Topband: Inverted L SWR Jumps ???

[Ashton Lee]

Ok, everyone thanks for all the help.

I rebuilt the antenna from new wire, built a two insulator termination at the end of the horizontal section where the high voltage is, I rehung the new antenna so that it doesn't touch anything… and the problem persisted. I then looked into Tom W8JI's suggestion about a bad lightning arrestor, and indeed that was the problem. I had blown the little cartridge in my Alpha Delta lightning stopper.

I don't know why the issue only showed up on a single antenna of the many I have fed through that device. But it did.

So Tom, thanks in particular.

I did leave the choke balun in place. Who knows if that makes a difference? 

Everyone, please listen for the weak signal from Western Colorado this weekend.

KQ0C
Ash


On Nov 28, 2012, at 10:30 AM, "Tom W8JI" <w8ji at w8ji.com> wrote:

> Remove the balun. It's not doing anything for your and is a potential source of loss and problems. Coaxial cable is unbalanced, as is a ground-fed inverted L. No need for a balun. >>>
> 
> Unfortunately, that is not a universally true statement.
> 
> MOST antennas are in a "neither" world of being neither perfectly balanced nor perfectly unbalanced.
> 
> Perfectly balanced would be equal and opposite currents entering and leaving each conductor at each end of a balanced line, with equal voltages to the world around the line from each conductor.
> 
> Perfectly unbalanced  would be the same equal and opposite currents entering and leaving each conductor (shield and center) at each line end, and zero voltage from the shield to the outside world around the line.
> 
> Very few antenna systems meet that criteria, although Marconi systems with many radials are close enough to be nearly perfectly unbalanced. Significant departure from UNbalanced occurs when radial systems are sparse, or truncated, or the feedline exits above the plane of the radials. There isn't any clear boundary, but a slow system dependent transition from the perfect case (feedline exits below the radial plane and an infinite full size radial system) to the worse case (a single radial of any design). Even four 1/4 wave radials have significant voltage to "ground" at the common point.
> 
> Choking impedance required varies with the number, configuration, and length of radials and how the feeder is routed and grounded, and in nearly all cases a few hundred ohms is enough. An exception might be if the ground system common point has abnormally high voltages to earth (for example, a single truncated radial) or if the coax is elevated and coupled to the antenna.
> 
> 73 Tom
> 
> 
> 
>