N-connectors - good element, but do not buy fakes...

For people working in telecommunications, it is known that approximately 90% of the malfunctions of the telecommunication technology sets are caused by faulty connectors. However, the general term "defective connectors" means not only poor quality connectors, but also poor quality connections, or poor quality connectors due to the wrong connector
+ cable pair was selected. Not surprisingly, telecommunications companies are sacrificing so much finance and organizational effort to train technicians and select the appropriate components. If we leave aside historical so-called UHF connectors (which are not UHFs at all) of type PL259 and SO239, which actually are not, because they do not meet the basic premise of RF coaxial connectors - ie repeated assurance of nominal impedance - and BNC, N, and SMA connectors are by far the most widespread among radio amateurs aware of the technical context. These connectors cover the most commonly used radio frequency bands up to (albeit with some compromises) up to 24GHz and are capable carry of transmitting power up to 1kW (on lower frequency bands up to 1GHz). While BNC connectors are very often available on the market today as very cheap and therefore usually a poor quality substitute for other professional connectors (leading to their poor quality and endless manifestations of different bags), radio amateurs often reject them and have gained great popularity with SMA connectors. with the undesirable manifestations significantly better. However, their design is not designed to transmit higher power (max 200W). Therefore, probably the most widespread connectors on VHF bands today are type N connectors, which were created during World War II in the US to connect the first radar systems in the US Navy.

But: history and technical theory is one thing and today's commercial world is another one. Although politicians shout out the phrase about the digital omnipotence, life is still primarily analog. The connector parameters are measured for conductivity, attenuation, impedance mismatching, reliability and especially cost. And among radio amateurs, few realize that the price is parameter number 1. and other parameters are solved by some compromise - at a given price to meet the parameters of the equipment, its reliability and transmission capacity - all of course for a given project, which represents assemblies that need to be properly mounted, connected and energized for the final assembly. But the techno-economic life of the device is getting shorter and especially for IP technology, it has now fallen from the original 10 years to half when the device goes into scrap - not because it no longer works but because the new device has a higher transmission capacity and other features - it is not necessary to set anything on it, can work at a higher temperature, consumes less electricity, etc., etc. Well, and the liquidated device, which in his lifetime has never been disassembled and done nothing, becomes a grateful source of material for amateur radio designers. Many then believe that the connectors removed from such a device must be a quality standard. It does not have to be. In addition, the situation will deteriorate in the coming years, as all radio transmission devices are moving to an antenna. You can use from it just a piece of waveguide connected to some microstrip structure because the whole device is without connectors - if we skip the matter of optical connectors connecting ODU and data technology somewhere below the mast. Today, the industry has the latest equipment, equipped with connectors, and in a few moments will have to buy them in electronics stores. And unlike semiconductors, they will be very expensive. This article therefore aims to introduce the amateur radio community to what is important and what to watch out for N-type connectors.

The brand is still a standard of quality! I will borrow the answer from one TV contest: "yes, yeah ..." There are several traditional manufacturers in Europe and the USA who simply produce 1A quality connectors and it is their professional pride to leave high quality connectors to the market - sure you know them and I would include Spinner, Suhner, Rosenberger and Radiall. If you reach for them, they will serve you for years without necessity to pay attention to them. Well, then there are brands like Amphenol and Telegärtner. Also very sophisticated and experienced connector manufacturers - but they are already on the order of equipment manufacturer or market, able to produce connectors 1B quality, because they are cheaper and certainly suited to the application ordered. And then there is a whole host of other manufacturers. How do you recognize the good ones? Simply - for the highest quality connectors, the manufacturer usually does not hesitate to state their name or logo. Incidentally - in Czechoslovakia were once manufactured connectors in Mikrotechna belonged to the best quality, which could be obtained on the market and had certificates for use in the civil aviation industry and Army. Where are those times ...

Chinese connectors are a phenomenon of a time when European and especially American economists moved production (and related know-how) to Asia get a short-term savings without realizing it. that in doing so they are liquidating the domestic industry in the medium term. So today you can buy top quality as well as 3rd quality in China. Be careful. There are Chinese 1A quality connectors with the name and logo of the above reputable manufacturers, but also fakes. You can find out what to watch out for below.

Gold? The connector contacts are only covered with a microscopic (if any) gold layer. However, the yellow color of the contacts tells nothing about the quality of the connector. Above all, it is good to realize that gold is soft and rubs. Therefore, the reputable manufacturers are covered with various hard alloys of gold, silver, rhodium and other metals with good conductivity. Gilded contacts made sense in the Czech Republic when the North Bohemian coal-fired power plants spewed millions of tons of sulfur dioxide into the atmosphere, causing silver to black. Fortunately, the time is gone and the same (or better) service on the contacts and silver, respectively. its alloys. Although I saw the answer of a famous "guy" that gilded PL259 connectors go to 23cm ... hihi

Teflon? Another myth. The plastic in the connectors is usually Teflon, but it does not have to be Teflon. Since many plastics have similar dielectric (dielectric constant, voltage strength and delta tangent dielectric loss) and mechanical parameters like PTFE at normal temperatures, replacing Teflon with connector quality may not be an obstacle - with one crucial exception: If the contacts are in plastic ("like a teflon only") internal parts of the connector anchored permanently, cannot be soldered! And the contacts of high quality connectors for medium and larger power are soldered! So if you have a connector where you can remove individual plastic insulators from the contacts and solder the contact separately to the cable, there is no obstacle to using the such Teflon replacement, since you will not assemble the connector parts until the parts have cooled down. However, if this is not possible, avoid such a connector. Teflon in the connector has one more feature. It has a high thermal expansion and if the connector heats up when transmitting higher RF power, the Teflon exerts a pressure inside the connector which leads to a reduction of clearances and thus transient resistance. The same function in the connector is the rubber ring, which maintains a constant pressure and thus small transition resistances at the outer conductor of the coaxial cable. Take care: in the crimp connectors such flexible element is not used, so rather reject the cable connector that does not have a rubber ring.

Construction: it is tied to the respective cable. Never install a connector on a cable that is not designed for that connector. Cables are different, some time not very good ... A copper foil cable and a few hairs with a tenth of mm diameter instead of shielding, of course, install poorly into the connector. The connectors for such a cable (similar to those for aluminum cables) have a tube in their design that must be plugged into the cable (heat the cable sheath with a hairdryer). However, if possible, for type N connectors, preferably use cables with a solid (preferably) 100% braid of wires and if you want to minimize its attenuation, then with a foil that can easily be aluminum (on a plastic carrier), which is in mechanical resistance better than copper foil alone (without plastic carrier), which is brittle and cracking. Therefore, I recommend the RF400 cable and its equivalents for type N connectors. And even though the N connector connector is presented as waterproof, don't believe it! Water always enters the connector. Therefore, after assembly, we recommend wrapping the connector joint with a self-curing rubber tape and, for permanent assembly, add a suitable wax insulator coat.

Male and female? - this problem directly focused to gender is (as in nature) one of the most important factors of good connector connection. Generally today, there is no longer a problem with the incompatibility of dimensions as 50 years ago. However, the connector itself is realized as the insertion of the contact tip into the connector collet (tie, ferrule). And if the connector collet is not permanently spring and flexible, there is a problem with the connector wear. Do not break the head with the male connector for N connectors. This is practically always OK, unless there is a major problem in the connector (see above). In other words: cough on the N connectors of the "male" type, the problem of connector connection occurs in the vast majority of cases in the "female" female (female) and the problem is called the collet of the N connector "female"type.


OK1VPZ video - click on to arrow


Materials and contacts (!): In accordance with the above, an alloy must be used on the female connector collet of the N connector to ensure permanent elasticity and not to expand. See video. Such alloys are CuBe, or CuPbP in other words, beryllium bronze, phosphor bronze, and somewhere Beryllium copper name can be found. Spring collets are also labeled "spring contact" at some manufacturers and who knows how. However, it is clear that ordinary bronze, brass and similar materials do not have such flexibility and the collet expands, resulting in poor contact, noise, intermodulation, or overall loss of connection and burn out. And why aren't steel collets? It is simple - see above - the metallization is easy to rub off and then the conductivity of the material is decisive. And the steel is not exactly at its best ... The collet of the female connector N is therefore an Alpha and Omega quality connection! If you are buying connectors at a specialist store, request a datasheet of the connector, if you are buying somewhere in a flea market, take the pin removed from the male connector (dad) soldered on it, insert the PIN into the collet of the connector you want to buy, click a few millimeters to the right, left, up and down ... and either the collet expands and do not buy such connectors, or the collet stays tight and resilient, so you can hang two more such on the pin inserted into the collet after such a test. connectors and pin will not pull it out of the collet. Try it, it's easy! And remember: with a simple glance you will not find out anything!

So that's more-less everything I wanted to tell you about N-type connectors. And of course - the familiar saying is true: I'm not so rich to buy cheap things! When you are at VHF contests, overhead a large antenna system, which you have laboriously mounted and built in the wind and rain, so saving the cost of one poor quality connector is not worth a corrupt race ...

Well, and for final some pictures about the described test:

73 de OK1VPZ