#605

Episode 605
SO-239 (UHF Female/UHF Jack) PL-259 (UHF Male/UHF Plug) measurement for useable frequency range, compared to N-type connectors. The spec is 300MHz. Let's measure it.
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[@yuriantunes2916]

Hello there, thank you for the videos you are always uploading, i'm learning a lot from them

[@IMSAIGuy]

Glad you enjoy them!

[@davo99]

Yes PL259 connectors are crap, and should not be used above 30Mhz, why Ham and CB manufacturers still use them is down to marketing bit like VHS and Beta in the video tape days. Well done in showing the comparison, in reality in your measurements the electrical length should be adjusted for the difference in physical length. This is a note for everyone, when screwing connectors, keep the inner stationary and only rotate the outer ring, otherwise you wear the inner mating surfaces to the point that you will get unreliable connections. I believe UHF stood for Universal HF.

[@Michael_x00]

The connectors use the old definition of Ultra High Frequency which in the 1930s meant everything above 30Mhz. The german term UKW (translating to "ultra short wave"), which seems to have originated around the same time, still refers to the 30-300MHz range. Maybe coincidentally that also fits with the mention at the beginning and the measurement at 3:26 where the limit seems to be at 300Mhz.

[@davo99]

@@Michael_x00 I have read some where that when they were developed they were know as Universal High Frequency, but have a look at the Wiki en.wikipedia.org/wiki/UHF_connector. They are absolutely crap connectors, the better ones will work ok to 150Mhz but because of the way they are manufactured they do not present a constant 50ohms. If there is any doubt measure them with a TDR. I used to work in a RF lab and I wouldn't use them past 30 Mhz. What I don't understand is why they are used on CB radios, where you will be very lucky to get 1/2 the power generated at the antenna. It's probably marketing bit like VHS & Beta and Watts RMS (there is no such thing as RMS power)

[@Michael_x00]

@@davo99 I know they aren't good but good enough for Ham radio. I also did my measurements and it seems to agree with the findings of most other people that non crappy ones are certainly usable to 150MHz sometimes even 300MHz above which the losses of a N or BNC connector are much lower than the UHF. And of course there are crap ones out there I also had a few crappy BNC connectors that where completely unusable above 100MHz. Certainly not good enough for laboratories where you want the connector to be as "invisible" to the network as possible. As to why they are still used, I think it's mostly people not wanting to replace existing perfectly functional gear just because of a connector that in most HAM and CB radio instances isn't an issue. I don't see a whole lot of marketing for the PL259 basically everywhere you look you find the PL259 is worse but old habits die hard.

[@davo99]

@@Michael_x00 Ok, but not good enough for Ham Radio. I mainly operate 2, 70 & 23 cm and even at 70 the losses are to great, 23cm would be a disaster using PL259. I use heliax with N connectors, even when I changed from RG213 to heliax was quite an improvement on the 2 bands

[@davo99]

should be 3 bands

[@subramanianr7206]

SO239 (socket) and PL259 (plug) are also called UHF connectors. Because there's a time when anything beyond 30 MHz was catagorized as UHF. BNC, TNC, SMA and the bulk head N connectors are all having the characteristic impedance of 50 ohm. But the so called UHF connectors are not of 50 ohm impedance but something around 30-35 ohm. But the whole amateur radio industry has been using it as a standard type of connector for some reason and maybe because of lower cost of production (!!??). Any coax connector/cable with a characteristic impedance would carry more power. A 75 ohm contraption would be great to carry UHF frequencies with little attenuation. Many SO239 connectors on the back of the SWR/ power meter would be having a "honey comb" dielectric to hype the impedance to around 50 ohm to avoid impedance bumps.

[@CarrotDugTooDeep]

And Kenwood still feels the need to use UHF connectors (PL-259 & SO-239) on their commercial mobiles (NX-5000 series), even on the UHF models. I was completely baffled when I received my new NX-5800 and it had an SO-239 connector. It also had full length power leads on both the negative and the positive wires. The whole setup screamed amateur radio, not commercial grade. Neither L3Harris nor Motorola use UHF connectors on their current radios, because they know better. They also don't run the negative lead all the way to the battery and actually instruct people to ground the radio at the closet ground to the radio. It was off-putting to say the least. That coupled with other issues is why I sold that radio and is part of the reason why I won't buy another one for commercial use. When I see an SO-239 or PL-259, I think ham radio and that is fine, but leave them out of the commercial radio market.

[@davidholman2536]

Many radio professionals in Britain call them insulated banana plugs and they shouldn't be used above medium wave 😂. I just know that PL259 family doesn't have a constant characteristic impedance like proper RF connectors (as you ably demonstrated) so will be a source of reflected power.

[@M0UAW_IO83]

Interesting, can you quantify it? Wonder how the MIL-SPEC PTFE, silver plated ones stack up...

[@PapasDino]

And thus why dual-band VHF/UHF radios have SO-239's on the 2m side and female N connectors on the 70cm side.

[@GateKommand]

I read somewhere that the PL259 was developed during WW2 for use in the atomic bomb project and wasn't intended for use over 30Mhz. Maybe this is true, maybe not but they are omnipresent lol.

[@subramanianr7206]

Any coax connector/cable of 35 ohm would carry more power but as the frequency goes up there's attenuation limiting the power handling capability.

[@BrendaEM]

There are VNAs that could show in the time-domain the launch and the transition of each of those connectors. At it's maximum (stimulus) frequency, in the time-domain, what can the NanoVNA show?

[@IMSAIGuy]

I have a friend more savvy than me. He uses the Nano and downloads the S11 parameters into MATLAB and does the time domain stuff. He uses it to do PCB trace reflections.

[@ahbushnell1]

you should do the transfer function. S21

[@OC35]

I call these connectors screened banana plugs!

[@subramanianr7206]

And in the video, the N connector/BNC 50 ohm termination shows up as 52 ohm with good return loss. But the "UHF" connectors/BNC load shows up as 42 ohm at 300 MHz and it must be still less beyond 300 MHz.

[@brunobassi2440]

Standard 300Mhz max De luxe 500Mhz max