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Author Topic: Why Are PL259/SO-239 Connectors Preferred for HF Instead of N- Connectors ??  (Read 2858 times)
K1JOS
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« on: April 28, 2012, 06:11:20 AM »

I had to replace some damaged coax and the removal of the weatherseal around baluns, lightning arrestors, etc is such a mess.  Plus soldering PL259's outside is a PITA especially when the weather is cold.  Male N connectors with proper glue heat shrink provides a great long-lasting weatherproofing and they are so much easier to prepare than PL259s.  But all HF antenna and related parts still use SO-239?  Is there any reason to prefer the SO-239/PL259 anymore? Even the prices have become the same.

73 Jerry
K1JOS
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N3JBH
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« Reply #1 on: April 28, 2012, 08:28:50 AM »

Well Jerry i going to say it just a matter of convention. So many radio's and antenna's already use them so it just became the norm. Now i wonder if a company like the big radio manufacturers or  MFJ started placing only N connectors on all there items how many ham's would be yipping about it? I do agree the N connector has a lot going for it. And if my memory recall's right i think Collins used them a lot. But i also recall the use of RCA connector's as well for RF. And personally i happy to have seen that one die out.  Jeff
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KCJ9091
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« Reply #2 on: April 28, 2012, 12:08:30 PM »

Cheaper.
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N3OX
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« Reply #3 on: April 28, 2012, 04:36:43 PM »

I've heard W8JI discuss this topic and it seems from his comments that it's easier to keep a big radio operation in reliable service with PL-259's than N's.

I believe they stand off more voltage which is better for high SWR operation if you need to just load the amp into a mismatch. The innards of a N connector are the same dimensions as the innards of a BNC.  If you pop the freely rotating bit with the grooves off a male BNC  you can very literally plug it into a female N connector for example.

So in terms of voltage handling robustness, when you're using an N it's not too much different than using a BNC.  For power in general, a N will handle more but a lot of that is due to the fact that the overall connector parts are heavier.  But a PL-259 center pin is heavier yet and will handle more current, maybe important in a very high SWR situation when the connector is at a current max.

I guess PL-259's handle lightning surge currents better.

A lot of N connectors don't have a captive center pin and I've heard some reports of intermittent connections caused I guess by differential expansion of the center conductor and the shield.  The pins can pull in to the body a little bit.  Even cheap PL-259's usually have a well captivated center conductor.

So I think they've got some ruggedness going for them anyway.

The inherent weatherproofing of N's is attractive, ESPECIALLY at junctions with boxes or splices that might be exposed to a lot of water but need to be undone frequently, but they have some disadvantages too.
« Last Edit: April 28, 2012, 04:40:07 PM by N3OX » Logged

73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
WB4SPT
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Posts: 135




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« Reply #4 on: April 28, 2012, 05:16:03 PM »

For power in general, a N will handle more but a lot of that is due to the fact that the overall connector parts are heavier.


I read that to mean the N will handle more power than a BNC.  So, yes, I agree with this argument.  In a nutshell;  for HF applications, the UHF will handle more current, and more voltage.  The weatherproofness hat goes to the type N.  For UHF and above, certainly 800 and above, the type N is generally more favored due to its constant Z design.
On a tower, one could argue the UHF is a bit easer to deal with, since there are no small parts to drop/lose.  At least the conventional type N has seals, a small center tip and still needs a soldering system.
« Last Edit: April 28, 2012, 05:17:51 PM by WB4SPT » Logged
W0BTU
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« Reply #5 on: April 28, 2012, 05:33:52 PM »

N connectors are for 220 MHz and above. Below that, forget it. PL-259's are the way to go for anything under 220 MHz. And they will handle a lot more power than N's will even with higher SWR.

You have to be really careful assembling some N plugs, constantly watching the distance between the center pin and the end of the connector. It's critical. If they stick out too far, they'll jam against the female socket and damage it. If they don't protrude far enough, they won't contact the socket pin enough (if at all!). This is a direct function of the coax center conductor length, which is just too critical.

And that's not the least of the issues. In cold weather in longer coax runs, the coax cable center conductor  can contract and pull the center contacts in an N connection completely apart to the point where they don't even touch. Just imagine the SWR under those conditions!

I always used N connectors that 'captivated' the center pin. That's supposed to prevent that, but the captivating washers are made from Teflon, which can cold flow over time under pressure, and they don't fix the issue above.

I don't plan on ever using N connectors for anything below 220 MHz again. They are just plain unnecessary at two meters and below.

If you want waterproof connectors, then stretch-wrap the PL-259's with electrical tape after you fill them with non-hardening silicone dielectric compound to keep moisture out.

I've seen UHF connectors used at MF at the 10 kW power level, continuous duty (and W8JI says he's seen them used at 20 kW). I would never trust the flimsy N connector center conductor to hold up under those circumstances.

Check out post #11 by W8JI at
 http://forums.qrz.com/showthread.php?278609-How-much-power-can-i-put-through-a-BNC
and the comments by WB2WIK on a source for good N connectors at
 http://forums.qrz.com/showthread.php?269535-Coax-connectors
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AA4HA
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« Reply #6 on: April 29, 2012, 04:21:24 PM »

One thing I like about N for test cables;

I can attach them to N female connectors, press them onto TNC and BNC female connectors (for temporary work). I have yet to have an N connector that was assembled properly ever fail to make a center pin connection...

(correction on that point. I did find ONE type N connector that some idjit managed to thread a PL-259 male connector onto a Type-N female-female adapter and it busted off two of the compression points on the gold center pin.

I have always used Andrew connectors that are made of stainless steel (ring flare type) and not the brass thread on type connectors. If you do a great many connectors then you want a cable prep tool that chucks into a cordless drill so the end is completely done for you in about 5 seconds. I always put about 2 oz of silicone grease (not silicone adhesive, if it smells like vinegar you have the wrong stuff). This displaces any water that may get into the connector body and provides a bit of lubrication for the red O ring that goes between one of the copper lands and the connector body (on Heliax type cable). LMR cable also has a similar set of cable prep tools that cut the jacket, braid, foil, foam and center conductor to the proper lengths.

Even a Type-N connector needs to be properly weatherproofed with rubberized mastic tape covered with '33.

I have done thousands of N connectors and only when I did not have the proper tools and resorted to a box cutter razor and a small pair of wire cutters did I have problems getting the flare to work.

I have never seen one fail, even on lightning strikes or extraordinary SWR problems at high power.

The two big disadvantages? 1) Price. 2) Hams hate moving to a new standard.
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
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