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Author Topic: Feed Line Shield  (Read 4249 times)
KD9FRQ
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Posts: 175




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« on: September 10, 2017, 06:00:34 AM »

My shack is in my basement.  My QTH is an older home and all the wiring is exposed in my basement and is it is not run neatly. it crosses it self in several locations.

What can I use to help shield about 15 ft of feed line (HF and UHF/VHF) from this to help minimize any interference?

Thanks in advance.   KD9FRQ
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W9IQ
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Posts: 1707




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« Reply #1 on: September 10, 2017, 06:23:38 AM »

Good quality coax cable is self shielding. But when there are common mode currents present on the oitside of the shield, interference problems are possible.

The use of a good quality choking balun for the frequencies in use, installed just prior to the coax entering the house can be quite effective. Placing another choke at the antenna feedpoint is also recommended.

Installing an RF ground at the entrance point of the cables to the house and grounding all shields to this ground can also prove helpful. This RF ground should be properly bonded to your house electrical service ground.

- Glenn W9IQ
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- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
KD9FRQ
Member

Posts: 175




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« Reply #2 on: September 11, 2017, 03:27:28 PM »

Thank you for your reply.

My feed line is a solid run from the antenna in the attic via access in the roof, down a wall with no wiring into the basement.  Now wiring in the attic to speak of. All is from basement up the wall to a switch. Only one run up to light/fan in center each room.

The biggest mess is in the basement.

I was hoping to find something to use as an additional shield.  The antenna is grounded at the switch to the common station ground.

I will work got get chokes as funds allow. Right now not a lot of noise but more for prevention.
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WB6BYU
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Posts: 17051




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« Reply #3 on: September 12, 2017, 07:15:27 AM »

What type of antenna are you using?  That has a big impact on the
potential for common mode current, which is the main factor for
noise pickup on the coax.

Otherwise I wouldn't expect the exposed wiring by itself to be a problem.
I've lived in older houses and never found it to be an issue.

(Unless something in the wiring is arcing, but that needs to be fixed
as a safety issue regardless of interference.)
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KH6AQ
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Posts: 7718




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« Reply #4 on: September 12, 2017, 07:25:54 AM »

Is there currently an interference issue, and if so, what is it?
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KD8IIC
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Posts: 648




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« Reply #5 on: September 12, 2017, 08:18:47 AM »

Make sure to properly ground the rig.
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KD9FRQ
Member

Posts: 175




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« Reply #6 on: September 12, 2017, 03:41:52 PM »

Rig is properly grounded.

Antenna is RadioWavz Saturn 4 (40, 20, 15 & 10).

Not hearing a lot of noise when using SSB but a lot shows up when using SSB or PSK31 via FLDIGI.  I will be checking all the PC to Radio cables tonight. Not a lot I can do short term because I do not have any clip on beads available.

Was just wondering about the electrical wiring so I can hang the feed line out of the way an not impact the overall signal in or out.
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