HF Antenna Mounting Considerations on the Freightliner Century

[kc8vje]

Hi all,

I'm in a bit of a quandary. I am leaving soon to go back out on the road for a small O/O, and wanting to take my HF radio out with me.

I will be in a Freightliner Century tractor.

My last truck was a daycab Western star which has an all metal cab, thus antennas weren't a real problem. The antenna I have to take with me is a Yaesu ATAS-120 to go with my FT-857D.

I have heard several different options from simply putting it on the mirror, to using the step on the fuel tank to mount it. Now, I realize that this antenna is a compromise in it's self, so I don't want to add insult to injury by having no groundplane.

I used to repair/install radios at the last trucking company I worked for, however everything was VHF and UHF and not requiring a huge groundplane. Most of the antennas were modified NMO mirror mounts that had radials attached.

Here's a couple of things I thought of.

I have a Comet CP-5M mount that I could use on the bottom of the truck where the tractor floor is, however, I don't know how sturdy nor how the groundplane would be this way. I also thought of using a non destructive mount, like a clamp mount with the little set screws to hook to the steps on the fuel tank, then bonding the step to the frame to keep down noise.

Any suggestions on where to mount the antenna would be most helpful.

I'm really iterested to find out some good solutions to this as this will be my primary radio out there besides the ol' trusty CB.

[kc8vje]

Bump...........

[Gadfly]

I'm hesitant to tackle this, but I've seen screwdrivers mounted on the side and secured to the mirror. You might try attaching one or more grounds to the metal floor and see if that works............................................



Gadfly

[kc8vje]

Thanks for the reply...

I went down to the company the other day and looked the truck over. It is not the type of century that has the exposed tanks (which I was kinda wishing it had), instead it has the fiberglass farings that cover the tanks from the hood to the drive axles.

I am unsure as to the composition of the floor in this particular type of truck, ie: all metal, plywood with metal ribs, etc...

Anyway, I figure worst case scenario I could mount it on the side at the floor line and bond both sides of the cab to the frame. Maybe it'll work.

That is, unless the steps are still electrically connected to the frame by the tank straps.

I am sort of against using a mirror mount with this antenna because I don't think it'll even tune without a good ground. I do have a solution for my Dual Band, Scanner, And Cell antennas. I have made a long groundplane/mount out of sheet metal and drilled 3/4" holes for the antennas. It's about 25" long by 4" deep. Not a great groundplane, but usable none the less. It will be mounted above the visor with heavy duty sticky tape.

So, right now HF is the major problem.

[Gadfly]

Is there any way to attach it to the back of the cab and run grounds down to the frame?


Gadfly

[kc8vje]

Hadn't thought of that......

Could do that, but wouldn't that alter the radidation pattern into 2 side lobes and a null at the middle? Given the presence of the sleeper and trailer (dry van).

I could be wrong though.. I'm sort of new to HF when it comes to installation and repair on comercial vehicles, I'm just going on past experience with VHF/UHF problems.

I know on my 4 wheeler the ATAS had some problems to begin with as I had to bond all the doors and hood to reduce radiated noise and by doing that I also was able to get a better match and a lower SWR. (it may not have been truly resonant, but it sure fooled the radio).

I guess it's just a trial and error thing. There isn't much on the net anywhere else on this topic as I googled it and came up with a bunch of junk.

[Gadfly]

*IF* you can get the coil above the cab--and that IS important--it should mostly negate any "lobes" or nulls. It might make it slightly directional from front to rear given the large van behind you. The one thing you might run into is resonant grounds where long, excessive grounds act like "antennas" and allow RF to travel to places where you don't want it, or cause wierd things to happen---wipers to come on, strange noises, engine slowing down when keying the radio, or, perhaps, getting "bit" by the mike. If you can find a way to deal with the grounds, actually, getting that ATAS antenna up near the top of the truck, you would likely have a FB signal inspite of the low "Q" of the ATAS.

Consider this, too! It is possible to mount the ATAS sideways INSIDE the sleeper cab out of sight! WHAT?????!!!!!! This can be done with a regular screwdriver across the back of the cab, whip on the CB mount! If, as you say, the cab is non-metal, then you can attach the body of the SD at the very top of the cab, then bring grounds down to frame. attach the top of the coil via regular, flexible wire. then ground the the bottom of the screwdriver/ATAS body via non-resonant grounds to frame. I know this sounds wild, but there are pictures in Don Johnson's sequal book, "Everything you FORGOT About to Ask About HF Mobileering". His illustrations show a pickup truck with a fiberglass camper shell with a screwdriver mounted up inside the shell. A ball mount is installed on the non-conductive shell up near the top in the usual way, then the whip is installed on the ball making it look like a normal "CB" station. REAL "stealth"! Remember to mount the ATAS body so the loading coil can move as usual! There is NO reason this can't work, and with your familiarity with radio, you could install this easily. It IS an intriguing way to mount it!!!! And it gets it up out of the way. You can even lean the whip forward like the "BAD" boys and make it look "cool"!
They'd never know that there was a "hammie" station in there!


73

Gadfly

[kc8vje]

I might try that...

I actually remember seeing the horizontally mounted screwdriver with external whip before. There's a guy here local that has one similar to the "camper shell" design you spoke of. Never did get to see it in action though.

I know I'm gonna upgrade antennas ASAP, just need to get money before I can. (Hence the job change) The coal business has all but dissapeared down here.

I think my next antenna will probably be either an Icom AH-2B and tuner, or an SCG whip and Super Tuner. I'm kinda waiting until Dayton Hamfest as this run I'll be on will have me through Dayton 2 times a week.

And "Oh Boy", when I get there, The first thing I'm gonna do is get me an Icom IC7000 and a new ant and tuner.

Daddy wants a 7000!!!! Actually a 7800, but momma don't like the 10k price.

She about had a coronary when I came home with a Motorola R2001A Service Monitor last year and found out it cost 3200.00!!!

[kd5drx]

I will throw my 2 cents worth in here after a million miles of HF mobile operation in a big truck. First as you have said the ATS is a compromise antenna and really want work well for you from past experiance I have seen to many of them tryed and they wound up going to a true screw driver type antenna. My suggestion is bite the bullet and get your self a Band hopper and mount it off the grab rails on the sleeper on the drivers side with the stinger right at 13'6" this has worked well for allot of other drivers and the initial expense is more than offset by the durableity of the antenna and the performance. You only have to run the grounds to the frame from there and it works great. HF needs no real ground plane do to the take off angel of the antenna they work real well on mobile set ups. If you do use the ATS you can monut it between the cab and the trailer on the grab rail in the back and then run your ground to the frame and it will work but like i said and you allready know it a compromise antenna at the least and does not work well below 20m it is almost useless. Just a word from one that has been there done that and learned some expensive leasons doing it. The band hopper is at [LINK POSTED BY MEMBER] Only Members Can View This Truck Forum Link. if you want to look at it and some of the installs they have there.

[kc8vje]

I like the price of the Bandhopper.....

I also thought of the High Sierra screwdriver as well, but till money gets a flowin' again, the ATAS-120 will have to do.

I do like your mounting suggestion. I could mount the antenna on the rear grab rail and route the coax through the sleeper floor.

Good thing I just bought some more bonding braid. Probably will need quite a bit.