Slack cable, laid out or coiled?

[UlteriorModem]

I think this is the right section for this...

I have some slack cable in my LMR400 cable that leads out to my discone.

Similar situation with a lead out to a G5RV.

I was wondering if it is better to loosely coil the extra cable, or to just sort of lay it out in a big loop?

Or does it make any difference at all?

 

[KB4MSZ]

If it is enough cable to have to coil it up I would think it best to shorten it. Especially on VHF/UHF bands.

 

[UlteriorModem]

Yea thing is it's LMR so expensive as heck and I am not really all that good at terminating it.

The old saying "I cut it off twice and it's still too short"

 

[Ubbe]

I was wondering if it is better to loosely coil the extra cable, or to just sort of lay it out in a big loop?

Tighly wound in a smallest possible diameter that the coax can take without damage, maybe 2ft. One coil as close to the antenna as possible and another coil as close to the receiver as possible. They will work as choke baluns and helps keeping RFI out.

/Ubbe

 

[prcguy]

Sort of but not really. Ok, its a waste of time doing that. At some very narrow range of frequencies with just the right inductance it will reflect some RF back towards the source but if you have RF on the coax you want to absorb it with ferrite and not reflect it back so it can bounce around and still be there.

In the testing I've done where there is obvious RF on the feedline, I've never been able to cure it with coiled coax but I have totally eliminated it with a good ferrite choke.

Tighly wound in a smallest possible diameter that the coax can take without damage, maybe 2ft. One coil as close to the antenna as possible and another coil as close to the receiver as possible. They will work as choke baluns and helps keeping RFI out.

/Ubbe

 

[vagrant]

1. Avoid making a small diameter coil/balun using LMR-400.
2. When you go to coil it, it may tend to form back to the spool it was on which is okay, or loosely coiled is fine. No need for a big loop.
3. Buy/build an RF choke balun, or two, if you need a choke balun. You would test it at the antenna feed point first. You may not need one at the transceiver.

As previously noted on VHF and especially UHF less coax is better, even if it is LMR-400. If it is under 25' I wouldn't bother to shorten it, but to each their own. Also, if you can hear UHF signals and you're happy, stay happy and leave it alone.

 

[Ubbe]

Ok, its a waste of time doing that.

Seems to work when I use RG58 and takes 10 sec to do and two tie wraps. At some points in the coil the RF riding on the outside of the coax will meet the RF in opposite phase from another turn of the coax and cancel each other out. It doesn't hurt to do it and you'll get rid of the excessive coax in a nice looking coil.

/Ubbe

 

[jonwienke]

That's not how choke baluns work. And shorter is better.