| Author |
Message |
    
Joey_migs
New member
Username: Joey_migs
Post Number: 1
Registered: 9-2009
| | Posted on Tuesday, September 08, 2009 - 1:36 pm: | 
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First off, I am new and I think this is a great site.
I want to set-up a horizontal dipole for 11 meters and I want to feed it using RG-8. How do I match the RG-8 with a impedance of 52 ohms to a dipole that has a feedpoint of 72 ohms? Thanks for any advice you can give me.
Joe |
Tech833
Moderator
Username: Tech833
Post Number: 1733
Registered: 8-2002
| | Posted on Tuesday, September 08, 2009 - 5:47 pm: |
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The 50 ohm to 70 ohm difference is minimal. Most people just feed directly.
Others use a 1:1 balun to convert the unbalanced coax to the balanced dipole, which may also help reduce noise in your receiver too. |
Five
Junior Member
Username: Five
Post Number: 21
Registered: 7-2009
| | Posted on Tuesday, September 08, 2009 - 6:36 pm: |
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Do you have one you purchased or are you building one? Takes about 30 minutes to build one for 11 meter band. I made one with a two conductor extension cord cut at 9' and split in two 18' total. I soldered each end to a SO-239 connector and made an insulator for each end out of plastic tubing. I trimmed each end till the SWR was flat across the band. I use RG-8 from the radio to the dipole and it works great. If used outside it would need to be sealed where the SO-239 is soldered. |
Joey_migs
New member
Username: Joey_migs
Post Number: 3
Registered: 9-2009
| | Posted on Tuesday, September 08, 2009 - 10:05 pm: |
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I was planning on building it, but does it make a difference if I solder each side of the dipole directly to the RG-8, one side to the center and the other to the shield and use a piece of Plexiglas as the center insulator. Then, cover with some good quality silicon sealant. Its good to know that the 50 to 70 ohms will not matter much. Also do I ground the shielded side?
Thanks guys, appreciate it.
Joe |
Tech833
Moderator
Username: Tech833
Post Number: 1734
Registered: 8-2002
| | Posted on Wednesday, September 09, 2009 - 12:48 am: |
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A balun isn't a tuned device. If your balun requires tuning, then there is something amiss.
Yes, you can connect your coax as described, Joe. Your SWR won't be perfect, but definitely useable.
You can ground the coax shield where it enters the shack, but not up at the antenna feedpoint. If you use a 1:1 balun, then you can ground it anywhere it is convenient. |
