Balun and Heliax

[Cajun Invader]

Do you have to still use a balun if using heliax to prevent CMC?

My concern is this. I have 100' of LDF4-50A Andrews. If I put a balun on the feedpoint of the antenna I can't make it out of the hardline so I would have to use something like RG 8. Doesn't that defeat the purpose of having the hardline in the first place?

To me it seems like having nice rims and bald tires.

 

[Captain Kilowatt]

Use a good cable like RG-213 or LMR-400 for the balun. Many stations have to use a coaxial balun when running heliax and do that. It's no differant than running heliax up to the rotator and then using a good RG type cable to get around the rotator to the antenna. The few feet required will not have any noticable loss.I have three runs of Andrew LDF4-50 going to the top of the tower with several feet of Belden 8214 going past the rotator to the antenna. Works well even on 6m and 2m.

 

[Cajun Invader]

That sounds reasonable. How about from the radio room? That heliax is some stiff stuff. Could a sacrificial run of coax be used from the output of the amplifier to a coax panel to join the hard line or would that introduce problems?

I was also wondering where to attach the balun. I know it should go at the feed point but on this antenna the ground radials are at a 45 degree downward slop. Does the balun need to be below the radials to be effective?

 

[Captain Kilowatt]

All my feedlines come into the basement and terminate right below my operation position. I use about ten feet or so of Belden 8214 to connect to my heliax and bring it up into my shack.As for the balun placement, right at the feedpoint is the best place. Don't worry about what the radials are doing or where they are positioned.

 

[Cajun Invader]

All my feedlines come into the basement and terminate right below my operation position. I use about ten feet or so of Belden 8214 to connect to my heliax and bring it up into my shack.As for the balun placement, right at the feedpoint is the best place. Don't worry about what the radials are doing or where they are positioned.

What did you use to terminate into? I'm trying to figure out the best way to run this heliax. I have no experience with it at all.

 

[Captain Kilowatt]

What I meant by my heliax terminating in the basement below my operating position was simply that they end there and connect to the flexible coax via a UHF barrel connector and PL-259's. Actually I have female SO-239's on the shack end of my heliax and simply connect the male PL-259 from my Belden directly to it.The main thing about heliax is not bend it too sharp and kink it. You do that and you are screwed. Installing the connectors are a bit of a pain also but each one comes with instructions and if followed carefully you should have no problem. Just don't get impatient doing it. They are nothing like PL-259's.