Re: Topband: Feedline Grounding and Feedline Chokes
About a simple Bulkhead-Entry-Point. A success at lowering man-made local noise for me. This is a simple solution I use successfully at home: https://www.flickr.com/photos/pa5mw/28796976750/in/album-72157667970861390/ 73 Mark PA5MW -Original Message- From: Topband On Behalf Of Bob K6ZZ Sent: Wednesday, March 25, 2020 23:24 PM To: topband Subject: Topband: Feedline Grounding and Feedline Chokes Folks, I see a lot of references to grounding coaxial feedlines at the top of towers, bottom of towers, and at house entry points. Is this purely for static and lightening protection purposes or does it also help mitigate Common Mode problems as well? If feedlines are well grounded, are chokes still useful for controlling Common Modes problems? I suspect that both can be used, and should be used, in a well designed station. Are there specific recommendations on the use of chokes on grounded feedlines? Does placement matter? Thanks, Bob K6ZZ _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Feedline Grounding and Feedline Chokes
Thanks Jim and Frank. Yes, bonding not grounding. Thanks for the correction. I know better but got lazy with the terminology! 73, Bob K6ZZ Sent from my iPhone >> On Mar 25, 2020, at 7:44 PM, donov...@starpower.net wrote: > > Hi Bob, > > Bonding (not grounding...) coax to the bottom of a tower helps to > divert lightning currents from the coax shield to the ground system > at the base of the tower > > Bonding coax to the top of the tower helps to equalize the voltage > between the coax and the tower face. This helps to avoid pin holes > in the coax during a lightning strike. > > Bonding all coax, control cables and all other external wiring to the > a ground system at the entry to your shack forces the voltages on all > of those those cables to be equal. > > None of this is related to common mode suppression. That is best > accomplished by a choke near the feed point of the antenna. > > 73 > Frank > W3LPL > > > > From: "Bob K6ZZ" > To: "topband" > Sent: Wednesday, March 25, 2020 10:24:11 PM > Subject: Topband: Feedline Grounding and Feedline Chokes > > Folks, > > I see a lot of references to grounding coaxial feedlines at the top of > towers, bottom of towers, and at house entry points. Is this purely for > static and lightening protection purposes or does it also help mitigate > Common Mode problems as well? > > If feedlines are well grounded, are chokes still useful for controlling > Common Modes problems? I suspect that both can be used, and should be > used, in a well designed station. > > Are there specific recommendations on the use of chokes on grounded > feedlines? Does placement matter? > > Thanks, Bob K6ZZ > _ > Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Feedline Grounding and Feedline Chokes
Hi Bob, Bonding (not grounding...) coax to the bottom of a tower helps to divert lightning currents from the coax shield to the ground system at the base of the tower Bonding coax to the top of the tower helps to equalize the voltage between the coax and the tower face. This helps to avoid pin holes in the coax during a lightning strike. Bonding all coax, control cables and all other external wiring to the a ground system at the entry to your shack forces the voltages on all of those those cables to be equal. None of this is related to common mode suppression. That is best accomplished by a choke near the feed point of the antenna. 73 Frank W3LPL From: "Bob K6ZZ" To: "topband" Sent: Wednesday, March 25, 2020 10:24:11 PM Subject: Topband: Feedline Grounding and Feedline Chokes Folks, I see a lot of references to grounding coaxial feedlines at the top of towers, bottom of towers, and at house entry points. Is this purely for static and lightening protection purposes or does it also help mitigate Common Mode problems as well? If feedlines are well grounded, are chokes still useful for controlling Common Modes problems? I suspect that both can be used, and should be used, in a well designed station. Are there specific recommendations on the use of chokes on grounded feedlines? Does placement matter? Thanks, Bob K6ZZ _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Feedline Grounding and Feedline Chokes
Hi Bob, Lots of well established science on most of this. Bonding to the tower top and bottom is for lightning protection. Combined with proximity to the tower, the feedline and the tower are essentially one conductor for common mode, so whatever is induced in the tower will couple to the feedline, except that the tower, by virtue of its cross-section will carry much more of the common mode current. Chokes are always a good thing at antenna feedpoints to prevent noise (or other signals) picked up on the length of coax near the antenna from coupling common mode to the antenna, thus filling in the nulls. The single most important place for a choke is right at the antenna feedpoint. In general, it should be in addition to whatever "balun" or matching network is supplied as part manufactured antennas. Lots of detailed info at k9yc.com/2018Cookbook.pdf 73, Jim K9YC On 3/25/2020 3:24 PM, Bob K6ZZ wrote: Folks, I see a lot of references to grounding coaxial feedlines at the top of towers, bottom of towers, and at house entry points. Is this purely for static and lightening protection purposes or does it also help mitigate Common Mode problems as well? If feedlines are well grounded, are chokes still useful for controlling Common Modes problems? I suspect that both can be used, and should be used, in a well designed station. Are there specific recommendations on the use of chokes on grounded feedlines? Does placement matter? Thanks, Bob K6ZZ _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Topband: Feedline Grounding and Feedline Chokes
Folks, I see a lot of references to grounding coaxial feedlines at the top of towers, bottom of towers, and at house entry points. Is this purely for static and lightening protection purposes or does it also help mitigate Common Mode problems as well? If feedlines are well grounded, are chokes still useful for controlling Common Modes problems? I suspect that both can be used, and should be used, in a well designed station. Are there specific recommendations on the use of chokes on grounded feedlines? Does placement matter? Thanks, Bob K6ZZ _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
