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Author Topic: SO239 connections at wall in shack  (Read 9057 times)
W0TLP
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« on: March 26, 2011, 03:41:11 PM »

I would like to have a panel of UHF (SO239) connectors on the wall of my shack. Each connector would have its own coax line to an antenna. I will have no more than 4 antennas.

I prefer a panel because the shack is a shared family room and is also my home office. I'm trying to keep it fairly tidy.

My plan is to cut a hole in the sheet rock wall and install a 2-gang old-work electrical box, through which the coax would be run. I would put PL259 connectors on the ends of the coax.

The PL259s will attach to 1" SO239 bulkhead connectors that will be fastened to a metal 2-gang blank plate, through which I will have drilled 4 5/8" holes to mount the bulkhead connectors.

I can then connect my radios to up to 4 different antennas by connecting a jumper from the radio to the connector on the wall. The wall plate also keeps the system fairly clean, so that if I need to move furniture I don't have just a bunch of cable running through the wall.

Imagine this wall plate, but with UHF connectors, not XML connectors:  http://ecx.images-amazon.com/images/I/31KtRHeYSwL.jpg

Here is the bulkhead connector:  http://www.universal-radio.com/catalog/parts/ug363.html

My questions are:

1: Is this a good idea? It seems good in my head, but I know that the more connectors I have the more likely I am to experience RF loss. The total run of coax is fairly short, 50' or less. I can't think of any reason why mounting the bulkhead connector to a metal plate would affect performance, since that what MFJ pass-through panels do.

3: Has anybody else done this?

2: Does anybody know of a commercially-available 4-uhf connection wall plate? Making one would be easy, but it might be easier to buy one instead of buying 4 1" bulkhead connectors.

Leviton makes a single-gang wall plate that will accommodate the SO239, but I cannot find a two-gang plate with four holes.  http://www.leviton.com/OA_HTML/ibeCCtpItmDspRte.jsp?item=9354&section=10996&minisite=10026

Thanks

Teak
KD0KVV
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W8JX
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« Reply #1 on: March 26, 2011, 04:23:01 PM »

Why don't you simply put in a remote antenna switch and bring one coax in?
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W0TLP
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« Reply #2 on: March 26, 2011, 06:52:08 PM »

A remote antenna switch would be fine, except that I will be using multiple radios, probably 2 or 3, so each radio will still need a connection to the appropriate antenna.

I really don't need the four connections now; two would suffice but I am thinking I'd do four in the event of expansion.

So two on the wall -- one leading to a VHF/UHF antenna and another to an HF antenna -- would suffice. The HF antenna connection could be replaced by the remote switch if and when it is necessary.

So that still leaves me with the issue of the two coax cables entering the shack. Maybe a single-gang box with the home-brew plate would work.

Thanks for the suggestion. This makes it easier.
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W8JX
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« Reply #3 on: March 26, 2011, 08:49:52 PM »

You might even consider N connectors and bullets at feed thru point. Much higher quality and lower loss thru UHF frequencies and weather proof by design too. Mil Spec N connectors are solderless on shield too. They would make a nice permanent feed thru. When I worked in R&D years ago I put on a ton of N connectors.
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WB2WIK
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« Reply #4 on: March 26, 2011, 09:36:22 PM »

Your idea is fine, and I've done this same thing lots of times.

I never homebrewed the plate, I've used dual CATV plates with F connectors (as used for cable and satellite TV connections) and just punched the holes out to be larger for UHF bulkheads. 

High quality (Amphenol) UHF connectors and bulkhead adapters have immeasurably low loss through 222 MHz.  If you're going to use any for UHF (440 MHz or above), switching to Type N fittings is a good idea.

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W6RMK
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« Reply #5 on: March 27, 2011, 07:44:54 AM »

You may want something bigger than a double gang box. 

They make all manner of boxes designed to mount in a wall with access doors, sealable ports, and a removable panel.   Look at the ones intended for installation of cable tv drops or telephone lines.

Or, a standard small disconnect box, without the switch or circuit breaker/fuse holder.  Like the ones used for the lines to an a/c compressor-condenser
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W0TLP
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« Reply #6 on: March 27, 2011, 08:20:07 AM »

Great tips, thank you all for taking the time to reply.

I doubt I'll do much UHF work beyond local repeaters. But having the four connections through a 2-gang box will give me options for growth.

Access to the wall and crawlspace below is pretty easy, so I think I'll start with a single box and two UHF connectors on it. I can add a second box in the future if I need.

@W6RMK: Good suggestion for the disconnect box. I am going to probably going to use one at the coax entrance to add a little more protection for the lightning arrestors. A flush-mount box in the shack might work, too.

I like the idea of an auto antenna switch. That would be easy to deal with if I add antennas.

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K1CJS
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« Reply #7 on: March 27, 2011, 08:49:45 AM »

A few things come to mind here.  First, is this a direct pass thru to the outside of your home?  If it is, there are bulkhead connectors that have sufficient length to 'pass through' the wall entirely.  On the outside of the wall, you can mount your static discharge/lightning arrestors and your single point ground panel, all in a weatherproof box for easy access and ease of connection.

The turning radius of the co-ax cables may have to be taken into account too, if you aren't passing the cables directly through the wall, and at the inside, where your cables will be plugged into the SO239 connectors.

Your best bet is to plan out your shack location so there is no need of changing it at all, then planning accordingly so that you have your co-ax cables at that location.

Lastly, and it's just a thought, but have you considered coming up through the floor if you can?  Sometimes that is the better choice by far, there is a lot more room to accommodate turning radius for the co-ax cables, and the cables can come straight up right under your operating position.  If a finished basement, access panels can be cut right into the ceiling so you can have access to the underside of your cable runs, and the access into the house through the basement is much easier too.  Also, the chance of drafts and cold spots in your family room will be lessened.
« Last Edit: March 27, 2011, 08:51:24 AM by K1CJS » Logged
W8JX
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« Reply #8 on: March 27, 2011, 08:51:31 AM »

I would suggest that when you install box that you install 3 N bullets even thought you only plan to use 2 now. It would be better to have it and not need it than need it and not have it. When I worked for military and government in R&D they never used a PL259 for anything. It was N's mostly with few other exotic ones too. You should be able to find N bullets and connectors surplus and as N's went  King's brand connector were the best and when properly assembled that are weatherproof too.
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W0TLP
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« Reply #9 on: March 27, 2011, 10:19:02 AM »

K1CJS:  Good points. Thank you.

Unfortunately, the coax must enter the house on the west wide, and the shack is on the east side. This is due to a power line dropping on the east side without enough clearance to safely route the RF coax.

Going through the floor is possible, and I'm not opposed to it -- I was just thinking that a box with connectors would be a little nicer. If it's all behind a desk it shouldn't matter. and you make a good point about causing too much of a bend/kink in the coax if I route it through a wall and a box.
Teak
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W3LK
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« Reply #10 on: March 27, 2011, 02:56:58 PM »

If it's all behind a desk it shouldn't matter.
Teak

In your quest for a "neat" installation, don't forget the convenience of getting to your patch panel. If you have to lean over the desk and equipment or crawl under the desk, you'll quickly find yourself looking for a new location for the connectors.

Good luck with the project.
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W8JX
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« Reply #11 on: March 27, 2011, 04:01:57 PM »

If it's all behind a desk it shouldn't matter.
Teak

In your quest for a "neat" installation, don't forget the convenience of getting to your patch panel. If you have to lean over the desk and equipment or crawl under the desk, you'll quickly find yourself looking for a new location for the connectors.

Good luck with the project.

Being that the panel is basically a feed through there really is no need to see it or have easy access. It just needs to be able to be disconnected if equipment is removed.
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K1CJS
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« Reply #12 on: March 31, 2011, 07:33:14 PM »

If you do go through the floor, you can use a heavy brass plate to mount your so-239 connectors.  If you ever choose to move your station, (or move to another home) the brass plate can be removed and a simple floor grating for a cold air return can be used to cover the holes.  To stop drafts, cut a strip of tarpaper and a strip of plastic to size to fit the register underside.
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W0TLP
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« Reply #13 on: April 01, 2011, 02:21:14 PM »

With all the good suggestions, I have been rethinking this a little. How about this:

I ordered a copper grounding bar from Georgia Copper: http://www.gacopper.com/GroundBars.html.

This will be used outside the home at the point of coax entry. I will mount to it the lightning protection (I chose the Alpha Delta ATT3G50, based on reading reviews). It will be bonded to a ground rod at the entrance

I will get a second grounding bar to put in the shack, to which I will ground station equipment. The bar could be grounded to the house ground, which is at the service entrance for the water supply (it's an older house, that's how they did it then and my electrician has signed off on it as being OK by code, due to the age of house) or I can ground it to another rod just outside the shack. Getting through the wall with a short section of 4 or 6 gauge copper will be easy.

I can pass the coax through the floor/baseboard, reducing strain on the feed line. I can run the lines directly to the radios (scrapping the in-wall box, which is unnecessary) or I can attach the feed line to a second surge protector mounted on the bar in the shack.

This, in theory, would give me secondary protection and bond the equipment coax grounds together. It is would be more money (worth it if it provides more protection), perhaps overkill.

Would this really add more protection? Would it potentially cause more problem to have the coax grounded twice and grounded to the same as the equipment? I think I've read that a common ground is preferred.

Thanks again for all the suggestions. You've all been helpful.

Teak
KD0KVV
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K1CJS
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« Reply #14 on: April 01, 2011, 09:01:55 PM »

Teak, The outside bar to attach the suppressors to is good, so is the inside bar--but you do not need suppressors inside, neither do you want to bond each co-ax to the inside bar.  Doing so would give you multiple ground loops, and you want to avoid these at all costs.  The purpose of the inside bar is to ground all the radio equipment in your shack to it.  Also, the inside bar must be grounded to the same ground the outside grounding bar is connected to, and that outside shack ground must be bonded to the house electrical service ground, as the NEC demands, with number six cable.  

One other thing to make sure of is that the outlet(s) serving your shack be properly connected--all three wires--black, white and ground, and that the ground wire is actually connected to the electrical service panel ground.  All too often, two wire electrical outlets are replaced with three wire outlets for convenience--and the ground terminal is left unconnected.  A simple plug-in tester is available (for purchase) at most home centers to check this.

The only piece of equipment in your shack that may not have to have its chassis connected to that inside bar is your power supplies--and that is only if they're already grounded by a third wire on their power plug.  If they aren't, then they should be connected to the shack ground bar.  If the power supply is connected (grounded) to both, the result could be another ground loop, resulting in a possibly dangerous electrical situation, and possible noisy, poor reception.
« Last Edit: April 01, 2011, 09:14:16 PM by K1CJS » Logged
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