ladder line fed vertical

[Lazybones1222]

Thanks for the info.

I have almost decided on building a 40 meter 1/4 wave vertical, ~33.4 feet long with two 34.4 feet radials, (One north and one south)like an upside down T) and feed it with this ladder line:

http://www.w7fg.net/ladder/totower.JPG

Should be able to tune in 20 also, and maybe even 10. I have a Dentron Suer Tuner. It is awesome.

 

[HiDef]

Should be able to tune in 20 also, and maybe even 10. I have a Dentron Suer Tuner. It is awesome.

You have picked the best feedline possible without building it yourself.

That antenna will be too long on 10. Length cannot exceed about 20 feet either side of center before the radiation pattern starts to shoot straight up in the air. 40 feet centerfed vertically is about the maximum for low angle 10 meter radiation. Another compromise is when you put up the short version to keep 10 working well and load it on 40 where it is pretty short. That is where large feedline and a really good tuner pay off. The Dentron Stupid tuner is a good box but you may want to lose the 4:1 BalUn in some situations for a 1:1. Remember to use the tuner settings with the most capacitance for maximum power transfer.

2 radials aren't necessary. I really don't know if there would be much of a drawback to using 2 or more like you propose though. Results would be interesting.

Happy experimenting.

 

[Lazybones1222]

How do you loose the balun, it is rigged to the two posts for the ladder line.

 

[W5LZ]

Simple answer to 'loosing the balun' is to start taking things apart. I would replace the balun (if it's a 4:1) with a 1:1 balun. Not really much need for a 4:1 in most cases, who/what says the impedance is going to be 4 times whatever you want? I also think I'd try it with this 'as is' first. May not need to do anything.

This part is sort of being 'picky' about names, but it really does help when asking or figuring what something will do.
A "long wire" antenna is one that's length is 2 or more wave lengths long at the operating frequency. that typically means a really long antenna as compared to ones you normally see. Something less that 2 wave lengths long is called a "random wire" antenna. There's a lot more of those things around that are called by the wrong name than you might think. What's the difference? Well, a random wire antenna's performance is sort of 'random', not very predictable, a 'try it and see thing'. Some can work very well, some don't really do so good. A 'long wire' antenna is predictable in most cases. They exhibit some directionality depending on length, longer ones are more directional than shorter ones. Don't know about you, but I just don't have the room to put up a 'long wire' antenna for most anything below about 15 meters, and just barely enough room for 15 meters. Oh well, 'nuff of that.
- 'Doc