Interestingly, "UHF" connectors (Amphenol 83-1SP) have slightly less insertion loss at 450 MHz than type N (UG-21D/U) connectors do. I've measured both many times. But going above 500 MHz, Type N, as well as C, BNC-TNC-SMA etc. are a better match and lower loss.[/QUOTE] Well, I eliminated PL259 & SO239 long time ago - may be they are ok for DC up tp 100MHz or so, but measurable mismatch (even if small losses are measurable with a good NA) Properly assembled N-connectors are better - However I have seen many N-connectors poorly assembled - and their quality and tolerance highly depends on their manufacturer - Proper N connectors are good to 18 GHZ - but lousy ones may have poor performance on upper UHF bands. Still prefer to minimise number of connectors as it avoids losses.
What you say is essentially true, however, there is a lot of inertia built into connector choice and usage. The PL259 connector is somewhat more robust that a type N connector, and that counts for a lot. If you install connectors outside, you will do a good job of weatherproofing them anyway, whether it be a PL259 or a type N connector. That weatherproofing will also prevent the connector from coming loose. These connectors have been successfully used for decades. For the most part, people don't have problems with them. The TNC would be a good choice for LMR and other situations where the attaching cable is primarily RG58 size, since those connectors are readily available. However, RG214 cable will put an unusual stress on TNC or BNC connectors, so you don't see them used a lot on base station equipment, where RG213/214 size cables are the norm. So, type N connectors are used a lot on modern base station equipment, but SO239's are predominant on VHF mobile equipment. The center pins on both the male and female type N connectors are more subject to breakage, due to their construction. I think that may be a primary reason that the UHF connectors are so popular.
Hi all, Here is link to some 239/259 loss test data. A calorimeter was used. Loss in the HF range was less than 0.01 dB. Loss for VHF/UHF was 0.01 t0 0.1 dB. http://www.k1ttt.net/technote/connloss.html
Carl, please educate me about the silver plated BNC. Don't have any but if some came up for cheap I would have thought I was doing 'a Good Thing'. Thanks
Some of the modern QRP rigs use the RCA jack for an antenna connection.today. They claim because it is compact and light...I think the real reason is CHEAP.
The BNC connector can also be a type that is mounted on a PC board and not bolted on the panel. This means more compactness and no wires floating around inside the box. And you are right, they are probably cheaper since they make so many of them and sell in bulk which also means they are cheaper to transport by being lighter the the SO-239's.
Collins used RCA phono receptacles (pretty good ones with ceramic insulators) on the S-line. Motorola used something very similar but with a slightly shorter pin all over the place on VHF/UHF LMR equipment for decades. Not because they're cheap.
Many plating types also protect the metal from oxidation. Like gun bluing, for example, which is nickel oxide. At one time, some finger contacts were intentionally plated with a thin layer of silver so the oxide can be limited and when the connectors are mated, the finger contact wipes off the oxide allowing a good metal-to-metal contact. At one time, this was common with IC leads. However, technology changes so you don't see this kind of plating, anymore.
I see that here on several surplus UHF cavity amps, especially built for the military or federal agency such as the FAA such as at AM/6154 and 6155 dating into the 60-70's. I dont know what is used for Eimac finger stock on my 3CX1000A7 2M amp and 8877 for 222 MHz. Carl
There are many alloys but at one time, many finger stock was composed of Beryllium Copper. It is a good conductor and has inherent springiness so a good contact is better guaranteed. The same as used as the finger contact with UHF front ends cover/caps on the little converter. There are also some of the same looking finger stock used on some PC board components today. But, whether Beryllium Copper or similar alloy is unknown to me. The is at the core of metallurgy.
