How to attach a 1/8" brass rod stock to an SO-239 chassis mount connector?

[WF7A]

The title asks it all: What would be the best way of doing that? I'm trying to build a 1/4" wave groundplane antenna for 127 MHz using 1/8" brass rods as elements. I tried a tap-and-die set to thread the rod stock for the four holes used to mount the connector to the chassis but brass being so soft, the nuts stripped the threads silly, so I suspect tack-welding them into the holes in my next option? (I thought of using a torch and solder, but I'm afraid I'll melt the insulator inside the connector.)

The radiator's diameter is a little wider the than connector's center pin so again, same problem: how to attach it?

After all is said and done, the antenna will be placed inside a PVC pipe cap then sealed with some kind of goo--any recommendations for that as well? (I thought of JB Weld since _nothing_ can get through that! :)

[VK2TIL]

Use of a Teflon-insulated socket will help with the excess heat problem.

For the radials, get or make four substantial eyelets (used in electrical work); solder each radial to an eyelet and bolt each to the SO-239.

Or roll the end of each radial into a loop (if the brass is ductile) and attach with nuts/bolts/washers.

For the vertical; solder is easy if you have a Teflon SO-239. It can be done with non-Teflon insulation; heat the rod, not the centre-pin, until the solder flows at the joint. You are, effectively, using the rod as the soldering iron "bit". A small gas torch will do.

There are lots of other ways I can think of; the above seem simplest.

I would use silicon sealer for the pipe cap housing.

[K9FV]

Perfect way to attached the brass rod to the center pin is just as previous poster say.... If the brass rod does not bend easy to an eyelet, you might heat it red hot then dunk in water to cool - that's the way to aneal brass, while with steel/iron it makes brittle....


Remember normal silicone RTV has acetic acid as the solvent......

73 de Ken H>

[WF7A]

Thanks, guys--great input! I was desperate and picked up an SO-239 chassis mount connector from *ugh* Radio Shack, so I'm pretty sure there's no Teflon in there.

I take it the "eyelets" are ring terminals, but if not I'll find out when I go to Gnome Depot tomorrow.

Thanks again!

[VK2TIL]

"Ring terminal" sounds about right.

You could make some; a short (1" or so) strip of brass (1/4" or so wide) with a hole in one end.

The centre vertical/pin connection could be "sleeved" with brass tube as sold by hobby shops.

The problem with soldering cheap connectors often comes from the metal they're made-from and/or the plating. You heat & heat and the @#^* solder won't take; then the insulation collapses. :(

If you can avoid soldering to the body of the RS connector you will have less trouble. The pin should solder OK if clean.

The ARRL has details of a ground-plane vertical;

http://www.arrl.org/tis/info/pdf/0791033.pdf

A similar design appears in the Antenna Book.

[WF7A]

The sleeve is a great idea...though it'll cost me more in fuel to buy it than the tubing (the nearest hobby store is about 80 km from here). :S

The Wifoid is going to laugh at me:

"So, how much did your two-dollar antenna cost when all was said and done?"

"Oh, about thirty."

[VK2TIL]

I share your pain; "odd" things are difficult to get where I live, too.

Over the years I have followed the practice of buying several items when I only need one; my junquebox is huge!!

The upside is that I can make most things from materials/parts that I already have.

We know what many others don't; it's not about $$$, it's about satisfaction, learning and a few other things.

"I made it myself"; a wonderful phrase.

[ZL3GSL]

If the rod is too big to fit in the centre of the socket, file it until it does. ;)

[KR2D]

If the rod is too big to fit in the centre of the socket, file it until it does. ;)

Or use it as an excuse to buy a lathe. One can never have too many tools ;)

[N5RLR]

The Wifoid is going to laugh at me:

"So, how much did your two-dollar antenna cost when all was said and done?"

"Oh, about thirty."
Tell her that it's good ol' American capitalism at it's best: High labor cost for an inexpensive item. :p

A bench grinder can be handy for dressing down the diameter of rod stock to fit into the center pin of an SO-239. I've done this with welding-rod λ/4 2m groundplanes. :cool:

Also, an SO-239 bulkhead jack mounted to a large fender washer can work. This would offer room to use larger screws to accommodate a loop bent into the end of a ground radial.

Make a downtube from 5/8" ID tubing; hose-clamp this over the body of the PL-259 connecting to the groundplane. Also use hose clamps to attach the downtube to a mast.

Whoops...we may be edging toward $45-$50, now... :D

But...I wouldn't recommend using JB Weld. It contains iron/metal powder, which may "excite" in the presence of RF [you didn't say if the antenna was to be for transmit; if only for receive, then this point may be moot].

[W7WTO]

I used welding rod also and hammered the end flat then drilled a hole through it. Used screws and nuts to mount them to the SO239. I chucked up the center welding rod into my drill motor and filed it down in no time so it would fit into the center pin.
The blacksmith method almost always wins out.

[K8ERV]

If the rod is too big to fit in the centre of the socket, file it until it does. ;)

OOOH! That might hurt!!

TOM K8ERV Montrose Colo

[KD8CGF]

Quickest way to do this for a 1/8" rod not longer than 2" would be to chuck the piece in an electric drill, then wrap a bit of emery cloth or similar around the rod while spinning it in the drill. Burnt fingers possible here. Easier to over-remove material, stop & check frequently.

[W6GQ]

Gorilla glue!

http://www.gorillaglue.com/

OR

Since the money is just rolling out of your pocket, get a discone.

[N1UVW]

"For the radials, get or make four substantial eyelets (used in electrical work); solder each radial to an eyelet and bolt each to the SO-239.

Or roll the end of each radial into a loop (if the brass is ductile) and attach with nuts/bolts/washers."

That's the way I also make my connection, But I'd like to pass a tip along with this. After you make your end connection you'll want to harden the brass rod. I chuck one end into a drill chuck and hold onto the other with vise grips and twist the rod about 8-10 revolutions.
This does two things ,straightens the rod and cold rolls it in a sense, which adds a lot of strength . Try it on a scrap piece first you'll be amazed!. "73" from N1UVW

[W0HU]

Having built quite a few of these for easily deployed portable antenna units, I found that if you form the end of the rod (for radials) around a 1/8" drill bit, then use a 1/8" x 1/4" long "pop" rivet, you can make a good solid attachment to the SO-239 (if it needs tightening, you can do it with a flat-ended punch). The other wisdom mentioned above for soldering the center to the radiating element is valid, try to not melt the white cheap plastic center. If you were fortunate to get the brown phenolic center, not to worry much. You can use 5 minute epoxy to seal the center if required, and work it to a taper so that water will run off. Your $2 antenna may cost you $5 if constructed this way.:cool:

W0HU

[AE5JU]

Don't solder brass rod directly to the center. Instead, solder brass tubing. Available in almost any hobby shop and some hardware stores in the K&S brass rack. Less mass, easier to solder, lighter, so less strain.

http://www.ksmetals.com/

They make brass tubing in telescoping sizes.

[KD5ZPG]

Here is a good article on making a dual band for your consideration.

http://www.eham.net/articles/7005


KD5ZPG

[KA7LGF]

Take a wood dowel & fit it into the back of a "PL259". Start with a Dowel a bit larger than the hole & see if U can, kinda "Screw" it in for a tighter fit. Now use a drill bit that fits into the center conductor to drill through the wood "Insulator" using the "Center Conductor" as a "Guide". I think it will be 1/8" same as Ur "Rod". If not, open up the hole from the back & then grind/file down the rod until it fits the "Center Contact Hole". Solder & that's done, ready to screw into the SO-239. Now, "Flatten" the Brass Rods ends to drill them for a screw & it's nut that fasten it to the SO-239. All done & it "Breaks Down" quick too! :cool: John KA7LGF

[KB1KIX]

Lots of difficult methods here.

I drilled a hole in the center of the plug, ran the LMR 400 (solid) right up through the middle.

Radials as normal.

Works fine 4 years now.

Jonathan