Antenna Cable question

[dgoodson]

I am about to re-roof my home, so I must temporarily remove my external antenna. Its a basic setup that works well... a simple quarter wave ground plane with (don't laugh-) a preassembled 50' length of Radio Shack RG-58 cable; About 10 feet of the 50 foot length is excess... I have never bothered to cut to length. Its all set up for plain vanilla VHF monitoring (154 MHz range)

So after the roofers leave and I reinstall the setup, I want to upgrade the cable to something with less loss, and move the mast to a little higher spot on the roof. So I'll probably need about 60 feet of cable total.

The antenna accepts a PL259 plug, and the radio a BNC, at the wall entry, I'd like to have PL259 female to female feedthrough mounted to a wall plate.

I do not want to get into big bulky cables, so is RG-6 the right choice?

Will I add significant loss by installing the wall feedthrough (versus having continuous cable from antenna to radio)?

Is now the time to add a preamp at the antenna? I'm in a fairly rural area so I don't think I have much of an intermod issue. But I don't know if those things are considered more trouble than they are worth....

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Finally, I'd appreciate any recommendations on where to buy online... I have a couple of weeks to get all this together.

Thanks,

dave

 

[crayon]

I do not want to get into big bulky cables, so is RG-6 the right choice?

Splitting hairs here .. RG-6 is a 75 ohm cable. If you are wanting to upgrade your RG-58, RG-8 is a good choice.

Will I add significant loss by installing the wall feedthrough (versus having continuous cable from antenna to radio)?

You are always going to have insertion losses anytime you have connectors.

Bulkhead (or wallplate) connectors are used all the time, and as with anything else in life, you get what you pay for.

 

[gcgrotz]

I just re-installed my stuff after moving and since I have a much smaller space I decided to go with a metal wallplate. I used 2 bulkheads for HF and V/Uhf antennas, and I also ran 1" tinned braid from a 1/4' stud on the wallplate down to the entry point. I had conduit put in the attic space of the addition we just put on, it goes through the wall in my upstairs room, across the new attic space and out under the eaves where I ran it down to a box that has grounding and lightning protection. This seems to work good although I haven't yet tried transmitting since I don't have that antenna up yet.

Anyway, use a wallplate, and don't worry about a feedthru or bulkhead adapter. Worry more about doing a good job installing the connectors. And if you use a stainless steel plate like I did (double gang size), do yourself a favor and take it to a machine shop and have them punch holes in it. Mine cost $16 to do and worth every penny. If you've ever drilled one of these you will know what I mean and they did a neater job than I could have.

RG8x works good for runs of say 75' or less and is flexible and easy to work. But don't get RS stuff, order some decent stuff on line like the wireman or cable x-perts.

Good luck!

 

[buffalogoat]

I agree with crayon, if you want to stay with 50 ohm coax, go with RG-8X. For 75 ohm coax, I would use RG-6Q (quad shield). As far as signal loss from a wall plate... Don't worry about it. If you use good quality connectors that are crimped or soldered properly, your signal loss should be less than you could even see with a S-meter.

 

[kb2vxa]

Hi Good and readers,

Just to get this silliness out of the way first;

"You are always going to have insertion losses anytime you have connectors."

Lindsay should dump all this nonsense into one thread and make it sticky just so you won't have to search all of them to have a good laugh. I won't even bother, the horse being whipped is so dead.

Knowing nothing about your specific situation a specific answer is not forthcoming. Just do what works for you and keep it simple, only scrap that crap coax and shoot for something like RG-8AU polyfoam for the best bang for the buck. I used to say Belden 9913 but the real deal is becoming hard to come by being it's air dielectric cable being rapidly supplanted by semi-rigid line.

A VHF groundplane is on a par with the Scantenna and the like, you won't get signal gain on any common scanner antenna. You may consider the Traintenna (Google is your friend) or the equivelent VHF gain omni rather than an amplifier since using one to make up for an inadequate antenna makes no sense at all. We hams have a saying, "90% of the shack is on the roof" and we didn't pull it out of thin air.

A good antenna and transmission line are all important, a receive preamplifier is the court of last resort and our use for them is specialized and quite unlike yours, even the amps are totally different. With few exceptions those "DC to light" craplifiers cause more problems than they solve and intermod is but one of them.

All of this comes down to KISS, keep it simple stupid, and if it ain't broke don't fix it. The more you complicate things the more there is to go wrong, if it worked before don't chance lousing it up. I remember a near disaster the Allies made in WW2, they even made a movie out of it. Don't you go A Bridge Too Far with too many "improvements" or you may end up a POW, a prisoner of work. Ja gut? Iss nicht werken dumbkopf! (;->)

 

[crayon]

Just to get this silliness out of the way first;

"You are always going to have insertion losses anytime you have connectors."

Lindsay should dump all this nonsense into one thread and make it sticky just so you won't have to search all of them to have a good laugh. I won't even bother, the horse being whipped is so dead.

lol. Between posting wrong information, marginal attempts at humor, and gnat straining rebuttals .. your killing me!!

As I was typing the orginal post, swear to god, I thought that if I did not acknowledge the existence of insertion losses, some moron would pipe up and complain about. And yet I did and look what happens ... :roll:

*sigh*

What kb2vxa ment to say is: Insertion losses are so neglible for the average Joe, they can be ignored.

 

[dgoodson]

Yes, LOL. I was particularly struck by the rhetorical "just do what works best for you...". If I knew that, I wouldn't have asked. And I am not interested in changing antennas, just soliciting advice on cable and antennas. Anyway, thanks for all the tips. I guess its going to be some flavor of RG 8 with feedthru's.

 

[buffalogoat]

"AMEN" crayon!