On 11/2/2014 1:04 AM, Jim Brown wrote:
On 11/1/2014 6:01 AM, Hans Hammarquist via TowerTalk wrote:
Using a metal box to contain your current choke is OK
I install the chokes as close to the antenna feed points as possible
and ground the braid(s) at the top and bottom of the tower. Before they
connect to the remote antenna switch. I use bulkhead connectors
through 1" X 1/8" Aluminum angle through the one side of the angle
The chokes have the coax and connectors waterproofed with flooded heat
shrink, liquid electrical tape, and sealant tape where appropriate. The
connectors and bulkhead connectors add so little loss under 30 MHz it's
not worth worrying about. Grounded top and bottom of the tower and at
the SPG where they go through Poly Phasers mounted on the grounded plate.
My chokes are pretty much open to the elements. I try to increase the
cooling and do not worry about the elements. (note the 1/4" spacing)
I've never noticed and effect from snow, rain, or ice. The wind moving
the antenna shows more effect than the elements on the choke and that so
tiny as to easily be neglected. I can read the SWR and other stats to 4
decimal places and only the last place moves much. Once on a great while
I see the third place move . I agree with Jim. Actually I use his
figures for building the chokes. They work very well. Feeding a half
sloper on 160 at the top of the tower is a good test.
73
Roger (K8RI)
I disagree, because the box contains any heat produced in the choke,
reducing the dissipation of that heat to the outside air, thus
reducing the power handling of the choke.
The reason for bonding coax at top and bottom of a conventional tower
has nothing to do with the shack, but rather is to keep the shield of
the coax at the same potential as the tower, with the intent of
reducing the likelihood of arcing between the coax shield and the
tower in the event of lightning. In other words, it is to protect the
coax.
73, Jim K9YC
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73
Roger (K8RI)
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