antenna/swr frustration

Study a base CB antenna like the Alpha V-5/8 to understand a radial. Yes a whip is what was described by another and myself, you could use a metal tube just like the radial (grounded at the coax shield shell on the PL-259, insulated from the vehicle the rest of it's length) but it is long, the whole reason for using a whip in the mobile. Yes wire on a plastic rod works, in effect you just built a whip. Anytime you geometrically shorten or compress an RF component it performs worse. A stainless 102" works better than a Francis CB-25. A Francis CB-25 does not throw sparks from the pavement like the 102" would. Common sense. You find the best compromise which works for you.

 

I think I'm gonna start simple and build a base type antenna first, to get the basics. So, the shaft would need to be a full 1/4 a d the actual radiator would need to be 1/4, correct?

 

I would have a 1/4 antenna with a 1/4 counter poise. Keep the counter poise from grounding anywhere but the feed point. Then, raise the whole assembly on a mast. Sound like it may work?

I know I could just buy one, but this is mainly just for learning purposes.

 

Outlaw: Saw an antenna one time using two 5x5 Francis antennas........the word di-bar comes to mine as well. Does that in any way sound familiar???? Pictures would be nice if you know what I'm talking about.

 

No pictures. That was back before digital cameras, old 110 film was the best camera I owned back then. I still have a couple Di and a couple quad bars but where would you get the antennas today? I have not seen a Francis Wheeler Dealer or CB 50 Amazer in over a decade. I did build a dual quad bar setup once. Used RG-11 in a custom dual harness and eight Wheeler Dealers. Strongest mobile I ever ran using a pair of 600 Plus amplifiers. One on each quad bar and the dual harness feeding the amplifiers. Had to use a Ford starter relay to key power to the amps to stop them from keying each other up when you let off the mike key. The incredible bandwidth between 2:1 points was the real beauty of the quad bar.

Maybe later I will take a couple pics of the bars, minus the antennas and vehicle they were mounted on. OK it's later, two quad bars, a Di-bar, and one Di-bar spreader. All I have left except a couple old Francis Tunable tips.

 

You guys with your own trucks should be running one of these. I though the one I saw 5 or 6 years ago was using 5x5 Francis??? The guy ran for UPS and reported awesome improvement over a single antenna. But, the company saw it and made him take it off. If I drove my own/assigned truck..............

 

I set up many of them using a pair of CB 26 Francis antennas for the mail haulers between Billings and Fargo, mounted on the grab bar in the rear. I was told often that in all their years driving they had never in an 18 wheeler had such distance capabilities not to mention over 400 channels below 2:1. Plus the setup is more forgiving of poor ground and proximity to metal. You had to use two tunable tips for it to work right. One day Francis stopped producing them but I found if you took an aluminum anti theft door lock knob common at Checker and Auto Zone, drilled it the correct diameter where the inside threads were you could replace the rubber cap with them and epoxy in place. Worked identically to the Francis tips and was actually cheaper. Those were the good old days.

 

Pictures, pictures, we need pictures! These guys that drive an assigned truck ought to commission you to build them one of those. I do remember how impressed the UPS guy was with his......wonder if he still has it???????

 

Did some playing this weekend.



Will show it mounted once I do so. Will also report results.

 

I don't have any. It was the 70's and 80's, no digital cameras. The best thing I had was a crappy little 110 film thing for 20 bucks. I assume you remember how much it cost for film in an old Polaroid, probably the best camera I had until I spent a couple hundred on a 35 mm thing. And even then it never occurred to me I needed a picture of what I did all day.

Put out a general request for pics, a lot of people built Di-bar setups back then. Someone surely was into photography at the time.