Big Truck: Dipole Antenna Install

[slowmover]

Can’t get the immediacy of a dipole for big truck out of my head. The typical vertical can take more than a day of work to route coax and install RF bonds.

When one is assigned another fleet tractor, the leisure to do that work (if ever done) is off in the future. I figure that a sort of pre-assembled antenna rig of this type might exceed vehicle manufacturers antenna, and be easily transportable.



Put things together while stationary a few days.

MFJ-347 dipole hamstick mount

TopGunTec Z-Perch spot mirror mount.

Francis CB26 5.5’ antennas

Palomar Engineers MC-1-50-500 Line Isolator/Mini Choker

RG-59 jumper to radio.

Spot mirror mount shown. (Will continue; shipper finally finished my load).

 

[prcguy]

If the cab or most of the front end of the truck is fiberglass a dipole should work better than most any other type antenna. I was doing this in the mid 70s working out of a shop in Colorado Springs, CO and we got a lot of big rig customers. I came up with the idea trying satisfy some difficult installs and I had never heard of anyone else using a pair of CB whips to make a dipole before. I usually went with a 4ft or so Firestick top antenna and something smaller like a 2 or 3ft Firestick for the ground side on a mirror mount.

 

[slowmover]

Yessir, I’d cross-referenced the term in a forum search against your user name as I’d seen you mention it. Then went back to an online search and re-read some of what I’d tried (and posted) before. Have a little more savvy with each passing year.

The truck body is composite (we all call it plastic; “plastic trucks”), and from windshield back above the frame (top entry step is co-located) there’s substantial metal structure to hold that skin (but not as with cars where crash protection is paramount). With a burnt truck it can be seen there isn’t much metal above frame past windshield/firewall header.



Another angle. This is maximum distance outwards from cab obtainable with this mount. In any event, wouldn’t want to get any farther out than mirrors.

I canted it forwards slightly so as to get lower (cold) antenna away from metal entry steps (frame height). The upper (hot) antenna thus has more clearance over its length than when perfectly vertical. Plus gets total height down closer to 14’



Below is the Z-Perch after using two (2) layers of 3M Temflex with (2) layers of Scotch 88 as overlay.

— My current understanding is to have no electrical continuity between antenna mount & body

A rubber wedge was obtained to hold the mount rigid, and more Temflex used to insulate mount at door on three surfaces.



Took it apart this morning after a day of use before breaking out the DVM.

A). It’s better in TX distance than the factory HIRSCHMANN Thin-Film Antenna molded into the plastic above the windshield. It seems comparable with a slight edge in RX.

B). OTOH, it’s nowhere near the RX quiet & distance of the Sirio Performer 5000 on the drivers mirror (coil atop 44” SS shaft, whip stretches length to 84”) which also tops at 14’ (15-degree cant built into P4 mount). Nor the TX distance (I was in a truck crossroads heaven at two locations near or in Fort Worth).

This is more expense than most would want if considered temporary. But it’s a step in the right direction if better-than-factory is desired, thus expense can be mitigated by choices other than the ones I’ve made (gear I’ve had for years).

I’m not done. It’s a start.

(More detail below now basics covered).

 

[slowmover]

From a 2012 thread

“ . . One trick we used 35yrs ago was a pair of Firesticks with factory 75ohm phasing harness mounted to the mirrors and a second short pair (3ft was the shortest at that time but 2ft would work) inverted and grounded mounted to the same bar of the mirror.

This makes each antenna a dipole, improves matching and relieves some of the problems of inadequate counterpoise or ground plane on a fiberglass cab.”

prcguy


— Not clear to me if cold antenna should have “ground” with truck via mount, not simply coax shield.


— Am using RG-59 jumper made up by a CB shop. Straight to radio. (Have 50-ohm jumper with me; LMR-400).


— SWR is 3.0 on Ch 1, and 4.0 on Ch 40 (20 seems midway). Also didn’t get out separate SWR meter, just used display on the Q5 (which was consistent with that meter on other antenna).

A 2:1 Balun is mentioned by some.


Am looking for all advice & suggestions on what to test (and how), what maybe to change, and what goals seem reasonable.

My own goal is one thing. I’d like this thread to represent a starting point for other truck drivers which is why I’ve written it in the manner displayed.

I know just a little. Other drivers may be starting totally from scratch. Thus would prefer we take time with detail for those men. (Links welcome even if seemingly above the heads of “dummies”; I believe He provides insight for those who seek).

Mobile is different, and big trucks are weird enough variants on that.

Big trucks also represent the significant income in many families. To those men I wish to be of service via this thread and related (see B-T 12V power source upgrade).

The highway has become significantly more difficult this decade.

Thx

.

 

[slowmover]

I also have a collection of fiberglass antennas at home in varying lengths, from 4.5’ on up to 7’. Tune-able tips. Chose the Francis for least wind load and their advertised lowest need for tuning. I’ll be glad to use others if recommended.

Other choices in stainless steel for antenna mounts versus common (soft) aluminum from same manufacturer:

TopGunTec

Top Gun Stainless Steel Antenna Mounts

Top Quality and Heavy Duty All Stainless Steel antenna mounts designed to provide the best alternative when traditional antenna ground planes are not available.

www.topguntec.com

I have most of these. Pro-Comm is the likeliest source for fleet tractor antenna mount gear.

— DIY flat bar drilled to accept antenna studs another path given truck location “strength” plus low interference (if that’s the word).

Coax Cable Length I’m using is six feet. It’s a little short when opening the door. Nine feet is ironically about right if radio is dash-top mounted.

To fit thru window I’m using a snap-over ferrite:


Any sort of “hard collar” thru which the coax & PL-259 end can slide will work (PVC pipe). I ensconce it in memory foam a few inches thick to fit in opening and run window glass up to close against it. (Work out position front or rear of glass to accommodate door open & close).

Idea is to have gear ready to attach to truck and run coax to radio. Be ready to run in an hour or less given needs for 12V also accomplished.

Antenna Tuning remains, but RX would be fine until then.

On that subject, does anyone think the FTL brand embedded antenna poses de-sense (?) problems when not in use? (From backside centered above windshield).



FTL brings dirt-cheap coax from this to overhead console center radio mount in Cascadia along with 12V in super-light AWG (noise can be detected) from fuse center to hook up radio.


This is your 30% of all fleet tractors (set up to pull enclosed vans). Embedded antenna above center clearance lights.

An ordinary truck driver hooks up a Cobra 29 or Uniden 880 and can’t hear much nor reach out very far (1/2-mile to a mile) even though the radio is capable of more.

Given an AM/SSB radio with integrated NRC (and addition of an external speaker), RX distance goes up, but 12V and TX need a great deal of help (to reach five miles consistently under good conditions). Staying out of trouble means being able to Hear, and Get Heard.

2023 Best Mobile CB

Via mobile experience as an OTR truck driver. Several thousand hours annual use. Earlier references to the Qixiang factory’s new circuit board elsewhere. Several brands. The above possibly the best known example at present. Paired with the equally new Driver Extreme DRX-9010 External Speaker...

forums.radioreference.com

The latest dipole go-round above had me near to that in RX, but I wasn’t there for TX (with radio & speaker from 2023 thread).

One hears what he thinks is a warning: it needs defining (location & type), and it needs confirmation. Then one may need to find a diversion route if truck travel-approved for that.

Definition, Confirmation, Solution.

And it’s all with other mobiles heading to different compass points at 60-75/MPH.

No time to waste.
.

 

[slowmover]

Second Consideration for a Dipole



For truck drivers reading along:

My backup radio is a Galaxy 86V I purchased off a man a few years back. It’s the same size as a 979 (smaller case size as that was once reckoned; the 99V2 and 959B are its large-case siblings).

SSB is pretty good on all (4) of these. But not on that embedded antenna.

I “get it” that most truck drivers aren’t interested in Sideband. Until the day it’s time for ET to phone home (SHTF, etc).

On that day to get home may have new difficulties. Sideband may be an ace-in-the-hole to find out what’s going on at much greater distances. Pre-arranged comms with home base station, etc.

Why get a faincy radeeoo if the antenna system ain’t up to par?

I can talk Skip somewhat with the Sirio, and I can hear some mobile truck operators on LSB when things are hot (solar propagation). Those “old” Galaxy’s (design) can still be competitive even if not up to latest standard (NRC).

The first Dipole attempt got that edge established above the factory antenna.

(Installation was a breeze compared to getting a typical antenna installed, bonded, and tuned).



For John Q. Public: Citizen Band is today for The Few. Seems most will disregard or deny it’s utility.

Contempt prior to investigation.

— What the majority will or won’t do is beside the point of the principle in this thread.

— I had to run 100-miles from SE to NW across the D/FW metro late yesterday with a 43,000-lb load and altered course four times based on radio reports and slower GPS data to effect a good exit in the timeliest manner given all eight million residents appeared to also be on the road, F’ng up right & left.

I couldn’t change the five hour delay at the shipper, but I’m 45-60/minutes ahead of where I would have been without a good radio system.

Today it’ll be cattle haulers and Oversize loads plus some oilfield and dairy across the rest of my route. No sweat.

I did my part to reduce the lateness of delivery to the receiver. I “should” still be able to get the pre-plan next load on time: Experience . . and a damned good radio.

Antenna system matters most.


.

 

[prcguy]

From a 2012 thread

“ . . One trick we used 35yrs ago was a pair of Firesticks with factory 75ohm phasing harness mounted to the mirrors and a second short pair (3ft was the shortest at that time but 2ft would work) inverted and grounded mounted to the same bar of the mirror.

This makes each antenna a dipole, improves matching and relieves some of the problems of inadequate counterpoise or ground plane on a fiberglass cab.”

prcguy


— Not clear to me if cold antenna should have “ground” with truck via mount, not simply coax shield.


— Am using RG-59 jumper made up by a CB shop. Straight to radio. (Have 50-ohm jumper with me; LMR-400).


— SWR is 3.0 on Ch 1, and 4.0 on Ch 40 (20 seems midway). Also didn’t get out separate SWR meter, just used display on the Q5 (which was consistent with that meter on other antenna).

A 2:1 Balun is mentioned by some.


Am looking for all advice & suggestions on what to test (and how), what maybe to change, and what goals seem reasonable.

My own goal is one thing. I’d like this thread to represent a starting point for other truck drivers which is why I’ve written it in the manner displayed.

I know just a little. Other drivers may be starting totally from scratch. Thus would prefer we take time with detail for those men. (Links welcome even if seemingly above the heads of “dummies”; I believe He provides insight for those who seek).

Mobile is different, and big trucks are weird enough variants on that.

Big trucks also represent the significant income in many families. To those men I wish to be of service via this thread and related (see B-T 12V power source upgrade).

The highway has become significantly more difficult this decade.

Thx

.

If your asking if the grounded dipole should be grounded to the truck chassis, no it would be best if the two antennas and mount were isolated from ground but a small or moderate amount of metal like a metal mirror should be ok. The snap on bead shown above is useless by itself and depending on the ferrite mix you might need 10 to 20 of them to be an effective RF choke at 27MHz. And even then you will max out around 20dB isolation where using a large ferrite ring and wrapping the right amount of turns can get up to 30dB isolation.

 

[slowmover]

Okay on isolated mount. Need to test it to be sure. (Details of how are above).

Ferrite is only a crush collar at window. (Details above)

Choker at antenna and coax filter at radio.

2:1 Balun (?) and whether 75-ohm is best choice for a single.

Looking for things to try.

Thx

 

[prcguy]

Okay on isolated mount. Need to test it to be sure. (Details of how are above).

Ferrite is only a crush collar at window. (Details above)

Choker at antenna and coax filter at radio.

2:1 Balun (?) and whether 75-ohm is best choice for a single.

Looking for things to try.

Thx

A full size dipole in free space is close to 72 ohms but when you shorten the elements with loading coils it lowers the impedance. When you place it close to the ground or large metal objects it can also lower the impedance so I would expect a loaded CB dipole on a truck to be close to 50 ohms, could be a little higher or lower.

If the dipole is completely isolated and tuned properly both whips will radiate equally. If the grounded dipole is connected to a substantial piece of metal then it may not be able to tune up and the dipole will become unbalanced forcing RF currents onto the coax. If you can swap the top and bottom dipole after its tuned and it doesn't affect tuning, that would be a good sign that its balanced. If the match gets worse then the mount or the coax is having too much influence on things.

 

[slowmover]

A full size dipole in free space is close to 72 ohms but when you shorten the elements with loading coils it lowers the impedance. When you place it close to the ground or large metal objects it can also lower the impedance so I would expect a loaded CB dipole on a truck to be close to 50 ohms, could be a little higher or lower.

If the dipole is completely isolated and tuned properly both whips will radiate equally. If the grounded dipole is connected to a substantial piece of metal then it may not be able to tune up and the dipole will become unbalanced forcing RF currents onto the coax. If you can swap the top and bottom dipole after its tuned and it doesn't affect tuning, that would be a good sign that its balanced. If the match gets worse then the mount or the coax is having too much influence on things.

Great. Stuff to try!!

Thx

.

 

[slowmover]

 

[slowmover]

May have time the next few days to experiment with what I’ve got with me while on the road. DC Ground, Ohm-meter applied, etc, to get mount isolated.

Then,

Picked up some shorter Francis antennas while in Nebraska, and a new RG-58 jumper to compare against the RG-59. New SWR meter as well.

Have two (2) each of 5.5’; one (1) each of 4’ & 3’ of these antennas:

CBXX - Francis Hot Rod Fiberglass CB Antennas (Select Color & Length)

CBXX - Francis Hot Rod Fiberglass CB Antennas

www.wearecb.com

— Description outlines their different design approach (meaning not really tune-able; leave’ em alone is the idea).

With two (2) antenna systems on the truck, I ought to be able to get some feedback from other drivers switching between them.


As in earlier post it’s the very light weight and very low wind load that gave them the nod (as mount location isn’t best for either weight or load).

Further re-cap:

If this can be made to work, then it’ll be a component list & some instructions for other drivers wanting to get around low quality factory set-up for better performance at relatively low expense + ease of installation.

— A Rig Expert 55 is on my purchase list, so that’ll be applied to this as well. (Some more data offered).

Other mount locations may be tried as well.

.

 

[slowmover]

They kept me moving, so no time to experiment.

1:1 Balun

All About the 1:1 Current/Choke Balun

How a 1:1 Guanella-Balun (Current-Balun) Operates By Jerry Sodus, KM3K In the spirit of the hobby, I pass along what I have learned and don’t profess to know all the answers. 1. The primary reason for this work is to explain how a particular Transmission-Line-Transformer (TLT) known as a 1:1...

www.balundesigns.com

Picked up a Driver Extreme SS DX-185 6.5” Mounting Bar (M8 thread) to also try this antenna at the more conventional location of the rear view door mirror versus the spot mirror location in use (where most drivers would prefer to mount them is my guess).

 

[slowmover]

Here’s an example of a mounting bar dipole:



Info is scarce. I also don’t recall whether this system was tested with an antenna analyzer, or against a more conventional antenna set-up at this location.

— One doesn’t see a 1:1 Balun (current choke of some type) in use at the feedpoint.

This “edge” in performance may be what separates experience desired today against that of the drivers who were slip-seating in the 1970s and using Vise Grip attached dipoles as they moved from one tractor to the next.

“West Coast” mirrors were the order of the day. Cab-over tractors the norm. I don’t have a technical description or a picture of how it was done. But oral history of such is common.



The mirror arms made it possible to have gotten the antenna substantially farther away from the cab than I’m able.

Lagniappe: Cold start of a two-stroke V-12 Detroit Diesel.

.

 

[KMG54]

Just don't ever overfill the oil in that beast, bet you know what will happen! Better have good brakes or a manual fuel cutoff in the cab, and even that won't help much.

 

[slowmover]

Stuck at Denver on National CB Day (10/4/23). Weather finally nice (no rain or winds; with moderate temps), so . . maybe tomorrow.

Bumped this so I can find it.

Paired the 86V Galaxy with a stock mic (great sound) and the cattle haulers unloading 1.5-miles away nearly around the clock should be good respondents. (They check in/out on CB).

Tried this GALAXY mic awhile back (came with my MY2021 959b), and was surprised at how good it was. Can’t recall it as recommendation, but it has mine.



The Dipole Test will be pretty much with same gear as what the cattle taxis run: an export radio (but as an upgrade thru a KES-5 extension speaker).

Their passengers never whine, “are we there yet”?



.

 

[prcguy]

From a 2012 thread

“ . . One trick we used 35yrs ago was a pair of Firesticks with factory 75ohm phasing harness mounted to the mirrors and a second short pair (3ft was the shortest at that time but 2ft would work) inverted and grounded mounted to the same bar of the mirror.

This makes each antenna a dipole, improves matching and relieves some of the problems of inadequate counterpoise or ground plane on a fiberglass cab.”

prcguy


— Not clear to me if cold antenna should have “ground” with truck via mount, not simply coax shield.


— Am using RG-59 jumper made up by a CB shop. Straight to radio. (Have 50-ohm jumper with me; LMR-400).


— SWR is 3.0 on Ch 1, and 4.0 on Ch 40 (20 seems midway). Also didn’t get out separate SWR meter, just used display on the Q5 (which was consistent with that meter on other antenna).

A 2:1 Balun is mentioned by some.


Am looking for all advice & suggestions on what to test (and how), what maybe to change, and what goals seem reasonable.

My own goal is one thing. I’d like this thread to represent a starting point for other truck drivers which is why I’ve written it in the manner displayed.

I know just a little. Other drivers may be starting totally from scratch. Thus would prefer we take time with detail for those men. (Links welcome even if seemingly above the heads of “dummies”; I believe He provides insight for those who seek).

Mobile is different, and big trucks are weird enough variants on that.

Big trucks also represent the significant income in many families. To those men I wish to be of service via this thread and related (see B-T 12V power source upgrade).

The highway has become significantly more difficult this decade.

Thx

.

For a single dipole you should be using 50 ohm coax, the 75 ohm coax I mentioned was part of a dual mirror antenna phasing harness, which is not what you have. I would not ground the mount if possible, that can unbalance the dipole.

 

[slowmover]

For a single dipole you should be using 50 ohm coax, the 75 ohm coax I mentioned was part of a dual mirror antenna phasing harness, which is not what you have. I would not ground the mount if possible, that can unbalance the dipole.

Thanks for the update. I’d seen that recommendation on 75-ohm elsewhere, also.

Still don’t have a RigExpert (haven’t gone past an HRO of late), so this’ll be Step One.

Finding a few unencumbered hours out of the heat hasn’t been possible till now.

.

 

[slowmover]

“ . . using a large ferrite ring and wrapping the right amount of turns can get up to 30dB isolation.”

My attempts in past wrapping Mini-8 weren’t too good as to performance.

Used the well-known chart.

Latest reading brought comment that turns tightly wrapped was an ideal.

Tight wrap isn’t what I achieved. I was worried about “crush”. Large (2”) loops used with Mini-8 per some reference now forgotten.



— What coax type would be recommended? Just how tight, or does it matter?

58, and looks like above would be easy enough with (8) turns?

I have RG58 & Mini-8 jumpers. Can acquire other. Still have RG59 aboard. An FT240-31 toroid.

For now I’ll use the P-E feedpoint choke, but it’s an expense I don’t want to recommend to others, nor is it easy to securely attach.

Thanks, @prcguy

Post Reference:

Post in thread 'Question about pass through cable and SWR Flip-Flop...'
Question about pass through cable and SWR Flip-Flop...

.

 

[prcguy]

“ . . using a large ferrite ring and wrapping the right amount of turns can get up to 30dB isolation.”

My attempts in past wrapping Mini-8 weren’t too good as to performance.

Used the well-known chart.

Latest reading brought comment that turns tightly wrapped was an ideal.

Tight wrap isn’t what I achieved. I was worried about “crush”. Large (2”) loops used with Mini-8 per some reference now forgotten.

View attachment 149222

— What coax type would be recommended? Just how tight, or does it matter?

58, and looks like above would be easy enough with (8) turns?

I have RG58 & Mini-8 jumpers. Can acquire other. Still have RG59 aboard. An FT240-31 toroid.

For now I’ll use the P-E feedpoint choke, but it’s an expense I don’t want to recommend to others, nor is it easy to securely attach.

Thanks, @prcguy

Post Reference:

Post in thread 'Question about pass through cable and SWR Flip-Flop...'
Question about pass through cable and SWR Flip-Flop...

.

9 turns through a FT-240-31 core makes a very good broad band choke for 80-10m, a good 20dB isolation at 40 and 10m with about 30dB on 20m. On CB/10m only you can do better with an FT-240-61 core but I forget how many turns to use at the moment. For a stand alone choke I use RG-142B/U Silver/Teflon coax which will handle more power than you can make. I also pun a male connector on one end and a female on the other.