ground plain or no ground plain cb antenna for m1009

[richingalveston]

I am looking at installing dual 3ft fires stick antenna's on my 1009. The antenna will be mounted directly over the wire holes in the fiberglass top, thus the antenna will be mounted to fiberglass and not metal. The will be very close to the metal and only stick up about a foot above the roof line.

Not a radio antenna expert in any way. The cost of the no ground plane antenna is almost double the cost of regular antenna so I do not want to pay for something I do not need.

I am going dual just because I like the balanced look and since both are short and partially blocked by the cab I thought two would work better.

Thanks for any help.

Rich

 

[ke5eua]

Do yourself a favor and just put a 102" whip on it. You'll thank me in the long run. No ground plane antennas on cb offer poor performance.

Duals antennas need to have the proper phasing cable.

Do you have a antenna bracket for military antennas on your truck now?

 

[richingalveston]

I had 4 brackets with guards but sold them, I do not like driving with them they block the mirrors and stick out to far. I just want small antennas that I can mount tight to the body and that are short.

I have a whip on large spring base but without the CUCV mount there is no good mount on a 1009. And it looks like crap.

The phasing cable is not expensive. The two antenna's with mounts and cable will be around $100 or less, maybe $150 if I get the no ground plane antenna

I plan to get two, three foot FS series firestick's with proper cable. I will use two of their small side mounts that will cover the holes in the side of the 1009 top.

I am pretty sure this is what I want and my only question is in regards to the ground plane.

Thanks for the input.

 

[ke5eua]

Have you though about running a hood mount or off the back gate?

To bad your 200 miles away, could give you a hand with it all.

 

[richingalveston]

Hood channel mount is my second option if I go single antenna. Plan to add tire carrier and some other stuff on back when I build a new bumper so I really do not want to put it back there.

I like the look of the side mounts, they are small, just a little over 3 inches by 1 inch. They will cover the holes in the top very neatly. And as stated earlier, I really like a balanced look. Having one antenna makes this difficult to achieve unless you center mount it.

From my minimal studies so far I see no down side to the dual antenna especially when using short antennas.

 

[ke5eua]

One down side to using phased antennas is that they are no longer a true omni directional antenna.

Phasing antennas are great when you stack them horizontally, not so vertically.

The antenna doesn't have to be centered to achieve optimal performance, just installed correctly. At 27 MHz with a loaded antenna your already loosing performance, add no ground plane antennas to mix and you cut the performance of what was there in half as half the antenna has to be used for loading.

I'm offering sound advice as radios and antennas are something I've been doing for over 10 years.

Mounting antennas to fiberglass has always been an issue for hams, especially in the hf range as grounding is critical. Understand that the ground source is close but unless you make a physical connection between the mount of the antenna to the nearest point of ground it's not going to make a difference.

 

[cbear]

I'm pretty sure the dual antennas truckers put on their mirror brackets are no ground plane. The mirror bracket doesn't offer a useful ground plane. A ground plane should to be a horizontal surface, the length of the antenna in all directions, ie the middle of a steel roof.

 

[Flyingvan911]

You'll want to have the antenna attached to metal for sure. It makes the body of the vehicle part of the antenna.

 

[ke5eua]

I'm pretty sure the dual antennas truckers put on their mirror brackets are no ground plane. The mirror bracket doesn't offer a useful ground plane. A ground plane should to be a horizontal surface, the length of the antenna in all directions, ie the middle of a steel roof.

They are grounded, if it is a plastic mount with the built in antenna bracket it is factory grounded.

The mirror offers the nearest ground source which is connected to the door then to the body.

A ground plane doesn't have to be horizontal to the antenna, just needs to be bellow the radiating point point on the antenna.

Look at a nvis antenna and how it is setup, the antenna provides its own grounding with the radials.

A true ground plane should be twice the length of the antenna, and doesn't have to be in all directions. Look a a yagi antenna, grounding radials are in the back of the stack.

I build antennas for lower frequencies than cb and higher power output. A lot of work goes into it, not just slapping a rod to a cable.

I've talked all over the world with antennas I've built using only 5 watts of power on frequencies 14 MHz and below.

Antenna building is fun, my first antenna I built I destroyed my tuner cause I messed up, just glad it was the tuner and not the radio.

 

[richingalveston]

http://www.claysradioshop.com/citizensband_firestick_LG-M2.html

This is the NGP base and antenna I am looking to use if I have to have NGP. I can get this in a dual setup.

I am not looking to talk to the moon. This will just be a convoy and trail talker I am not a trucker.

two foot of the antenna will run very close to the metal at the back of the cab, about one foot will stick above the roof line. Inside the top, I can easily ground it to the truck using one of the screws that hold the top down if needed.

 

[firefinder]

richingalveston,

I am new to SteelSoldiers and I am really enjoying all of the knowledge available on this forum! I am starting from ground zero with personally owned military vehicles, however I am glad to contribute where I can in my humble way. I spent close to 30 years in the communications test and surveillance industry and I hope to convey some of that knowledge as I learn from others.

True phased antennas are difficult to achieve. As noted earlier, splitting the signal for the two antennas and then attempting to phase the antennas will probably lead to more loss than connecting to a single one of these antennas. You could still mount both for aesthetics and only connect one antenna to the radio directly and without the phasing cable. It is important to use good quality 50 ohm coaxial cable for maximum signal output.

Another misnomer that is often used by truckers is mounting the antennas at a forward angle in hopes of "pointing" the radio signal ahead of them. In reality, it is just helping (ever so minimally) to melt the snow in front of them! Keep monopole antennas upright for maximum performance on vehicles.

Try to minimize the SWR of your system to match your installation. Local amateur radio operators could probably assist you with minimizing SWR. With a large portion of the antenna mounted close to the metal cab, the transmission output of the radio will be compromised, however the difference in reception may not be as severely affected. These antennas would operate best with as much open space as possible (such as near the roof top, etc.).

 

[cbear]

A ground plane doesn't have to be horizontal to the antenna, just needs to be bellow the radiating point point on the antenna.

Look at a nvis antenna and how it is setup, the antenna provides its own grounding with the radials.

A true ground plane should be twice the length of the antenna, and doesn't have to be in all directions. Look a a yagi antenna, grounding radials are in the back of the stack.

True, your ground plane doesn't have to be horizontal, or in all directions. HOWEVER, your antenna will not longer be omnidirectional, which is the goal of most CB antennas.

A antenna location on a vehicle is almost always a compromise. I use to run a 1/4 wave mag mount in the middle of my roof when on the interstate, tuned with a bird watt meter.

 

[swbradley1]

Find your local amateur radio people and they will help I'm sure.

You have a few in the area.

Amateur Radio Clubs


Anoka County Radio Club & Emergency Services (Minnesota)


Austin Amateur Radio Club & Austin Repeater Organization


Bay Area Amateur Radio Club (Nassau Bay)


Beaumont Amateur Radio Club


Brenham Amateur Radio Club


Brazos Valley Amateur Radio Club (SW Houston)


Clear Lake Amateur Radio Club (NASA-SE Houston)


Compaq Amateur Radio Club (ACE)


Galveston County Amateur Radio Club (GCARC)


Houston ECHO Society


Houston Vintage Radio Association


Huntsville (Walker County Amateur Radio Group)


Jefferson County Amateur Radio Club


JSC Amateur Radio Club


Northwest Amateur Radio Society (Houston)


Orange Amateur Radio Club


Temple Amateur Radio Club


Texas A&M Amateur Radio Club


Texas DX Society


Texas VHF-FM Society - (League City)


Tidelands Amateur Radio Society (Texas City)


Walker County Amateur Radio Group (Huntsville)

 

[ke5eua]

Find your local amateur radio people and they will help I'm sure.

You have a few in the area.

Amateur Radio Clubs


Temple Amateur Radio Club

Great bunch of guys right there

 

[tennmogger]

Hi Rich,

You have gotten some really good technical advice from the fellows already. With your non-critical use requirements, and the ability of modern CB's to protect themselves against mismatch, you might just try the mounting as you initially described and see if that dual mount setup works adequately for you.

Not knowing diddly about your truck so I am guessing, but it sounds like your preferred mounting location is low down and in close proximity to the cab. But the cab is fiberglass, right? The fiberglass is mostly transparent to the RF. What is behind/underneath the mounting holes? Can you put in a criss-cross of copper flashing centered on the mounting hole and providing a ground plane on the inside surface of your cab? Just stick the flashing to the wall with double-sided tape. That could work surprisingly well and if it is underneath headliner of behind the seats it might look ok.

Another trick for a fiberglass cab/cover is to mount the antenna on the floor of the cab or bed. The floor provides the ground plane and the fiberglass around the antenna has little effect. Of course you don't want to have an antenna right behind you back or head, etc.

As with most radio installations, just try it and see how it works.

Bob WB4ETT