| Author |
Message |
    
Boxcar
Intermediate Member
Username: Boxcar
Post Number: 379
Registered: 4-2002
| | Posted on Thursday, February 23, 2006 - 10:30 pm: | 
|
I've heard of this but wondered what it does. When coiling coax around the pole just right under the connector plugs in or coil it in a 6 inch coil right beside the pole and taped to the pole........what do these coiling the coax issues do? Stray rf? TVI issues? Just curious!! |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1227
Registered: 9-2004
| | Posted on Friday, February 24, 2006 - 12:41 am: |
|
it is a choke to cancel out common mode currents on the sheild of your coax.
common mode currents can cause TVI and other problems.
do a google search on "common mode currents"
to learn more.
here is a link to show you how to build one for your antenna.
i do this to all my antenna installs.
matt
http://www.hamuniverse.com/balun.html |
Bruce
Senior Member
Username: Bruce
Post Number: 3586
Registered: 9-2003
| | Posted on Friday, February 24, 2006 - 7:18 am: |
|
It acts like a choke and stops RF from going back down the coax .... it does help TVI and stray RF problems and is CHEEP! |
Tech833
Moderator
Username: Tech833
Post Number: 1223
Registered: 8-2002
| | Posted on Friday, February 24, 2006 - 10:31 am: |
|
A simple inductor. It will not 'solve' TVI unless the TVI is being caused by stray current coming back down the coax shield and overloading the victim device. |
Roninboricua
Junior Member
Username: Roninboricua
Post Number: 27
Registered: 1-2006
| | Posted on Friday, February 24, 2006 - 1:20 pm: |
|
How can you do this with LMR400? Wont it damage the coax? Its not that flexible. |
Boxcar
Intermediate Member
Username: Boxcar
Post Number: 380
Registered: 4-2002
| | Posted on Friday, February 24, 2006 - 4:47 pm: |
|
How far away from the antenna should this choke balun be? I figured right about a couple feet or maybe as close to the connector going into the antenna? |
Silverfox
Junior Member
Username: Silverfox
Post Number: 14
Registered: 3-2006
| | Posted on Saturday, April 01, 2006 - 3:17 pm: |
|
Yeah...I'd like to use LMR400 too but that choke issue is a problem. Kid Vicious told me about the diameter I could use though. Trouble is that it adds another 18 feet to the coax and further ups the price of the already expensive LMR400. By the way...just how much DOES the LMR400 cost?? I don't even know. Whenever I go to a coax sales site I can never figure out what type of coax I'm looking at because they just give all their respective cables numbers. Anyway...I think I would like to use it if I can afford it. Thanks,
silverfox |
Gator44
Junior Member
Username: Gator44
Post Number: 14
Registered: 1-2007
| | Posted on Tuesday, January 23, 2007 - 9:43 pm: |
|
My question exactly...i have tvi problems too! Everything is grounded and my antenna base is at 56'. Should'nt that be high enough to solve "most" of what my problem is? I heard of coiling my feed line 5-6 3" tightly wrapped coils as close to my pl-259 is at the base of the antenna but...i did'nt know if it would affect my power output, swr's, etc..any help would be greatly appreciated. |
Tech237
Moderator
Username: Tech237
Post Number: 689
Registered: 4-2004
| | Posted on Wednesday, January 24, 2007 - 9:39 pm: |
|
By the way you should never coil coax too tightly and usually it is recommended not to bend coax in a radius of less than 8 times it's diameter.
For example a 1/2 diameter coax should never be coiled or bent with a radius less than 4 inches. Why? Bending coax tighter than this can cause the inner conductor to creep with in the dielectric (plastic insulator) and thus change it's characteristics. Bending it too tight can also damage the cable in other ways
Simon
Tech237
KD7IEB
|
Slugo4449
Intermediate Member
Username: Slugo4449
Post Number: 160
Registered: 7-2004
| | Posted on Saturday, January 27, 2007 - 1:58 am: |
|
Thanks Simon,
I have seen people yanking lmr-400 off of a spool and kinking it and then telling the other person, "that doesn't hurt it".
It actually can break the center conductor.
73,
Marty |
