the day" all my friends and I had "redneck cell phones" in our vehicles. :D

I might be getting a traveling job in the near future and that's why I have moved the CB up on the project list. My roof is at 7' now and with my SAS (down the road) it'll be at 7 1/2 '(ish) so I'm looking at clearance (not that I go under a lot of low passes "just saying".)

I was also exploring the functionality of making the antenna look more "factory" just for shits and giggles, but based on Bernie's knowledgeable explanation I would be jeopardizing usefulness for looks. :facepalm:
 

Texas Jim

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If I am not mistaken... and Bernie can correct me if I am... the wave length for a CB is 102 inches...which equals 8.5 feet.
If your dual antennas are an EXACT portion of the length apart, they will not interfere with each other.

That is one reason you see so many double antennas on the mirrors of BIG trucks.

Another for instance.... if you had 2 of the 5/8 wave antennas and mounted them 63.76 inches... they are now EXACTLY a 5/8th wave apart from each other.

The wattage that is referred to is the max output the antenna can handle if you wanted to put an illegal booster on the CB radio... they are called linears...
 
B

Bernie

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Fwonk me Bernie :eek: Let me quote myself:

When it comes to communications Bernie DEFINITELY knows his shit.:thumbs:

Thank you SOOOOOO much for that VERY descriptive detailed explanation. :cheers:

I heard the term "ground plane", but was unclear as to the specific definition.:dunno:

and the NOAA frequency compatibility didn't even occur to me. I would have been pissed and confused had I got an antenna that didn't receive those frequencies properly.

To tap your knowledge a little further, the 2 Firestiks (for example) one (the 2 Ft 5/8 wave) is rated @ 100 watts) and the other (3 Ft 5/8 wave) is Rated @ 300 watts.

What exactly is the 100 and 300 watts referring to.:confused:

Thanks again Bernie. :cheers: Based on your advice I now have to decide if I want to have an antenna on my roof or back fender.

If not I can expect less then optimal signal or just not go with a CB all together.
Between those two choices, the 3' (36") would be the better choice. Remember, longer is better with antennas. (I won't go into the different ways of "loading" an antenna, but I will say that a spiral wound top load is the most efficient in comparison to center load and base load) Ignore the power ratings. A) unless you run an illegal amplifier they won't matter and B) if you do run an illegal amp you probably won't be satisfied with those antennas anyway.

Don't give up on a CB,they're very usefull when traveling in a group,especially when off-roading.

I bought a cheapy Cobra last year and mounted it where the tape deck was..I already had a magnetic antenna so I mounted it on the roof above the rear doors and ran the wire down the rear door jamb under the rubber door seal,then under the driver's seat and up under the dash.I don't really know the range of the signal but when in a close group it doesn't really matter.

No cutting or drilling :thumbs:
You need to be careful how you run the coax because sharp bends, hard edges and frequent bending can all damage it internally, and your first clue anything is wrong will be a CB that receives okay, but doesn't transmit worth a lick... and a hefty repair bill to fix it.

If I am not mistaken... and Bernie can correct me if I am... the wave length for a CB is 102 inches...which equals 8.5 feet.
If your dual antennas are an EXACT portion of the length apart, they will not interfere with each other.

That is one reason you see so many double antennas on the mirrors of BIG trucks.

Another for instance.... if you had 2 of the 5/8 wave antennas and mounted them 63.76 inches... they are now EXACTLY a 5/8th wave apart from each other.

The wattage that is referred to is the max output the antenna can handle if you wanted to put an illegal booster on the CB radio... they are called linears...

There's a difference between two antennas resonating and interfering with each other (which can happen at various fractions of a wavelength) and two antennas co-phased so they act together and compliment each other (which requires certain specific physical and electrical distances between the two - and a very carefully measured and cut co-phase harness that gives the correct impedance)

Also, CB frequencies are in the 11 Meter band, meaning a full wavelength at those frequencies is about 11 meters tall, or just over 36 feet, so your 102" would be a few inches shy of the 9' whip that was very common "back in the day" and which was actually 1/4 wavelength.

:)
 

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