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[TowerTalk] entrance panels for grounding

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Subject: [TowerTalk] entrance panels for grounding
From: (Mark .)
Date: Tue, 21 Dec 1999 08:55:43 EST
Jim Clark asked:
<< snip.. If I have a 2nd floor shack, should I use a Polyphaser entrance 
panel, or ground the antenna at ground level with a suppressor, and run coax 
up into the shack?  Hate to drill all those holes in the house.  Same 
applies when I start using rotator cable.  Your thoughts? >>

Hi Jim, good questions.

There are a lot of approaches out there. I recently went through lots of 
posts to try to decide what to do. I also have a 2nd story shack.
I made what I call a 'gounding switchboard.' The approach I adopted is 
simplisistic, and effective, based on the following goals:

1) Disconnection of all conductors between tower and shack when not 
2) Shunting all conductors from the tower to a low impedance ground when not 
3) Allowing varied rig/antenna connections
4) Isolation of hamshack gear from ground when not operating.
5) Do not operate during threatening weather
6) Develop a habit of always disconnecting after operating.
7) Don't spend too much money!
8) Have fun building something that really works!

Here is the scheme, in summary:

1)Install a conductive panel in a window
2) Tie in the panel to the electrical service and tower ground system 
(single point) with a low impedance conductor, such as copper pipe or wide 
3) Connectorize and label all conductors and feedlines coming into the 
4) Make shorting plugs that mate with the connectors and shunt all 
connectors to the panel. They should be quick "push-on" types so it will be 
easy enough that you will actually *use* them! :~)
5) Make choke coils in the conductors between the tower and shack.

OK, for those interested and still reading, more detail on my specific plan:

Like you, I did not savor drilling through a wall. I built an insert for one 
of the shack windows. It consists of a rectangular, 1/8" thick aluminum 
plate (try 5052-H32 soft temper, easy to drill, from an *old* road sign 
<uhh- *sheepish grin*>), framed with pressure treated lumber. I rabbeted the 
edges of the frame with a router to fit the contours of the sill and the 
sliding operator such that the insert is captured and secured when the 
window is closed on it. I added some self-stick weatherstripping "V" tape to 
complete the seal.

I installed Amphenol UHF female bulkhead connectors in the plate for each 
coaxial cable desired, plus spares.

For each wire antenna fed with open wire line, I installed two bulkhead 
connectors and used shielded parallel lines from two conductors of RG-58 
(see ARRL antenna handbook). If you like remote baluns, you can get by with 
a single connector and one coax.
For the rotor, I bought 8-pin trailer connectors. I built a clip that 
retains the tower side connector in a cutout in the panel.

I bought a slew of PL-259 quick 'push-on' adaptors. To make the shorting 
plugs, solder a "L"-shaped pieces of 12 gauge copper wire into the center 
socket of the female UHF side of the adaptor, with the short leg soldered to 
the edge adjacent threaded part. Don't let the short leg jut out past the 
threads. Then, using a vise, I pressed a short piece of 1/2" PVC over the 
threads on the female side, making a short, insulating handle. Then I filled 
the pvc cavity with hot melt glue.
I made a shorting plug for the rotor cable using a mating connector. I 
soldered all the wires from the pins (wires are already molded into the 
connector) into one large copper cable lug and bolted the lug to the panel. 
When you mate the connectors, all lines are shunted to the panel.
Next, I made jumpers of RG-8X for every single antenna connection for all of 
my rigs and put push-on adaptors on the panel ends. I made a jumper for the 
rotor using the mating connector for the one in the panel. I Labeled and 
color-coded all ends.
  I put a little silicone grease on the quick disconnects and connector 
pins. One cheap source is Dielectric grease at Advanced Auto Parts.

I grounded my panel using 3/4 copper water pipe down to ground for its 
large, smooth surface area. I put little stub legs in it using "T"'s every 
few feet to cable tie the hardlines and coaxes to it for support. Don't 
forget to use pieces of stainless such as washers or foil, plus antioxidant, 
wherever the copper and aluminum mate.

In practice, it's real easy - which is a key element in human habits! Just 
reach over to the panel, yank the shorting plugs out of the jacks you want 
to use, and plug in your jumpers. At this point, the rigs also become 
grounded through the shields of the jumpers. It's essentially a switchboard, 
too, so you can connect any rig to any antenna. When done, yank of the 
jumpers and push on the shorting plugs. Rigs become ungrounded and present 
no path to stray lightning energy.

Good luck with your tower!

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