I'm looking for advice for running coax cable to my shack on the second floor of my house. I'm planning to use this coax line for HF (recently upgraded to General!). I'm a newbie and I am very handy, but have never done something like this. I haven't bought an HF radio yet because I want to make sure I have a solid plan for the antenna first.

Here is a rough diagram that I drew of my house + listed two options that I have come up with:

Rough drawing of my house

Two options for connecting an outside antenna to my shack:

  1. Repurpose comcast TV coax that is already in the walls (probably 75ohm). There is already a run from the utility room in my basement to my shack. I know this route is problematic because of the impedance of the coax designed for TV.

  2. Run a new proper 50ohm coax line to the shack using the easiest route that I can find (~130 feet of cable inside the house). I'm confident I can do this successfully. My only concern is the length of cable required (~130 feet inside + ~150 feet outside to the antenna = 280 total feet).

It would be possible to create a shorter path by drilling a hole from the attic + running a cable across the roof and down the side of the house. I'd really like to avoid having to do anything on the roof though. This also is maybe a little more complicated for grounding the cable. I'd really like to avoid this option entirely if the route I have already worked out seems reasonable.

The left side of the house is my best option for putting an antenna, so I'd like to avoid any cable runs that originate from the right side.

I'm open to other ideas if people have any. Please let me know if either of the options I listed seem worthwhile.

Update 12/30/2021: I ended up deciding on a different location for my shack that will result in a much shorter cable run. Thanks for the feedback!

  • $\begingroup$ Can you pull new coax through the run that's currently being used by the 75-ohm stuff? 75-ohm isn't the end of the world, but it's probably not the best quality. $\endgroup$ Commented Sep 30, 2021 at 2:47
  • $\begingroup$ @hobbs-KC2G I am pretty sure I cannot pull a new coax through the existing 75 ohm run. It isn't a straight shot and I wouldn't be surprised if some of it is tacked down. I'm not opposed to running a proper 50 ohm line through the path I marked on my diagram. Is the length of cable required for that concerning at all? $\endgroup$
    – kr4sh
    Commented Sep 30, 2021 at 3:10
  • $\begingroup$ Do you need it for reception or also for transmission? Have a look at coax losses with such lengths. May be it is good for RX and have a TX antenna on your roof. $\endgroup$
    – user16925
    Commented Sep 30, 2021 at 12:03
  • 1
    $\begingroup$ @MikeWaters I suppose I could just try my existing 75 ohm line first since it is zero effort. I just need to poke a hole in my basement utility room + ground it. Do you recommend using 75 ohm coax for the new cable outside to the antenna? Or should I use 50 ohm? $\endgroup$
    – kr4sh
    Commented Sep 30, 2021 at 17:30
  • 1
    $\begingroup$ You should not mix impedances. $\endgroup$ Commented Sep 30, 2021 at 20:20

1 Answer 1


I'd go for drilling the hole and having a shorter cable. Go for the thicker cable (RG223 I think). This is a permanent installation, it pays to go the extra mile on this one. Make absolutely sure you have a ground where the antenna enters the house that is also connected to the utility ground via a low-impedance path. If I can recommend a website for good reading for you: https://www.w8ji.com/

  • $\begingroup$ I was thinking about going with LMR-400 if I went for a new line. I have seen lots of references to this cable type on ham forums. There doesn't seem to be as much on RG223. Any reason you prefer RG223? Thanks for the note about grounding. I think I need to have an electrician come out for that. My house seems to only be grounded to the copper water service pipe (multiple clamps). I can't find a ground rod anywhere and my meter is attached to a wood post by the street ~300 feet away from my house with service lines buried. Weird! $\endgroup$
    – kr4sh
    Commented Sep 30, 2021 at 17:40
  • $\begingroup$ RG-223 is special-purpose cable with an outside diameter of about 5.4 mm (0.212"). I think @Jack0220 meant to recommend RG-8 or similar with a diameter of about 10.3 mm (0.405") and rated for more power. I believe RG-8 is a generic specification; LMR-400 is one of the best examples of cable in that class. $\endgroup$
    – rclocher3
    Commented Sep 30, 2021 at 20:22
  • $\begingroup$ To find your ground rod, find your service panel with the circuit breakers in your house, go outside the house to the spot that is the other side of the wall that the service panel is mounted on, and look down. You should see a thick wire (current code calls for 4 AWG or thicker) from the house to the ground rod, which is usually driven into the earth close to the foundation. $\endgroup$
    – rclocher3
    Commented Sep 30, 2021 at 20:28
  • $\begingroup$ I admit I don't know my way around cable very well :) I just meant for whatever cable to go with the upgraded version if you can, thicker cable is harder to route around corners but has less loss, the is also good for receiving weak signals. The ground rod is one thing and is important but another is the ground coming from the utility service drop. Both those grounds, from your antenna and from the utility need to have a low impedance connection. This is according to w8ji who says his antenna gets hit at least once in every lightning storm :D $\endgroup$
    – Jack0220
    Commented Sep 30, 2021 at 22:44
  • $\begingroup$ LMR-400 comes in regular and "UltraFlex". However it turns out that the bend radius specification is the same for both: 1" (25 mm) at installation, and 4" (100 mm) "repeated". I think they mean that you can put it through a bend with a 1" radius during installation, but as installed the cable should have a bend radius of 4" minimum. The difference between regular and UltraFlex is that UltraFlex can be bent repeatedly. If your coax needs to go through sharp bends, you could use right-angle connectors. $\endgroup$
    – rclocher3
    Commented Oct 4, 2021 at 14:04

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