Horizontal dipole using telescopic whips

[Sergeant Bilko]

While trying to design a 10-12 meter horizontal dipole for use in a portable installation, I'm trying to decide if it's better to utilize 2 standard stainless steel whip antennas, cut resonate for 12 meters and utilizing a stainless steel coupler to extend the tips to resonate at 10 meters when on the 10 meter band...

Or...

Utilize heavy duty 10 foot telescopic whips, marked at the 10-11-12 meter lengths, and simply extend to the desired length and fine tune with an antenna tuner.

Can a telescopic antenna be made resonate when partially extended?

 

[oldtymer]

Never tried this yet but looks interesting
http://www.hamuniverse.com/kl7jr1012wirebeam.html

 

[Sergeant Bilko]

Actually, I'm starting to lean towards three pairs of tuned whips, each with a roll pin inserted through the wrench flats to facilitate a wingnut kinda thing. This way, depending on what my SDR is showing, I can quickly connect the band specific whip pair, hoist, then fine tune with the antenna tuner and key up.

This dipole assembly is being mounted on an extendable fiberglass mast that is mounted to the headache rack in my semi truck. When I shut down for my 10 hour sleeper berth, I can scan the 10 and 12 meter HF bands for action with the SDR, jump up on the catwalk, quick time the antenna pairs to the mast, hoist and have me some ragchew.

 

[Captain Kilowatt]

I think you mean make the dipole resonant on 10m and add extensions for 12m. Personally I would go with one dipole that was telescopic and just mark the tubing at the points you want on 10m 11m or 12m.

 

[w9cll]

How about making a "fan" dipole for those three bands?

 

[fourstringburn]

an a telescopic antenna be made resonate when partially extended?

Yes,

The overall length in 2 even sections will determine the resonate point of the frequency/band.

It would be easier to get 2 sets of tubing (one for each dipole side) with one set slightly smaller than the other to slide into it for a telescoping effect. Then just mark the inner tubing for each band you want at the optimum length. Drill holes below those points and secure it with an easy removable bolt for quick adjustments like a wingnut, clevis pin, cotter pin, etc.

MFJ sells telescoping whips ready to go but you can rig up something for less $.

This one will work for up to 12 meters but you"ll need of them. You"ll need just under 20ft overall length for a 1/2 wave 12 meter dipole.

https://www.mfjenterprises.com/Product.php?productid=MFJ-1976

 

[fourstringburn]

cut resonate for 12 meters and utilizing a stainless steel coupler to extend the tips to resonate at 10 meters when on the 10 meter band...

You have that backwards.

12 meters (24.890 - 24.990 MHz) requires a longer antenna than 10 meters (28.000 - 29.700 MHz).

The lower the frequency, the longer the wavelength and the longer antenna is required.

 

[Sergeant Bilko]

Yup, i did type that backwards. Derp. I considered a fan dipole but, it's all about the deployment. I need something that can go up and down with minimal conflict while mounted to the back of a semi truck. There are proximity conflicts all over the bottom 13 feet of elevation. I started thinking about Breedlove folding mounts but, that's added cost for multiple antenna side pieces, and I could probably more easily deploy a dipole by threading in two whips horizontally then I can trying to erect them from a folded position. The telescopic option definitely has potential. Fortunately, I'm still in brain storm mode with this so, I'll mentality stress test each option in my mind and make a call.

 

[BJ radionut]

https://www.mtcradio.com/texas-bugcatcher-photos/

http://www.kj7u.com/

https://www.dxzone.com/catalog/Manufacturers/Antennas/HF/Mobile_Antennas/Screwdriver_Antennas/

 

[Sergeant Bilko]

https://www.mtcradio.com/texas-bugcatcher-photos/

http://www.kj7u.com/

https://www.dxzone.com/catalog/Manufacturers/Antennas/HF/Mobile_Antennas/Screwdriver_Antennas/

All of those are real nice however, I have a DOT hight limit of 13.5 feet, and the top of the truck is close to 12 feet so, it has to be collapsible in order to be legal on the road. That's why I'm going for a telescopic fiberglass mast with either folding or removable elements. It cannot be used while underway. For that, all I have is my 11 meter tuned cophased predators.

 

[BJ radionut]

https://www.tarheelantennas.com/big_rig_photos

As you can see many ways to adapt these very good antennas to Big Rigs.
Some really good op's on this site have done so.
I have worked many-many Big Rigs on HF running these types. Most can be mounted for road use...or as portable set-up like your thinking, they can be adapted to remove quickly. The Best part of these is tunable from inside the cab and can handle various power levels from 100 watts to a Kilowatt if need be.

https://www.opekantenna.com/proimages/20090806093505_1.pdf

Here is another option, which is adjustable and could easily be set-up and removed. Or when parked 2 could be used in a "L" configuration (like a Dipole) and used on multiple bands with small tuner.
Just some thoughts Sarg:...
Having run HF Mobile many years with great success.
I worked Mexico from Mobile couple weeks ago coming out of Chicago on 6 Meters.

I hope some of these other Big Rig guys chime in, These fine op's can offer some really good ideas which should prove to be much more versatile and better options/More bands/ better efficiency etc... Producing better RadioFun as you move thru HF operation while on the road.
GL
All the Best
Gary/W9FNB

 

[AudioShockwav]

For static horzontial use between the options you listed in the original post, I would choose to use the telescoping whips and mark them for the different bands.
Fast, easy to remove and you can quickly adjust them for the band you want to use.
The Screwdriver antennas are the way to go if you want to cover the rest of the bands with a full on HF radio .
I take it from your post above that you are only concerned with 10 thru 12, running horzontal, and your idea with the fiberglass push up is easy for what you want to do when parked.
73
Jeff