Shielded Banana Plugs

I don't know what an arm and a leg goes for these days, and I've not bought anything myself there so far, but here is one vendor:

Hint for your web searches: The popular term is shrouded banana plug, not shielded.

More than those plugs, apparently:

Thanks for the tip.

Now that I know what to look for, I see that Newark has them.

Probably around the same price. This stuff is specialty gear. However, even Radio Shack seems to have them, at least in fire engine red:

You could try these guys:

$2.15 for 10+

(they are Aussie dollars too - by tomorrow they will probably cost half that in USD terms)

I think Digikey, Mouser and Newark all carry them. You may even catch mjpa.com with inventory.

Pomona will have the name brand price, but there are always generic knock-offs. Be advised: There are a few different sizes out there, so make sure you spec the right one.

A shielded banana plug is called PL 259, also UHF connector.

By construction that's not really a banana plug -- banana plugs have the spring on the plug, not the socket -- but you've certainly captured the level of sophistication of the PL-259 and its close relatives!

It has been much maligned but I have to say that the PL-259 has always been good to me. You can safely get a kilowatt across. Plus banana plug fit into the socket, in a pinch.

It's easy-peasy to solder it onto a piece of RG-8/U, or RG-58 or -59/ U, with the adapter.

I stuck a piece of 300-0hm twinlead into one once, to drive my 40M folded dipole; the pi-net output of my 75W transmitter tuned up just nice, and I made some contacts! (The rest of the family complained about the key clicks in the [AM] radio, however.) ;-)

Cheers! Rich

The only two strikes that I see against it is that (a) it can be hard to solder correctly, and (b) in light of the performance of a constant-impedance connector, the term "UHF" is laughable, however much the connector may have outperformed whatever it replaced.

(b) is just a marketing problem -- the connector works fine at HF.

(a) is just a training problem -- given an iron with enough thermal mass those things solder up just fine.

I have used them at 430MHz with a substantial amount of power (tens of watts). Nothing got hot, VSWR was fine.

Yes, you need big bertha to do that. 150W is sort of a minimum, I prefereed a 500W iron for that, it was faster.

My understanding is that the original meaning of the acronym was "Universal High Frequency", and was not intended to refer to "ultra high frequency" operation.

I believe that was its original intended application.

I have one that's only 200W or so, but it's HUGE. It takes a long time to heat up, but the tip is about 3/8" diameter solid copper two inches long -- so it retains the heat really well, too.

Yes, although I believe there are some PL-259s where they mess around with the insulator's dielectric constant to get it much closer to 50ohms than the usual ones provide.

Agreed, although in this day and age I kinda think crimping is the better way to go anyway: Easier and faster to do correctly than soldering.

But everyone certainly *should* solder a few just to get an idea of what the original ones were like... :-)

---Joel

I normally use one of those really small blowtorches (like the ones that use cigarette lighters for their source of gas) -- the small size makes them rather more maneuverable than a big iron.

Oh, plus I'm cheap at times and the good quality big irons are spendy. :-)

The PL259 is W.W. II vintage and replaced real crap. Look at some of the photos of earlier military radios to see for yourself. Some were a pair of binding posts. UHF starts at 300 MHz, and the PL259 has been used at higher frequencies. they were used in early TV pre amps on both VHF & UHF.

As far as soldering, it's easy if you know what you're doing. I used to assemble a lot of cables with PL259 connectors.

The first thing you do is run a drill bit through the four holes where you solder the shield to the shell to remove the pretty plating. Then you tin the braid with liquid RMA flux & good solder. I used a SP-175 175 W Weller soldering iron for this. Then a quick pass with a small tubing cutter to trim the tinned braid. Slip on the connector and fill all four holes in the shell with solder, then solder the center conductor. I used the same soldering iron for this. It took a little over a minute per connector when doing a small batch of cables. I only had one ever give me a problem when a single strand of braid shorted out a used connector. I fixed that with a pair of automotive jumper cables and a car battery. One quick flash, and the short was gone. To reuse the connectors I remove the outer shell and heat the inner shell. Then I drop the connector on a sheet of aluminum. The solder splashes out of the shell, onto the aluminum. That leaves it freshly tinned for the new wire.

So does an open flame from a gas stove or propane torch. :)

I have two from grandpa. Copper tips of about two cubic-inches at the end of a stick, with a wooden handle. You make a nice wood fire, have a beer, roast some marshmallows, and when it's down to glowing coals put them in there. Those even work during a power outage :-)