In-line joining of coax

VK2CSW · Post by **VK2CSW** » Sun Apr 17, 2016 10:17 am

I need to relocate my radio set up. To do this will obviously require the re-positioning of my coax runs.

Now, before all and sundry decide to offer their vast experience and tell me, in no uncertain terms, that I should never make joins in the coax run, or I should use ladder line, etc, please accept this as being immutable: At this point in time I can do none of these things - I will need to make a join in the cables. mmmkay?

So with that out of the way, what is the best method to join coax in-line? It is RG-58 and is used for both UHF/VHF and HF.

Thanks

VK1JA · Post by **VK1JA** » Sun Apr 17, 2016 10:41 am

Hi Colin,

RG-58 is quite thin when it comes to inline joining without the use of connectors. There are ways of inline joining hardline which can be 'ok'.

Are you able to use N connectors to join the two pieces?

VK4GHZ · Post by **VK4GHZ** » Sun Apr 17, 2016 11:05 am

RG-58 at VHF and UHF???

In no uncertain terms, replace it all with runs of LMR-400.
Do it once.
Do it right.

VK3TU · Post by **VK3TU** » Sun Apr 17, 2016 1:04 pm

If it's only RG-58 that you intend joining, clearly the majority of the losses are going to be in the coax and not any additional connectors you might install. I'd simply put in a male/female BNC pair in each coax. If you use crimp types, the tensile strength is pretty good because it's mostly the braid that takes the load and if you wrap the whole thing with Butyl rubber tape, it should last ages.

In the overall scheme of things, the connectors will not account for much additional loss and any impedance bumps the connectors introduce will be smoothed out by the fact that the coax loss will be present in both forward and reflected directions.

Bert
VK3TU

ZL3RC · Post by **ZL3RC** » Sun Apr 17, 2016 1:57 pm

You can join RG58 any way you like at HF it simply doesn't matter.

How long are these "coax runs" as even at 10m "good" RG58 has a loss of around 6DB over 100ft.
Its not the coax you should be using at VHF and at UHF its an attenuator.
You say its RG58 and not even the U type so if its been outside exposed to the sun its stuffed anyway.

Chuck it all out and start again with LMR400 you won't regret it.

The RG58 you have now will make a good draw wire

to pull the LMR400 through with

VK4KX · Post by **VK4KX** » Sun Apr 17, 2016 2:50 pm

As others have said RG58 is a bit on the light side for the job.
I see no problem with it being used on the lower HF bands but it's not suitable for VHF and UHF as it is way too lossy, and with regards to joining it you can use 2 pl259 connectors with a barrel in the middle with minimal insertion loss and still maintain 50ohms impedance. It can also depend on how many watts you put through it as well.
It's not advisable to connect the conductors to each other and the braid to each other with joiners or solder and then tape over it, that's a bad way to do it.

For VHF & UHF you would be best suited to, at a minimum RG213, but LMR400 would be more suitable with "N" connectors of course, but I'm guessing you don't have that luxury or can afford it in long runs.
If you have the funds and need to make a long run you could use 1 long length of LOW loss cable to feed them all and switch between antennas near the feed points with a relay switching circuit, either home made or the MFJ/Ameritron device. RCS 4 or higher, I have an RCS 8 for HF and can switch between 8 antennas and also have a 2 position antenna solenoid as well for UHF/VHF.
Hope that helps.

Regards
VK4KX

ZL1TPH · Post by **ZL1TPH** » Sun Apr 17, 2016 3:10 pm

Hi Colin,
This is my input of how to join.
I'm reading you just want to join together, rather than upgrading.
Trim up both ends ready to butt together for joining and then solder the two inners together.
Then join the two outers together by rapping around some aluminium tape or maybe some aluminium kitchen foil.
Then tape up or use a suitable size heat shrink.
I don't think you would go wrong with above and it wont cost nothing.
Cheers, Steve

VK4TI · Post by **VK4TI** » Sun Apr 17, 2016 5:15 pm

Joining will produce yet another impedance lump , spend 20$ and upgraade to at least rg something thicker

VK4GJW · Post by **VK4GJW** » Sun Apr 17, 2016 5:35 pm

Well Colin as it is immutable, you have to do what you have to do. Use the best high quality connectors that you can, take your time, make sure it is all clean and precise, and do it! Yes as has already been said, RG-58 is not the most ideal, but I use it here for my 2/70 Yaesu FT-8800. My run from the radio to the antenna is at most 7 Mtrs, but like you, it is what it is. Each inline join typically adds 0.1 to 0.2 dB loss in signal, unless you do a really BAD termination! Try not too! You will get more loss in the coax, but again because it is immutable, you will live with it like I do. Just do a good job on the connectors and dont sweat it! And yes, ONE DAY I will replace the coax with something better, but right now, like Colin it is immutable here too!

VK3KCX · Post by **VK3KCX** » Sun Apr 17, 2016 5:53 pm

Hi Colin, I use LDF450 Heliax and N type connectors on everything here and you can also!

This is what you do, the very next time that you out driving around and you see a crane or bucket truck alongside a cell tower, go and speak with the riggers and ask if they are doing an antenna upgrade.
Should this be the case there is a very good chance that they will be fitting new multiband panel arrays and also replacing the feedlines with bigger coax that has better performance in the GHz range.

The old coax is usually just scrapped - I was able to get 6x 35M lengths for a slab of beer!

You will be shocked how much more you will hear on UHF when you ditch the RG58.

- David

VK4WDM · Post by **VK4WDM** » Sun Apr 17, 2016 7:10 pm

"The old coax (actually heliax) is usually just scrapped"

Yes, and so are the connectors. This is a criminal waste!

You can sometimes buy it back from the metal recyclers at a reasonable price.

I am lucky, we have a local ham who is involved in the industry and he collects some for the local club which sells it off to members. My latest 20m run of LDF450 cost me $20 at the club auction!

By all means do what you have to do now but as others have said look for a chance to upgrade.

73

Wayne VK4WDM

VK5PJ · Post by **VK5PJ** » Sun Apr 17, 2016 8:06 pm

Hello Colin,

VK2CSW wrote:I need to relocate my radio set up. To do this will obviously require the re-positioning of my coax runs.
So with that out of the way, what is the best method to join coax in-line? It is RG-58 and is used for both UHF/VHF and HF.
Thanks

Do you know anyone with a crimping tool for RG58, you can buy some BNC male and BNC inline female and do the join that way at no great expense and the result is quite small if you need to hide it.

Using CRIMP is the neat method and avoids having to heat the inner of the coax with a soldering iron, as that is usually the part that most get caught on as the inner dielectric melts.

Good Luck,
Peter, vk5pj

VK2AVR · Post by **VK2AVR** » Sun Apr 17, 2016 8:11 pm

Crimp or solder a connector onto each cable and use a joiner.

It won't talk to Voyager but you'll still be on air.

VK2CSW · Post by **VK2CSW** » Mon Apr 18, 2016 6:08 pm

Thanks for the replies and ideas.

While I understand that RG-58 is less than ideal, at this point in time, it cannot be avoided.

I think the crimped BNC connectors will be the solution - I had completely forgotten about those - I've terminated thousands of the buggers in a past life (anyone remember token ring networks?). I've probably got the connectors and joiners kicking around in an old tool bag, along with the crimping tool and stripping tool.

The 2m/70cm stuff is generally FM and repeaters so to be honest it really isn't a big deal. If/when time makes itself more plentiful then some of the more exacting modes will come into play...

Thanks again.

ZL3OZ · Post by **ZL3OZ** » Wed Apr 20, 2016 10:41 am

Every one else has thrown their opinions in so why not me too.

In my years of land mobile vhf coms in vehicles and buildings making joins in RG58 whether its U or AU or what ever or plain old RG104 in the old days I made coax joins almost every day.

Yes it make impedance "bumps" introduces tiny parts of a dB of loss etc. The science says never do it but the practicality says "hey no problem" if you are not doing EME or scatter etc.

30 years ago I wanted to put up some 2M aerials at my first house newly married low paid job and no spending money.
I hauled all the small scraps of a mtr or so of RG58 out of the offcut bin at work. I made about 16 joins to get to my 6el X beam on the roof. Tweeked the gama match to a low SWR and during the mid eighties worked 150Km into Christchurch most days I wanted to and over 30 VK qso during SpE season over a few years on 2mtrs till I could afford some RG213.

Steve gave it the simplest and thats my way. Strip the coax open and fold the braids inside out back over the outer insulation, solder the centres. Wrap a few turns basic plastic ins tape around the centre connection. Push one braid back over the tape and twist it down hard. Push the other braid forward over the first one and twist it down firm. Spot solder in just one place through both braids in a way that doesnt melt through your insulated inner joint. (just a spot through both braids) then tape the whole thing up with self amalgamating rubber tape.

I will not put an embarrassed emoticon up for this. I would do it again today after lunch if the need arose.
Sure you do it with Heliax if you want to do low sig work all the time but to trigger the local repeater....?

proud Kiwi.
OZ

ZL1TPH · Post by **ZL1TPH** » Wed Apr 20, 2016 6:00 pm

Thanks Ken,
Keep it simple is best.
Cheers, Steve

ZL2WHO · Post by **ZL2WHO** » Wed Apr 20, 2016 6:55 pm

Strip back the ends, expose the conductors, twist them together and bung some tape over it. If it works for 230v then it should work for RF.

ZL3RC · Post by **ZL3RC** » Wed Apr 20, 2016 7:09 pm

ZL2WHO wrote:Strip back the ends, expose the conductors, twist them together and bung some tape over it. If it works for 230v then it should work for RF.

You bloody animal

VK3ZAZ · Post by **VK3ZAZ** » Wed Apr 20, 2016 7:49 pm

VK2CSW wrote:I need to relocate my radio set up. To do this will obviously require the re-positioning of my coax runs.

Now, before all and sundry decide to offer their vast experience and tell me, in no uncertain terms, that I should never make joins in the coax run, or I should use ladder line, etc, please accept this as being immutable: At this point in time I can do none of these things - I will need to make a join in the cables. mmmkay?

So with that out of the way, what is the best method to join coax in-line? It is RG-58 and is used for both UHF/VHF and HF.

Thanks

RG58? just solder it together its that crappy a join wont make any difference.
I just joined my TH3 choke 12 turn lead today after I inadvertently tightened up the nut and crimped it so I went up cut it stripped it plucked out the braids soldered them and then joined the inner and wrapped it in tape but it is HF / DC.

I ran a fly lead of rg58 once on my hf amp and it melted.. it was 12 inched long

VK3KCX · Post by **VK3KCX** » Wed Apr 20, 2016 7:56 pm

Re: In-line joining of coax

30 years ago I wanted to put up some 2M aerials at my first house newly married low paid job and no spending money.
I hauled all the small scraps of a mtr or so of RG58 out of the offcut bin at work. I made about 16 joins.

Groan... if only you could see what the swept response of this looks like... this is probably quite ok at 80m, but the only reason that you might see an acceptable VSWR on 2m is because the loss happens in both directions.

- David