New ham looking for wiring advice

I'll be installing a pair of antennas in the attic (a discone to attach to an rtl-sdr, and a DBJ-1 to attach to my dual band radio). I will run LMR-400 from the antennas, out the attic wall, down the side of the house, and back through the wall into my shack, terminating at a pair of N female connectors on a wall plate. I'm aware of the need for drip loops. The total length of the cable run is going to be less than 50'.

For passing through the exterior wall, I'll be drilling 2" holes and fitting them with a PVC pipe with an elbow on the end, sealing that in with great stuff spray foam, then stuffing the inside with insulation after passing the cables through.

Inside the shack, I'm planning on running LMR-240 from the wall plate to my equipment (I wanted something more flexible than the LMR-400 inside the room).

Does this seem like a reasonable plan?

Sounds like it'll work fine.

I'd avoid using the spray foam, however. It's a pain to deal with if you ever want to add more cables. Digging that stuff out of an elbow can take a lot of work.
An easier solution would be to get some "duct seal". It's a grey putty/clay like compound that we use to seal around conduits coming in from underground. It's easy to remove, reform and reinstall. You don't need a bunch of it, just enough to cover the opening and about an inch or so thick. Follow that up with some insulation.

While you are at it, run a #6 ground wire through there to a ground rod outside your shack. Make sure it's also connected with your homes existing ground rod.

Personally I would run the 400 as much as I can then use jumpers to radio eliminating the need for the 240 and a wall plate


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Frankhappyg said:

Personally I would run the 400 as much as I can then use jumpers to radio eliminating the need for the 240 and a wall plate

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I'm not sure I follow you here. By "jumpers", I would assume that you mean some cable type other than the LMR-400...which seems to be pretty much exactly what I get by running the LMR-400 to a wall plate. I'm guessing that I don't understand exactly what you are describing...

Actually I like the idea of the wall plate - makes a nice neat job - you can add extra connectors later - no fumbling under the desk looking for that connector that has come loose - you can also add sockets from a large power supply to run all your equipment - one socket in, many coming out, all in parallel - even a volt and current meter - and you can run a good ground to the wall plate if its aluminium or other metal - it'll look really cool - and label the connectors with whatever antenna they are connected to. Go for it - the world is your oyster.....

mmckenna said:

Sounds like it'll work fine.
I'd avoid using the spray foam, however...

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Sorry, I meant pink fluffy insulation for the inside of the pvc pipe (spray foam for sealing the outside of the pipe in the wall opening). I agree, I don't want to find myself trying to extract spray foam from the inside of the pipe at some point in the future!

mmckenna said:

While you are at it, run a #6 ground wire through there to a ground rod outside your shack. Make sure it's also connected with your homes existing ground rod.

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That's going to be "tricky". I'm not sure it's really an option at this point. The entry point of the LMR-400 is on the opposite corner of the house from the main ground rod, and there's no good path from point A to point B. With a trencher and some way to dig underneath either the driveway or the front steps I could maybe do it, but that would one heck of a project.

The best option I have for antenna ground is probably the plumbing stack in the attic.

larsks said:

Sorry, I meant pink fluffy insulation for the inside of the pvc pipe (spray foam for sealing the outside of the pipe in the wall opening). I agree, I don't want to find myself trying to extract spray foam from the inside of the pipe at some point in the future!

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No, I understand what you meant about the fiberglass insulation. That would be fine. It's the spray in foam that's the issue. It's a real mess to deal with if you need to remove it. The duct seal stuff will work just fine and is easier to work with.

larsks said:

The best option I have for antenna ground is probably the plumbing stack in the attic.

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That might be grounded, but it's not a suitable antenna ground in the eyes of the National Electric Code. Getting everything properly grounded and protected is a good idea. Getting your grounds all bonded together is a real good idea.


I agree about the jumpers, the difference between a few feet of LMR-400 and LMR-240 will not be noticeable. It's much easier to route the LMR-240, and it'll put less strain on everything. Also much easier to make changes as you need to.

Have you considered drilling a hole from the attic down through the wall top plate, or whatever the thing is called that is above the wall and running the coax inside the wall? You can use a stud finder to see if there are any horizontal fire breaks in the wall and even if there are its not a big deal to drill those from above or below with a long flex drill.

mmckenna said:

An easier solution would be to get some "duct seal". It's a grey putty/clay like compound that we use to seal around conduits coming in from underground. It's easy to remove, reform and reinstall. You don't need a bunch of it, just enough to cover the opening and about an inch or so thick.

Click to expand...

Another vote for duct seal.
Make sure to use the stuff rated for outdoor use.

Back in the lab when I was working on 900 Mhz SMR stuff, we did something similar.

We terminated the incoming antenna lines with male N connectors, and had bulkhead N barrel fittings installed in holes in an aluminum box. The antenna lines were connected to the back side of the barrels, and then on the front side we would use something flexible, either RG-213 or RG-400, to connect to test gear or jumper it to another lab.

That worked out well, and I would suggest it rather than terminating the incoming cable with female connectors. The loss in a good barrel connector is negligible.

Be sure you use a suitable connector for the frequency you're using.

I ran my 400 all the way. It is obnoxioius but I hate extra connections. Not going to move once installed.

larsks said:

For passing through the exterior wall, I'll be drilling 2" holes and fitting them with a PVC pipe with an elbow on the end, sealing that in with great stuff spray foam, then stuffing the inside with insulation after passing the cables through.

Does this seem like a reasonable plan?

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As someone else mentioned, that foam spray stuff is nasty to work with it. Don't never say never, you most likely WILL have to gain access to your feed port in the future. I used fine steel wool and crammed it into my antenna feed access hole until I could not see daylight - done. I used a hinged utility junction box (Home Depot) mounted on the outside and attached with JB Weld, ran all my antenna lines into it thru elbow into PVC sleeve thru wall, and plugged the excess space with the aforementioned steel wool. No cool breeze in the winter, no spiders n' critters, no hassles whatsoever. Had to run a Dish Satellite line into my radio room since then and it was a cinch - pinched out the steel wool and ran my line thru and repacked it around the cables.

Badda-bing-badda-boom!!

JD
kf4anc

Be cautious with steel wool and anything carrying current.
Stainless steel wool might be a better choice if it's exposed to moistures/outdoors.

This is why bulkhead connectors exist. UHF (SO-239) female connectors, back to back, with anywhere from 2" to 12" of solid metal connection between them. Drill a hole in the wall, insert the bulkhead connector with sealant for a permanent installation (slanting it slightly to ensure any moisture runs out not in) and then just put a PL-259 standard cable into each side of it.

One hole, one fitting, quick and easy.

Thanks everyone for the input! It has been very helpful.

The long SO-239 bulkhead connectors are great for certain things but I've never been a fan of them for going through the walls of a house to the outside. You would need a backing plate on either side, especially if the outside is stucco or brick, etc, because the nut will not cover the resulting hole. Most I've seen end up puckering the inside wall plate when the nuts were adequately tightened.

I've never seen one work out where you have the normal length of threads sticking out, one side usually has a couple of inches extra sticking out. Then you have the extra length of a coax connector on the outside, pushing the coax further out from the wall before you can bend it back toward the wall for routing. Waterproofing usually turns out looking quite messy.

I think a better and commercial approach for the outside is a 4 X 4 X 2" grey plastic waterproof junction box from Lowes or Home Depot attached to the outside wall and you can have a length of PVC electrical conduit run from the box through the wall so it will be easy to push future coax through without snagging insulation, etc. In all the commercial installations I've done they required some sort of pipe through the wall for any wires to pass. The coax can then run down the outside wall, make a U turn for a drip loop and enter the bottom of the box keeping all the coax tight against the wall.

These boxes have a cover you can remove to deal with coax and when the cover goes back on its sealed with a gasket and waterproof. The junction boxes start around $7 and come in different sizes and configurations. On the inside you can cut out a rectangular hole for a low voltage bracket that holds a standard wall plate with any connector(s) you want.

Rred said:

This is why bulkhead connectors exist. UHF (SO-239) female connectors, back to back, with anywhere from 2" to 12" of solid metal connection between them. Drill a hole in the wall, insert the bulkhead connector with sealant for a permanent installation (slanting it slightly to ensure any moisture runs out not in) and then just put a PL-259 standard cable into each side of it.

One hole, one fitting, quick and easy.

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Hi PRC, you can get the nuts that are oversized for barrel connectors from American Radio Supply, They work very well for outside connections.
https://www.americanradiosupply.com...-uhf-bulkhead-connectors-nickel-plated-brass/
You can also get the washers that are oversize also.
https://www.americanradiosupply.com...-uhf-bulkhead-connectors-nickel-plated-brass/