Longwire --> coax Balun??

[neilbell]

Right now my 100 ft longwire comes directly to my radio with no coax feed. Comes through a hole in my wall and into my computer and radio room. I get local noise for sure and am planning on running some coax in room and out through the wall (about a 15 foot total run). So, my question is how important is a balun for a receive only short wave listening?

I'm retired so would rather not spend the $40-50 is it won't make a significant difference to my Eton E1 radio.

 

[zz0468]

A balun is for transitioning from a balanced line to an unbalanced line, or a balanced antenna (like a dipole) to coax. A long wire isn't balanced, so a balun isn't what you would need. Just start out by trying a run of coax to the antenna, and just couple directly to the 100' wire with the center conductor and let the shield of the antenna end be unterminated to anything. If that doesn't work well, there's plenty more you can try.

 

[ka3jjz]

To be honest, I've only fooled around a little with MLBs (Magnetic Longwire baluns, as they are sometimes called), and it's effective, at times, in cutting the noise - and all I have are indoor antennas. Any little bit helps, and you don't need to spend USD40 or 50 bucks on them. The SWL antennas Yahoo group has plans for building your own, and if you've already got the toroid and box laying around, it's considerably cheaper than that.

Certainly using a coax lead in, and most important, getting the antenna away from the home as much as you can, will play a role in getting the noise down. In addtion, there's a couple of articles - somewhat technical, admittedly - linked on the HF antennas wiki (Forum Specific topics/Antennas). There's a section called 'Magnetic Longwire Baluns' that might prove informational. The Yahoo group is also linked there. If you join the group, there are photos and a writeup on how to wind the toroid in their files area.

73s Mike

 

[gcgrotz]

Read this article, linked in the HF Antenna wiki page:

http://www.wellbrook.uk.com/UMB.html

The PAR End Fed SWL works like this also and has a reputation for being quiet. It will be a big help to get the wire out of your shack and use coax to feed it. TV coax works great, don't get hung up on what to use at HF frequencies as long as you are not using it to transmit.

 

[k9rzz]

You can simply connect the wire to some coax and feed that to your radio, but the mismatch in impeadance _may_ hinder your recepton. A 4:1 UN-UN (unbalanced to unbalanced) may be your solution.

http://www.k0bg.com/unun.html

I use one on a vertical ... awesome!

 

[key2_altfire]

Great thread. This appears to be some of the best straight-to-the-point info I've seen on this subject.