Need Suggestions- How To Bring Transmission Lines Into The Building

[WA1KBQ]

I am looking for suggestions on how to bring antenna transmission lines into a new home construction radio hobby space which is two second floor rooms end to end measuring 62' x 15'. The plan is to have various period stations arranged on benches along the two long walls and I would like to have a convenient way to attach an antenna to whichever particular station is chosen for operation. I don't think I want to have them all connected at the same time with a network of coax and coaxial switches. Also I want to have the ability to experiment with different types of antennas and feedlines from time to time so this probably means having the capability to swap and change coax, ladder line or open wire feeder around. I am trying to think of a professional looking properly engineered way to bring transmission lines into the building and get them to the equipment. What should I consider?

Thanks in advance!
Greg

[n2bc]

For routing antennas our club built a coax patch panel.

We had a total of 12 feedlines and 3 rotors. The goal was to be able to route up to 4 feedlines and all the rotors to any of 3 rooms in the club's hilltop building.

We used a cable 'tray' built onto the wall that circled from room-to-room with each room having 4 coax runs going to the patch panel. 

The rotor control cables entered the building and went to individual terminal blocks. From the terminal blocks the cables were run parallel to each room and each rotor's cable was connected to a unique jack. The control box had a mating unique plug.  So simply moving the control box to the desired room and plugging it in gave rotor control to that room.

The patch panel used some simple home brew coax connectors. Rather than use pricey double female connectors, we built some out of SO-329s and 45 degree 1/2" copper elbows. If you carefully cut the elbows in half lengthwise (bandsaw), you can 'wrap' it around a pair of SO-239s connected together with the proper length of #14 wire in the center conductors. Some careful soldering with a small propane torch will fasten the '239s to the elbows and solder the elbow halves together, worked slick.

The 45 degree double females were mounted on a metal panel which in turn was well bonded to station ground.  The 45 degree angle of the fittings made running the many cables quite neat and minimized stress on the coax.

At the patch panel we simply provided a bunch of RG-8 patch cords and carefully labelled all the connectors.

This does not address cable entry - all of ours came up through the floor. 

One caution:  Since 'switching' is completely manual, running multiple stations - especially in the heat of a contest - requires care and communication when changing patch cables!   I still have the evidence for this in the palm of my hand after taking a 1500W "CQSS" back in 1989.

Hope this helps some.

73, Bill   N2BC

[WBear2GCR]

The multiple antenna input to the shack at the RPI club station W2SZ was made by placing feedthrough SO-239 type connectors on a large aluminum panel that was sized to fit between two studs on an outside wall. The panel was run to ground right there with some ground rods, bonded well on both ends.

This was at ground level, so it worked well. Not sure the same trick of the grounded bulkhead will work as well on the second floor...

No matter what if it was my place I'd want there to be a convenient path to physical ground for the coax before it went up to the second floor. That is between the ANT and the house. It might be away from the house (heresy perhaps) but that's how I see it. My thinking is that I don't want to provide a good ground return path for lightning via the shack to ground, rather have it be a lousy path thanks.

I'll give up the perfection of a single run of anything on HF for lightning safety.

So that brings up the disconnect/ground method.

You might want to consider some sort of remote relay switcher set up too...

Depends on how many rigs you want to run at the same time I expect?

Also, do you want your unused ANTs floating or grounded?

Are they on the same band or different bands?

Maybe someone else has a definitive idea, I don't.

                    _-_-bear

[WA1KBQ]

Thanks for the replies!

The planned shack will be the bonus room over a three car garage with a two stall carport on the end; total length is 62'. The planned point of entry into the shack for antenna transmission lines is the left corner at the end of the room over the carport. Current thinking is maybe connect an inside access panel on the left corner wall of the shack to a similar panel just below in the carport with two or three lengths of 2" PVC elbow conduits. Would also provide a strain relief at the lower panel to support weight of open wire feeder and other types of lines. The drywall is not going in for another week so there is some time to decide the best approach.

For open wire feeder... would the best plan be to attach the parallel feedlines to the outside corner of the building, connect to a balun and from the balun bring coax into the shack to an antenna tuner or just bring the open wire feeder in and connect to the shack antenna tuner?

Just one antenna is planned for now, probably a dipole for 80 and 40 meters but we want to plan ahead and provide built in access for bringing in other types of transmission lines for any possible future antenna experimenting or to add operating capability on other frequencies. We plan to set up several different vintage stations to pick from for operation from time to time but will only want to operate one rig at a time. Am planning to try to arrange operating stations close to antenna line point of entry but there will be lots of vintage receivers set up on benches along both long walls toward the other end of the shack. We would like to be able to conveniently connect an antenna to any receiver at any given time but we think we want to avoid having a network of switches and cables as we don't think we need them all connected to an antenna at the same time.

[WBear2GCR]

Ferrite core balun?

Probably not a good way to go, or so I am told.

          _-_-bear

[W1AEX]

For open wire feeder... would the best plan be to attach the parallel feedlines to the outside corner of the building, connect to a balun and from the balun bring coax into the shack to an antenna tuner or just bring the open wire feeder in and connect to the shack antenna tuner?

The purists will tell you to bring the open wire line right into the station to a balanced line tuner. When I operated from my basement station, I did run the balanced feedline across half the length of the house, through the basement, on ceiling mounted stand-offs, to my tuner. Worked fine and caused no issues at all unless my kids messed with it or my wife hung a coat hanger on it while doing laundry. Now that I operate in a "civilized" room upstairs, I don't like the idea of running open wire line past the computers and TV over to the operating desk, so for the 256 foot center-fed I mounted a W2FMI balun box right outside the window on a steel mast and ran the open wire over to it, then ran coax through the window threshold and over to the tuner on the operating desk (about 18 feet of LMR400) and it works great from 160-40 meters.

http://members.cox.net/w1aex/balun.jpg

Again, the purists will point out that I am probably losing 1.27 dB on 40 meters, but I'll live with it.

:O)

Rob W1AEX

[k4kyv]

If you have a window near where you want the open wire line to come into the shack, you can replace one of the glass panes with a sheet of plexiglass.  Just drill holes in the plexiglass and feed the wires through them.

If you plan to come through a solid wall, I would look for two sets of Dolly Parton insulators for each feedline, drill appropriate size holes for each wire for plenty of spacing between the conductors and any wall material, run threaded copper or brass (preferably copper) rods through the insulators, which would serve a terminals on each side of the wall for the open wire line.

For grounding purposes I would look for a big-arsed DPDT knife switch that would switch the feedline running from the antenna either to the rest of the feedline or to ground, preferably with the switch located outside the building.
Maybe rig up a mechanical arrangement like I have seen on utility poles to provide a manual cutoff from the ground, operated by a couple of wire rope cables down to a point where it would be reachable by hand.

I wouldn't dick around with relays.  Too easy to fail from lightning jolts, power outage or just plain corrosion, just at the time when you need them.

If the open wire line is to operate as a tuned feeder, I would avoid baluns like the plague.  A good balun should work OK for a nearly flat balanced line, with 2.5:1 or so SWR or less.  Baluns were designed to act like transformers working into resistive loads, not to handle a large amount of reactance.

[ke7trp]

Do not screw up a perfect multi band open wire antenn with a Balun and Coax.  Trust us that know and use open wire line.  You can lose 20DB or MORE doing this.  Three of my friends mounted big Baluns outside and hooked to the Open wire line. Then ran the coax in to the tuner.. All of them went down so much in signal they all ended up ripping all that out. Stop and think about what you are doing when you use an installation like this.

Here is how I arranged all my stations..

I have a 3.5 inch PVC pipe with turn down connectors(so water cant come in) on it through the wall in the corner of the room. I drilled the pilot hole with a long bit through the wall. THen used the hole saw on the inside and then the outside of the wall. I inserted the pipe and and sealed it with building grade sealant. After I ran my three runs of Andrews hardline through this hole, I filled this pipe with expanding foam. Its sealed tight. When I needed to run a nother Coax in, I easily pulled this foam out, ran the cable and sprayed more in. To me, This was cheap and easy to do.

This handles My 2m/70cm cushcraft vert, My Inverted L for 160, and my tower mounted multi band vert for 10,12,15 and 17 meters.

For open wire line, I used the line from Trueladder line.com   I removed one spacer, marked the wall at table level, Drilled two holes and ran the line into the house. I then put the spacers back on the line and ran it 1 ft to the Johnson KW matchbox tuner.

THe FLOW OF RF is important.   You want Reciever, Transmitter, (amp if any)Scope, watt meter, Tuner and OUT the building.. All in a line on the tables. This way, RF at its maximum will have short runs and wont double back over other gear causing interference.

I have a Globe king 500C with hallicrafters SX110 as my 75 meter station.  I have a SX100 with a globe Champion 300 for 40 meters. I use a Valiant or a ranger with an R390A for 160.  I also have an FT1000D and a Steel tube amp for 160 or for HF SSB use.  All are in lines and complete stations using Coax over to the tuner.  I dont care for Coax switches as all of them will add loss and some will bleed over.  I just unhook the coax cables from each station and hook to the Bird 43 depending on which one I use with the open wire antenna. I can only talk on one of them anyways.

DOnt fall into the trap of mounting a Balun outside and running coax out the shack.  You will have big losses doing this and most likely RFI issues. The reasons are simple.  You want to use the open wire line with a True balanced tuner. If you do, You will enjoy fantastic Multiband performance.

Hope this helps.

Clark

[Opcom]

Baluns get maligned because they are not well understood (least of all by me) but what people miss is that the balun must meet the requirement of the moment, and that can change with a slight bump of the VFO as the sharply resonant and carefully cut antenna goeth from 50 Ohms to 900, or to 10..

Considering a 1:1 balun and an arbitrary frequency F, one for 50:50 Ohms and one for 600:600 Ohms are very different mostly with respect to the number of turns.

The one with 9 turns is likely poor when balancing the output of the ATU at 600 Ohms (little transfer of energy to the core, too low an inductance).

The one with 20 turns is likely poor when the antenna Z is 15 Ohms (saturates the core, high inductance).

This is the same as with any transformer, the ampere-turns factor, and/or, turns per volt. I have yet to see one with taps.

Now throw in a requirement for coverage of 1.8 to 30 Mhz. That is mostly the core, but it does matter.

A set of several baluns would be needed to be versatile. If the tuner has a wide range so that the baluns can all be 1:1, maybe a choice of three to five 1:1 baluns would be good to have fine performance balancing the antenna tuner's output. To operate in the nether regions outside the ham bands, where the antenna looks like a total mess, no balun may do well at 2 Ohms or 2500 Ohms.

It becomes very inconvenient and so unbalanced tuners with internal fixed baluns on the output always are a rotten compromise born of convenience and they are no substitute for a flat antenna.

I suppose that is as close as I can get to maligning baluns without actually doing so. The unbalanced tuners deserve the same comments, except when feeding a long wire.

If a tuner and balun will be used, the best thing (IMHO) is a 1:1 current balun before a well-balanced tuner. It is what I am planning and most of the L and C pieces are here!

I could be wrong; these are opinions, someone can correct me.

[ke7trp]

Baluns are so misunderstood.  Its actualy funny to me that some hams think they are required even on a simple coax diople. 

On the open wire or ladder line.. Run the line to a true balanced tuner. That was my point.

Cya

Clark