Antenna Feed-Line Project (* also see follow-up info at http://home.comcast.net/~k8bb/bulkhead.htm *)

Against my "radio" better-judgment, I bought an old (1929) house in the Seminole Hills Historic District in the city of Pontiac, Michigan. I have a big enough yard (125x145) to erect some wire antennas, lots of tall trees, and the neighbors aren't as close as one might expect for a city lot. While this is not exactly radio Utopia, it will be home for the forseeable future. The following article explains what I did to route antenna feedlines from the yard to the basement in what might have been otherwise considered a "difficult situation." Maybe what I learned along the way can help another.

First, there were not any "no-brainer" ways to connect feedlines through. The house is brick and all of the masonry is intact and the foundation is very solid. The basement windows are all glass bloc, without vents. The basement room which serves as the radio room is finished entirely in wet plaster. This could be a mess . . . 

After some deliberating, it eventually came to me: In 1978, a family room was added on to the northeast corner of the house. The northeast basement window (in the radio room) that normally would have looked outside to the world now looked into the crawlspace under this new addition. When the other basement windows were replaced with glass bloc, this one was left original, to serve as an access to the crawlspace.

I decided the best way to get feedlines into the room would be to go from the outside into the crawlspace and then through the access window into the basement. My good friend Jay Radcliffe, N8OS, was once looking for very long double-SO-239 bulkhead connectors for a similar project at his house. Though he ended up taking a different approach, the idea stuck in my head: if I could get my hands on some long bulkhead connectors, I could mount them through the wall under the family room. I could then mount short bulkheads on a piece of plywood, in place of a window pane (this is what we did at Jay's house) in the "access" window, and connect them together with coax jumpers. I would end up with a "patch panel" of sorts inside and outside. Lastly, the connectors could all be grounded easily outside and disconnected, if necessary.

My plan was formed. Now to put it into action:

I found 8" bulkhead connectors on the internet at Global Connections in St. Joseph, MO. When I called to order them, the lady on the phone recommended I also purchase the "extra large mounting nuts." This would allow for more solid mounting and the very small, supplied nuts could act as lock-stop bushings. I said "OK" and ordered eight 8" connectors for the wall, eight 4" connectors to go through the wood "window pane" and sixteen heavy-duty mounting nuts.

I drilled a pilot/test hole (from the outside) and it entered the crawlspace in just the spot I had anticipated. This was good.

I purchased some 9913 equivalent and a mess of PL-259s from a local CB shop and built the jumpers to go under the crawlspace. I then had a piece of 1/2" plywood cut to fit the window pane. I removed the old window pane (with a hammer) and glued the plywood in its place with Type II clear silicone.

Since there is newer, narrow aluminum siding on that part of the house, I put four connectors in a row in the center of the bottom level of siding, and another four above them on the next level of siding, offset. I mounted each row of four connectors to a common aluminum plate, so I could ground all the feedlines at that point, before entering the radio room. I figured this would help eliminate common-mode currents.

Once the connectors arrived, I prepped the coaxial cables by attaching the 8" bulkhead connectors to one end of each cable, complete with all of the inside washers and jam-nuts in place. Then I shoved them through the holes from inside and went outside to secure everything.

The plan worked and it went together pretty smoothly. The advice of the sales lady at GC to get the heavy-duty mounting nuts was sound, indeed. They are absolutely necessary to mount the connectors in a physically competent manner. On the first (upper) set of four connectors, I used 5/8" cut lock washers to ensure nothing would come apart. In retrospect, it was overkill. Those enormous lock washers require so much tightening force to close them that I slightly stripped one of the big  mounting nuts. When I installed the second set of four, I did not use the lock washers. After tightening everything up, I used the small mounting nuts as lock-stops and it seems to work just as well, and with less stress on the threads.

If anybody else is ever to embark on a similar project, I hope what I have shared here helps them out in some way.

This is the window in the radio room, leading under the Family Room. The back of the house is to the right.

This is what it looks like looking through the window to the right. It is about four feet to the back wall of the house. I prepped the bulkheads with the cables and the bushings so that once I crawled up into the crawlspace, I only had to push the bulkheads through and then get out.

These are the four new bulkheads (on the bottom) after being pushed through from the inside. Next, I installed a large flat washer around each to act as a spacer. Then the plate went on. Then another large flat washer, then the big mounting nuts. Finally, once everything was very tight, I installed the little mounting nuts as "lock stops" to prevent movement. The upper set of four, installed earlier, got big, 5/8" cut lock washers. They turned out to be way too strong for the job and required way too much torque to fully tighten. The third one from the left on top is slightly stripped . . . oops . . . 

This is the grounding system. Both plates are connected via 5/8" tinned braid to two 4' copper ground rods about 6" apart. This is intended to eliminate common-mode currents from entering the shack. So far, it has seemed to be effective. Nothing in the shack is properly grounded (really) and all seems well, with all the amplifiers going at full-bore . . . 

The Finished Product (outside): I hung four caps from the first plate for use if any of the sockets would not be connected. 

The Finished Product (inside):