9

Just looking around at various rigs online for a fiend. Lots of them look really attractive TS-480, K2, K3, FT-450D, FT-950, IC-78, FT-897 to name just a few...

These rigs are mostly HF, albeit some are also VHF/UHF capable. Yet the antenna connector used is usually either PL259, or SO239. Both mentioned connectors are known UHF.

Community
  • 1
VU2NHW
  • 2,834
  • 2
  • 20
  • 43
  • PL-259 and SO-239 are the same. PL-259 is the male connector (PL "plug") whereas SO-239 is the female receptor (SO "socket"). Why they choose to use different numbers for the pair is beyond me. Source: https://en.wikipedia.org/wiki/UHF_connector third paragraph, although without inline citation. – user Nov 07 '13 at 12:32
  • Yaesu FT-857 and FT-897 actually have separated HF from UHF/VHF. SO239 is used for HF but N connector is used for VHF/UHF. – Pedja YT9TP Nov 06 '13 at 10:14
  • 1
    This is not the whole truth - only the European version of FT-857/897 has N for VHF/UHF. Other models have SO-239 for 2m/70cm too. Check the manual (section REAR PANEL CONNECTORS, connector 7) if you have one. – oh7lzb Nov 06 '13 at 20:31
  • 1
    @oh7lzb It also doesn't seem to address the question as asked as it only provides an additional example of a transceiver (the FT-857) that uses SO-239 for HF, which the OP already has multiple examples of. The question asked is why the seemingly non-obvious choice is made to have a "UHF" connector used for signals in the HF range. – user Nov 07 '13 at 12:29
  • I guess there is only one reason: compatibility.

    If you use different connectors for VHF/UHF then you have to have different set of cables too, which you cannot swap if needed (except by using converters, which is another source of loses). At least that is reason for me to use SO239 everywhere.

    After all, SO239 actually works pretty well on higher bands.

     – Pedja YT9TP Apr 28 '14 at 06:19

2 Answers2

20

The "UHF" PL259/SO239 connector, which was originally designed at World War II times as a shielded banana plug is actually not a very good connector to be used on UHF frequencies, due to its non-continuous impedance and other properties. The common name is a bit misleading, since it's old - at the time of the design, UHF referred to frequencies above 30 MHz, and by today's standards UHF is 300 MHz to 3 GHz. A measurement found online at the time of writing this answer documented 0.2 db insertion loss at 144 MHz and 1 db insertion loss at 432 MHz, and with low-quality connectors (or higher frequency such as 2.4 GHz) it would be worse. The connector works fine on the frequencies it was designed for: HF and VHF.

Most modern HF rigs come with these connectors mostly because it has become an industry standard for amateur HF transceivers, and it works. It might not be the best connector on the face of the earth, but everyone already has them on their rigs, cables, amplifiers, tuners and antenna switches. When someone produces an HF rig with some other connector, most users will have to use adapters or build adapter cables. Cost, convenience, standard solution.

oh7lzb
  • 2,391
  • 1
  • 15
  • 38
  • As a corollary then, what factors would one consider in choosing the antenna connector for a home-brew rig? ... or would this better be suited as another question? – VU2NHW Nov 02 '13 at 22:05
  • Probably good as a second question. – oh7lzb Nov 03 '13 at 05:32
  • 1
    It is standard in the US for amateur and CB radio. It is less common for amateur equipment in the rest of the world, and almost never used for professional equipment. – Walter Underwood K6WRU Nov 05 '13 at 18:46
  • @WalterUnderwoodK6WRU Fairly common in South Asia too ... afaik – VU2NHW Nov 06 '13 at 16:42
  • Walter, the connector is standard for amateur HF equipment in the Europe too. Some radios (FT-857D for example) have 2m/70cm with N connectors in the European model while the US model has an UHF connector for both HF and 2m/70cm. – oh7lzb Nov 06 '13 at 20:29
  • My Elecraft KX3 and KX1 have BNC connectors which were chosen since the profile/footprint of these rigs is small and not much room to allow SO-239 for example. However, everyone of my BNC cables includes an adapter for PL-259 connections. For portable use though, I made my own coax runs with BNC adapters on them to use with my Buddipole antenna. – K7PEH Dec 29 '16 at 17:41
  • BNC is better, but this would be better posed as a second question - you'll attract more thorough answers and also help build the database. – SDsolar May 03 '17 at 03:06
  • 1
    The claim that the PL-259 / SO-239 is not a good connector at UHF frequencies is largely urban legend. Here's a test result at 430 MHz : https://www.iz2uuf.net/wp/index.php/2016/01/08/pl-259-vs-n-on-430-mhz/ – Noji Jul 17 '21 at 22:14
  • 1
    @Noji Did you notice the comment on that page? Also see this page. And see Care and Feeding of Transmission Lines (ARRL, Newington, CT: American Radio Relay League. ISBN 978-0872594784) by Hallas, Joel R. (5 October 2012), the reference listed in the Wikipedia article. – Mike Waters Jul 19 '21 at 12:54
4

The "UHF" connector, as stated, is a hold-over from World War II, and has become an industry standard. A lot of hams "know" how to put them on coax, and, since radio is, overall, forgiving, most don't notice the folly of their installation processes (melted dielectric, poor solder wetting, etc). Me? I can install them, but prefer to crimp them on. That, however isn't pertinent to your question.

Your original question has been answered well enough already, but you posed a corollary question. In my opinion, it depends on the target frequency you're working with and the size of the hardware. In general terms, I use a BNC connector for most of my lower frequency work (yeah, because they're easy to crimp, too), and SMA for anything about 1.2GHz. For me, it's often about saving space and still having efficient connectors. Both the BNC and SMA (and even the N) demonstrate a smaller impedence "bump" than most UHF connectors I've looked at.

GerryC
  • 41
  • 2