I caused a minor kerfuffle on Twitter recently, when I posted this:
This connector, properly called a PL-259, is the most common RF connector for ham radio use. The female counterpart is called the SO-239 connector. While these connectors are often called “UHF” connectors, they actually don’t perform very well at those frequencies (300 to 3000 MHz). So I feel justified in disparaging that name.
The tweet generated a large number of replies, mostly in support of my anti-UHF-naming sentiment. It seems that other highly-educated and thoughtful radio amateurs agree with me. (It seems that the wise hams out there always agree with me.) You should be able to view the thread here: https://twitter.com/K0NR/status/1653575723838492672
Some people pushed back on the anti-UHF sentiment, usually saying that it is the common name for this connecter. A few folks pointed out that Amphenol calls these things “UHF Connectors”, which did surprise me. Who am I to disagree with this manufacturer of high-quality connectors? Of course, Amphenol also says this:
Originally intended for use as a video connector in radar applications, UHF coaxial connectors are general purpose units developed for use in low frequency systems from 0.6 – 300 MHz. Invented for use in the radio industry in the 1930’s, UHF is an acronym for Ultra High Frequency because at the time 300 MHz was considered high frequency. They can be used when impedance mating is not required.
Well, there you have it: the connector was named UHF back when UHF meant up to 300 MHz. (Today, UHF means 300 to 3000 MHz). I particularly like the comment “They can be used when impedance mating is not required.” What? That does not sound good for RF applications. I do agree that these connectors can generally be used to 300 MHz, but these days the ITU calls that VHF (30 to 300 MHz).
Wikipedia provides a more complete explanation, worth reading.
OK, so the name “UHF” is archaic but it has kind of stuck, the way old terminology sometimes does. I am still going to avoid using this term because it really should be deprecated.
And don’t use these connectors above 300 MHz (UHF frequencies). Unless you have to. Which I did last weekend when the only cable available for my 440 MHz antenna had a PL-259 connector on it.
73 Bob K0NR
Glad you have “connected” with this important issue!
I think you are wasting your time Bob. The mobile antenna manufacturers use the term “UHF” to distinguish the connectors on their antennas from NMO, SMA, and BNC. There is not going to be any change at this point.
Bill, W8BC
But this is my quest, to change the world.
Not really.
The UHF connector is not a 50 Ohm device even when it’s terminating coax such as RG-213. I once measured or “characterized” as we engineers call it several PL-259s using a lab grade S parameter test set and found them to be around 65 + or – Ohms.
They have been used on UHF two way radio equipment, including filters and duplexers
since the 1940s. The threaded shell does become loose when vibration occurs.
Even more appalling than the name of the connector is that there are people who use this connector outdoors with no weatherproofing. Also, soldering the braid is very problematic for many folks. I ranted a bit about all this a few years ago: https://www.amateurradio.com/we-need-a-better-uhf-connector/
I’m an (old) novice at soldering, but followed the online guides and have no problem with the braid. I did notice that the good makes of RG58 were fine, but there are cheap cables around where the braid is thin and badly wrapped. Chuck this type away and use a good brand name, and soldring it should be straightforward.
I have Press Jones N8UG (SK) Wirebook V. On pages 43-45 of his book, there is a great defense of the UHF PL-259. He calls it an excellent conductor that worrying about in your average amateur system as the smallest problem you will see. The comparison is to switch out PL-259 to N connectors which have 3 to 6 times the cost.
He has a table of insertion losses, comparing N to PL-259. N connectors measured no losses up to 900 MHz. The closest UHF band frequencies listed are 200 MHz with 0.015 db loss to 600 MHz with 0.09 db loss for the PL-259.
Worrying about PL-259s in the UHF band should not be a worry. I you you are above the UHF, you are likely already measuring your insertion losses anyway, and the argument is moot.
Dennis,
Thanks for passing this along.
I don’t have access to N8UG’s book but frankly, it probably would not matter.
First off, the point of my post is that the name “UHF” for this connector is fundamentally incorrect. This name was assigned back when UHF was considered to be up to 300 MHz. Today, UHF is defined as 300 to 3000 MHz.
Second point, I am not opposed to the occasional use of these connectors in 430-440 MHz systems but I try to limit the number to one or two.
Third point: Back to N8UG’s numbers as described in your comment. I wasn’t there when he made the measurements but I find the claim of an insertion loss of 0.015 dB up to 600 MHz for a PL-259 to be highly unlikely. I base this on my use of these connectors at 440 MHz and associated measurements using a VNA, SWR meter, power meter, etc. These connectors work, but do not perform well, at 440 MHz.
But don’t believe me. There are plenty of carefully done measurements available on the web by competent engineers. For example, take a look at the work by John Huggins, KX4O.
https://www.hamradio.me/connectors/uhf-connector-test-results.html
He shows that the insertion loss of “UHF” connectors at 400 MHz is in the range of 0.5 dB to 1.5 dB.
These values are believable to me. Explore his website to see other articles he has written on connector performance.
Should we care about a dB or so of loss? Well, that depends.
I covered that topic in a previous post:
https://www.k0nr.com/wordpress/2021/06/a-decibel-is-still-a-decibel/
73 Bob K0NR
Apparently the N connector has become extinct.
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