Solderable Brass Body S0-239 for J-Pole

[KJ4CYV]

Help!

I am working on a 2m/70cm Copper Cactus J-Pole Antenna and I need to solder the body (The ground side flange) of a SO-239 connector directly to one of the radiators. I quickly found out that the ones sold at RS (#278-201) are made of zinc and quickly melt away when breaking out the propane torch to solder it to the 3/4" copper pipe. Worse, they are chrome plated which has to be ground or filed away prior to soldering.

The first attempt ended up with a completely melted mess - the zinc flange simply collapsed altogether and was a 'surprise'. On the second try, I realized that zinc just isn't going to work. I tried to apply the heat to the pipe and not the flange as well, but the solder and the zinc flange on the connector seem to melt around the same temperature.

I had no problems keeping the plastic center conductor cool as I screwed in an old PL-239 plug wrapped with a wet paper towel on the SO-239. This worked well to help sink the heat away from the insulator when trying to solder one of the flanges to the pipe.

Does anyone know where I can get a SO-239 that has a body made out of brass instead of Zinc? I really need one that is solderable - on both the center conductor and on it's body (flange) as well. I just can't tell what's good or not (or if they are all zinc anyway) from the varous ham stores that are online.

You can see exactly what I am trying to do, in the 'Copper Cactus J-Pole" elsewhere in this forum.

http://forums.qrz.com/showthread.php?t=154609

[VK2AKG]

I am working on a 2m/70cm Copper Cactus J-Pole Antenna and I need to solder the body (The ground side flange) of a SO-239 connector directly to one of the radiators.

I used a length of 1 inch diameter galvanised water pipe for my 2m J pole and ran the coax _inside_ the pipe exiting through a hole at the tapping point where the braid was connected to the mast (active element) section and the coax centre was connected to the quarter wave stub (made from 1/2 inch diameter galvanised water pipe welded to the mast).

The antenna has been up for over 28 years so I don't really remember how I connected the coax to the antenna but I think I used small lugs secured by 1/8 inch screws inserted into tapped holes in the pipes. I must also have sealed the coax (most likely using silicon rubber which was then coated using a 2 pack epoxy as I was using that technique in other areas at the time).

This method of connection:

- removes the need to attach a connector to the pipe

- locates the connector in a more protected (and accessible) environment

- helps protect the coax from bird attack (cockatoos (http://images.google.com.au/imgres?imgurl=http://www.currumbin-sanctuary.org.au/graphics/popups/wildlife_birds_sulphurcrest.jpg&imgrefurl=http://www.currumbin-sanctuary.org.au/content/standard.asp%3Fname%3Dsulphurcrestedcockatoo&usg=__YT2hj-stq0R-HB-TH7SU1tS_ZWI=&h=520&w=347&sz=26&hl=en&start=14&tbnid=nymXgV-xlK_CtM:&tbnh=131&tbnw=87&prev=/images%3Fq%3Dsulpher%2Bcrested%2Bcockatoo%26gbv%3D 2%26hl%3Den%26sa%3DG)love coax)

- has lasted 28 years so far (as has my brother's antenna made at the same time)

If you still want to place your connector on the antenna then why not make it easier for yourself, solder a "flag" onto the pipe and screw one side of the connector to that flag?

73 Frank

[KC4YLV]

You can get a solid and long-lasting connection by cutting the head off a brass machine screw and soldering that well to the copper pipe, then using star washers and nuts to secure the SO-239 to the pipe. Dope it with nail polish all around when you're done.

If it's up long enough to deteriorate, you aren't experimenting with your antennas enough. :D

[WB2WIK]

If you use a real Amphenol brand SO-239, it solders just fine (the body and flange are silver plated brass, standard).

They're easy to find at any Amphenol distributor, which number in the hundreds.

[W8JI]

Help!

I am working on a 2m/70cm Copper Cactus J-Pole Antenna and I need to solder the body (The ground side flange) of a SO-239 connector directly to one of the radiators. I quickly found out that the ones sold at RS (#278-201) are made of zinc and quickly melt away when breaking out the propane torch to solder it to the 3/4" copper pipe. Worse, they are chrome plated which has to be ground or filed away prior to soldering.

Radio Shack is an exception. Those connectors are pot metal, not zinc. If they were zinc you could solder to them.

Almost any SO-239 except Radio Shack's trash will solder.

Some have nickle plating and you have to grind the plating off, but with the exception of Radio Shack I've never found one I could not solder.

Just go on line and search for a "teflon SO-239" or "teflon UHF female". Any of the teflon connectors will be silver or nickle plated brass, and the worse you have to do if they are nickle is file a clean spot.

73 Tom

[VK2AKG]

re my:

I used a length of 1 inch diameter galvanised water pipe for my 2m J pole and ran the coax _inside_ the pipe exiting through a hole at the tapping point where the braid was connected to the mast (active element) section and the coax centre was connected to the quarter wave stub (made from 1/2 inch diameter galvanised water pipe welded to the mast).
it was a good day for a photo so have uploaded.

73 Frank

[KJ4CYV]

OK - I'm back again...

I am going after Dale's (N6JSX) idea of making the long end of the J-pole 63" and the stubby part 19" - Dale says that it improves performance on the 440 band, leaving 2-meters 'as-is'.

http://www.eham.net/articles/2418 (http://www.eham.net/articles/2418)

However, Dale also mentions an alternate feed method by WD8LLN. I am trying to improve that my making a drip shield as well. I took a SO-239 connector and ground it to a circle to fit inside a 3/4" FIP (threaded female copper pipe connector) - I want to heat up the pipe so I can solder the edge of the S0-239 connector and lock it in there. I have a grommet where the wire comes out of the side of the pipe and can keep it cool with a wet rag. (By the way, I am going to order the Amphenol SO-239!! - Just my luck to start out with the only unsolderable -Radio Shack- connector that's out there - Thanks for the heads up Tom!!)

A few questions though, Frank (VK2AKG), has his feed the other way. The center of his coax goes to the stub instead of the long pipe. Some have the center of the coax going to the stub and others have the center going to the long pipe. Does it really matter which side you feed it from as well?

I'll admit, I don't quite fully understand the physics behind how this matching transformer works, and I am getting a high SWR of around 2 on this thing right now. Perhaps the WD8LLN feedpoint method is for a shorter length 57.7" element instead of a 63" element. Any ideas there?

A few last things to mention - I am also using 3/4" inch copper pipe instead of 1/2".

Attached are some jpg's of what I am trying to do..

Thanks for your help guys!

73 -Stu

[ZL3GSL]

The "physics" of the transformer isn't too hard, Stu.

The radiating element is a halfwave (or multiple of halfwaves) long. That has a high impedance at each end, so a direct 50 ohm feed at the bottom would give a gross mismatch. So it's fed from the transformer which is a 1/4 wavelength transmission line, shorted at the bottom end -- "zero ohms". At the top, it has a "high" impedance, matching the radiator. At some point on the line, between zero ohms and high ohms, there will be a match to 50 ohms. Of course, this is exactly true at only one frequency. ;)