It's important to remember that when the "UHF" (239 series) connectors were developed, UHF meant 28 MHz! Almost no work was being done at over 100 MHz and the FCC did not even care what one did over 300 MHz: My 1941 ARRL handbook shows that Hams could do whatever they wanted at such absurdly high frequencies, nor does the handbook show how to produce RF above the 112 MHz band (112 became 144 MHz when the FCC reorganized the early TV channel allocations.)
That changed very quickly during WWII. Wars do have a habit of spurring technological development. But the name "UHF" stuck with the SO and PL 239 connectors. As Alan points out, they are quite useful up into what we call VHF and possibly low UHF today. 73, Ron AC7AC -----Original Message----- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Alan Sent: Tuesday, January 23, 2018 3:18 PM To: elecraft@mailman.qth.net Subject: [Elecraft] UHF connectors [was: Array Solutions Lightning Arrestor] On 01/23/2018 11:05 AM, Jim Brown wrote: > On 1/23/2018 10:29 AM, Walter Underwood wrote: ... >> But I mostly like them better because they are engineered instead of >> a historical accident.:-) > > The technical superiority of N-connectors for use at HF is a wild > exaggeration, to the extent of being an urban myth. Yes, there is a > SMALL impedance difference at a junction, but it simply doesn't matter > at 6M and below, both because the difference in Zo is relatively > small, because the length is small as a fraction of a wavelength, and > because as frequency increases, small mismatches are reduced by the > loss in the feedline (and NOT loss due to mismatch). > > There is, of course, a FICTIONAL loss called "mismatch loss," which > shows up in the lab with test equipment that is carefully engineered > to have 50 ohm output Z. ... Yup. Here is a posting I made 25 years ago that has actual data: From: ... (Alan Bloom) Date: Fri, 18 Sep 1992 23:03:13 GMT Subject: The Truth about UHF Connectors Organization: Hewlett-Packard, Santa Rosa, CA Newsgroups: rec.radio.amateur.misc Ya gotta feel sorry for UHF connectors. Recent strings on this notes group lambasted them as worthless at VHF and above, and barely tolerable at HF. One poster called them "5 dB attenuators", and many agreed that there must be some sort of conspiracy among ham equipment manufacturers to inflict such garbage connectors on the amateur community. Today I finally remembered to bring some UHF adapters from home so I could do some relative measurements of UHF versus type-N. As expected, the type-N showed lower insertion loss at high frequencies, but the UHF connectors were hardly "5 dB attenuators." For the test I connected an HP8753 RF network analyzer through two short BNC cables into the following arrangement: _______ ____________ ___________ ____________ _______ | | | BNC female | | N female- | | N male to | | | __| 10 dB |__| to N male |__| N female |__| BNC female |__| 10 dB |__ | Atten.| | adapter | | adapter | | adapter | | Atten.| |_______| |____________| |___________| |____________| |_______| Then I repeated the measurement with the N adapters replaced with UHF. I normalized the measurements by replacing the 3 adapters with a BNC double-female. (That is, this was assumed to have 0 dB loss.) Since two N or UHF adapters were used, I assume the loss per connector is half the total. The vertical scale was .1 dB/division, so I estimated the insertion loss to the nearest .01 dB or so: --------- Type N -------- ---------- UHF ---------- FREQ (MHz) TOTAL LOSS PER CONNECTOR TOTAL LOSS PER CONNECTOR 1.8 0 dB 0 dB 0 dB 0 dB 30 0 0 0 0 100 0 0 0 0 150 0 0 0.02 0.01 200 0 0 0.03 0.015 450 0 0 0.18 0.09 600 0 0 0.26 0.13 900 0 0 0.66 0.33 1000 0.05 0.025 0.8 0.4 1300 0.1 0.05 0.86 0.43 1600 0.05 0.025 0.5 0.25 2000 0.05 0.025 0.02 0.01 Insertion loss increases until about 1300 MHz, and then starts to decrease until it is almost zero for the UHF connector at 2 GHz! At that frequency, the connectors are about 1/4 wave long (1 inch, assuming .66 velocity factor), so I assume that the two adapters are providing a conjugate match to each other. This confirms my assumption that the insertion loss is due to reflections (impedance mismatch), not absorption (true power loss). Bottom line: UHF connectors work fine through the VHF range, and are not too bad even on the 420 MHz band if you can stand about .1 dB mismatch loss per connector. By the way, I did not do the full 2-port calibration on the HP8753, so there was a couple hundredth's dB ripple in the plots. I averaged this out by eye to come up with the numbers in the above chart. AL N1AL P.S. Sorry, I guess I violated the Usenet rule against posting objective data... :=) ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to r...@elecraft.com ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
