Coax Cable question

FORD77 · Oct 13, 2014

I just purchased a new BCD536HP and looking for cable to run from my antenna to the unit. I got a used discone antenna from my buddy and will be mounting it on the roof this weekend. The run will be across the roof, down the side, in the window and across rec-room to my listing station. Run is about 125 feet or so. Here is the question. what cable should I use? I have access to RG-58 however reading that LMR-400 is the best.... Don't have any access to that so would need to purchase online. Options? Just in case you need it here are my specifics. New BCD536HP, used radio shack discone, listen to pretty much just Colorado Springs Fire and EMS and El Paso County fire. Thanks for the help.

ofd8001 · Oct 13, 2014

LMR-400 would be your better choice. RG 58 is pretty bad about line loss, especially with higher frequencies. So anything you gain by having an outside antenna is gobbled up by line loss as you have a pretty long run.

The link below is to a pretty handy chart showing line losses:

Coax Attenuation Chart

There cardinal rule about outside antennas: "Mount as high as possible and use the best cable you can afford".

joeuser · Oct 13, 2014

FORD77 said:
I just purchased a new BCD536HP and looking for cable to run from my antenna to the unit. I got a used discone antenna from my buddy and will be mounting it on the roof this weekend. The run will be across the roof, down the side, in the window and across rec-room to my listing station. Run is about 125 feet or so. Here is the question. what cable should I use? I have access to RG-58 however reading that LMR-400 is the best.... Don't have any access to that so would need to purchase online. Options? Just in case you need it here are my specifics. New BCD536HP, used radio shack discone, listen to pretty much just Colorado Springs Fire and EMS and El Paso County fire. Thanks for the help.

For that long of a run I'd go with RG6. You want some good cable esp. with a Discone. You'll lose quite a bit on the run if you with anything less & assuming you'll be monitoring 800's. You could use RG8 if you had a shorter run... LMR400 is good also!

mmckenna · Oct 13, 2014

Why does the antenna need to be across the roof? 125 feet of cable isn't going to do you any favors. You really want to keep the coaxial cable as short as possible. The longer the cable is, the more signal you will lose, and that means there will be radio traffic you may not be able to hear.

FORD77 · Oct 14, 2014

mmckenna said:
Why does the antenna need to be across the roof? 125 feet of cable isn't going to do you any favors. You really want to keep the coaxial cable as short as possible. The longer the cable is, the more signal you will lose, and that means there will be radio traffic you may not be able to hear.

Well, have to keep the wife happy as well. She wants in mounted on the back north side of the house and i will be shielded from view by trees from the street. It is either that or no roof mount..........

joeuser · Oct 14, 2014

mmckenna said:
Why does the antenna need to be across the roof? 125 feet of cable isn't going to do you any favors. You really want to keep the coaxial cable as short as possible. The longer the cable is, the more signal you will lose, and that means there will be radio traffic you may not be able to hear.

Exactly and on a no gain antenna its crucial!

DisasterGuy · Oct 15, 2014

RG-6 quad shield cable or RG-11 will do the trick assuming you aren't trying to pull in a really weak signal (if that were the case you would want a different antenna anyway). Just make sure you ground and bond using a ground block at the point the cable makes its bend from the mast to the roof and again before entering the house.

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joeuser · Oct 15, 2014

FORD77 said:
Well, have to keep the wife happy as well. She wants in mounted on the back north side of the house and i will be shielded from view by trees from the street. It is either that or no roof mount..........

Yes, the wife. How about an attic install? The loss you'd take in the attic would be less then running 125ft. You really want that run under 50ft...

ridgescan · Oct 15, 2014

You would think that a wife should encourage a man's hobbies to a point. A scanner antenna is barely obtrusive IMO compared to even some TV aerials. I have a d130j and a Wellbrook SW loop on the roof of my apartment building-and because they look professional and unobtrusive even on 10' masts, the owners approved, as did my girlfriend when she first saw them-"oh those aren't bad at all". And she doesn't take to too much antennage either. So long as you don't get all crazy with stuff popping up all over the place, maybe show her what it'd look like up there one time-she may just feel the same.
BTW I run Times LMR240 cable here-numbers close to LMR400 but not as fat=easier to work with.

copperhd · Oct 15, 2014

I have a Diamond discone with about the same run (120') of rg6 put to a 996xt & I'm between two hills in a valley, yet it picks up digital radio 50+ miles away easily. I have access to and have always used rg6 (tv cable) its small diameter, low loss, & connecters/adapters are readily available. Don't let the 75 ohm impedance fool you, it doesn't matter for receive only purposes.

joeuser · Oct 15, 2014

copperhd said:
I have a Diamond discone with about the same run (120') of rg6 put to a 996xt & I'm between two hills in a valley, yet it picks up digital radio 50+ miles away easily. I have access to and have always used rg6 (tv cable) its small diameter, low loss, & connecters/adapters are readily available. Don't let the 75 ohm impedance fool you, it doesn't matter for receive only purposes.

Yeah RG6 is the best bang for the buck right now. I have RG8 on my main antenna now, but only because of the proximity to electronics, computers ,& other pollutants...

FORD77 · Oct 16, 2014

Well I think I won half the battle. Moving the antenna closer and now run will be about 80 feet. Best I can do... Thanks for all your help guys.

ofd8001 · Oct 16, 2014

While a goal of antenna cabling is to keep the run as short as possible, be sure you leave a "little extra" at each end should the need for connector replacement arise.

FORD77 · Oct 16, 2014

ofd8001 said:
While a goal of antenna cabling is to keep the run as short as possible, be sure you leave a "little extra" at each end should the need for connector replacement arise.

Wow, good point. Did not think of that one.

DJ11DLN · Oct 17, 2014

FORD77 said:
Wow, good point. Did not think of that one.

Yeah, having to put a splice 2' from a termination is aggravating. You don't want any splices at all, if possible. :wink:

Coax Cable question

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