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Open Wire Feed Through




 
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Author Topic: Open Wire Feed Through  (Read 732 times)
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Carl WA1KPD
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« on: October 15, 2018, 06:49:00 PM »

Looking for ideas on how to feed through 450-ohm feedline into the house. I am planning to have it come through a space between the window sash and frame. I can put a piece of wood in the space and will put several barrel connectors for some coax feed-throughs. What are your experiences with feeding the OWl and taking up the stress?
Thanks
Carl
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« Reply #1 on: October 15, 2018, 09:55:00 PM »


C,


Is there any reason why you cant drill through the window frame and use these things?



klc


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w7fox
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« Reply #2 on: October 15, 2018, 10:00:45 PM »

Carl,
It depends a lot on whose house it is.  Here is my example.

73 Fox


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Patrick J. / KD5OEI
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« Reply #3 on: October 15, 2018, 10:27:11 PM »

In your piece of wood, drill 2 holes and slip two "knob and tube" ceramic tubes into them. bring the separated (center web removed) ends of the line in through them, one through each, and on the indoor side, place a washer over the line, and solder an alligator clip on each conductor, so that the washers keep the clips from being pulled back through the tubes. The knob ends of the tubes are on the inside so they can't be pulled out through the holes. Indoors you can use the alligator clips to attach to your line to the transmitter. If you don't like alligator clips, a screw terminal or something else soldered on like a large ring terminal can be used. I've had this setup for 10 years with no trouble.

knob and tube hardware is pretty cheap on ebay and it's very durable for this use.
https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=knob+and+tube&_sacat=0
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k7mdo
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« Reply #4 on: October 16, 2018, 12:49:09 AM »

I have somewhat a similar question.  My radio room is inside a metal sided building.  Even the outside entry door is foam filled metal both sides type.

I don't mind opening a massive hole but don't know how much clearance one needs around the perimeter of the two wires to the metal door or siding.  ??

Thanks, Tom
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N1BCG
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« Reply #5 on: October 16, 2018, 07:20:04 AM »

The size of the holes largely depends on the power level you expect to run and the impedance of the line at the feed through. In most cases, using 1 holes and adding ceramic insulating sleeves around the conductors between the end insulators should work well.
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WD8BIL
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« Reply #6 on: October 16, 2018, 09:01:18 AM »

Got a couple of these.... works great!

http://www.mfjenterprises.com/Product.php?productid=MFJ-4602


(I do not work for them!)
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KB2WIG
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« Reply #7 on: October 16, 2018, 11:24:21 AM »




B,

The MFJ thingie looks OK, IF you can cover the mfj logo up.


KLC
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W1AEX
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« Reply #8 on: October 16, 2018, 12:13:51 PM »

Hi Carl,

I just went through this and for my latest version of a sash - threshold project I switched from wood and used vinyl trim materials. I have had no problems feeding full legal limit through the OWL insulators. On the inside, I use banana jacks and plugs to allow quick disconnecting during the summer when the lightning is inbound. The OWL feedline comes down from the center of the dipole and goes to a balanced line lightning arrestor mounted on a 10 foot steel pole (with multiple ground rods and bonding to the electrical neutral) that bleeds off static through resistors and also has gas discharge cartridges to ground as well. It has been durable and with some decent hardware store foam to seal up the seams no bugs get through during the summer and very little wind breezes through in the winter.

I got a C+ in wood shop in high school so no doubt you can make it much prettier!

73,

Rob W1AEX


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Carl WA1KPD
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« Reply #9 on: October 19, 2018, 12:06:32 PM »

Thank you all for your suggestions. I am going with one of the MFJ units, primarily because the workshop is not set up yet, but I plan to make some mods to it based on the experiences.
73
Carl
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« Reply #10 on: October 20, 2018, 04:04:49 PM »

The MFJ units look very well made and should last a long time. There's certainly a lot of guys using them.

The other part of your initial question was about dealing with the stress of that long open wire run that continuously swings gently back and forth 24/7 and whips around like crazy when the wind catches it. Initially, my non-solution was to run the OWL right down from the antenna feedpoint and connect it directly to the lightning arrester terminals. I learned quickly that #14 stranded wire breaks without warning at around 6 months right at the lightning arrester connection point.

So... I started catching the wire about 10 feet above the arrester with a rope fastened to the center of one of the feedline insulators. That worked pretty well and the #14 stranded wire I used for the feedline survived for a couple of years before breaking. I just ripped that antenna down yesterday after 10 years of use and replaced it with #12 stranded wire and added another feedline rope to reduce the stress at the connection terminals even more. The two rope method is really keeping the open wire stationary at the connection terminals even with some +25mph wind gusts. So far so good, but of course the antenna is only one day old!

In the photo, you can see the feedline coming down from the antenna on the left, then it transitions over to the first tie point and from there it traverses over to the second tie point where it then descends to the connection terminals of the lightning arrester. I haven't seen that last section move at all so far which is a good thing.

That's my current setup. So far so good!

Good luck with the new antenna and be sure to share how it turns out!

73,

Rob W1AEX


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Patrick J. / KD5OEI
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« Reply #11 on: October 20, 2018, 07:30:04 PM »

I have somewhat a similar question.  My radio room is inside a metal sided building.  Even the outside entry door is foam filled metal both sides type.

I don't mind opening a massive hole but don't know how much clearance one needs around the perimeter of the two wires to the metal door or siding.  ??

Thanks, Tom

Exactly my setup with the "knob-and-tube" ceramic tubes. The tubes fit holes in the wall of the metal building which are sized just a hair bigger than the tubes are and they are siliconed in place. I have noticed no problems with HV or RF issues caused by the proximity of the conductors to the edges of the holes in the thin steel wall of the metal building, er, 'bunker of doom'.  I think yours with the dual wall and insulation would be the same result.
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