Well, thanks guys. You've given me lots of good advice and good ideas. Next step is to just start experimenting.
It'll be a couple of months before I get the truck set up for HF but then the fun begins!
 I wish I had more experience in antenna theory and design but I just haven't been able to read through all that technical stuff.
If I happen upon the perfect radiator, I'll keep it to myself, patent it, and you all can keep me on the gravy train buying my stuff!
Thanks again.

Rande N4ZYV

you guys are so negative.

Actually the roof rack would be mounted on the fiberglass bed cap not the metal roof of the cab.

Ok then, capacitance on the far end of the bent-over whip because it is too close to the metal body of the truck. How much capacitance do you think there would be with about 1' foot of that end near the body? What effect would this capacitance have? Would I have to move the end very far away to reduce the capacitance to a manageable level? Could I just use a piece of plastic rod or pipe to move that end of the whip up to clear the body and fix this capacitance problem.

You see, I have read several threads about the short length of the mobile whip but I don't remember seeing any serious discussion on methods to increase its length. Any discussion I did see, revolved around making the whip taller and thereby hitting overpasses and low-flying aircraft. Why can you only make the whip taller? Why not just make it longer?

Its always said that a whip/tuner combo will not radiate well at lower frequencies because of the extreme difference in what is needed at low frequency to make a 1/4 wavelength and what can be dome with a 102" whip. Well then, lets make that silly whip longer.

What about these small loop antennas that have a tuner built into them? Iso-loop I believe is what one is called. How is that different from my fiberglass bed cap mounted roof rack? I know for certain that attianing the efficiency of a full size 1/4 wave vertical can't be done. But can we improve on the 102" whip/tuner combo?

In another thread in this same forum, someone is looking for a taller whip. Could this do the same thing without going higher?

Ok, so I feed one whip normally and tie the tops together, leaving the other whip unfed at its base. Now I have an 18' whip if I just bend tops together and weld them up. That increases the electrical length. Now I wonder about the voltages and current on the antenna and will the "top" of the antenna (which is now actually the bottom of the other whip) cause any trouble being that close to the body of the truck?
 
/\ like so, only the tops actually welded together.

I know there is current and voltage on the antenna that varies along its length. These can both get pretty strong as I understand it. So, having the "top" of the antenna bent over and attached to the other, unfed, mount puts it close to the body of the truck. Is this likely to cause trouble?

The idea of just going ahead and doing it to see how it works will just have to wait a couple of months as I need to spend my money on my old Mustang and my truck first (I don't yet have a mobile HF rig). Thought I would spark some conversation here to get a better grip on what I'm trying to do.

I could also build a roof rack for the fiberglass bed cap and feed that. How about a recangular loop antenna, 6' on the long sides and about 4' on the short side. Not a very big loop. I think the two whips tied together, either directly to one another or via another piece of stainless rod between them would give me the extra electrical length and allow the tuner an easier time of matching and also (hopefully) get a bit more signal out.

I'm kind of surprised that this hasn't been done before. Either it has and didn't work so good, or I just think wierd.

Ok, so a "T" is not the way to go. Electrical length is what I need to get. So then, if one of the whips is fed in the normal way, then another coax is taken to the other side of the truck to the other whip, wouldn't the radio see that like an antenna fed part way up the length? Like a wire that has the two 102" lengths plus the length of coax between them and that length of wire is fed 102" from one end? Problem is, the center section of the antenna would be surrounded by the braid of the coax run between the two whips. But wouldn't this create more elctrical length thus allowing the tuner to more easily match to antenna at lower frequencies? And with twice as much metal in the air, would'nt it radiate better?

If that is not wierd enough, how about two 102" whips, fed at the bottom of one and the two tops connected by welding a rod between the two tops. The top flat piece and the other whip would add to the length and but the other whip would have no coax attached to it. The mount would act as an insulator. The antenna would look like a tall, thin, square roll bar on the truck.

Impressing anyone was not the idea.

Forget it.

Not why I'm thinking of this. The problem with mobile antennas is the lack of length for the radiating element. So, instead of going longer, how about using two whips.

I'm not trying for directivity or gain. Just better effeciency at the lower freqs.

Thinking that more metal in the air is better, has anyone tried using two 102" whips and a tuner(s)?

I know nothing about and have never used a screwdriver or the whip/tuner combos. Was just thinking.

Many here have far more knowledge about antennas, being able to calculate radiation resistance etc. Has anyone done this in-depth analysis of a mobile antenna system using a tuner and two whips? Or, is there something simple and fundamental that I am missing? The idea being not for directivity, just somwhat more effecient tuning or radiation.

Clint does it! Thanks Clint. I was able to find a pic of Rohn BX tower and that's what I got.

Now, If I could just be sure what the antenna is. I haven't been able to find a pic of the Wilson antenna. I know it isn't a Hygain TH5mkII. The Hygain antenna has two traps per element and what I have has only one trap per element.

Ok guys, I have been given a 45' tall free standing tower. I'd like to figure out the manufacturer of this tower. I got the beam antenna also.

The tower is not tubular. It is flat, shaped steel. The cross braces are also shaped sheet steel. I can see no label or tag. I have been told the tower is about 25-30 years old (unreliable figure though). It is triangular. I am trying to identify the tower in the hopes of finding the base pieces that I will sink into the concrete base. Is there anything in particular to look for in its construction that would nail down who made it?

Now, the antenna. I don't know anything about beams like this. It has 5 elements. Two reflectors. The big one has a trap on each side. There is a smaller reflector closer to the driven element that has no traps. The driven element has 2 small aluminum tubes running parallel to the boom towards the two reflectors. This must be a matching section. The boom is aluminum with a center section and an extension at each end. The elements are tapered with one section in the middle and two extensions on each end and the traps. I can find no label or name. I am thinking the antenna is a tri-band, 20-15-10. It has a cable truss on top also. The elements are attached to the boom with aluminum, one piece, clamps that squeeze the boom with two bolts on the bottom and a flat top plate that uses u-bolts to hold the element. Some of the u-bolt holes have been wallered out due to the elements moving in the wind. So, I would like to find new ones if that is possible.

Any ideas on what to look for to help identify it?

Since the antenna is old, is there a method of testing the traps to be certain they are ok? I'd hate to put this antenna up and find out there's a problem.

If it's going to take photos to help me, who would be willing to look at them for me? I can get digital pics and email them. I could fab some base supports for it but would prefer to find some made for the purpose. I'm hoping the manufacturer is still in business and still makes what I need.

I got the tower, the antenna, and a Hygain tail-twister rotor for free. I just had to hire a couple guys and a crane to get them down ($450). To put the tower up, I would need some info from the manufacturer on what is required for the base.

I saw one tower locally that looked just like it and was told it was a Rohn. I'll be going back to look that one over better now that I have mine, so I can really compare the two. If someone out here has a Rohn tower like this, I would appreciate some pics to compare with what I have.

Thought this would be a good place to start. Thanks for any help and advice you guys can give.

Thanks Tim.

I might not have been clear on the installation. I am going to use 20' masts up on the roof of the house (about 15' at the peak) and the garage (about 10' at the peak) so the house end of the flat-top part would be about 35' and the garge end would be about 30'. I was thinking of using PVC at the base of the mast on the house because it will be held by a mount that will be in contact with the soffit fascia and that is aluminum. The garage end would be on the wood roof.

My lot is long enough to hang the G5RV as a dipole with the entire length flat, but that would mean having a mast at the front of my house and I don't want to do that. My lot is also very narrow at about 26' with most of the space taken up by the house and garage. So, radials for a vertical are out. Seems for now, some sort of dipole arragement is the best option.

Also, I am thinking having some of the antenna vertical would help. I don't yet know alot about antennas (can you beleive that?) but will be learning. I have been out of the hobby for quite a while but kept the license current. Putting up a tower is not something I really want to do here due to the narrow confines of my lot. Finances would rule out a tall tower right now anyway as I am making double payments on the house to pay it off fast. I could put up maybe 30' but that would be it. A multi-band beam would overhang my neighbor's property so that option is out.

I could hang a G5RV if I can shorten it up a bit. Perhaps only using the first 10' mast section on each end would be better. Anyone have experience with that? Since I am going to have 20' of metal mast, I thought using the entire 20' length at each end would give me some vertical polarization and shorten the antenna to move the house mast farther back. I have a cheap 15' tower section on the side of the house at the rear corner and could use a 10' mast for something else there. Perhaps a radial-less vertical like a GAP Titan. It seems the Titan should be ground mounted but that just isn't an option here. Anyone have any experience with mounting a Titan or something similar up about 25'?

Right now, I have a wire strung between the house and the garage with most of it about 5-10' off the ground and about 1/4 of it at about 20'. Overall length is about 100'. I figure if I get am amp, I could keep the local area free of clouds.


My friend, Jeff, has a farm with all the room one would need......the bum........he's on top of the highest hill for about 15 miles too....I hate him.....

Well, I guess I'll just put it up and not worry about it. Something up in the air is better than nothing....

Looks like I'm going to put up a G5RV antenna here. Just don't seem to have room or money for anything better. To get the 35' recommended minimum height, I'm going to use 20' of mast at each end. I'm thinking of using those two 20' masts as part of the antenna to shorten the overall length.  One mount will be in contact with the metal eave and fascia, so I must insulate the mast from the mount. I was thinking of using a short length of PVC to do this. How far should the bottom end of the mast be from the mount? I also read that there is high voltage at the ends, will the PVC stand up to this? Seems to me it should be ok but I'd like to hear opinions on that.
 The feed line is supposed to hang down for 34' but there's no way I can allow that. I can let it hang for about 20' but then it has to run horizontally to the house. Will that have much effect on the antenna? The horizontal run towards the house will not be inline with the antenna, it will be running off to one side anout 25-30 degrees. Should I let the hanging section curve to the horizontal, or should I tie it so that it hangs straight down and then turns sharply to the horizontal? Letting it hang and curve naturally towards the house would be my preferred method. To tie it off so it hangs straight down would require a line about 30 feet long to my garage and I just would rather not do that.
 
 
 

If it fits in my lot, the bandwidth is a negative number.

Any hardware store or home-improvment store should have it in their electrical department.

Interesting thread here as I am contemplating a mobile installation in my old IH ScoutII. I currently have just a 10 meter radio with a ball mount on the right rear sail panel just behind the rear side window.
 I am wondering about how to improve operation on 20, 40 and 80. Would mounting another whip on the other side of the truck and feeding them in phase help at the lower frequencies?
 I really don't know much about antennas (couldn't you tell?).