Help keep this site free:
I have no financial interest in RadioWorks, but I have been a satisfied customer for some time and I recommend them. Besides, their web site is well laid out and contains a lot of useful information, in addition to detailled specifications and prices for their products. I have also found the people there to be very helpful and friendly on the telephone.
For instance, there are 2 basic types of coax cable in use in amateur operations. Go to the RadioWorks catalog page 62. You will see the 3 types to the left are about 1/4 inch in diameter and the others are about 0.4 inch. If you look at the table below the cable types, you will see that the attenuation per 100 feet for the smaller cables is generally much greater than for the other cables. So the smaller cables are OK for short runs, or for low frequency antennas. I typically use RG-8X for short interconnect cables inside the shack, and for temporary use in the field when the runs are short or the frequency low (as on HF). At higher frequency (such as 2m, or 144 MHz, and higher), the larger cables will always be better.
For instance, if you need 50 feet from your VHF radio to the antenna (make sure to measure the actual length you need, including bends and turns, as you can easily underestimate by 50% if you just measure the straight line distance), the 1/4 inch type cable will loose about 1.85 dB (one half of 3.7 dB) of the power fed to it. That's about one third of your signal, both on transmit and receive. That's too much for most installations as far as I am concerned.
Rule of thumb: 1 dB means you loose 20% of your signal. With 2dB, you loose 36% of your signal and with 3dB of loss, you loose 50% of your signal (that's a whole half). Even worse, with 10 dB, you would loose 90% of your signal, a pretty good dummy load :-)
On the other hand, if you use RadioWorks' SuperCable, you will loose 1.15 dB for 50 feet, which is negligible for all practical purposes. For 50 feet, even RG-213 is OK (1.45 dB loss) at VHF.
If you look at the specs closer, you will see a parameter called Velocity Factor (VF). Typically, the cables with lower VF are more lossy, but that's because they use solid insulation, instead of a low density foam or mostly air (with small spacers to keep the center conductor roughly "centered" inside the outer conductor), so they are also considerably more rugged (such as you can step on them without causing damage). The cables with higher VF are better, from a loss standpoint, but they need to be protected against mechanical abuse. They are also typically much more difficult to deal with when it's time to install connectors, and they have a tendancy to trap water inside if not terminated properly, which will ruin the cable very quickly.
Another fine point of the spec are the shields. The number in the table represents how much of the cable is covered by the shield. For instance, cable with one 95% shield means that the shield covers 95% of the cable surface. That means that signals can get in and out of the cable though that 5%, and that increases the loss. High quality cable has two shields, with one being rated 100% because it usually is a foil that completely covers the insulation inside the cable, while an outside braid gives the cable better power handling.
Connector styles will vary also. For 1/4 inch cable, you can use BNC connectors, which are very convenient (they are small and easy to connect/disconnect). You can also use PL-259/SO-239 sets, with the proper adapters. Most mobile and fixed radios use these larger types of connectors, while most HTs use BNC (newer, very small HTs also use SMA).
For short cable runs at home, I use crimp type BNC connectors with RG-8X cable. The center pin is soldered, but the braid is held to the connector body with a crimped ferrule. They are a good compromise between cost, performance and ease of installation. You need to have the right crimp tool, which you will amortize quickly as you will find it easy to make just the right cables you need.
It is best to buy the connectors and cable from the same place at the same time to make sure they are made for each other. Different vendors often have slightly different dimensions for what seems like the same product, so interoperability is not guaranteed.
BNC connectors are not recommended for outdoor use, but even PL-259/SO-239 need to be protected from the rain or else the rain will get inside the connector (bad) or even inside the cable (very very bad).
There are many different models of PL-259 connectors, the most common type of connector used on ham equipment up to
The main considerations are the finish and the insulator. The silver plated types are so much easier to solder that it would be inconceivable to recommend anything else. Yes, silver oxidizes, but the silver oxyde is a good conductor, so it should not significantly affect the performance of the connector.
The other consideration is the insulator material. Teflon has lower loss but melts easier, so you may cause more damage when soldering the connector. If you are not experienced, and if you operate at VHF and below, bakelite will be a better choice.
At my station, all the rigs have SO-239 sockets, but I have installed PL-259-to-BNC adapters on the rigs, and I use short RG-8X cables with BNC connectors to go from the radio to an interface panel near the hole in the wall through which the cables go. That allows me to quickly change antennas, or to disconnect the radios from the antennas directly at the panel when I don't use the station. A disconnected antenna is much safer than any kind of lightning protection device you can buy :-) Then, from the interface panel, I use 0.4" diameter cable (low loss for the VHF antennas, RG-213 type for the beam HF antenna) and SO-239/PL-259 connectors.
My house was hit by lightning in 1995. More precisely, lightning hit a tree in the yard, which had grown over the underground utility cable (which included the power cable, cable TV and telephone cable). It caused $7,000 of damage inside the house, all to electrical appliances, TVs, telephones, VCRs, computers, stereo, garage door opener, washing machine and so on. The only equipment that was not damaged was the ham station, which was completely disconnected from the antennas and from AC power at the time.
The more serious problem is that if water (or moisture) is allowed to get inside the cable, it will propagate through the coaxial cable's outside braid or even the center conductor, over long distances over time and ruin the whole cable. If you use a very low loss air insulated cable (such as LMR-400 or equivalent), water will easily get inside the cable itself and cause greatly increased losses. Once the cable has absorbed moisture, there is no repair procedure other than replace the entire section, from connector to connector.
You can use electrical tape to protect connectors that are outside. Make sure the tape is installed properly. RadioWorks has a page describing the proper installation of tape. They also have other products to make an even more durable protection for outdoor connections.
This is the reason why, for outside cable runs, I strongly recommend that you buy pre-made cable runs with professionally installed connectors, unless you know exactly how to install connectors.
A 1.0:1 VSWR is a perfect match. That means the load impedance is exactly 50 ohms. A 2.0:1 VSWR is obtained when the load impedance is either 25 ohms or 100 ohms.
Because most ham transceiver will deliver full power with a load VSWR of up to 2.0:1, this value is usually considered the limit for acceptable operation. Many hams prefer to keep their VSWR below that however, but for all practical purposes, it is unnecessary to spend time or money trying to get much below a VSWR of 1.5:1. The benefits will be hard to measure and even harder to hear.
On the other hand, coaxial cable losses increase rapidly, for a given frequency of operation, when the antenna VSWR exceeds 2.0:1. This can even, in some extreme cases, result in the coaxial cable burning, even when running 100 W. Using a higher grade of cable will definitely improve things, but even high quality coaxial cable becomes very lossy when VSWR exceeds 3.0:1 at higher HF frequencies (or VHF and higher). I remember seing a good article in a magazine about this, and if I find the link, I will add it here.
If you have a badly matched antenna, using an antenna tuner is the usual way to keep the transceiver happy. However, the antenna tuner, if it is installed at the output of the transceiver, will only keep the transceiver happy, but it will do nothing for the coaxial cable going to the antenna. The best place for a tuner is at the antenna feed point. Several compagnies (SGC, LDG and Icom are a few of them) offer remote antenna tuning units designed to be installed at the antenna feed point, even if that is outside.