I have a rago front hood bracket for cb and was going to use a 3/4' nmo mount to bracket

now to the antenna I was going to go with Laird brand

https://www.theantennafarm.com/catal...high-gain-447/

but I am confused a cb uses 26.96-27.40 mhz

so does that mean from the list of antennas i should go with one that is 26-28?

i see some antennas that are rated 27-30 etc why would these be for cb use if the range is off?

lastly do i go with spring or without?


model thinking about is the cb27 or cb27s

a 27-30Mhz antenna should work fine; the vast majority of NMO mount antennas that are CB-range compatible are actually intended for VHF-Low communication in a commercial setting or for the 10 meter band.

As far as spring goes, that depends on what antenna you're going with, its length, and what you expect it to come into contact with.

I use a whip style, so no need for a spring

Be careful of which NMO mount you get. Most mounts are for thin sheet steel like what’s on the roof. The Rago bracket is beefy and is 3/16” thick. It requires that you find the proper one. The Antenna Farm had a Larson NMO but required soldering the coax cable. Make sure you understand how that’s done.

I have been a ham since 1972 and the Rago bracket is the best out there, but takes a bit of work to get just the right mount for it.

Regarding the antenna, any one that fits 26-30 MHz will work fine. But, you will need to adjust it to resonate on the frequency for channel 20.


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i'm happy with my BR-140-B

I went with this base since it is made for thicker metal

Larsen LSN-NMOHFMID Middle Thickness NMO Mounts NMOHFMID - Free Shipping on Most Orders Over $99 at DX Engineering


little pricey but nice unit

as for cabling I am going to go with amazon they have r58 a/u with
Stranded Center Conductor for Flexibility

I found in my shop a my old antenna from my old cari had around its a pctel cb antenna 49' mlb2700 rated at 27-30 but i think it should find one that has spec of at least 26 to cover full cb band of the 26.96 or am i over thinking this?

Good choice for mount and for cable. I used 8x since I already had a PL259 on 1 end from a previous install.

Regarding the antenna, yes, you are over thinking it. Most individuals get wrapped up in a ‘perfect’ antenna!

Here’s the scoop! I will try to make it simple.....but what I’m about to explain takes hundreds of pages in a book! I will explain in generalities and there are exceptions and variations to the following - so no flames guys

1. Today’s CB’s and Ham radios are 50 ohm impedance into a load. A load is an antenna to dissipate transmitted power from the radio

2. Antennas are usually ¼, ½ or ⅝ wavelength long. Typically ½ or ⅝ wave for mobile use. However, we sometimes get creative for more ‘gain’. That means what it implies...greater distances.

3. Picture transmitted RF energy going down the coax cable like water through a hose. Bigger cable, doesn’t not mean more RF but greater protection from leaks. However, in mobile applications, size is not too important (RG58/RG8x) unless power exceeds 50 watts. Smaller coax than RG58 is like chloresetral to your veins.

4. The antenna is like the nozzle on the end of the water hose. You want it to spray as far as possible! However, far may not be practical. Antenna can’t be so big you hit tree limbs!

5. Go back to the transmitters 50 ohms as stated above. To be perfectly “matched”, the nozzle or antenna must be 50 ohms. But that’s not practical because there is only 1 frequency (channel) that could be perfectly matched, and that may not be totally possible.

6. However, in essence, if it’s not perfectly matched, the person on the receiving end will never know the difference. It’s only in your mind that it’s not perfect! So, if the load is 75 ohms and transmitter is 50, then the Voltage Standing Wave Ratio or SWR is 1.5-1. Today’s transmitters can safely take 3.0-1 at full power. Some reduce power if it goes over 3. The higher the first number, the nozzle is only letting a small amount of water or in our case RF. Remember the other person could not audibly tell the difference between 3.0-1 or 1.0-1

7. How each antenna will perform is dependent on placement on vehicle, it’s length and grounding of the radio and cable.

8. So the exact match is not critical.

9. Therefore, in all probability, your antenna tuned for 26 MHz is going to be ok for transmitting on 27.405, channel 40. However, buy or borrow a VSWR meter and check it. Lots of variables, but if it’s under 3.0-1 on ch 40, your done. Trimming it will only make you feel better!!!!

Now that I’ve totally confused you, you gave up !!!! JK! Let me know what you think


Bob

Hi Bob, Thanks for info. I do kinda understand what you mean I am no pro but your info is very helpful.

Glad the base I got is good As to cable I wanted to go with RG58u since easier to flex and from what I read is more then enough for cb vs the 8x stuff

everything on amazon is china you think that's ok also do you think I should go 8x?

I was told not to go solid centre wire which is why i am going to get the stranded centre core.

as to antenna I will use use my old antenna that is pretty much new

it is 49" pc tel nmo 27-31mhz

i already have a basic swr meter so all good there

lastly I have the rago fab front hood mount for antenna it is bolted thru the 2 factory 4runner hood bolts.

one member said that bracket does not have good ground and you can't add one to make it better which I am confused about that

forsure the hood bolts are grounded can you share your thought on this issue??

ps cb going to use is the cobra 75 st

Sorry @JSS16 for my late reply....somehow I missed this!



Naw, run is to short to need 8x....I happened to have a piece already laying around with a 259 on one end.......here's why you don't need it......in short, the longer the run of cable and the higher the frequency of transmission, the greater the need larger diameter cable......think of it as going from P metric tires to heavier trail rated tires....next time you pass a cell tower, look at the large black things going up the tower.....thats cable feeding the antennas - long run and high frequency = less loss of transmitted power. So for our uses, RG58 is plenty. Quite frankly for a short 10' run, at 27 MHz, RG174 is fine.


now using a stranded center conductor, that is a must! Why, solid copper will work harden over repeated bending by opening the hood and eventually split.

He is right about the Rago mount not having a ground (nor do any of the lip mount brackets by Diamond, etc)...but you still can do it.....grounding is most important to keep the transmitted power or what is called RF (radio frequency) off of the vehicle ground system and secondarily to provide a ground plane or reflection system to launch the RF into the air.....this sounds almost contradictory.....just like our 13.8 VDC truck batteries have a + and -!

However, I have used many different magnetic mount antennas, and they are not grounded.....they work just fine.

When I installed my Rago mount, I noted the same grounding issue.....but that's not a problem.....most likely at @3 watts transmitted output on CB (5 watts input = @3 watts output), just don't worry about it...it won't make much a difference.....however, there is a very remote possibility that RF could enter the in-dash radio unit...my guess is that it would be very rare if it did....I purposely bought the drivers side mount to run the coax through the firewall and to a sperate head unit under the drivers seat.....really short run and short run to the tap a fuse under the dash....if RF does get in your radio, simple fix....or if you're super proper about everything, then try each of these, in order -----

1. Make a coax braid jumper to ground. Get an extra length of RG58, strip the rubber off the outside and remove the white insulating material with the center conductor. This is easy to do a couple of inches at a time.....push shield back a couple inches exposing a hole in the braid and push out insulating material and center conductor....you want to end up with just the shield.....solder this shield to the shield at the base of the NMO....seal with a good silicone material. Then connect this flexible material to a ground in the engine compartment.....keep it flexible to open the hood, but as short as practical.

and/or

2. Inside the cab, connect a ground wire from the CB radio to a ground screw. Again, keep this as short as possible.....make sure to use a continuity tester to check your ground screw against the PL-259 connector's shield to ensure you are really grounding it!

BUT, quite frankly, I really don't feel the above is necessary. I did not do it and will not because I have not found any trouble running 50 watts output on 146 and 444 MHz. I might put another hood bracket on to run a screwdriver antenna for 3.5 to 28 MHz at 100 watts and I will definitely ground it as I described.

Hopefully, I did not confuse you. I have run ham radios in cars and trucks since the 70's and never had a problem. And, I only grounded 1, that one when I ran 500 watts output on 14.2 MHz.

Let me know how it turns out!

Bob

Just run a braided strap to the hood

Really don't have to unless RF entering other equipment.

Ok cool thank you will go with stranded in rg58.

and some sort of flexable cable to base of nmo to inside engine bay to ground. I will do that easy bonus thing to do

I have a spare bandit noise supressor think its called i was hoping not to use so less junk in my install but do you guys run them? thank you for taking the time i just want to get the right info before i have a good at her

No, start simple.....just mount the @RagoFabrication bracket, install RG58 and antenna and try out the radio for a week.

If you have interference from the CB into the head unit, or have ignition noise in the CB, install a ground (or 2). Ignition noise in the CB is tough to remove, but I have ideas on how to do that. Worry about that down the road if it happens.

you want the hood as a counterpoise, its a large flat metal surface

This is true if the 1/4 wave antenna is mounted on the ground, building roof, etc then a counterpoise of 1/4 wave or multiples thereof is necessary. Very easy to calculate and install. Typically in a vehicle, grounding to the vehicle frame is primarily for RF abatement to the other electronics.

While it is not impossible to figure out the exact wavelength of the vehicle and compensate for an additional length of wire to a multiple of a 1/4 wave to compensate, it is impractical to do so for logistical reasons.

This argument can be debated infinitely but the real question is, what does the other receiving radio notice? Sure we can take db ratings at various distances, but for the practical 4Runner person, it's of little consequence. They only care if the other person can hear them!

Ground for RF interference and be done.....RF limiting chokes can be placed on the coaxial line and 13.8 VDC line as well for RF suppression.

I have installed maybe a 20 or so different mounts plus either helped or talked with dozens and dozens of others on vehicles mounts utilizing Motorola through the roof types, trunk clip on mounts, ball mounts, hitch mounts, on the glass mounts, mag mounts and the overriding major factor in every case was antenna placement on the vehicle. The more dead nuts center the antenna is, the better the radiated take off angle. The ideal for long distance communication is a very low take off angle that is unrestricted in all directions. Conversely for city dwellers, a higher take off angle is desired due to building interferences, but that's a whole different topic. I have tried grounding and ungrounding, ¼ wave lengths of wire extending from the antenna base for a true counterpoise and 1 thing in all those installs that I found mattered. Was I happy that the other person could hear me!

We could debate until next week! Thanks for allowing me to pontificate! Antennas of all types are my favorite subject!

no, ground planes (counterpoise) are very important on vehicles for transmission performance